400 Heads...newbie question

[mrxlh]

If you can find one its title is "Harley Davidson Evolution 1340 Performance Tests", By Jerry Branch of Branch Flowmetrics. I have a copy of it somewhere, but I be darned if I can find it. If you go to his website Branch Okeefe you will see his passion is Harley Davidson. Look at the names of who he has consulted for over the years, its a bunch of automotive people.

 

[Bax]

Aussie heads will do just fine. Small port ( larger than a W ) closed chamber. larger valves than a W
Tim meyer has them if you want to look at a set.

 

[393clevor]

find some 71 to 74 2V Cleveland heads..... there is a huge difference in the exhaust port. The stock D5 heads they used on the 351M/400 suck, 4V heads are ok if you plan on moving the power band up the rpm rang.. I remember the 8000rpm's boss 302's ..... and there is no intake for the 400 with 4V heads... you would need adapters... I did a build here search "follow along as I build a 400" it was a 1500 build if my memory is still working...

I still have a 400 and 71 heads waiting I just don't have the cash to build it.. but it's gonna happen , some day...

 

[blackhat620]

The more I dig...the more it sounds like the 2v 351C heads and the 400 heads are the same????????

Yes the 351C/351M/400 2v heads are the same and have open combustion chambers which in this application is their weakness.

The 4 bbl heads are typically too large for a steet engine that is going to see most of it's life under 6000 rpm.

It is not that 351C-4V heads are too large for a street engine it is they are too large for this application. This engine is in a 4wd truck that needs its power curve in the low rpm band and lots of torque so that it can pull well etc. If this engine was in a go fast street car then the 351C-4V heads could be helpful. It all depends on the intended application of the engine.

I stand by that, I still say get a set and see what happens; I'll bet your surprised...

Doubt he will be surprised because he just isn't going to see much performance gain in this application for all the money he will have to spend to get everything to work properly. For the money there are much better ways to make power in this engine.

In effect yes....you need to keep the air velocity up for proper atomization...but as posted by Aaron, some of the new aftermarket heads give you the best of both worlds....but it boils down to the almighty dollar as well.

"Proper Atomization" is a mis-quoted term to use when deciding on head flow velocity characteristics. Keeping the air velocity up in a normally aspirated engine is not to achieve proper atomization, it is to achieve complete cylinder fill at lower rpm. When you switch from the 2V heads to the 4V heads, the increased valve/runner size reduces flow velocity so in order to achieve increased performance with the larger volume flow you must increase the rpm to properly fill the cylinders. It all boils down to where you want the power band to kick in, the lower volume/higher velocity 2V heads make there power at lower rpm which is good for a daily driver and a truck, but they sacrifice top end by starving the engine at higher rpm.

find some 71 to 74 2V Cleveland heads..... there is a huge difference in the exhaust port. The stock D5 heads they used on the 351M/400 suck, 4V heads are ok if you plan on moving the power band up the rpm rang.. I remember the 8000rpm's boss 302's ..... and there is no intake for the 400 with 4V heads... you would need adapters... I did a build here search "follow along as I build a 400" it was a 1500 build if my memory is still working... I still have a 400 and 71 heads waiting I just don't have the cash to build it.. but it's gonna happen , some day...

There is no performance difference between the 351C-2V heads and the 351M/400 heads, the exhaust ports are not a problem on any of these heads in this application.

Ben, basically you have to decide where you want your power band, and IMO you want to keep it in the low rpm band for your application. That being said 351C-4V heads will not give you the performance boost you are looking for without spending alot of money and running high rpm.
If you want to stay with OEM iron heads then as "Bax" said you want to get yourself a set of 302C heads (ie Aussie heads). 351C-4V & 302C-2V aussie heads have a closed combustion chamber where as all the other 351C/351M/400 heads have open combustion chambers. The open combustion chamber design is crappy to say the least and if you up the compression and keep open chamber heads the engine will pre-detonate terribly unless you run "high" octane fuel. If you increase the compression ratio and run closed combustion chamber heads you can run lower octane fuel without suffering pre-detonation.

