spark knock - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cvalcore · 10-02-2009, 11:45 PM

I have a question i have a 84 chevy one ton 454 that i installed a edelbrock rpm intake and a 750 cfm carb on and it has great power when im driving around in the valley but when i take it up in the mountains i have spark knock and not near the power i was wondering if it could be my distributor that's the problem. also it has been a pain in the neck to get it timed just right ive got the timing right but i just cant get ride of that spark knock. Also i have headers and a duel exhaust with a cross over pipe. Any help would be great.

cvalcore · 10-11-2009, 09:25 PM

any one got any ideas

Prong · 10-11-2009, 11:09 PM

What grade of gas are you running? Also, where exactly is the timing set at?

gchemist · 10-12-2009, 12:02 AM

The engine is probably warming up too much. A cooler thermostat might help. I suggest tuning the carb with a vacuum guage. Yea, the distributor may be adding too much timing. Especially if the initial timing is set above 6 or 8.

cvalcore · 10-12-2009, 10:17 PM

the timing is set in the only place that it will not diesel when i shut it off i have always set my timing by ear on all my vehicles i have not checked the degree it is set at i never had a problem with timing until i put the intake and carb on and also it will diesel after only running for 2 min. it also runs pretty cool about 160 degree's.

TurnNBurn · 10-12-2009, 10:32 PM

I run my big block a 32 deg total timing. I start a 5-6 intial. Check to make sure your weights are not sticking. That will hold it to far advanced a low speeds. Climbing hills will make timing rise but motor slow. Put a few gallons of e85 in your tank if its avaliable to you, its around 104 Octane that should bump up your fuel. That should rid you of the ping. Run a cooler plug, Check for vaccum leaks. Or back the timing off. That kinda of thing

In the past I took the vaccum pot off the dist and used a small file and filed the rod on the vaccum pot so it doesnt pull so far. Worked for me.

9 times out of 10 if it afterruns to much advance, or idle is to high with a vaccum leak.

nechevy · 10-13-2009, 02:13 AM

A raise in elevation sounds like the problem. The higher up you go the leaner the fuel mixture will get and on loads can cause a ping and lack of power. Some cars use a barometer to resolve that. You'll probably have to check you a/f mix and timing

10-02-2009, 11:45 PM	#1
cvalcore Registered User Join Date: Oct 2008 Location: Monroe IA Posts: 272	spark knock I have a question i have a 84 chevy one ton 454 that i installed a edelbrock rpm intake and a 750 cfm carb on and it has great power when im driving around in the valley but when i take it up in the mountains i have spark knock and not near the power i was wondering if it could be my distributor that's the problem. also it has been a pain in the neck to get it timed just right ive got the timing right but i just cant get ride of that spark knock. Also i have headers and a duel exhaust with a cross over pipe. Any help would be great. Last edited by cvalcore; 10-02-2009 at 11:47 PM.

10-11-2009, 09:25 PM	#2
cvalcore Registered User Join Date: Oct 2008 Location: Monroe IA Posts: 272	Re: spark knock any one got any ideas

10-11-2009, 11:09 PM	#3
Prong Registered User Join Date: May 2007 Location: CO Posts: 475	Re: spark knock What grade of gas are you running? Also, where exactly is the timing set at?

10-12-2009, 12:02 AM	#4
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: spark knock The engine is probably warming up too much. A cooler thermostat might help. I suggest tuning the carb with a vacuum guage. Yea, the distributor may be adding too much timing. Especially if the initial timing is set above 6 or 8. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

10-12-2009, 10:17 PM	#5
cvalcore Registered User Join Date: Oct 2008 Location: Monroe IA Posts: 272	Re: spark knock the timing is set in the only place that it will not diesel when i shut it off i have always set my timing by ear on all my vehicles i have not checked the degree it is set at i never had a problem with timing until i put the intake and carb on and also it will diesel after only running for 2 min. it also runs pretty cool about 160 degree's.

10-12-2009, 10:32 PM	#6
TurnNBurn Registered User Join Date: Oct 2004 Location: North Dakota Posts: 103	Re: spark knock I run my big block a 32 deg total timing. I start a 5-6 intial. Check to make sure your weights are not sticking. That will hold it to far advanced a low speeds. Climbing hills will make timing rise but motor slow. Put a few gallons of e85 in your tank if its avaliable to you, its around 104 Octane that should bump up your fuel. That should rid you of the ping. Run a cooler plug, Check for vaccum leaks. Or back the timing off. That kinda of thing In the past I took the vaccum pot off the dist and used a small file and filed the rod on the vaccum pot so it doesnt pull so far. Worked for me. 9 times out of 10 if it afterruns to much advance, or idle is to high with a vaccum leak. Last edited by TurnNBurn; 10-12-2009 at 10:34 PM. Reason: more to say

10-13-2009, 02:13 AM	#7
nechevy Registered User Join Date: Sep 2009 Location: omaha,ne Posts: 16	Re: spark knock A raise in elevation sounds like the problem. The higher up you go the leaner the fuel mixture will get and on loads can cause a ping and lack of power. Some cars use a barometer to resolve that. You'll probably have to check you a/f mix and timing __________________ What would foose do?

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