I am looking for input on building a new 460 for my mud racing truck. This might be kind of long, but please bear with me.

My truck is an 85 F250, 429, C6, 3.54 front and rear, 33" tall tires(max).

STOCK CLASS RACING RULES--
Stock heads--no porting, can change valves. Any year head.
Stock crank and rods--No stroking. C.I. limit for a BB is 477.
Any aftermarket piston, but no popups.
Any CR is allowed.
Vacuum must be minimum 18" at 1000 RPM.
No carbs without choke horns-1.686 bore max.
Hydraulic flat tappet cams only.
No full roller rockers, but can have roller tips.
Any torque convertor.
Any gear ratio, as long as front and rear are the same.
Only dual plane intakes.
Any exaust.

These are the main rules in stock class, there are more, but for this discussion, this should work.

I have been running fairly competitive this year, but the 1/2 ton Chevys with vortec heads are killing us. There are a few other BB Fords, and one BB Chevy, and we run close, but it is still tough.

My combination is a 429 with car rods(ARP bolts), stock crank, C8 (78cc) heads with stainless valves, forged flat top pistons (approx 11-1 compression), Edelbrock RPM intake, Holley 830 CFM 4150, stock dist. with MSD 6AL, custom ground indexed cam, Rhoads V-Max lifters, roller tip rockers, 3/8 pushrods, and this is chipped at 6000 RPM. 106 octane fuel.

C-6 with a reverse valve body, transfer case in low range (2.56-1) and a 4500 rpm 8" stall convertor.

My gear ratios put me at 65 MPH at 6000 rpm calculated, in top gear, and we sometimes hit the chip on the front stretch. During the main part of the race we are probably running in the 4500-5000 range, and the engine seems to struggle. Most of the other BB seem to be running in the 5500 range.

This is my solution, and please tell me what you think--

I have a 79 460 block in good shape to use as a start--

Bore this block to 30 over and install new forged flat-tops.
Should have truck rods now, and install ARP bolts.
Normal machine work(complete balance).
Use my old heads and valve train. (new cam and lifters?)
Add an air gap intake.
Old carb.
MSD distributor to go with box (trash the stock unit)
Chip to 6500 rpms
Change gear ratio to 4.10.

I am hoping the new gear ratio will put me higher in the RPM range for travelling (assuming the cam is ground to take advantage of torque at a higher RPM). And the extra cubic inches will help out.

Questions--

Will this reliably run at 6500 for 5-10 seconds per pass, then still hold for the rest of the run. (Our engine now has 50-60 races at 6k)

Do you know the best piston to run in this case-lightest and strongest.

I know the C8 heads are not as good as the D0OV heads, but are they good enough to flow to this rpm range.

Will this make 1hp/ci.

Do you see any other combinations that would work better.

I plan on staying in the 2-3K$ range to put this together, with me doing all but the machining work.

Thanks for ALL comments and advice.

Todd

 

First off, How did a 429 get in your truck? Since there were never any produced by the factory that way. It should be a 460.

 

The truck originally was, and technically still is, an F350, it has a Dana 70 rear, and a Dana 44hd front, and had a diesel engine.

This was bought from the original PO and stripped of its blown engine to make a mud truck. The guy I bought it from had started the process, which included rebuilding the engine from his old race truck. For whatever reason, many of the early race trucks loved to run the 429.

When I got the project, I had to finish much of the truck, and make motor mounts to fit the engine just a little lower than stock.

I am now looking for more cubes and horsepower than the 429.

My thinking is that 30 extra cubes + extra rpms = more horsepower.

Class rules state the engine family must be correct, you could run a 302 in a half ton Ford, but all will run the biggest, a 351w.

 

The larger displacement idea is great but I really question the use of the current heads.
With the flat tops you will gain some compression, but give it up using the larger combustion chamber. Perhaps the more desirable early heads could be a better choice here.

Which cam are you running now? Specs? This is probably gonna be the make it or break it factor here.
Most conservative cams are not gonna run the rpm you desire and still make power. Too small and you simply dont move any air. Too large and you dont meet the vacuum requirement.
I'm interested to see what you have in mind here.

 

The heads now are 78 cc, which I thought was a fairly small chamber BB head. With these now I am running 10.5-10.7/1 cr.
Custom ground cam that I am running now is
Dur @ .050 - 236 int 236 ex
Lobe lift .338 X1.73= .585 total lift int. and ex.
Lobe separation 114 + 6

This cam was designed to pull the vacuum, but still have good torque and HP in the 4500-5500 range. With the V-max lifters, I can adjust the cam to make it look bigger or smaller. Right now I have .026 lash on the intake and exaust, and I can pull 19" vacuum. I could reduce my lash to increase cam size, but then I would be coming close to not pulling vacuum. So, I will have a cam made to suit my needs, for this new engine.

The vacuum requirement is the great equalizer.

This video shows how we race it.
http://www.youtube.com/watch?v=_AZdeo2cTlk