The 351M/400 engines got a bad rap because they were introduced the same time emission control standards were mandated. In-order for FMC to meet emissions standards they emasculated these engines by lowering the compression ratio, and retarding the cam. The factory cam is 8 degrees retarded btw.
The closed combustion chamber of the 351C-4V & 302C-2V aussie heads do to their smaller volume (11-14cc) ups the compression ratio and because of the closed combustion chamber design have a quench area that reduces pre-detonation . The best way to wake a 351M/400 up is to change the cam and increase the compression ratio. Expect to pay $450-500 for a set of 302C-2V aussie heads.

Since you are not looking to spend a lot of money if it was me i would keep the heads you have, replace the valves with modern 1-piece valves (the oem step valves are known to fail easily) and get a nice aftermarket cam.

There are several ways to increase the power in the 351M/400 if you look around for parts. You can install 351C pistons if you have the 400 rod ends bushed down, 72 & later 460 roller rocker valve train parts are a direct bolt in operation.

As for installing headers unless you are going to be making other modifications save your money and just install a nice dual exhaust using the stock manifolds. If you decide to go the header route then definitely go for a nice set of 1-3/4" short tube style. 1-7/8" tubes will work but you will give up some scavenging effects with the 2V heads.

Here is a link to a chart comparing 351C heads to other FMC heads
http://home.comcast.net/~jelerath/mustang/Specs/heads-fr.html

The 400 has a few non interchangeable parts, connecting rods, intake, and all accessory brackets (this is do to the taller deck height). In addition the 400 was the longest stroke SB FMC ever built. The 400 is a square engine so it performs best in the lower rpm range (ie 6k or less). Also if you want to run high rpm reliably (6k-7.5K) in the 351C/351M/400 engine you need to install an oil restrictor kit in the 2-5 main oil galley's to reduce flow and not starve the main bearings.

 

[393clevor]

Yes the 351C/351M/400 2v heads are the same and have open combustion chambers which in this application is their weakness.

Guess you never did any port work on this heads... the D5 351M/400 exhaust port is completely different from the earlier 351C heads... they are not the same and can't be worked the same either, lots of water around the valve guide boss in the exhaust port in the D5.. ya can't even stick your finger through the exhaust port on a D5 but you can on the earlier 2V heads..

 

[blackhat620]

Guess you never did any port work on this heads... the D5 351M/400 exhaust port is completely different from the earlier 351C heads... they are not the same and can't be worked the same either, lots of water around the valve guide boss in the exhaust port in the D5.. ya can't even stick your finger through the exhaust port on a D5 but you can on the earlier 2V heads..

I am very familiar with the 351C/351M/400 engine and its components. The extended water jacket around the exhaust valve in the later D5 castings doesn't matter in the performance of this engine application. You want Ben to swap a set of 2V D5 heads for a set of 2V D1 or D0 heads and this is somehow going to make power increase? You can't be serious.

 

[393clevor]

You want Ben to swap a set of 2V D5 heads for a set of 2V D1 or D0 heads and this is somehow going to make power increase? You can't be serious.

Yes... The more air you get in and out the more power you make.. Ya know like buying a set of headers... is that a waste of money?... I Guess all the work I have done to ford heads over the years was a waste of time and all the aftermarket heads with better exhaust flow is just a sales gimmick... The 400 moves a lot of air and can use all the help it can get... I just don't see replacing the valves and rockers and all that on a head with choked up exhaust ports... when the early 2V heads are everywhere.. cheap.. sure there are better heads he could use but don't tell me the D5 are the same as a D1, huge difference

 

[blackhat620]

Yes... The more air you get in and out the more power you make.. Ya know like buying a set of headers... is that a waste of money?... I Guess all the work I have done to ford heads over the years was a waste of time and all the aftermarket heads with better exhaust flow is just a sales gimmick... The 400 moves a lot of air and can use all the help it can get... I just don't see replacing the valves and rockers and all that on a head with choked up exhaust ports... when the early 2V heads are everywhere.. cheap.. sure there are better heads he could use but don't tell me the D5 are the same as a D1, huge difference

All the work you have done on Ford heads and all the aftermarket heads with "better" exhaust flow can be and many times are, a huge sales gimmick and step in the wrong direction. It all boils down to intended application. "The more air you get in & out the more power you make" is an over simplification spewed about by people who don't spend the time on the track & dyno to understand the air flow & thermal efficiency of an internal combustion engine and how to achieve the best performance of the intended application. Do a little reading & research on Hemi heads and if you can find someone who has spent considerable time working with a Top Fueler ask them about the Hemi and how to best tune it. The Chrysler engineers figured out in the 1950's that too rapid air flow can be worse than not enough.

