taller 348 intake manifold

As is often the case, it is the inaccurate statements based on hearsay that cause a great deal of trouble. Bruce dedicated his career to building the best of the best and dealing with hearsay that folks read and accept as factual is frustrating to him. FBB and I set goals that matched Bruce's but attempted to accomplish same on a "shoe string" budget where Bruce had the finest / newest technology at his disposal. Understanding the above statement, everyone can understand why Bruce feels how he does. For him this is a career based on science not innuendo and hearsay.

"Couldnt fit a piece of paper between the stock valves and the pistons"??? This is the type of thing some will read and actually believe and it results in a damaged reputation for the marque. I no longer care if folks post this and don't get into debates regarding this type of thing. I just put on rose colored glasses and do my Stevie Wonder routine when reading it. There is so much good data on this site but it is hidden in layers of BS which in the end confuses many owners to the point of frustration and bail out. We need Bruce here as he still has the passion and a lifetime of exceptional data. He's an engineer that knows how to do it one way, perfect the first time, pro racing demands nothing less. As FBB stated, Im sure the others are great folks as well, just a different generation and background.

Hey Bruce, I have a spare pair of these pink glasses..... Get back here you old cuss!

MilkToast Dave

 

FBB,

Careful with your racing choices. You head into the Pro levels and its a whole new game, it becomes a job not a hobby. It took me 11 yrs away from racing to shake the "Need to Win" attitude and get it back to being an enjoyable hobby. It's fun to track a car again and I feel no need to fight for a corner. Choose carefully.

The IMSA has a locked spool and is an evil handling car. All our efforts went towards the 358 and I never got a chance to sort the IMSA. If I remember correctly we never had it on anything newer than 20 yr old race rubber (owners choice, not mine) just touring the car. If we actually get a new track out here, or I finish the street mods you can take this one out (once sorted and setup) and see if you like it.

Bruce has a prototype headlight setup that can be grafted into the area where the headlight covers are, that he will loan me to copy. Have you seen anything of this nature that would look good on the car? With the Enduro engine and a muffler I want this car quazi street legal for some fun runs in the mountains. I have already built a Boxer type wiper and have some tiny lights for turn signals. Now to design a flexible front spoiler for the inevitable. I plan on keeping it a race car but want a "Cross Over" vehicle for the short time I own it.

Dave

 

Dave,

I agree 100% which is why I have sat on the fence so long buying a real race car. I think about this compromise daily.

I would love to drive the IMSA car one day. That would be a real treat. Thanks for the tip on the spool. It sure sounds fun to try.

As to light buckets I have only seen modified versions for this picture. They seems simple enough and light vs. the stock buckets. I do have stock flush 348 turn signal lights front and rear if you want them but you will need to cut holes in the bumper to mount them. Little stick out button lights like the old boxers I think would be easier and quicker to mount.

As a side note I have also considered cutting the bonnet/nose like this picture for free downforce but now I decided against it. I added a removeable 4" carbon splitter and it made so much downforce that the entire balance of the car when to oversteer until I cranked my rear wing up for some more rear downforce. I am now just barely in balance. So now I got to get a new bigger rear wing to compensate for the splitter since I have run out of adjustment on my old wing and big angles make for big drag and wing stall. I can't believe there are so many pictures of 348/355's race cars with this bonnet conversion and those small rear wings not even in the clean airflow. I can't believe they handle well at all but they must be doing something that I have completely missed or a 4" splitter makes alot more downforce than a "mildly modified front spoiler and a bonnet hole". Anyway there is one more data point as you modify the IMSA.

Oh, I actually cut the stock bumper at the spoiler parting line and made my splitter/spoiler unit removable (5 Dzus fasteners) so I could get the car on and off the trailer. You may think about making different splitter/spoilers for different kinds of drives to minimized the results of the inevitable.
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Thats the look I am thinking of doing with the lights. Would be nice to find who did the plex covers so I dont waste the time regarding molding and fab there.

The 385 (up, another new project that is on hold for the time being) has the trunk lid cut and the oil cooler behind the front bumper and the fuel cell behind that. OK for a race car with side windows as your photo but I fought Rolands F40 setup with the hood exit. Yarn tufting showed there is some down force on his only if I fenced the roof section and had the side windows closed. Windows open had all the radiator air going in the cockpit.

