along with excessive timing.
Initial timing with cam
Thread Starter
Racer
Joined: Apr 2012
Posts: 257
Likes: 0
My idle is set at 750, ported vacuum to the vac advance after much discussion with my engine builder. He insists thats how it was designes and how it should stay. I'm not convinced after reading Lars" papers so im totally confused on that one. The initial is now around 12.
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Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
If I were tuning it with that cam, I'd set it up for 18 initial, 36 total, with a 2800 rpm total advance curve. Then I'd customize a vacuum advance to produce about 12-14 degrees of vacuum advance and run it off manifold vacuum. This will give you about 30-32 degrees of timing at idle, which will make it run exceptionally well.
These engines were certainly not "designed" for ported vacuum. Nonsense. These engines were designed for full manifold vacuum, and were "Band-Aided" to pass emissions by eliminating the vacuum advance at idle in order to get the timing retarded far enough to get the emissions down. If your goal is to pass an emissions test, run ported vacuum. Obama will be proud of you.
Lars
These engines were certainly not "designed" for ported vacuum. Nonsense. These engines were designed for full manifold vacuum, and were "Band-Aided" to pass emissions by eliminating the vacuum advance at idle in order to get the timing retarded far enough to get the emissions down. If your goal is to pass an emissions test, run ported vacuum. Obama will be proud of you.
Lars
Le Mans Master
Joined: Oct 2010
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
Lars as usual is 100 percent correct, however as a side note i have never been convinced that retarding the timing actually " helped " emissions.it seems as thats what they thought,but if mileage and performance improve with advanced timing how can emissions increase too? an i hope obozo isn't happy.
Thread Starter
Racer
Joined: Apr 2012
Posts: 257
Likes: 0
Thanks so much for the reply Lars. If I go much ovevr the 12 initial I get detonation, by advancing my initial do I understand that I am advancing the total as well, past 36, the way I have it set up now? My total is 36 at 3k, should I use lighter springs? I'm still frustrated after spending a small fortune on this rebuild with someone that was supposed to set it up too. It does run pretty good now so I can't wait till it is set up right.
Oh ya, there is no emissions for cars over 25 years old in CT.
Thanks,
Mike
Oh ya, there is no emissions for cars over 25 years old in CT.
Thanks,
Mike
Last edited by VetteNURSE; May 9, 2013 at 02:45 PM.
Racer
Joined: Feb 2013
Posts: 386
Likes: 3
From: Clifton Virginia
Thanks so much for the reply Lars. If I go much ovevr the 12 initial I get detonation, by advancing my initial do I understand that I am advancing the total as well, past 36, the way I have it set up now? My total is 36 at 3k, should I use lighter springs? I'm still frustrated after spending a small fortune on this rebuild with someone that was supposed to set it up too. It does run pretty good now so I can't wait till it is set up right.
Oh ya, there is no emissions for cars over 25 years old in CT.
Thanks,
Mike
Oh ya, there is no emissions for cars over 25 years old in CT.
Thanks,
Mike
My mallory HEI gives out 22 degrees advance instead 14 degrees written in the instruction and specs so I'm in pursuit of purchasing a new adjustable canister.
I do not know the laws in CT but in Virginia, if you want regular plates instead antique, you will need to pass emissions even if your car is 25 years old. Also, if your car came with cat converter (post 74' cars), you will have to install a cat converter to pass emissions.
Last edited by jackwabbit703; May 9, 2013 at 05:35 PM.
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
Thanks so much for the reply Lars. If I go much ovevr the 12 initial I get detonation, by advancing my initial do I understand that I am advancing the total as well, past 36, the way I have it set up now? My total is 36 at 3k, should I use lighter springs? I'm still frustrated after spending a small fortune on this rebuild with someone that was supposed to set it up too. It does run pretty good now so I can't wait till it is set up right.
Oh ya, there is no emissions for cars over 25 years old in CT.
Thanks,
Mike
Oh ya, there is no emissions for cars over 25 years old in CT.
Thanks,
Mike
Scott
Racer
Joined: Apr 2007
Posts: 275
Likes: 1
From: Lafayette/marquez La/tx
Lars helped me a lot. I set up timing as he said. With no vac installed. Gave him my vac reading at idle and he hooked me up with a vac can they gave me the correct vac at cruise. With manifold vac. I set timing to 36 total ended up being 18 Initial hooked full vac 52 degrees @ 3000 rpm. It hauls butt now
Thread Starter
Racer
Joined: Apr 2012
Posts: 257
Likes: 0
OK so heres the update. This saturday I was going to get this if it took all day. I set the initial to 18 with advance plugged and I had all in 36 degrees at 3000rpm. I then used manifold vac instead of ported and WOW what a difference! the idle rpm went up but it got alot smoother in a hurry. I found that I had 20 degrees of vac ontop of my 18 degrees of initial. I then put on the vac adv limiter, ( ya its an MSD, sorry Lars) I set it to 14 wich gives me 32 degrees at idle. I was on a roll so I played with mechanical springs and got the all in 36 degrees to come down to 2500rpm. I then tuned in the carb, set idle and A/F to get the most vac, which BTW increased 30 percent!
Now it idles much smoother, still sounds lumpy but the car doesn't shake as much. And Lars, it does now run "exeptionally well". It has huge power and it will roast the tires, no hesitation at speed.
so now I'm wondering if the all in rpm of 2500 is too low, should I play with the springs to get it to 2800? Ya and I agree the motor guy is a knuckle head.
Thanks to everyone for the advice and double thanks to Lars for the #s he really is a tuning guru!!!
Mike
Now it idles much smoother, still sounds lumpy but the car doesn't shake as much. And Lars, it does now run "exeptionally well". It has huge power and it will roast the tires, no hesitation at speed.
so now I'm wondering if the all in rpm of 2500 is too low, should I play with the springs to get it to 2800? Ya and I agree the motor guy is a knuckle head.
Thanks to everyone for the advice and double thanks to Lars for the #s he really is a tuning guru!!!
Mike
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
OK so heres the update. This saturday I was going to get this if it took all day. I set the initial to 18 with advance plugged and I had all in 36 degrees at 3000rpm. I then used manifold vac instead of ported and WOW what a difference! the idle rpm went up but it got alot smoother in a hurry. I found that I had 20 degrees of vac ontop of my 18 degrees of initial. I then put on the vac adv limiter, ( ya its an MSD, sorry Lars) I set it to 14 wich gives me 32 degrees at idle. I was on a roll so I played with mechanical springs and got the all in 36 degrees to come down to 2500rpm. I then tuned in the carb, set idle and A/F to get the most vac, which BTW increased 30 percent!
Now it idles much smoother, still sounds lumpy but the car doesn't shake as much. And Lars, it does now run "exeptionally well". It has huge power and it will roast the tires, no hesitation at speed.
so now I'm wondering if the all in rpm of 2500 is too low, should I play with the springs to get it to 2800? Ya and I agree the motor guy is a knuckle head.
Thanks to everyone for the advice and double thanks to Lars for the #s he really is a tuning guru!!!
Mike
Now it idles much smoother, still sounds lumpy but the car doesn't shake as much. And Lars, it does now run "exeptionally well". It has huge power and it will roast the tires, no hesitation at speed.
so now I'm wondering if the all in rpm of 2500 is too low, should I play with the springs to get it to 2800? Ya and I agree the motor guy is a knuckle head.
Thanks to everyone for the advice and double thanks to Lars for the #s he really is a tuning guru!!!
Mike
Scott