New Engine Knocking with Timing Set at O degrees!! - Team Camaro Tech
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post #1 of 19 (permalink) Old Sep 13th, 02, 02:02 AM Thread Starter
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Hey guys, I finally got around to setting my timing and set it to factory spec which calls for 0 advance, so I set it at 0 degrees.

I start driving it and it knocks under hard accel and when in overdrive at any speed. I tried going with 91 octane (highest I can get) and nothing has changed.

The motor is a rebuilt 383 stroker, mild hyd roller cam (.450", 200 [email protected]"), 9.4 CR, cast pistons, stock 350 heads, Performer intake, Edelbrock headers, Flowmaster muffler....nothing special. I am running all the factory crap, and California emissions except for an EGR valve and CAT.

I can retard the timing and the knock disappears, but that can't be good for mileage or power.

What do I do now? Thanks guys.

1987 Camaro 4bbl. (factory LG-4 car)
700R-4
2.73 open rear

[ 01-26-2005, 05:26 AM: Message edited by: BlueRebl ]

-Cable<br /><br />'75 Datsun 280z mild 383/TH350 swap (blew the 383)<br />'99 Grand Prix GTP (3.4" pulley swap)<br /><br />New SBC Motor: In Progess<br /><br /><a href="
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post #2 of 19 (permalink) Old Sep 13th, 02, 05:03 AM
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What is the quench height and dome configuration of the pistons? Is the 9.4:1 calculated using the longer stroke of the 383?
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post #3 of 19 (permalink) Old Sep 13th, 02, 06:20 AM
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Where did you get factory spec's to set a 383? What dist are you using? You should set the total timing to about 32degs with the vacuum advance disconnected and the source plugged. Sounds like an HEI with way too much mechanical advance built into it.

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post #4 of 19 (permalink) Old Sep 13th, 02, 09:11 AM
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Dennis has it right I bet. Time for a re-curve.

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post #5 of 19 (permalink) Old Sep 13th, 02, 12:21 PM
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he said all the electronic controls are in place, which would mean a small cap external HEI with no mechanical or vacuum advance of any kind. i bet the computer is still set to factory specs, which would call for more timing on a smog 305 than on a high strung 383 being choked by the stock emissions package.
is the knock sensor hooked up and working properly? maybe time for a custom chip.

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post #6 of 19 (permalink) Old Sep 13th, 02, 01:23 PM
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<BLOCKQUOTE>quote:</font><HR>Originally posted by novaderrik:
he said all the electronic controls are in place, which would mean a small cap external HEI with no mechanical or vacuum advance of any kind. i bet the computer is still set to factory specs, which would call for more timing on a smog 305 than on a high strung 383 being choked by the stock emissions package.
is the knock sensor hooked up and working properly? maybe time for a custom chip.
<HR></BLOCKQUOTE>

There's no mention of electronic controls in the orig or any post in this thread until yours. Did you get something in e-mail we didn't see?


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post #7 of 19 (permalink) Old Sep 13th, 02, 01:37 PM Thread Starter
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Dennis, I said that I have all the factory crap hooked up minus the EGR and the CAT.

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post #8 of 19 (permalink) Old Sep 13th, 02, 02:25 PM
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Ok and I guess I missed the '87's description as well... That LG4 is a computer controled carb'd 305 and I belive you need an in line adapter (I think edlebrock may make them) that will adjust the computer for the new hardware you hooked it too. I think the 305 was rated at 165hp in '87, how does that compare to the new 383? I would think running without the cat and EGR would play havoc with the computer as well. Not meant as a lecture but you'll have a hard time passing visuals at your next smog check as well.



