GM distributor recurve with adjustable vacuum advance
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- Опубликовано: 10 фев 2018
- I recurved the distributor in the Formula's 400 Pontiac engine. The factory mechanical curve was limited and I wanted a more performance oriented advance curve in the distributor. I use a Moroso mechanical curve kit and an Accel adjustable vacuum canister to set the curve I desired.
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This video helped me understand how the timing works. Great job.
Thanks! I'll be setting up a '70 Trans Am with the RAIII 400 using this information.
@@SPSteve I run 91 Octane and add octane boost. I also put lead substitute which I'm not sure that I need.
Why not limit mechanical advance to around 10° and put say 26° initial timing on the crank for around 36° for better snappier performance down low?
A good chance the starter motor may not like that. Depending on the engine it may also gas ping. One thing for sure- one size don't fit all. What you suggested WILL work well on many combinations👍
Thanks Steve! I've probably watched this video about 4 times. This a really good demonstration showing all the advance numbers with and without vacuum, and a good before and after result. I just bought an adjustable canister for my HEI, hopefully I can get my timing curve closer to yours for my chevy 283. Also I found a very good article online that discusses all of what you just demonstrated. In case anyone is chasing the same issues I included the link. Thanks for sharing, it is very helpful to watch.
outintheshop.com/faq/hei.htm
@@SPSteve It was very useful. My mechanical is right at 34 all in but my base is still high at about 17. Under full vacuum I'm at about 49. I think I'm getting close. At idle with full manifold it's a little above 30. I have yet to play with the mechanical and springs but from what you have shown I can fix that. The problem I'm facing right now is that when I put it into D or R the engine just stalls out and dies. It will not idle in gear which is really weird being that it's supposed to be a 1900-2200 stall converter. It's a bit of a hot cam and I have yet to really dial the idle mix with a my vacuum gauge. Also it runs up hot pretty quick. I wish I had 4 speed manual instead. I may have carb issues, I may have trans issues, hard to tell but it fires up right away, pulls hard under part throttle. I haven't given the it beans full rpm yet I just rebuilt this 283 but it sounds very strong. Sorry for the rant, thanks for the response.
Question... I am getting 20* from my vacuum can. It is adjustable type but changes nothing. could the diaphram still be good since it changes, but the adjustment part be bad? If I get a new one should I set it to give about 12/14? you did not talk about the adjustment you did to that after installing your new can.
Maybe a vacuum leak?Hate it when people wont reply. Like RUclips is so hard to interact with on smart phones. If ya maKe a video, ANSWER QUESTIONS!!!
I had a question but it looks like this person doesn't give a s*** anymore so I'll never watch it again. There's plenty of other people who care more out there to have better videos
Good vid ! I performed a full rebuild on my pontiac hei, and curved best i could for my 70 formula 400 with 13 iron heads. Still have a bit more fine tuning to do.
Have you had to shim up your distributor gear ?
SP Steve yea it is !
I think i recall to have about .060" or 0.075" of free play in mine.
I bought a shim kit for Hei's on ebay and shimmed it up, only have .020/.025 now.
What's the specs on your curve now ?
Do still get pinging ?
Every 10,000'ths of slop can mean around 1.2 degrees off on your timing, I shim mine to 15,000'ths.
Great video. I just bought an Innova light and really like it. Is yours holding up well so far?
Since your vacuum canister is not dropping off, how do you have the vacuum line hooked up. I also noticed the new looking tower clamp on your heater hose.. where did you get it? Thanks, great video
It's not supposed to be on manifold vacuum that advances way too much at idle why would you want that it's supposed to advance under real small part throttle to enhance drivability and fuel milage but at idle it should not make any difference most don't even use it idk I've never set mine up that way and I've seen only very very few cars that actually use manifold vacuum for it and none were GM's especially not pontiac
interesting; i didnt know about adjustable vacuum cannister, do you think there's a sort of universal application? lets say with some modification
it will fit other distributors?
The only adjustment is how much it advances not when smh I'm in total disagreement w hooking it to manifold vacuum it's gonna back off on the advance on part throttle and not advance it
@@glennmanchester1568 For the most part I agree with your statement regarding the ported vacuum source but one size don't fit all.👍Actually, the adjustment of the vacuum can with an allen wrench affects how much vacuum is required to activate it but not the amount of advance. There are units that have the total amount of advance adjustment, too, though.
@@mickangio16 My Rover V8 (Buick 215) needs like 30* at idle to run its smoothest, vacuum at 12-13 (with intake 280, exhaust 290 cam, intake max lift at 106.5*). If I put this timing in static it will be hard to start, solution is to use adjustable vacuum advance to achieve the 30* idle.
Very similar setup to the one in this excellent video.
As a matter of fact when you have it on manifold vacuum under part throttle load it actually backs off the timing when vacuum drops a bit so your loosing power de tuning it's not the way it should be check out all the videos on the subject anyone so I can be taught cuz maybe I'm wrong actually uncle tony's garage has a perfect demonstration of what I just said he does it in real time driving the car and shows it actually backs off on the advance on part throttle instead of advancing like it should
OK I am lost. You had a initial of 16* and 14* of mechanical advance with the vacuum advance unplugged giving you 30*. Then you clearly had the vacuum advance hooked up to manifold vacuum when it went up to 35* at idle. So how did you end up with 49* when you revved up the engine? Shouldn't it take you back down to 30* as engine speed increases and vacuum decreases if you had it hooked up to full manifold vacuum???
The vacuum advance should not make any difference at idle it should be hooked to ported vacuum if it does anything it should be very little. At idle but the minute you give it a little gas it advances to give good throttle response and milage at very little throttle till the Rpms come up enough to take over
Vacuum advance works better on manifold vacuum or atleast always has for me. Ported vacuum was a 70s era emissions crutch.
Thanks for the.video I need to replace the canister on a pertronix unit that was based on that design
You had a really good spark from that light nice and steady if you had a irratic spark and a few times the light showed you BDC instead of say 10 degrees BTC what do you think 🤔 woukd cause that ? A faulty light ? Miss fire ? Cross fire from another plug / cylinder that happened to me a few times setting my timing not a good sight .
It woukd be flashing 10 BTC then i woukd see The opposite side of the balancer on the light
I've never had a situation where a timing light would change between BTDC and ATDC. Is your distributor loose and moving around?
@@SPSteve not that i know of its a fairly new unit. Engine rebuilt with only 3,000 mikes im thinking of buying a better timing light .
@@TheThirdWheel618 worth a try. Good tools are always worth the investment
Great video, thanks. I can’t seem to figure mine out, I set my timing the same way, but it pings like a bitch.
When you did the last one it's still too far advanced 48 is too much