I have a stack of wings to play with including a couple of dual element types. I collected wings durning my DSR days. I will have to pick your brain regarding this. The Cow Catcher on the front of the IMSA has to go, too low for even paddock areas. The last low one I did I used Camloc fastners like you did and was quite pleased with the results. Obviously I will require a shallow and a deep version for the varried uses. The front bumper on this car is mostly cosmetic so there will be some build up required.

I bought a 2 post hoist for the home garage yesterday so there might be some progress after all. I knew building it with 12' ceilings would be worth it one day.

Dave

 

That 355 front spoiler looks pretty good... I wonder how it performs ?

 

Now there you go interupting our interuption of your thread, the nerve...

At what RPM are you wanting to make power? Are you looking for torque or do you want to play way up high in the RPM band?

Dave

 

This is a seriously important question which has no "seat of the pants" driver answer. You see we want it "all" like nitrous more hp and torque through the rpm range. We all know we are not going to get that. I have yet to see dyno numbers from plugzit, group 77, or andyhls all claiming 400hp numbers from their simple bolt on intake mods. While they may make 400hp what happens to the torque and drivability over the street rpm range? You can add hp and make it look good on paper but still not perform over the range as well as a stock 355. There is more to it than just big hp and big plenum or big MAF. So somewhere someone is going to have to do some trial and error after guessing at empircally "what happens if I add this or that". I think a simple set of bolt-ons is very doable but I don't have time or resources to figure it all out.

I did look at a Mercedes 320ml MAF and it looked alot like the 360MAF. I wonder if we could figure out the wiring and use a cheap 320ml MAF which is a larger diameter than out 348 MAF. Then we need a bigger TB or weld up a 348 TB and hog it out. Plenum spacers are easy and goth has some made I think. Other than cobbling up parts I don't know what to do. There are times when bigger is not better. Tehre are things like resonant frequencies that effect flow and that may mean a smaller plenum volume than you think. A smarter guy than I needs to guess at that stuff.

 

Thanks for this Dave. This is a classic goes to show you that what you think will happen may be completely wrong! If something like this happens to the 355 body then it may explain why they are able to use those tiny rear wings because they only "look" like they have downforce from the open bonnet.

 

Best example of what FBB points out is a 260 Comp. Cobra from many years back. The owner insisted on 400+ dyno HP out of a flat tappet cam and using the down draft Webers so it remained period correct, IE, Legal 260 Cobra engine.

I fought on the dyno for 2 days and could get 375 with a dead flat torque curve all day long but that did not meet the design requirements and upset the owner. Cam timing, jetting, ignition... 375 was it with that package but it was wonderful useable power from off idle to 8500 RPM.

A decission was made to show the owner actual dyno results for this engine that met his requirements regardless if it was useable. The venturi's were removed from the carbs all together to eliminate the restriction and the throttle was feathered until we hit the new torque band and then threw the load and thottle at it. Result: 437HP with a 600 RPM power band, a 60+ HP gain and not a bit of it useable. Requirements met, the optimum tuning was reinstalled and properly set back to the 375HP, owner showed the dyno sheets and everyone was happy. End result is he couldnt loose a race, power everywhere, passing before, in and coming out of corners, anywhere he wanted... with 375 HP. He never did know while he owned the car, he just saw the highlighted number on a dyno sheet. It wasnt until he sold that car and there was a fresh round of drinks on the table at Sebkins that he was told the truth.

Torque is what plants you back in the seat. What are you looking for? HP or torque? In a finely designed engine package it is difficult to achive a substantial gain in one without giving away the other. Rest assured Ferrari would not have hesitated to install tall manifolds, lg TB's.... if that would have given useable extra HP AND torque, met emissions requirements and still had some degree of longevity. Without question you would have seen it std on the SS's or Challange cars. Braging rights in this business sells cars.

Dave

 

The sharp fender lines and the somewhat concave front bonnet shape of the 355 may well contain the airflow, never have had the need to play with it yet.

With the F-40 aftermarket "LM" bonnet and its softer fender lines, the airflow spills off from turbulance generated by the windshield. Installing a small Wickerbill strip on the trailing edge of the opening showed a good deal of promise but instead I chose to just provide the cockpit with ram air to generate a positive pressure there.

Poor guy went pale when he saw a full roll of painters tape, half a skein of yarn and some angle aluminum taped to the front bonnet. Sometime you just gotta know....

