328 4V Heads vs 355 5V Heads

Lots of engineers here, and some have done far more challenging work than what you're proposing. The Williams Porsche engines were the work of several engineers and more than a million$ to get there. Thousands of hours of r & d in those things. There's not a lot of uncharted territory with 308/328 headwork and overall review for optimizing hp, it's been done many many times at very high levels. 12,000rpm fire breathing 3.0L naturally aspirated monsters with 400-500hp, it's been done.

In short, 5 heads won't fit without a massive amount of work and butchery. Lots of aluminum welding required, and you better be amazing with a Bridgeport, CNC programming, and fabricating anything in general. Anything is possible but is it at all reasonable if the end game is more poke from the engine? I say no. Lots of other far easier ways to skin that cat. If for some reason a person were hell bent on 5v heads it would indeed be easier to design new heads in Solidworks and have them cast. Then there's manifolds and the heat any 5v head produces and all that, it's sort of an academic discussion and in the end the build may catch a lot of flack for not being original or at least original in appearance. There's been no 'Singer' version of these because while they did make a fair few of these, they are cherished as mostly original and they still didn't make a huge number of them compared to say anything Porsche has made.

The 4v heads flow incredibly well when worked over. Some impressive stock-looking or EFI ITB builds using those heads, with more than a few 308/328 builds using 360 cranks or offset grinding a stock crank for more stroke etc. Lots of far easier ways to get more poke out of a 308/328.

 

It is not easy. The head stud locations and oil drain hole are different. The amount of work needed should be spent somewhere else. For example, I know of one 355 engine and subframe being married to a 308 body and body kit to make a sort of 288 GTO tribute. That project was full of pot holes and required three mechanics/builders to finish. I am not even sure if the car runs right.

I am a rare person who frankly does not find the Singer Porsche to be attractive or desirable. A Singer Porsche standing next a F40 or an F50 or a GTO ... no contest. Ferrari wins.

 

Moto Technique has a "388" engine with EFI, ITBs, 360 crank, etc.. I believe those start with a 308 motor, and end up putting out a little more than 400 HP.

 

If you were able to do the work yourself I would just do as the Moto Technique car referenced above.

If you are hiring a shop to do anything in the realm of what you mentioned I think 40-50k would probably be a good down payment.

 

I can't speak from experience to the 308 (although I did consider it, and even spoke with Kevin), but I did go down this rabbit hole for my '83 512 BBi – which has even more people in the "leave it alone" camp, is more expensive (12 vs 8), and has essentially zero examples to borrow from (as far as I know, mine is the only EFI/ITB example using the original motor). From basically every angle, it was a bad idea. It was a ton of work, required lots of education, and lots of money (despite having done all the work myself so far). That said, I don't regret it one bit. I much prefer the car in this incarnation.

Regarding the order, I did the EFI/ITB first. That is partially due to the engine internal upgrades being somewhat wasted on CIS (intake reversion issues prevent more aggressive cams). There is a lot to be gained by simply flowing more air, dialing in a proper A/F mixture across the entire range, and modifying timing.

IMO, if you want to retain the value of your car, don't do it. However, if you're a driver and you're willing to accept the value of the car will assuredly go down considerably (you and I are not Singer, and even other high quality 911 restomods do not appreciate), then go for it.


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If you're going to pay a shop to build you the engine you want, it's of course going to cost allot more. That makes it hard to say what it's going to cost.

We build very custom engines and I've done a fair number of crazy over the top ones as well. An engine build with different heads, the only cross over is between the 328 & 348.. small gain to do so and big cost to do it.. last one I did like that ended up costing just a hair over $50k for just the heads with new valve train and requisite machining to work on the 328 block. They are not plug in play, the raw casting is there but it's not machined so you gotta do the jig and setup to make them work. 328 with 348 heads, 360 crank. Custom cams and all new custom valve train, ITB'S etc.. pistons.. convert to dry sump.. that build would be $250k.
Most builds are 6 figure given the sheer amount of custom parts and Dyno tuning needed to hand back to the client.

If you're going to do the work yourself, then it's just parts and time. You might be able to convert to EFI with ITB's for $10-15k doing the work yourself. The difficulty is there's no real off the shelf DIY kits for this stuff. There's never been enough volume for it for that too happen. So you end up with basic generic 'kits' the require custom fitting and parts to be made.

