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Old 02-20-2013, 08:10 PM
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ggevaert ggevaert is offline
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Timing/Carb

Hi,

F-BIRD'88, Idle timing is rock solid. Interesting about the vacuum, i thought that was odd but attributed it to the cam and low idle RPM; I will have to review the cylinders if any are missing; not sure. (i'm rather hard of hearing so I need to use alternate methods to investigate those types of things, any suggestions?). I did check for vacuum leaks with propane and none were found. I will hookup the wideband AFR this weekend.

Using a Quickfuel SS 680VS with pri and sec idle air bleeds changed from stock 70's to 74's. (as recommended by quickfuel when I provided them with the engine specs). The high speed air bleeds were left alone and are 28/28.
Everything else on Quickfuel was also left alone (primary main jet 68, Secondary jet 78, pri nozzle 31, needle and seat 110, power valve 6.5). As I got through my carb dialin I will be reviewing each of these to ensure they are the correct setup for my application.

I actually bought a wideband AFR electronic setup that I have not yet hooked up. Was planning to get basics on engine done then go back over the setup with it on. Never used one before so need to learn how.

cobalt327, I understand; At the beginning of this timing exercise I started at 18 degrees initial with an advance stop of 18 degrees (which was working well) but I decided to go higher to see how that would look. Hence my original question as I was trying to understand the reasoning for why we set initial timing where we do and why we stop where we do. I did increase the timing 2 degrees at a time from there, every time checking for starter issues or detonation and found none all the way to 24. I stopped there for no reason other than I was worried about going higher. Also, keep in mind that I have not been able to take the truck for a drive as I have no windshield in it yet (and its 20 below out here) so my only load testing has been with my foot on the brake and with a chock block on the wheels.

Vacuum can is the stock MSD one, it has a vacuum advance stop plate installed and set to 13 degrees; with the vacuum hooked up, at idle my timing was 30 (so +6 from initial) and at all in (3000 rpm) it ran at 42. Keep in mind that was at idle and not under load.

Mine is a GM HEI so the article you note is very relevant and, yes, I did read it thorougly.

I do plan on adjusting the idle mixture screws; that is the plan this weekend; I just wanted to get timing done before going there. (but I do understand it sometimes is not a linear exercise; you think everything is set, take it for a drive and end up re-adjusting everything ) but that's the fun part.

Cheers

Last edited by ggevaert; 02-20-2013 at 08:19 PM.
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