Dave

 

Thank you Dave for the rose colored glasses, check is in the mail. To get the best protection I have found a pair of welding goggles to wear with them....lol

What precipitated the core melt-down which led to my nuclear explosion(i.e. goin off on redzone) came from my dealing with the idiots in my request for help due to Wheel Wizzard's botched wheel refinish. I must say the 348/355 brotherhood is pretty tight,but by my venturing into the Technical and regional areas of this forum I got crucified when I asked for this forums' help and support. Won't be doing that again....atleast outside this sections of the true "band of brothers".

I would like to apologize to you,"redzone"...I'll buy you a beer or two if we ever meet in person.

Out of respect for TexFerrari maybe it would be better to start a new thread to continue with this topic of developing a track car for the track(FBB) and a track car for the street(Dave).

Tex, I must say that the intake, whether on a 348 or 355, is an area that can really pay-off if done right. Taller intake stacks? The intake is a highly compex area that includes everything from the first event(picking up ouside air) to the final event(closing of the intake valve). Taller is just one part of the equation. On a fixed intake(348/355) there is always going to be a compromise. When I think "taller" I'm seeing a gain in bottom end torque and not necessarily hp(I do look at what is called the power index for purpose built engines)....I am also seeing an effect at the top end(WOT). Again, there is in fact a compromise, but I as a driver have to determine if more low end torque out ways the lose at the top end. One of the biggest draw backs may be in the gearbox itself....4spd to 5spd, and now the availibility of a 6 or 7spd gearbox. I can get away with alot of hp/torque issues with a 7spd gearbox that could never resolve with a 4 or 5spd drive train.

Having done primarly turbo motors alot of the issues with an N/A motor just weren't there. I must say that an N/A motor involves certain perameters that require extensive knowledge and technical expertise. An important intake system factor is resonance wave(Helmholtz) vs pressure wave. It has been my experience that the resonant wave tuning is good to about 8,000rpm after that the pressure wave is critical. Understand that an N/A engine that peaks at 8,500 rpm would be tuned using rw where in a car that has an engine idling at 8,000rpm would be tuned using pw. A misunderstanding from the muscle car era is that we want "ram-air".....but if you take F1 it operates differently...the incoming air is slowed down by increasing the plenum volume gradually via diffusers, and the decreased air flow increases pressure at the intake valve. Now we have a condition where VE is 100+%......on the intake side of the valve before it opens we have ambient air pressure(100%) and is the case on all F1 engine we may have actually gone to a + pressure of 20-30% over ambient. One must then consider in any intake design not only the car in a static condition turning thousands of rpms but now we have to take into account the car in motion from speeds as low as 40-50mph to 200mph.
A word of caution; as you approach VE's of 100% the manifold vacuum drops off significantly....if your EMS or other systems rely on manifold vacuum these must be changed because at 100% VE you are no longer creating any manifold vacuum. WOW, wouldn't that be nice to achieve.....lol

Since the placement of TB's,F injectors, and stack lenghts is critical I am offering the following as a guide to help you get started. If anyone is seriously interested you must understand that larger TB's and MAF's may or may not be the cure all. Depending on the rpm range of the engine dual injectors(one placed before and placed after the butterfly) may give you the winning edge...a Motec system can handle this. Fuel pressure, is something you can watch on the dyno, in many instances the pressure has exceeded the pumps ability to evacuate the fuel rail via the return line, in which case this can be rectified by adding a dedicate pump to handle the return fuel to tank.


What is the best throttle body diameter?
Factors influencing size are; Power output, RPM, cylinder head design, cylinder capacity, position of the throttle body in the inlet tract and position of the injector.

Choice of bore size is a balanced compromise resulting from the following;
1) A larger bore leads to lower flow resistance, but obeying the laws of diminishing returns.
2) A smaller bore leads to better throttle control and response (never underestimate) and improved fuel mixing.
3) The system should be considered in total - from (at least) trumpet flange to cylinder and proportioned accordingly.

Basic references for BHP per cylinder, assuming ca 120mm from butterfly to valve head and a max of 9,000 rpm are;
Up to 30 - 30mm, up to 33 - 32mm, up to 39 - 35mm, up to 46 - 38mm, up to 51 - 40mm, up to 56 - 42mm
Up to 65 - 45mm, up to 74 - 48mm, up to 80 - 50mm, up to 87 - 52mm, up to 93 - 54mm.
These power figures may be increased by up to 10% in a purpose - designed and well proportioned system.
As butterfly to valve distance increases, butterfly size will need to increase in proportion to system taper and vice versa.
Lower revving engines and those with injectors placed before the butterfly will generally accept a larger body.

