Thread: 70 429CJ Buildup Questions

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Originally Posted by DwayneD

Paul,

I'm looking for something in the neighborhood of 400-450HP. I'd prefer to have the power in the lower end of the RPM range. It will rarely see 5K. I'm looking for a cruiser, not a drag racer but I'd also like it to sound nice at idle.
Do you have any experience with the Offenhauser Dual Port intake? The only number I can find on it is 360 but I haven't had the time to do much checking as to what it really is. It bead blasted up nicely and is low so it would fit under the hood of the Cobra. I'd consider using it if it was half way decent.
One final question I have is can you suggest a good reference manual for helping me to optimize the valve train? I've rebuilt stock engines before but never had much experience with the high performance 385s.

Also wanted to thank techinspector1 for the post. It was timely as the block is at the machine shop getting bored and decked this week so I relayed the info to the shop.

Thanks,

Dwayne

Dwayne,

Personally I would not deck or final hone the block until the pistons are selected, in possession, and the shortblock has been mocked up to determine the actual deck height.

You're probably not going to like this next statement: Given your lower rpm preference due to the street use and in the interest of good throttle response, I feel the D0OE-R heads are all wrong. The intake ports are way too gargantuan and port velocity will be all but killed in the low rpm, especially with the reduced compression ratio (which equates to less engine vacuum as well). Those heads don't really do much at all for power until your combo is 500-cubes or so, and even then they are still a lot of head for a low compression naturally aspirated engine operating below 4000 rpm most of the time. Don't be fooled by the fact that Ford put them on a little ol' 429 in 1970; back then everyone believed that "bigger is better" but we are more wise nowadays. "Just right" is what makes and engine perform well, the entire engine combination needs to be a perfect symphony of componentry working together in harmony. This pertains even to a 2000-pound kit car.

I would much rather see you use some early-style passenger car heads such as the D0VE heads. In a 400-450 hp build such as yours and in your application, I guarantee you that the ported D0VE-headed engine will outperform the ported iron CJ-headed engine, all else being the same. In an engine such as you are planning, the intake port size of the passenger car heads will make for better port velocity, better cylinder filling, better throttle response, better low end and mid-range power, and the combo can be made to pull hard from 2000-5000+ rpm. If you want to build a 4000-7500 rpm screamer 460, then that's another story and use the iron CJ's. If you simply must have the CJ's on the engine for the bling factor, then go go ahead as the engine will still run okay....but it won't be quite as fast in the rpm range where you will normally be using it.

I am familiar with the Offenhauser intake manifold that you have. It was an idea in theory that Offy patented and while it is not considered a high performance state-of-the-art intake by today's standards, it could work okay for your application. I would prefer the Performer RPM that Techinspector suggested above. If you wish to use the Offy, I will suggest a modification to it.

I would be happy to include my thoughts on valve train geometry and camshaft selection as well, but maybe a little later and that feedback depends on which way you go with the cylinder heads.

Paul