Mondial 3.2 ported/polished head/big valve/big cam/header upgrade

As most know, I converted the Mondial 3.2 to Weber 40DCNFs 5 years ago. The final rear wheel dyno showed numbers similar to a Ferrari 348, with 243 SAE rwhp and 203 ft-lb of torque. These numbers were unchanged for either 34 or 36 mm venturis, and almost the exact same numbers generated with a higher lift longer duration (.367, 235*). So, combining this with the shape of the hp curve and with some certainty, we can say that the head flow now limits the power.

Old FChat poster Kermit had measured the head flow in the mid 90s CFM, and current supercharger Yoda Mark Eberhardt and his cylinder head specialist, Vic, place it similarly on a test QV head (QV and 3.2 heads are virtually identical). After several modifications, Vic now has a test qv head with larger intake valves flowing at around 112 CFM still with very high intake velocity (highest he has seen in any cylinder head) with stock cams. This is a flow increase of approximately 18%. This will be the maximum flow this head will generate without losing any velocity – i.e., the best street set-up in a cylinder head.

The test head is being sent to Laurie at Webcam to be used to develop the maximum safe lift intake cam specs for the QV engine. Issues such as interference and compatibility with the stock shim over followers will be worked out and the maximum reliable safe lift determined with this head - we're hoping for around .400 lift and keeping the duration around the stock 220. The duration will be similar to stock or a bit over to keep the same rpm power band as stock. This may cost some high end hp by keeping the rpm band lower, but the low end torque will be spared or increased. Interestingly, with the similar durations this cam could be used with QV K-Jetronic engines. This could be the ultimate street QV cam.

The maximum safe high-lift quick ramp cams will be installed on the ported, polished big-valve 3.2 liter engine. Carobu states that they have had as much as 340 engine dyno hp on 34mm venturi DCNFs showing adequate flow for this hp, but the carbs will have 36mm venturis (the largest side available) for initial testing. The exhaust will have provision for the wide band LM-2 A/F meter to tune the jetting. With the velocity remaining high, I am unsure which way the jetting will go.

We will keep the same pistons. The combustion chamber will be measured to determine actual compression ratio, and we’ll see if anything can be done short of new pistons to raise the CR a bit. Since this car is a street and trip car, it is nice to have safety from different gas options at less than 10:1 compression in this application - would like to target around 9.5 - 9.7 if possible.

The exhaust will be a set of port matched Tubi stainless Euro exhaust headers that will be ceramic coated inside and out leading to a true dual exhaust. The exhaust is modeled on the Euro Ansa and other Ferrari V-12 applications, but spec’d for very high flow and a smoother tone and moderate sound volume more acceptable on trips. This will be the Grand Tourismo tuned exhaust.

I’m hoping this will take about 6 weeks, then tweak the carbs over a few weeks, then do another rear wheel dyno to tune and will post results.
I’ve always wondered what an all-out hand massaged and prepared tuned and tweaked naturally aspirated Ferrari engine would be like. This will be pretty close to the max tuned naturally aspirated street engine. Many thanks to everyone in the subsystem threads (air cleaner, carbs, performance cams, headers, exhaust, etc.) that have helped so much. Even the P3/4 threads inspired this project to see the engineering, craftsmanship, art and beauty that reside in the heart of every Ferrari – the engine.

All advice welcome.

 

Engine is out
Heads are off - will be shipped out Monday with manifolds and a carb for flow benching.

compressions: 175, 181, 191, 190, 200, 188, 191, 197

leakdown: 15, 28, 10, 12, 10, 10, 14, 11

Will be measuring CC volume and doing a block compression check. James feels that the valve work will certainly tighten up the numbers.

Headers off to be ceramic coated.

Will also be doing an engine bay clean-up

Pictures next week.

 

Cam issues were covered in-depth in the Tech Section ‘Performance Cam Regrinding’ thread, but here are the much oversimplified basics.
The exhaust valve does not need to be enlarged – in fact, many strongly claim it is too large in the stock application. There is an empiric desired ratio between intake and exhaust flow, so in a practical sense on our cars, it is good to keep the current exhaust and focus on the intake (also saves $).