What is the correct overall system length?
Induction length is one of the most important aspects of fuelling performance engines.
In our experience an under-length system is the greatest cause of disapointment, with loss of up to 1/3 of power potential. There are a number of good books on the subject and the serious developer is referred to these and, in particular, dyno trials. A guide figure, from the face of the trumpet to the centre of the valve head is 350mm for a 9,000 RPM engine. Other RPM are proportional, i.e. for 18,000 RPM the figure is ca 175mm.
Any air feed system to an airbox or filter can have a large effect on the power curve and must be considered carefully - particularly if the airbox is small.
The induction system is part of a resonant whole - from air inlet or trumpet to exhaust outlet - and the ideal length is heavily influenced by the other components.

What is the best position for the butterfly?
The butterfly is an important aid to fuel mixing. When positioned too close to the valve this advantage will be lost whilst positioning far away may lead to a loss of response.
As with the injector position (see below), higher RPM demands a larger butterfly to valve distance. A practical minimum figure for a 7 - 9,000 RPM engine is 200mm, whilst the maximum is dictated by the need to fit an air horn of reasonable length to achieve a good overall tract shape. One solution to this apparent compromise is the use of bodies with fully-tapered bores which, in effect, extend the trumpet distance beyond the butterfly and into the manifold. For very high speeds above approximately 15,000 RPM, the ideal butterfly position is only just inside, or even outside the trumpet and a point is reached where a taper is no longer sufficient for good tract shape.

Where is the best place for the injectors?
Where one injector is to be used per cylinder the best compromise position is immediately downstream of the butterfly. This gains maximum advantage from local turbulence and gives results surprisingly close to the optimum at both ends of the rev-range. This is the recommended position for most applications
For performance at low RPM, economy and low emissions the injector needs to be close to the valve and firing at the back of the valve head. This is the favoured position for production vehicles.
For higher RPM (very approximately 8,000+) the injector needs to be near the intake end of the induction tract to give adequate mixing time and opportunity. The higher the RPM, the further upstream the injector needs to be. As a result, use of speeds above approximately 11,000 RPM may give best results with the injector mounted outside the inlet tract altogether. It is common to fit both lower and upper injectors in such a system to cover starting and low RPM as well as high speeds.


What manifold to use?
When injecting into the throttle body, most of the mixing occurs within the manifold section. It is therefore important that the manifold is suitably proportioned to evenly accelerate gas speed and thus help fuel mixing and distribution. The straighter the run in to the ports the better. A manifold which curves in the same direction as the valve throats is preferred to one which causes the flow to pass through an "S" bend.


What is the best Air horn ( / Trumpet / Stack / Bellmouth )?
The air horn serves three main purposes; 1) To convert the pressure difference between bore and entrance into air velocity with the minimum of energy loss. 2) To act as the interface between the induction system and the atmosphere, i.e. the point at which pressure waves change sign and direction. 3) To complete the system to the required overall length.
For ease of description the air horn may be considered in two parts; the 'flare' and the 'tube';
The main job of the flare is to spread the low pressure zone over the largest possible area - to reduce local pressure reduction - whilst guiding incoming air into the tube with minimum disruption or induced vortices. The flare should be shaped to encourage air to enter from the sides, but not from the rear, of the mouth. This is achieved by either finishing the mouth with a sharp edge when the arc is a little beyond 90 degrees from the air horn axis or by folding material back, parallel to the axis, when the arc is at, or just below, 90 degrees to the axis.
The main job of the tube is to accelerate the airflow smoothly and progressively. This is best achieved by an exponential shape - i.e. one where the radius of curvature is increasing constantly until the angle of the sides matches the next part of the system, usually the throttle body. At the intake end this should blend smoothly with the flare.

I'm sure I've left out alot, but hopefully all of this will get your brain thinking in the right direction.


Regards
Bruce

 

Bruce,

Wear the glasses in good health, welcome back.


"Out of respect for TexFerrari maybe it would be better to start a new thread to continue with this topic of developing a track car for the track(FBB) and a track car for the street(Dave)."