I think that's the biggest reason why turbo or supercharger options are preferred. For the similar costs and custom fitting one can force feed the power back out.

 

Thanks, I appreciate it. Although, I wouldn't say I had a ton of knowledge. As the saying goes, "I didn't know it was impossible, so I did it".

Aesthetically, a lot of inspiration was pulled from the Le Mans race cars (BBLM) which had a similar vertical / tall ITB aesthetic (Lucas injection using essentially hacked up Weber carbs as throttle bodies). They also ran BBS E50 wheels (albeit 16" where mine are 17").

Good luck with your project. Let me know if there are any questions I can help answer.

 

I will run contrary.....I'm pretty sure possible to put 355/360 heads on a 308/328. I've had people reach out to discuss it a few times now but I've never seen one actually built.

That said, the advantage of 5V is they have more seat perimeter and will therefore flow more air at low lifts, so less cam duration is required and its easier to make good hp while meeting EPA requirements on a carb or port injected set.

On my flow bench these heads make about 140cfm@10" H2O....which is like 242@24"? Stock 308/328 heads flow about 93@10" so a very clear flow advantage to the 5V heads. My TR heads are very similar to QV heads and were 94@10" stock, they now flow 156@10 with the manifolds and ITBs installed...but I was pretty aggressive with that work. 135-140@10" is a good number for well done QV heads with 31 or 32mm intakes so same flow and quite a bit less work than the head swap.

Match well done heads with a decent cam, intake, headers and as others have said its a 400-500hp build. Use a bigger bore and 79mm 360 crank and you might make that power below 10k rpm. A good engine is about matched components not any 1 think...so yeah, you can wake it up! ITBs and cams...300-320 probably? Then how much porting and such is how much above that you get. It ain't cheap of course......I get about $4k-6k to do heads when I get talked into doing them but maybe others are cheaper, don't know.

I think you'd do the 355 heads because you want a 308 with 355 heads and it certainly will make power but probably not more than you could do with 4V heads.

edit...just saw you mentions a supercharged. I was running my 308 basically stock engine at about 22 psi and it was making just over 500hp.....that was the very definition of woke up

 

Ummm.. It's not possible. The oil returns and head stud spacing is different. Already went down that road, the last matching casting is the 348. 308 is on it's own as even that won't accept the later Qv or 328 head.

The only way around it is to cut and weld a bunch.. Makes zero sense. Better off trying to adapt the 355 engine to the gearbox and even then I'd just skip right up the 360.

 

I have a pic somewhere of 355 heads in a 308 block and I've seen 348 heads on a running 308 engine. I think we have different ideas about what the word "possible" means....oh no, the oil feed is wrong...that's called an inconvenience

 

348 is the last casting that shares the same bolt spacing. 308 can be modified by extending the oil return passage.

But once you jump to the 355 too many things change and it doesn't make any financial sense to go down that road. Way less hassle to modify and fit the entire engine to the gearbox then try and fit the heads.

Money and time is better spend on internals and doing what you can to the heads it has. ITB etc..

And yeah, you're a unique bstd with a wicked tool case

 

I am doing a 360 engine / transmission transplant into my 308 GT4 with a lot of the aspects you are mentioning. I am doing it mostly all myself. Right now I am about $25K in parts for the engine alone. Let alone shocks, brakes, exhaust, wiring and all the other ancillaries that take a project of this magnitude. @smg2 is probably the most experienced at the 360 crank swap / bored stroker engines in all the 3x8 industry. Let alone all the R&D he has put in over 2 decades on this, what I learned there is engineering in every build because the whole thing has to be viewed as a system. Let alone the fit and finish and the output of a beautiful functioning car. It's not really a "kit" that can just be tossed in there. AND, there are finite outputs or at least ceilings of power that can be reached - in the 400 - 450hp realm for a 4 valve car.

@smg2 also does supercharger kits.

If you want power for dollar, slap on a turbo system. Norwood and Aaron ATS have been doing well with these builds. A turbo Mondial just sold on Cars & Bids for $37K - 470hp. https://carsandbids.com/auctions/370vELkq/1988-ferrari-mondial-32-cabriolet?ss_id=83190419-a1c5-4d34-b5a8-8301d3bb76b9&ref=pr_1_1
$30K but you have to check. I love these and there is more maturity to the projects over the last few years. Here's ATS youtube page https://www.youtube.com/@nitrusmr2

For all, you will get much better results from a 4 valve car - the heads just flow better. So 308 QV or 328.

