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Discussion Starter #1
Alright, I've been through my carburetor a few times, and can't seem to get everything to work perfectly together, and can't find a vacuum leak.

So lets try checking my timing, I've got a mild 355 with flat top pistons with four reliefs, 99 vortec heads with a few thou milled off, where should I start with on my timing? do the vortecs like more or less timing than double humps?
 

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Is this a new engine install or did you just upgrade the heads, need some more info on your whole configuration would be great. Is the car not running right? You running HEI
or MSD, regardless, I always start at 8-10 Degrees to get the motor running and drive around. Then move the timing up till you get the best responce out of your engine and without overheating it of course.

Jeff G.
69 Hugger Orange RS/SS 396 Vert
69 Tuxedo Black RS/SS 454 Hardtop
 

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Discussion Starter #3
I built the motor about 3 months ago just haven't gotten the car to run right at all yet, it idles great and out of gear blipping the throttle response is great

I'm running an msd HEI

Alright, I'll set the timing at 8 deg and bump up to degrees at a time after that then?
 

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Can you measure total timing? Do you have a degreed balancer or good dialback light?

Vortecs will want less total timing than double humps. 32 degrees, maybe 34.

For a good idle and good off ifle response, you want more timing at idle. I'd run initial at least 14 degrees, possibly as much as 18.

To do this, you need to check your total timing and modify your mechanical advance to limit it and keep the total timing where it needs to be.
 

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Are you running vac. advance? Reason I ask is on my 383 w/vortecs I tried going w/o the vac cannister and engine reacted poorly whenever I'd stomp on it from a cruise rpm. Also found that 30-32 total worked well and if I went higher would equate to slightly poorer performance. I need to run an experiment with what Jim is saying (above) about going with more timing at idle and less being brought on in the dist. I currently have about 11 at idle and 20 in the dist. Also - what is your curve set up like in the dist. What RPM is all your timing being brought in by?
 

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Discussion Starter #6
I've been going back and forth on running the vacuum advance.

Alright, little bit of a lengthy update; sunday I reset the timing to about 20 deg initial, a bit radical but I figured what the hey, it seemed to run "okay" around the block, connected the vacuum advance and went to bed.

Drove her to work this morning (22 miles approx. each way) going uphill a few different times the A/F gauge leaned way out and the coolant temp gauge went up rather quickly, when I left work I pulled the vac advance and plugged the hose, seemed to run a little better, but I really couldnt tell (started to rain and there was one HECK of a wind today)

From what little knowledge I have I was thinking the uphill was either an indication of advance curve or secondaries not kicking in, I couldn't get any secondary springs today but I got the mr. gasket advance weight and spring kit.

When I pulled the distributor apart I broke one of the "towers" that the center plate presses onto, had to pull it apart and see what I could do, I ended up canibalizing a broken dizzy for that job, got her back together and selected the "medium silver" spring set initial timing at 17 degrees and went for a ride, not so good throttle response at all.

Gave it one more shot and selected the black spring and kept timing at 17 degrees barely got out of the driveway, popping out of the exhaust and NO throttle response...

I'm at my wits end with this thing. Nice looking car but a definate pain in my behind!
 

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I would say 17- 20 is too much. You really need to know how much total timing you're running and at what RPM it's all in by to have some idea where you are and make your next adjustments. The vac admance shouldn't be hurting you and possibly only if you already have way too much. Disconnecting is more for if you intend on strictly driving it with the pedal to the floor all the time and Qtr. mile racing it otherwise it's your engine's friend on the street. How's your air/fuel adustment? Did you cover that aspect already?
 

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I'm at my wits end with this thing. Nice looking car but a definate pain in my behind!
There is a long thrtead over about a week ...talking a guy thru setting up dizzy curve and VA...and inbetween sxplaining what and why.
The thread is about 3 or 4 weeks ago.
unless u understand how and why everything works and know the spedc of the dizzy and the adnance range and vac range of the VA, and the Vac ranges of the engine you are jusyt banging your head against a brick wall.
 
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