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post #9 of 19 (permalink) Old Sep 13th, 02, 08:20 PM
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Just to add....on a stock LG4(or most engines with an EGR valve), an inop EGR valve would cause pinging as described...
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post #10 of 19 (permalink) Old Sep 13th, 02, 09:41 PM Thread Starter
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<BLOCKQUOTE>quote:</font><HR>Originally posted by DjD:
Ok and I guess I missed the '87's description as well... That LG4 is a computer controled carb'd 305 and I belive you need an in line adapter (I think edlebrock may make them) that will adjust the computer for the new hardware you hooked it too. I think the 305 was rated at 165hp in '87, how does that compare to the new 383? I would think running without the cat and EGR would play havoc with the computer as well. Not meant as a lecture but you'll have a hard time passing visuals at your next smog check as well.
<HR></BLOCKQUOTE>

The 383 runs awesome, the 305 doesn't hold a candle. I am guessing around 300HP/400TQ. It runs hard enough for cause my stock 700R-4 to slip under WOT during the 1-2 shift. Even so, I ran a 14.2 in the quarter with street tires and 2.73 open rear.

I do have a oil burning/smoking problem on accel and warm start-up (doesn't smoke when cold start-up) though. I am pretty sure its exhaust guides or seals. Guesses?

I planned on putting the EGR back on Monday (I'll report the results), and the CAT was plugged so I just hollowed it out for now. I plan on buying a high-flow unit before SMOG time. Just wondering, why would not having the CAT cause a problem with the ECU?

I do get a code 32 after a hard accel, then goes off after 20 seconds of normal driving. I also get that code on the Freeway about 70mph after I take my foot off the gas. Any ideas what's causing that?


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[This message has been edited by BlueRebl (edited 09-13-2002).]
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post #11 of 19 (permalink) Old Sep 14th, 02, 05:50 AM
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<BLOCKQUOTE>quote:</font><HR>Originally posted by onovakind67:
What is the quench height and dome configuration of the pistons? Is the 9.4:1 calculated using the longer stroke of the 383? <HR></BLOCKQUOTE>

This is a good point to bring up. According to Keith Black, you absolutely want to avoid a quench height between .060" and .120". In this range the quench area starts to act like it own combustion chamber and is a detonation nightmare. Above .120" there is no more quench area and the entire cylinder diameter acts like a single combustion chamber. Less than .060" and there will be a quench effect that actually cools parts of the combustion chamber and increases resistance to detonation (a very good thing).

9.4:1 is hard to get in a 383 unless you use a piston with a big dish or heads with large 76cc combustion chambers. Are you absolutely certain you are using 350 heads and not 305 heads? LG-4 engines are 305's and they have like 58cc combustion chambers - we're talking about 12:1 compression if you put these heads on a 383 with a flat top piston.

Have you done a cranking compression test yet? Anything above about 200 psi is likely to have detonation problems no matter how good or bad the factory ECU carb setup is working.
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post #12 of 19 (permalink) Old Sep 15th, 02, 05:53 PM Thread Starter
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I know they are flat tops with 4 vf, and the heads are 76cc '92 Truck castings.


I used 5.7 rods.

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-'70 El Camino 454 RAT

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post #13 of 19 (permalink) Old Sep 16th, 02, 12:24 PM
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I'm sure you changed Harmonic ballancer when you did the 383, did you change timing cover to match. There are two timing tab types, one at the 12:30 position and one at about 2:00 both require different marks on the ballancer, I've found them to be about 30^ apart. With the front pulley removed you'll be able to feel (maybe see) the keyway in the ballancer. if the timing on the ballancer is close to the keyway then the timing tab should be at the 2:00 position. if the mark is about .75", then the 12:30 position is correct.
Good luck
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Another way to verrify would be to get a tdc checker (screws into plug hole) and verrify mark line up
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post #14 of 19 (permalink) Old Sep 16th, 02, 01:47 PM Thread Starter
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.....

[ 01-26-2005, 05:27 AM: Message edited by: BlueRebl ]

-Cable<br /><br />'75 Datsun 280z mild 383/TH350 swap (blew the 383)<br />'99 Grand Prix GTP (3.4" pulley swap)<br /><br />New SBC Motor: In Progess<br /><br /><a href="
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
target="_blank">-280z Info & Pics</a><br /><br />"He who dies with the most toys....still dies..."
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post #15 of 19 (permalink) Old Sep 16th, 02, 02:33 PM
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Has the outer ring on your balancer slipped by any chance. Have you verified that when the mark on the balancer is lined up with the 0 mark on the timing cover, the #1 piston is on TDC.
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