Thread: 429 Help Please. It's A stumper

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Originally Posted by techinspector1

Anything before about 1972 would be a high-compression motor with non-hardened exhaust valve seats and small (~76 cc combustion chambers), although it would be fitted with the correct camshaft timing chain sprockets for hot rodders. The later timing chains (73-up) featured retarded cam timing (by about 8 degrees) in an attempt to lower emissions so the motor would pass Federal standards. The hot tip for these later low compression motors is to change out the timing chain and sprockets for a '68-'70 429 part number, so you have the proper timing chain and sprockets to begin with.

Your motor has probably around 10.17:1 static compression ratio and iron heads, so running it on pump gas probably won't work due to detonation. Back when this motor was new, we had Sunoco 260 fuel (110 octane) available on every other corner, so fuel was not the problem that it is today. Also, the fuel had tetraethyl lead in it to lubricate the exhaust valve seats so that the valves would not wear down into the heads. Actually, it didn't lubricate the seats, it made them dirty. Anyone who knows anything about welding knows that you have to have a clean connection in order for welding to work properly. What happened was that when the exhaust valve was seated on the seat, a little micro-welding would take place. When the valve was lifted off the seat, it would tear itself loose and take a little material from the seat and deposit it on the valve face. After a while, the exhaust valve would wear the seat away so much that the valve itself would be recessed down into the head. Engineers found that if they put a little tetraethyl lead into the fuel, it would dirty-up the seats and no welding could take place. We used tetraethyl lead for many, many years until it was discovered that we were destroying the planet with lead. That's why we have unleaded gas today and why we have a problem once again, with the valve recessing down into the head. To fix this, we have begun to add hardened exhaust valve seats into the heads so that recession is checked once again.

So, you have to address the valve seats as your first problem.

The second problem is the static compression ratio. Again, when this motor was new, the fuel that was available would prevent detonation on motors up into the 11.0:1 and 12.0:1 static compression ratios. Today, with iron heads, smart money limits the SCR to around 9.5:1 or just a little higher for using pump gas.
There are a couple of ways you can lower the static compression ratio of your motor. One is by changing heads to the later D3VE cylinder heads, which are ~95 cc's instead of the earlier C8VE 76 cc heads, or the one-year only E6TE heads from 1986. That would lower the SCR to about 8.65:1 SCR, which might be a little low for a performance motor, even a street performance motor.

If I were doing one of these motors, I would find a 460 crank and build a 460 instead of a 429. Check with local automotive machine shops for cranks that customers left and on craigslist. You shouldn't have any trouble finding a 460 crank. I'd bore the block 0.030" and use new Keith Black KB137-030 pistons. I'd zero deck the block and use Fel-Pro 17068 head gaskets to arrive at a 0.039" squish/quench. The best power will come from using a dual-plane, high-rise intake manifold such as a Weiand Stealth #8012, mounting a 750 carb of your choice.

This would make a 466 cubic inch motor with a 9.91:1 static compression ratio. You would have to run premium fuel with it, but the zero deck and tight 0.039" squish will help to keep detonation under control. I would use a cam with 214-222 degrees intake duration, cut on a 112 degree LSA. The higher the intake duration, the more the motor will need a looser stall converter if using an auto trans.

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Wow that's some awesome knowledge you've taught me and I'll definitely look into doing what you said you'd do with this engine. But the one question I have is should I replace the iron heads or leave them alone?

Originally Posted by NightHawk

. But the one question I have is should I replace the iron heads or leave them alone?

if you are looking for some better than stock performance then at minimum you should mildly port and polish the stock heads you have on the exhaust sides. i would not pay the 2 grand required to get aftermarket 429 heads for the minimal improvements you would get in a near stock build .. i did step up and get some edlebrock heads for my 351 but they are much cheaper and well worth the 1000 bucks ..you already have over 300 horses to begin with .. just bump up the cam a bit .. add an intake and headers and good ignition and let her rip .. what kind of car are you looking at ?

Originally Posted by HOSS429

if you are looking for some better than stock performance then at minimum you should mildly port and polish the stock heads you have on the exhaust sides. i would not pay the 2 grand required to get aftermarket 429 heads for the minimal improvements you would get in a near stock build .. i did step up and get some edlebrock heads for my 351 but they are much cheaper and well worth the 1000 bucks ..you already have over 300 horses to begin with .. just bump up the cam a bit .. add an intake and headers and good ignition and let her rip .. what kind of car are you looking at ?

Some good advice there. Hoss knows the costs, and how to get it done. Along with Tech's advice on the machining you're gonna be right, IMO.