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Old 09-17-2010, 10:02 PM
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replaced intake gasket, now wont idle

Ok i replaced my intake gasket because of an oil leak. Put everything back together, dropped the dizzy back in as it was (so i think). Got it running...but just wasnt running up to what it was it seemed. So i got to playing around and turned the fuel pressure up a little to much and got a back fire out of the carb. Well i took the carb apart and replaced the power valve and an already partialy broken metering block baffle. I put everything back together and now it will only run under a lot of throttle and is having some backfiring out of the exhaust. I could play with the timing some ( i dont have a timing tab..i know i need one :/ ) and that got it to some what idle but still not completely and very rough and a lot of backfiring out of ehxuast when it was running. I dont really know what to do. Should i go ahead and re-set the timing as that could be the problem? Could i have created another problem within my carb my fixing another? Also my main problem come to find out was a vacuum leak which is fixed. Any help is greatley appreciated!

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Old 09-17-2010, 10:11 PM
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going to put my 2 cents in...and if i am wrong someone will correct me, but you could also have a misfire somewhere. along with a few other things, but the exhaust backfire to me sounds like the first thing to check out since you did mess with the dizzy.
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Old 09-17-2010, 10:21 PM
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first things first, to get good responses we need good information. Tell us what engine this is. and second thing get a damned timing tab and set the timing then come back if you have problems
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Old 09-18-2010, 01:22 AM
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X2 on the Timing Tab ^^^. And make sure you didn't screw up the plug wire locations >> http://www.chevytech.com/1c10o1.html if this is the SBC400 in your Camaro.
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Old 09-18-2010, 06:29 AM
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Quote:
Originally Posted by blue400
Ok i replaced my intake gasket because of an oil leak. Put everything back together, dropped the dizzy back in as it was (so i think). Got it running...but just wasnt running up to what it was it seemed. So i got to playing around and turned the fuel pressure up a little to much and got a back fire out of the carb. Well i took the carb apart and replaced the power valve and an already partialy broken metering block baffle. I put everything back together and now it will only run under a lot of throttle and is having some backfiring out of the exhaust. I could play with the timing some ( i dont have a timing tab..i know i need one :/ ) and that got it to some what idle but still not completely and very rough and a lot of backfiring out of ehxuast when it was running. I dont really know what to do. Should i go ahead and re-set the timing as that could be the problem? Could i have created another problem within my carb my fixing another? Also my main problem come to find out was a vacuum leak which is fixed. Any help is greatley appreciated!
The first thing I would do is get the timing straightened out. You need a tab- either make one or buy one, but you have to have a reference for TDC in order to proceed.

There are several different dampers. Both the diameters and the placement of the line on the outer ring of the damper can differ. So you need to know what you have, to know what tab to use.

The three most common locations for the timing mark on the damper:

The pre-'69 damper has the TDC mark 2 before the keyway centerline, seen in the ID of the damper (or to the left, looking at the front of the engine).

The damper used from '69 to mid-80's is 10 before the keyway. You'll find that aftermarket dampers are the 10 type, as are the bolt-on tabs sold in the aftermarket, unless they're adjustable.

The third timing mark was used from about 1978 to about 1991-'92. It is 40 before the keyway. This damper uses a timing cover that has the tab at about the 12 o'clock position.

If you're unsure, or just want to check the accuracy of the tab/mark for TDC, DETERMINE TDC and MAKE A TIMING TAPE will help you to see for yourself.
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Old 09-18-2010, 03:54 PM
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Ok i put a timing tab on. Got the timing set to run it atleast should run decent. Now its backfiring out of the carb and wont really even start. So the only way to get it to even start was to have it pretty advanced. I put a 6.5 power valve in it when replaced the rear metering baffle and that was it. Im having a small leak from what almost seems to be the accellerator pump at the back of the carb. Im hoping i havent ruined another power valve because i had a backfire out of the carb that caught fire.
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Old 09-18-2010, 05:58 PM
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Did you verify TDC.
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Old 09-18-2010, 08:16 PM
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Sure did. I got all of the timing issues worked out. Right now it will only idle around 1500 and is around 8 degrees of timing. But the idle wants to flucuate like there is a vacuum leak but i am almost certain there is not. Its gotten a lot better...especially with the backfiring..but still isnt idling quite correctly. It seems to get it to run correctly im having to advance the timing to much almost. If it is idling at 1500 around where should the timing be?
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Old 09-18-2010, 10:31 PM
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Pretty much where should i be with timing and with what rpm idle. For the record i have this cam http://www.summitracing.com/parts/SUM-1108/ . World product sportsman 2 heads. 750 holley double pumper. 5 speed and 3.23 gears.
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Old 09-19-2010, 12:10 AM
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1500rpm and that cam I would expect to see the need to have the timing at that point partially into the curve and in the 22-26 range, but unless you have modified the distributor for performance use this will likely result in too much total timing at rpms above that point. Timing for that cam should be set up with 16-22 @ 950-1000 rpm idle, with 34-38 total timing all in by 3000 rpm. You will have to recurve the distributor, and shorten its amount of mechanical advance travel to accomplish this.

You are doing your checking and setting with the vacuum advance unhooked from the distributor, and plugged...correct??

Backfire through the intake is a sign of retarded timing.
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Old 09-19-2010, 10:13 AM
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Iv got it just about right now. Timing was the issue. Ill have to look into recurving the distributor. Yes im doing it with the vacuum advance plugged. Right now I just have an HEI distributor with an MSD coil. This is my first carbureted car so im learning along the way. Thanks for the help.
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