You brought up Singer, which really means Porsche. I would say Porsche are way more like Lego's that are easier to pick and pull from car to car. Ferrari's not so much, but there are some carryovers in weird places, Like the 360 crank fitting a 308 or 328. BUT oddly not the 348 or 355, which came in between.

Good luck and I hope you move forward!

 

I don't have a 328 but this is is the dyno (Dynojet, wheel horsepower) from my F355 if you try to go the 5 valve route.

I ported the heads, multi angle valve job, +.5mm Ferrea valves. Milled for 11.5-1 compression. Slightly advanced ex cams, slightly retarded intake cams. Ported throttle bodies and inlet bells. I built custom headers, y-pipe and muffler.


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Something doesn't sound right....I know I've seen a 5V head on a 308 block.....what I can't recall is if it was a pic someone sent me or if I did it when I had a set of heads here years ago....I'm vaguely remembering the 5V head wanting short studs or something like that?

I totally agree its easier and likely cheaper to rework 4V heads but....my brain is not letting me believe the 5V head are serious challenge to bolt to the block... I'm thi89nking?but I don't recall why that is in my head



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I’m building two of them right now. Both 3.6L with 5V heads on 308 blocks. One with ITBs and one with a plenum and boost.

i believe the engine Mark is referring to is one of the two I’m building. My motivation is it’s different and the sound will be killer.

 

At the risk of being obnoxiously obvious: among those of us interested in modifying our 3X8s, I'm going to go out on a limb and say most are either budget and/or skill challenged when it comes to the project you've described. Fortunately, there are many, many, many ways to skin this cat (with apologies to cats everywhere) and another way to "add horsepower" is by subtracting weight. This build is focused on exactly that (for the moment as I understand): https://www.ferrarichat.com/forum/threads/my-77-308gtb-restomod.706757/
I plan to go down a similar path because I too have a 2-valve motor, am not interested in forced induction, don't have $50k laying around for a hotted-up engine at the moment, and don't have the skills to build it myself. Maybe down the line increased power will come into play, but in the meantime every pound I drag out of it is simply a monthly payment on my "More Power" account.
Really though, the bottom line is this: do what makes you happy, screw everyone else, and don't have any regrets. ¯\_ (ツ)_/¯
- Dave

 

Well lookey there.. Guess it's doable. I'm gathering you started with QV/328 blocks. I do recall trying the 360 heads and they just didn't line up..
Learn new things!

Interesting project. Look forward to updates!

 

What's different about the 360 heads? Should have the same mounting as F355.

 

Variable cam timing and details related to controlling it. One of mine has 355 heads the other 360 heads.

 

^Yes that, I meant in response to what didn't line up.

 

Oiling was the other end of the equation. The stock 3x8 oil pump isn't enough for the more advanced 355/360 and the blocks lacks oil squirts for the pistons. Going to dry sump was already a pile of work, adding extra oil pump sections just wasn't on the project budget. Add in that the 348 are good to go with only needing machining for the tensioners. Simplified the project where needed.
Hats off to using the 5 valve heads, I'd only suggest looking at oil pressure and flow rate as I recall the equations between 308 and 355 for the pump sections are different.

 

Boy @FastandSlow did you manage to pull some of the best of the mindshare on this thread, which proves, "there's no dumb questions". It's kind of the greatest minds of 308 hot rodding!!! and me...

I saw you mention Nick's Forza - just in case you didn't know, @smg2 posting in your thread is Nick's partner and engineer. @mk e is famous for his V12 308 - hes kind of our mad scientist with the skills and results to back it up. @Newman has a shop that has also done some very impressive builds.

@Newman pics of that motor please!!!!!

Also note the reason for so much of this development is because a straight swap of a longitudinal setup won't fit in the back of the 308 GTB or GTS chassis. I have seen the pics of the car with the 355 motor but the axles were cocked at a 45* angle from diff to hubs, which makes horrible driving characteristics. It would make the car much worse, defeating the whole project.