The stock 328 intake cam has:
.343 lift
intake - 16 btdc to 48 atdc (244 duration @020); Lift @050=224

My current cam has:
.368 lift with 235@ .050 duration (total 261 @ .020)

As stated before, the new cam generated the same hp figures as the stock cam since the head was actually the flow restriction. Interestingly, we did not lose low end with the increased duration.

I know some cams have run as much as around .400 lift; The reported clearance between valve seat and piston to prevent interference is about .100 . Since we are going to larger valves, getting this clearance right becomes an issue. Another issue is at much larger lifts, reliefs must be cut into the head to clear the cam sweep and you may flip off the shim. In our application, the goal is to keep the stock shims and not cut the reliefs. If flow is significantly increased from .368 to .400, then will add lift. I may actually almost have all the cam I need now, but we’ll see.

Since the goal is to keep a strong low end, will probably keep near or only slightly increased duration. Duration has a lot to do with the power rpm range, and I would like to keep this around stock for a street application. May keep what I have since the low end stayed the same as stock. Lift adds power (to the extent the head can accommodate it) throughout the band.

More as things develop.
best to all

 

Yes, and the 3.4 liter heads already are a better design than the 3.0/3.2 qv; I would also recommend you look ar the 355 manifold on a 348 threads in the 348 section for more specific (and enthusiastic) discussion, but the cam/head flow discussed here applies to the 348 qv engine as well.
Have fun

 

Here is the engine out now minus the heads. It does come out in a compact package. This will also some more engine bay detailing (wish Spasso was here to help!).

Now - the challenge of the intakes. Since I've gone to the dual plenums, I am using the low rise radiused intakes to give more volume in the individual plenums. The stock air horns WILL fit, but there is only about .5" - .7" clearance between the top of the air horn and the top pf the plenum. With these shorter ones, I get over 1" to the top of the plenum. Since I want to keep the stock bonnet height, really cannot make the plenum any higher. So, will probably have to come up with a more clever way to do this - it's kinda kluged now as you can see, but if any of you can make some short airhorns, pm me...otherwise I'll come up with something a bit nicer. Of course, I could always go back to the stock airbox sans internal filter and duct it to a large K&N cone at the side duct.

Still waiting on intake cam data, but I'm still intuitively thinking intake lift to .400, quick ramp, stock or slightly longer durations. Someimes I think I may stay with my .368/235s.

Headers are off to be ceramic coated, and mufflers and resonators are ordered.

Will hopefully know more this week. All advice appreciated.

best to all
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Here are some measured specs off our 1988 3.2 liter US spec engine from the Mondial 3.2:

Dish Vol.- 25.6cc
Piston Deck- .020" plus (above block deck)
Gasket- 3.312" x .061" (compressed)
Bore- 3.268"
Stroke- 2.90"

These numbers will be used to calculate the actual compression ratio and used in the computer modeling. I imagine they are the same for all US 3.2 liter engines (328 and Mondial).

 

In addition to the tubi Euro headers, the s/s exhaust silencers came today - 4 Magnaflow dual in / dual out units (two per side) followed by four resonated tips. The system will be a true dual exhaust with each bank having non-connecting flows.

To briefly review from the several ( "exhaust-ive" ) exhaust threads, each side will use 2.5" s/s mandrell bent tubing in a system that is a combo design of a flow enhanced Ansa qv system and a 250 GT TdF sytem folded twice. There are minimal bends in the system, and the 2.25" tubing is more than flow adequate. The goal tone is to be smooth and tonal enough to be pleasant as a daily and on long trips, but still sound like a Ferrari.
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Vic and Laurie are now going to test an qv intake cam with:

Total lift: .400-ish
Duration [email protected]
Rapid ramp opening

This is a bit more duration than stock, but less than the current 236; the lift is more than the current .368 and WAY more than the stock 3.2 .348 and WAY WAY more than the 3 liter qv .

We were even talking that keeping the fairly near stock durations, this cam would be compatable with K-jetronic injection; I think to at least 270 hp on a 3 liter qv with the stock head (this is what a stock Euro 3.2 makes with K-jet).

Although it is very early to predict final numbers, the computer says the output may be as high as 330 - 340 hp at the flywheel and keep the same or more torque (240+ ft-lbs) in the same power band. This is based on head flows keeping about 20% over stock at all lifts, which is what the test head flowed (with a target max of about 110 - 112CFM@10" versus a stock 88-89CFM@10").

