I have a question on rebuilding my 400 for my 79 F250 SC. I bought an unused rebuild kit with rebuilt heads and the camshaft is a Speed Pro CS1085R. Pistons are the stock 8.4 to 1 .30 over. Going to be running stock manifolds and an Edelbrock 2171 Performer 400 4V intake with Holley 600 vac/ electric choke. My question ( and I know it has been asked somewhat before) is with the stock pistons and this cam ( 282 intake/ 292 exhaust, 204/ 214 @.50, .484/.510 lobe is 112) what kind of numbers for torque/ HP. If I go with the pistons from Tim Meyer that give you 9.3 to 1 , I believe, what kind of difference and is it worth it. Thanks guru's !

 

Worth it?

For me the answer is yes. With the time, effort, and expense of a full rebuild, the added expense of TMeyer pistons isn't too bad. If you are on a tight budget YMMV.

 

Thank you for the reply, I know they are a far superior product. Was just curious on what kind of difference it would make on torque/hp?.

 

2 to 4% according to:

https://www.motortrend.com/how-to/co...ns-more-power/

But, you could spend days trying to figure it out.

We had a '66 wagon, 390 2V, advertised 9.5 CR. My dad had a '73 or '74 that was supposed to be a 390 2V, compression was probably in the mid to low 8s. That was pretty soft compared to the wagon.

YMMV.

IMO get the better piston. Besides compression, you get better quench and will have overall better performance and fuel economy, if such a thing is possible to think about with a 400 or similar size V8.

With more statiic compression, you might also be able to make use of a slightly "better" cam.

 

A set of headers will help the performance more than different pistons or a better cam in a build like that they will probably be worth around 30 horsepower.

 

A lot of "worth" will hinge on your own use and habits behind the wheel. My 400 on the stand still has new rebuiler's pistons, and will use the same Performer 400 intake, a 600 Edelbrock carb, and while the jury is still out on cam choice, likely nearly same as the 2172 as in my 351M. Got other fish to fry first.

 

I am in a similar situation, except my truck's 400 was rebuilt shortly before I paid $600 for it. Driving it I found it had a real tendency to spark knock. Regardless of what some "Ford Believers" say, the open chamber head promotes knock. I don't care what the 1969 designers say. An OHV engine with 8:1 compression shouldn't knock. The KB piston brand, part of Silv-O-Lite, has had great success with their step dish pistons in Mopar open chamber head engines. The pistons they make for Tim Meyer do the same thing for the Cleveland open chamber head.

Here's the theory: flame speed in a non-swirl chamber is surprisingly slow. As the flame is meandering across the chamber, the heat and pressure precede it and cause the fuel in the farthest parts of the chamber to decompose into knock-prone compounds, that detonate before the flame can get to them. So what to do? provide "squish". Sir Harry Ricardo did his signature work on this issue in the early 1920s. What he did was create an area in the chamber where the piston would nearly collide with the cylinder head, forcing or squishing the mixture out into the rest of the chamber. This provided motion in the chamber that physically transported the flame to the far points of the chamber, burning whatever was there before it had a chance to self-ignite. Thus, spark knock is eliminated. The chamber becomes more resistant to detonation, allowing higher compression to be used. Thermodynamically, higher compression ratios always result in higher efficiency which translates into more power, better mileage, etc.

This is why I am putting Tim Meyer's $450 pistons into my $600 truck. I suggest you do the same.

Best Regards and Merry Christmas!,
R.

 

Higher compression ratios don't always make the engine more efficient. It all depends on how you achieve that higher compression ratio. I've tested two 350 inch engines on my dyno back to back and had them make identical torque and HP numbers, one was a flat top piston with 10.5:1 compression and the other one was 13.5:1 compression with an angle milled head and a 13cc dome piston.

 

Domes suck. Certain Harleys and big block chevy engines have terrible flame propagation.

 

The 400 has a few problems to overcome when it comes to performance
Tall deck means long rods and the low compression and the low rpm with the 4x4 bore and stroke
That said If you were to put 4v 351C heads on your 400 you would have 10.5 or so compression with the factory piston
Carbon buildup was a big part of the problem with these old 400s for spark knock and run on
I have a boss 302 with 4v cleveland heads on it and suffer no spark knock at roughly 11 to 1 compression
Those heads are pent roof closed chamber fairly hard to find
Bronzewall the valve guides and away you go with todays gas
All that said you will have fun rebuilding yours with what you have
The intake will be great and the carb too.
Jet it down you will not need a ton of fuel

 

I don't have tims Pistons as they were not fully to market in the early 2000s when I did my motor. But what I can tell you is that a zero deck or near zero deck really wakes the 400 up. I have custom Ross blanks in mine that were for a Cleveland with the CH changed and the stock 400 rods bushed to the .912 Cleveland pin. A decent camshaft and headers this motor came to life.