I've always been told 4v heads are a waste on M blocks, that they kill your lowend...

dunno how accurate Dyno 2k3 is, but it's telling me that they do hurt lowend, but only by a tiny amount, however they keep torque high all the way to redline by a significiant amount.

I'm confused.. if this thing is accurate and this is really what my engine's numbers will be, I'm sold on 4v heads.

A built 400 with aussie heads (TMI pistons? 11:1 ratio) shows 453ft lbs at 2000RPMs --- 367 ft lbs at 4000RPMs --- 330ft lbs at 5500RPMs

A built 400 with 4v open chamber heads (9.5 ratio, TMI pistons of some kind) shows 428ft lbs at 2000RPMs --- 480ft lbs at 4000RPMs --- 468ft lbs at 5500RPMs.

and this is with the 255DEH.. so what's the deal here? Is Dyno2k3 full or crap or are people wrong about 4v heads on these engines? I know it would be better to have a Cleveland, the 400 would explode when this thing hits peak horsepower (it's a waste, I get it) but why do people not recommend using 4v heads IF this program is accurate for those of us who don't want to dump our 400s.

I trust you guys enough if you tell me Dyno2k3 is full of crap.. I really want it to be right though, I could turn my 400 into a monster that's still capable with cheap 4v open chamber heads.

 

I don't know about the dyno program...but do believe that 4V heads will work just fine on a 400. Remember, on a 351C the 4V was no slouch...we have 50 extra CI to work with. I do think that using the 4V makes your came choice more important. If/When you talk to cam companies; I would reference a stroker 408C with 4V heads. I am pretty sure most of them won't have a clue what your are talking about - Ford 400 with 4Vheads - and will just continue to recommend the RV cams they always do. They will likely treat the whole concept differently if they are thinking Cleveland...which is pretty much what it is...a tall deck Cleveland. Perhaps and experiment would be in order. Call the same cam company and give the two scenarios...a 400 with 4V heads and at 408C with 4V heads and see what they say.

 

Nice q.
Very curious at that one indeed!
Maybe trying a nice dyno'd out combo with a roller cam, and then ask the "pro's" their opinion?

 

hmmm good idea, but what cam would go with a 408c 4v engine 9.5 scr?

Iv always thought of the 400 as a cleveland...cuz logic tells us that thats what it is...

 

I was mistaken too, that's with a stock cam, power numbers are even better through ALL ranges with an RV cam.

This program has just about every cam edelbrock has ever made, I'm green when it comes to cam selection but I can toy around with it.. in the end it could all be BS though, I've heard from a few trustworthy people that this program is great for finding out information but I'm still skeptical.

here, check out the 255deh.

2000RPMs is 453ft lbs ---- 4000 shows 503ft lbs --- 5500 shows 484ft lbs.

any bigger and you get drops across all ranges.. I think I'm going to try this build

 

First you can't build an 11:1 motor with a 255DEH cam, and run it on pump fuel.

Even at 9.5:1 a 255DEH cam is going to present a fuel problem with open chamber heads.

The larger valves and better head flow of a 4V head will extend the torque curve beyond the 3500 RPM of a 2V head.

I don't think that any sim program takes into account things like fuel dropout due to lower manifold velocities that you will see with 4V heads.

I ran 4V closed chamber heads on a 400 with good results. My CR was 10.2:1, but I had a much longer duration cam than a 255DEH. Even then it was marginal on 91 Octane.

 

Not sure what it takes into account.. you know, I'll just PM you a link to it.

edit: I'm not sure the one on the internet is legal, lemme know if you still want it? It's essentially a demo version because it has no cam/flow files but the actual demo is non-functional in some areas, this one is functional all around.. the one I bought had a lot more files with it

 

Dan,
Here in the netherlands we standard use 95 octane, and premium of 98 octane.
This would mean that your setup shouldn't be a problem here.
Also, i ride 99,999% on propane, and use gas solely as a backup when propane's out.
This would mean then that the 4V heads are well suitable for my application, right?
Now, i don't know wich program you guys use, and where i can download it, but, as my engine is in a heavy boat:the Lincoln Towncar, Torque is what i need.
I am currently upgrading my engine with a new RV cam, edel intake, and Impco 425 carb/Holley 600cfm carb, and a full MSD setup.
But... As i opened it up, the virus got me....
Now, i'm thinking of building a fresh complete new engine from scratch, as i have a 351M in the barn, wich core i could be using for that purpose...
Looking at the heads again, i indeed read everywhere that 2V is the Torque to go, due to air velocity and appropreate filling.
This is why the 4V thread has my interest
Only thing is: when i cruise the highway's, i do 2000-2100RPM... Not that much actually...
So, i need my bulky torque in the really low rpm numbers... Not sure if a 4V will do that...

Any info (software?) always welcome!

thank you.

 

You certainly do not need 4V heads. The 2V heads shouild be quite adequate, but larger valves and some porting work on the exhaust side will help.

I believe that in Europe, Octane is calculated differently than in the US. However with Propane you can run higher CR without detonation.

The 255DEH cam is suitable for your application, unless you want to use a Custom Hydraulic Roller cam. You can get more lift and duration and spread the lobes to reduce overlap.