Should be interesting - we are about 3 weeks away from finishing the heads if all goes to plan, and will know the final flows with the carbs. Will take a while for me to fully tweak the carbs, but will have an initial rough dyno to get a starting point in a mos or so.

Thanks to Vic Chichester, Webcam, Carobu and Norwoods for all the great work and advice.

 

The heads are apart now, and there was one leaky exhaust valve and pretty well pooped out seals.

"Raising static compression is a band-aid for poor head flow"

Discussion with Vic today focused around compression and flow. He said that the remembering that one idea is to get the most pressure in the cylinder, you can do that with actually flowing in more air or raising the static compression. He stated that my head may not need that much more compression if the head/cam are flowing in that much more air.

This was a new concept for me.

There was one cylinder that had a much higher pressure test (200) than the others (175 - 190), and that it may have shown some signs of detonation. With the other cylinders not flowing as well, this one cylinder was genertating enough pressure to come close to detonation. So the issue is, once ALL of the cylinders are flowing well (targeting around 210), I may need to come BACK off the current 35 degrees of advance down closer to the factory stock 32.5 or 31 as all of the cylinders will be drawing in much more air and generating much more pressure for the same combustion chamber volume. Vic said it was not uncommon to bring well flowing efficient heads down to advances of 30 degrees, or even less. This also fits with why 2 valve engines can run greater advances as they dflow more poorly, i.e. less efficient. We'll address the issue as the engine goes back together, but certainly a fascinating concept. Especially interesting as I will be running on pump gas.

Because I did not lose any bottom end when I increased the cam duration, the new cams may instead keep a little more duration than the original plan to have stock durations. The flows will be calculated and we'll see. Laurie at Webcam is running some profile tests now.

Spoke with Mike Pierce at Pierce Manifolds today about increasing the size carburretors. He said that the carbs are still likely to outflow the head, and typically a barrell of a 40 DCNF with 36 mm chockes is good for about 400CFM; so with the head flowing at 110 - 115, we should be ok with the 34 or 36mm venturis. With the increased flow, the current settings will probably be too rich and require smaller jetting.

So big lessons for today: With increased head flows, we'll start off with a much lower ignition advance due to higher cylinder pressures, and expect to go down a jet size.

 

I ordered a new set of tires for the Mondial to achieve two goals, remembering that this is not a track car so ultimate grip was not as much an issue as having a good street GT. This is somewhat cross-posted from a tire thread, but it fits in with this thread as well for completeness.

1. Lighten steering and keep it precise. Previously had 225/50 Pilot A/S on 7.5" rims. Ordered a set of PS2 205/55 to reduce contact patch and have the widest rim for the same wall height as the previous 225/50. While I will lose the all wx capability I needed in DC, I don't need it here in San Antonio.

2. Functionally have a taller final drive to take advantage of increased torque. I had looked at different drop gerars and even ring/pinion, but figured out the easiest and WAY WAY cheaper way to do it would be by upsizing the wall height on the rear tire. The previous 245/45 P A/S on a 8.5" rim had a height of 25.8 and rolling ratio of 811 revolutions per mile. By going to a newer technology higher grip tire in a PS2, am trying a 235/55 on the same rim, again the widest rim recommended for the tire. The new tire height is 26.6" with a rolling ratio of 777 revolutions per mile. Using tire sizes, I have functionally reduced my differential ratio by 4.3%, taking the original 4.06 ratio and funtionally making it more like a 3.86 (essentially the Mondial 3.2 Euro spec 3.82). This slightly reduces the cruise rpm from about 20 mph per 1000 rpm to about 21 or so (about the same as the Euro spec 3.2 and Mondial t). I do not worry about speedometer error as it is so wildly inaccurate to begin with, and if anything, this makes it closer.

I do have adjustable spring perches, so ride height adjustment is not as big an issue. I've heard that PS2's have a good ride and very good steering response with the newer technology rubber. Coincidentally, these are the same f/r tire sizes on a newer Porsche Boxster and have the N0 designation. I ordered the tires today, so I'm hopeful this will work out.