Have you now gone PC on us too?

Only exception I have to your reply is I have found a number of times where a velocity stack with a wide radius rolled edge approaching 330 degrees gave much improved airflow if it was installed in a contained cold air box.

Dave

 

Ultimately it comes down to 2 choices: you either keep the stock TBs or not. Group77racing, aka Dave the maniac tunerman, went all out and swapped 348 tbs for a 65mm Volvo part x 2. The MAFs were changed to 75mm Volvo parts too, I think. This obviously necessitated the conversion of the plenum and runners since none of this stuff bolts on the stock unit. This is radical thinking. It takes the car out of the realm of stock too and might complicate smog compliance in CA. Due to the ground covered by the tuner maniac, we figure the power gains are there for the adventurous. Plugzit is on a similar path.

Track 2 is to work within the stock design. Say you are keeping the stock tbs, like I am. Ok, now you can enlarge them, which I am. They are stock 55mm. Your stock MAF is 65mm. What's the point of changing the stock MAF now even if you increase your tbs to 57-58mm? True, your stock 65mm MAF has some restriction built into it - there are screens on both sides (easily removable) and cooling fins next to the meter (easily reduced). I will be keeping them stock for now, but might remove the screens and about 50% of the fin mass to increase flow. Depends. The screens are there for a purpose - like keeping your degrading paper air filter from clogging your engine and keeping oil and grime from blowing back through the intake to your MAF meter). The fins are there to reduce heat in the MAF in order to better maintain resistance (so they work). If you operate your car in cooler climes, this probably isn't an issue. For us in SoCal, it may be.

Continuing on with Track 2, I figure there are no other changes necessary before the tbs since the inside diameter up to this point is 65mm or greater. Unless you increase your tbs diameter (and flow) substantially, I don't think there's anything to gain. As for after the tbs, well, that's partly what this thread is about (plenum volume), plenum shape and runners and more, which is what we are exploring. There is a point where a smaller plenum will impact airflow compared to a larger one. We're trying to figure out how much it matters. Obviously, the factory thought so, hence the "H" motor which is rated at 8 HP more than my SS engine with the same exhaust.

And on it goes. We'll do our mucking around, testing and let you guys know what works for us. Remember though, my personal goal is to find gains that are not too exotic or expensive and will keep the cars smog legal. For FBB's and Plugzit's race cars, they can go quite abit further. And that's all I have to say about that for now.

 

Gone PC? Heck, I thought I would give it a try, but just aint for me....glad you pointed it out. Won't be happin'n again....lol

If 330 degrees works for the N/A engine with that kind of airbox, then I'd do it for sure. Sometimes things on paper just don't always behave like they are supposed to....that is why dyno testing is a must most of the time.

 

Did some actual track testing with cutting the screens out of the MAF........out of 20 runs I found a measureable constant. Screen out for 10 runs and screen in for 10 runs I observed the sreen out MAF to be a consistant .2 sec slower than with the screen in MAF. I've never heard of the screen being a backup for debris, I was always taught that it was just a physical mechanism that controlled the airflow over the MAF sensor so that it would/could maintain an accurate reading.

Instead of going to a larger TB and MAF, could you not increase the VE just thru intake/plenum design? By maintaining the stock MAF/TB and just increasing the VE wouldn't this make a major improvement in performance gains?

What is difficult on these cars is the fact it has 2 plenums(receiving chambers for distribution on demand)....first plenum is on the outlet side of the filter housing, and of course the second being the part that srrounds the intake stacks. First factor is that you cannot flow more cfm than the air filter's capacity(this implies sufficient air is supplied to the inlet side of the filter), second rule is that you slow down the air speed going to the second plenum after it has left the first. This is the principle used by Micheletto Engineering as pictured.....the shiney aluminum connector between the air filter plenum and the intake plenum starts with a smaller bore and gradually increases to max. opening just prior to mating with the TB. There are NO MAF's, simply because the EMS system they are running does not require this means to calculate A/F ratios.

Wouldn't just simply cooling the intake A/F(the mixture entering the combustion chamber), pay off a whole lot more than increasing the MAF/TB size(say from 2mm-4mm)?

These are just some ideas as my N/A experience is lacking.
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I think those shiny pipes start so small because there is a restricted opening size in the racing class this car was used in.