As far as headers go they are extremely over marketed and many times reduce power instead of increasing power for the intended application. Far too many people get hung up on increasing exhaust flow because they incorrectly assume that since increased intake flow is always better, increased exhaust flow must always be better. Internal combustion engine designers & racers figured out early on that you always want less exhaust flow than intake flow. Furthermore the overriding factor in proper exhaust flow is controlled by the downstream components after the head. When the NHRA mandated mufflers for many classes the racers quickly learned that the increased back pressure actually increased performance.

The Cleveland heads in all their forms flow a tremendous amount of air, and air flow is not a problem with the 400 in Ben's truck. If you are so worried about air flow in the 400 for Ben's application have him put 4V heads on there and see what that does for hurting his performance for his application.

Anytime you free up the exhaust side of an internal combustion engine you move the Torque curve up, the last thing you want to do with this application is move the Torque curve up. The 400 is a long stroke, square-engine, just like under-square engines they do not work well at high rpm.

Ben's application is a 5k+ pound 4-wheel drive truck, running on unleaded pump gas. In this application you want to make as much torque as possible at the lowest rpm possible. Increasing the exhaust flow and moving the torque curve up is a step in the wrong direction. Ben wants to increase power, performance, fuel economy and dependability.

The first thing to do to increase the power & performance on any 351M/400 is to change the cam & timing chain, the factory cam & timing chain set did more to kill this engine than anything else FMC ever did to this package. The second step is to increase the CR. Do to the open chamber 2V heads and emissions requirements FMC dropped the CR severely thorough the years on the 351M/400 to meet emissions and to prevent pre-detonation as the open chamber heads are notorious for this problem and especially running unleaded pump gas.
For dependability the valves in the Cleveland heads need to be changed to 1-piece with hardened seats. The factory 2-piece valves & multi-groove keepers are notorious for coming apart and rattling around in the top of the engine. As far as rocker arms the factory arms are fine for this application, I just included the roller rocker info to let Ben know about the parts interchange availability.

For Ben's application IMHO the best bang for the buck is to change the cam & timing chain and replace the 2-piece valves in the factory heads. If he has more money and time then he can get a set of 2V-Aussie heads with closed chambers. Spending the time and money to swap 2V D1/D0 heads for 2V D5 heads is an exercise in futility and at best a lateral move for Ben's application.

If money is no object then by all means he can get a nice set of aftermarket heads for North of $2k and tear down the engine to fix the oiling deficiency inherent in the Cleveland and strengthen the bottom end of the motor while he is at it. But this option is spendy and Ben will not get a good performance return in his application for the money spent.

Bottom line Ben is not building a high rpm light bodied drag car, he is building a low rpm heavy 4-wheel drive street & occasional rock crawler.

 

[393clevor]

Come on dude... he is not going to lose any low end by running 351C 2v heads... It's a 400... I have personally built 3 400's and one was with the stock D5 heads that were later swapped out for some 351 2v's, huge difference.. But whatever, I speak of stuff I have done myself not things other people have done... I'm not talking about porting the Cleveland heads "he said he could get some"

So to the OP go ahead and run those choked up D5 heads with stock exhaust manifolds and it will fall on it's face at 3500 like it does now no matter what you do to the rest of it.. I'm done...

 

[blackhat620]

Come on dude... he is not going to lose any low end by running 351C 2v heads... It's a 400... I have personally built 3 400's and one was with the stock D5 heads that were later swapped out for some 351 2v's, huge difference.. But whatever, I speak of stuff I have done myself not things other people have done... I'm not talking about porting the Cleveland heads "he said he could get some"

So to the OP go ahead and run those choked up D5 heads with stock exhaust manifolds and it will fall on it's face at 3500 like it does now no matter what you do to the rest of it.. I'm done...

