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Discussion Starter · #1 ·
I finally got the 429 in the 66 and running. Now, the motor will backfire up through the carb randomly. No rhyme or reason, just a big backfire and the engine dies. I have good fuel pressure and stock dist. with pertronix. Stock block and heads, XE 274 cam, perf. rpm intake, and a holley 850. I checked the timing twice and it is set to factory specs. Any ideas?
 

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There is a vavle in holley that will make it pop and backfire, I think it is called a power vavle but not sure, also it the distubrator in right?

<font size=-1>[ This Message was edited by: Nourse on 5/7/06 6:55am ]</font>
 

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You will get better feedback if you posted this in the techboard.
 

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On 2006-05-06 15:39, galaxiedrvr wrote:
I finally got the 429 in the 66 and running. Now, the motor will backfire up through the carb randomly. No rhyme or reason, just a big backfire and the engine dies. I have good fuel pressure and stock dist. with pertronix. Stock block and heads, XE 274 cam, perf. rpm intake, and a holley 850. I checked the timing twice and it is set to factory specs. Any ideas?
What year is the 429? When you changed the cam, you did change the timeing chain, gears too? Many of the later model LIMA (429-460) had builtin retarded timeing to satisfy smog police, I think it started in 1972. this was actually built into the timeing gear, so even if you installed it straight up...it was actually 4 degrees retarded.

The worse part of the issue is you can never be 100% sure of what you get...unless you know a lot about the engine you started with and ask a bunch of questions when you start buying, mixing and matching cam/timeing gear and cam parts.

Plus, just to make it ever more interesting, some cam mfg. try to be helpful and sell cams where they have added it back or took it out or set it like the factory cams.

Blow back thru the carb is almost always a timeing issue. The problem you have to figure out is whether or not its ignition timeing or cam timeing that is the problem.

I can't even guess where you started from. As mentioned...maybe one of the guys that hang out at the Tech forum can give you some down and dirty advice that will cure the problem.
 

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You may have an Intake valve that is not closing on the power stroke???
Check out the article on the "Streetwise 460 Build Up", they had a cam lobe go bad. Good luck.
Bill Bailey

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<font size=-1>[ This Message was edited by: billbailey on 5/7/06 2:30pm ]</font>
 

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Don't panic. Start with the basics.

I am betting that you have the distributor stabbed 180° out. Pull the valve cover and watch the valves on number one as you bring it to TDC. The intake valve should close and you should get up to the mark with no other valve movement. Look at the rotor in the distributor and if it is not pointing at number 1, re-stab it

There are other things that can do this, but lets try this first.

<font size=-1>[ This Message was edited by: BillBallinger on 5/8/06 5:37pm ]</font>
 

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Discussion Starter · #8 ·
Sorry about the delay in the response, I have been very busy lately. Well on Sunday I decided to pull the intake and make sure the cam was ok. I read the 460 build on this site and their problem seemed very similar to mine. Sure enough, two lobes were toast. The two corresponding lifters were toast as well. I traced the problem to my moronic preload of the lifters. Thank you all for the replies. Hmmmm... maybe I should go bigger....
 
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