 

Yes, they used a restrictor(28.8 or 30.8mm?) in FIA GT2(prior N-GT also ??), and this appears to be the beauty of the Michelloto set-up.....what did the rules say?? 2 restrictors for this engine, but where were the restrictors to be placed according to the rule book? Was it left upto the constructor.....as to how and where, just so long as it was before the TB's??

What I believe ME did was to use their expertise in the technical/engineering design to incorporate the restrictors furtherest from the TB's(I don't think this was just a given). In so doing,this pressure differential at the first plenum connection not only minimized the effect of the restrictors, but by gradually increasing the volume over the entire lenght of the connecting tube after the initial constriction, the now slower moving air assisted the main variable plenum in building pressure at the intake stacks. Kinda interesting was the power output of these GT2 engines w/restrictors. I know the updated electronics and some other mods helped, but more importantly is how well did the "restricted intake" flow, and did it in fact contribute to the increased overall output?

Another question I have is,"was there any appreciable cooling effect on the intake air due to this constriction/expansion process?" Doubt it, but you just never know what tricks are in a race engineers' little bag of goodies...lol

Just some interesting things to kick around, but kinda doubt if any of these tuning concepts will ever be used on the 348...

 

It's a venturi basically. I built a formula SAE car in college and the rules required a single 20mm restrictor. With a desing very similar to the one in the picutre we were able to make 75rwhp from a 600cc engine....3 rwhp more than it made with it's 4 factory 32mm carbs. As I recall it as a 30 degree inlet angle and a 7 degree exist angle. Just for fun we reversed it on the dyno and got 32 rwhp, which becasme the new driver training set-up.

anyway, a pair of similarly desing "restrictors" would be flow enough air for about 340 rwhp or 400ish crank hp

 

Vince,

I hate to say it but your post shows that you either did not read or did not understand post #37. I applaud your and Goth's efforts but the food for thought is there in post 37. If you follow your course of action you basically are swinging at every pitch hoping to get lucky. I hope you do get lucky because then I would like to copy you. I think by just guessing you may do alot of work and actually make less HP and reduce driveability. Well...we'll see. I hope you hit a homer but don't be surprised if you hit a grounder.

 

Have you tried a couple of spray cans of starter fluid with the cold plugs rather than swapping from hot to cold?

 

The shadetree 348 owner can get to 360hp with new chips, hyper-flow cats, and better air filters (though larger fuel injectors might also be required). The compromise there is that fuel octane become crucial. The chips have to advance the ignition timing into the red zone (pun intended). Plug back in the old chips and you're smog legal for the street. Plug in your race chips and you are good to go on the track.

Some engines might require slightly larger MAFs and tb's to reach 360hp, too. And obviously the cam timing has to be precise.

The jump in effort/expense/risk is going above 360hp on a 348 motor. I'd wager that there's a large difference in going from 360hp to 385hp, and yet another level going from there above 400hp.



(unless you use nitrous to get there)

 

I used to be a big fan of Nitrous before I started wheel to wheel road racing since it is illegal for road racing. I still have a whole D cylinder of nitrous. Anyway Nitrous is the best power adder for the street IMO because it is transparent and does not effect emmisions yet can give you dial what you want HP and Torque across the entire RPM range. I actually think this idea of intake mods rather a waste of time for you street guys because I can beat you every time with nitrous for less money and pass smog and have 100% of Ferrari intended drivability. When done right like anything else you won't destroy your motor either. I have many nitrous datapoints on nitrous use in Porshes and Ferraris. However, I do hope one of you guys stumble on simple bolt on HP and torque and then tell me how to do it so I can use it on the track. If something does not break soon I'm going to turbos or just race a faster car.

 

This is truly a black art because some 'rules' do not apply to every engine configuration. Thankfully alot of them still do...... we can take mathcad to help with the arduous calculations and still the results are only as good as the numbers fed into it.

I am in product developement and even when we have plenty of creative as well as educated minds on a project, things still change when put into test. A single test can sometimes render thousands of calculations suspect and in need of re-examination....... sure it may be difficult and time consuming.... but thats what makes it worthwhile IMO!!..... speaking for myself.... what else is there?? I can only watch so much TV before it gets old...... this on the other hand is just the opposite !!!

IMO The existing manifold has proven to be a good basic design and the visible change on the 'H' engine, is more plenum volume. The factory has done it........

 

Not with this compression ratio.

Dave