He is not going to see any gains switching from 2V D5 casting to D1/D0 castings (BTW they are all 351C heads), the exhaust is not the problem. And yes you brought up porting the heads, which will shift the torque curve up. As far as owning and working on these, I grew up at the dragstrip, had & drove an original factory Clevor (btw power doesn't come on till about 4K) and climbs nicely up to about 8k where they have a real bad habit of leaving the lower end on the track. Also ordered and took delivery of a 79 Bronco 4x4 with a 400 owned and drove it for 20 years, heads were not the power problem, the problem, as with all of these is the Cam, first and foremost, followed by low compression. FYI the CR of the 400 runs from 7.3 to 8.4 depending on the application and year, the only year the 400 had a good CR was the first year of production at 9. As far as seeing the power flatten out at 3500 this is no surprise as the 351M is done at 3400 and the 400 is done at 36-3800 depending on the available pump gas quality and the cam & pistons it was stuck with. (And yes you could get the first year 400 to not max out until 4K).
If you saw a noticeable difference on the dyno swapping 2V D5 heads for 2V D1/D0 heads it was not from the exhaust port it was do to you correcting a vacuum leak, faulty rockers or springs or switching from one end of the chamber size to the other with the head swap. Bottom line the 2V open chamber heads are a poor design and switching between D5 & D1/D0 heads is a lateral move at best. To fix the 351M/400 you need to swap the cam & timing chain, then get the compression up about a point or so. The easiest and best way to raise the compression without encountering pre-detonation is to install closed chamber heads. After this the rest of it is window dressing.

 

[393clevor]

hey I hear ya.. we all know what ford did to the 400.. cam, compression, etc. but they also choked the exhaust port.. you must not have looked closely to a D5 head dude.. take a look.. why change everything ford did except the exhaust port.." change out the Valves in a D5 head... Why??? get some better heads before you spend any money on D5's...I bet a small block exhaust port flows more than the D5 head.. and with that huge intake port the % is way off... The Cleveland heads have a much better flow ratio than the D5 ... HUMMMM didn't hear you mention anything about that..

http://www.toyfarm.org/mystuff/pictures/400head/
wish I had got better pics of the D5..

And a Clevor is a Windsor with Cleveland heads (so many people call the Cleveland a Clevor) .. I built a 351W with C heads had plenty of power below 4000... any 302 with Cleveland heads is not going to have any low end we know that, I remember the boss 302... this is a 4" stroke 400

I did not say anything about porting the heads.. I said I have ported them didn't tell him to port anything..

Have a nice day

 

[393clevor]

Oh ya and there was nothing wrong with the 400 I built with the D5 heads on it.. it ran very well.. I've been doing this **** for years...

 

[393clevor]

yup the compression is a problem that's why I changed the pistons

also the original poster will more than likely never do a thing to his 400... just saying..

 

[LEB Ben]

also the original poster will more than likely never do a thing to his 400... just saying..

That's where you're wrong...I have done most of this...myself. Just didn't know anything about the C heads on the 400. Admittedly, ignorant about heads, I didn't know if the C's were worth the time or not. And if they were, and I could score some cheap C heads before bumping to the Aussie's, I will.

 

[393clevor]

That's where you're wrong...I have done most of this...myself. Just didn't know anything about the C heads on the 400. Admittedly, ignorant about heads, I didn't know if the C's were worth the time or not. And if they were, and I could score some cheap C heads before bumping to the Aussie's, I will.

The Aussie's are the way to go for sure, best of both worlds... just don't put any money or time into the D5's (they are different)

sorry about the comment.... If you could find some 71 to 74 2V C heads cheap I would run those before I would spend a penny on the d5's .... again that's me that's what I would do and that's what I have done..

Good luck and please keep us up to date on your build..

 

[LEB Ben]

No worries man...after the basic bolt ons/ins, I still wasn't pleased with the engines performance. Gotta tackle the bottom end of this build, regear and decide where to go with the heads. But I have the same problem as most, when you have the time, you don't have the money and when you have the money, you don't have the time.

 

[393clevor]

No worries man...after the basic bolt ons/ins, I still wasn't pleased with the engines performance. Gotta tackle the bottom end of this build, regear and decide where to go with the heads. But I have the same problem as most, when you have the time, you don't have the money and when you have the money, you don't have the time.

here is where I bought the pistons if you rebuild it... the only place that make them... they are are Keith Black hyper... well the number on them is . I couldn't cross reference the number.. I thought I could buy them cheaper somewhere else..
http://www.tmeyerinc.com/400ford.html

 

[LEB Ben]

Thanks...I'm well acquainted with Tim.

 

[DNFXDLI]

Who's Tim?

 

[fatherdoug]

Who's Tim?

You know, the guy that turns misnomered boat anchors into awesome engines. I only wish I would have known about tmeyerinc BEFORE I had my engine rebuilt.