1970 429 SCJ

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1970 429 SCJ - Page 3 Empty Re: 1970 429 SCJ

Post  BOSS 429 on July 13th 2019, 11:37 pm

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1970 429 SCJ - Page 3 Empty Re: 1970 429 SCJ

Post  BBFTorino on July 14th 2019, 1:36 am

Dragkid, maybe you should pull it out, tear it down and at least do a quick cylinder hone and put some new rings and bearings in it. That will eliminate the possibility of this problem, but maybe a few other common problems as well. Its cheap insurance!

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1970 429 SCJ - Page 3 Empty Re: 1970 429 SCJ

Post  rmk57 on July 14th 2019, 12:22 pm

Mark Miller wrote:
BBFTorino wrote:I will assume that you have already done a compression check, and they all show within specs?

He posted Compression was between 148-151 psi but somebody said a stock 429 SCJ should be 190-200 psi?

Thats if it has the original D0AZ SCJ-Boss 429 solid cam and forged flat top pistons. I agree with BBF Torino. With a rare engine like that I would want to invest a bit of time to make sure everything is up to snuff.

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1970 429 SCJ - Page 3 Empty Considering your low vacuum of 10in that makes me think it is mechanical. Ie, valves tight

Post  1979cvx20 on July 16th 2019, 3:49 pm

Considering your low vacuum it sounds like valve timing is off. This can happen either at the cam and crank sprocket or valves being to tight. If upon acceleration it pops back through the carburetor that is most likely valves too tight. On another note make sure your crankcase isn't full of fuel from an internal leaking fuel pump. I can almost guarantee it is not a carburetor problem even though on your Holley you probably will have a problem because of a now busted power valve. It only takes one good backfire to cause it to leak. I have a 500 horsepower 460 in my 79 CVX20 jet boat and run my base timing at 14 degrees and maximum 32° at about 3,500 RPM or more. 850 double pumper Holley, HEI distributor, performer RPM intake, timing gears straight up, CP performance hydraulic cam, roller rockers, CNC ported 1968 C8VE cast iron heads with oversized stainless valves, intake and exhaust port matched to heads,10 quart pan with scraper/ windage tray. I thought it was only 475 horsepower but after talking to CP performance they said according to my 4800 RPMs and impeller size AA it had to be at least 500 horsepower. I have been a Master ASE TECHNICIAN WITH ENGINE PERFORMANCE since 1976 and have been the engine performance and carburetor specialist at most of the places I've worked at over my 56 year career. I'm also an Acura Master Tech since 1992. https://images.app.goo.gl/4LUUudx9sqnBxh256.
https://photos.app.goo.gl/kDjyxWCZpxsVtR3W6.
I forgot to say that valves to tight causes valve timing to be more advanced. Of course, too loose retards valve timing.

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Post  1979cvx20 on July 16th 2019, 4:10 pm

We you said, "When i go to shut my engine off, it tends to "diesel" and i hate that it does that." indicates that your throttle plates are too far open because you were trying to get it to idle with only 10 in vac which probably cam timing/valve adjustment. If somebody decided to put hydraulic lifees on top of the original cam would also cause this and many other problems. I have seen it happen before.

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