Lost My Lope
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Racer
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From: Bishop CA
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
your base timing is ok and the car would certainly run with that setting, some people like it higher but you are in the range of operating properly for sure.....with the vacuum canister disconnected does it have the idle you want? i don't know any thing about those multi spark units but i could see where that could smooth out things.
the only thing i can think of is that the new HEI unit had the vacuum canister swapped out so that it is pulling in full vacuum advance at a lower " of mercury.....i did this on my engine on purpose.....can you give us the numbers off the vacuum cannister and we can see if someone changed it from stock. these cannisters are about $18 from napa and are easy to swap
the only thing i can think of is that the new HEI unit had the vacuum canister swapped out so that it is pulling in full vacuum advance at a lower " of mercury.....i did this on my engine on purpose.....can you give us the numbers off the vacuum cannister and we can see if someone changed it from stock. these cannisters are about $18 from napa and are easy to swap
Le Mans Master
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From: Seattle Area WA
Bob, he has an adjustable vacuum can in it so he can set it where he wants.
Not much info availble for an old Viking cam, 100H No. 112061 290 adv. 224@.050 .447 lift, Fair idle amd I think its a 114 LSA with a 109 ICL so it looks like a copy or very similar to a GM "151" cam with good idle at 800 RPM.
Compare that to a more radical 224 @ .050" Comp 270 magnum with 270 degrees advertised.
I'd still set it at 36 @ 3,000 and see how it runs. My "151" has a slight lope to it but I have 10.25:1 and its very noticeable.
Not much info availble for an old Viking cam, 100H No. 112061 290 adv. 224@.050 .447 lift, Fair idle amd I think its a 114 LSA with a 109 ICL so it looks like a copy or very similar to a GM "151" cam with good idle at 800 RPM.
Compare that to a more radical 224 @ .050" Comp 270 magnum with 270 degrees advertised.
I'd still set it at 36 @ 3,000 and see how it runs. My "151" has a slight lope to it but I have 10.25:1 and its very noticeable.
Last edited by Scott Marzahl; Jul 3, 2011 at 05:09 PM.
Le Mans Master
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From: Glen Allen, VA
When I adjusted the timing curve on mine, it definitely took some lope out of the cam, which I didn't like, but since the timing comes in faster, I like the tradeoff, it's much more responsive and faster now.
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Racer
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From: Bishop CA
How do you tell if a HEI is a multi spark. Thanks for your help Scott, everything you said today was helpful and made sense. Happy 4TH
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
ok i missed that in the first couple of posts.....Scott i am on the same page as you.....i think the advance is coming in earlier now then it did before and the advanced timing is smoothing out the idle.....i wonder if he put the cannistor to ported vacuum if it would give him his lope back?
Last edited by bobs77vet; Jul 3, 2011 at 09:41 PM.
Thread Starter
Racer
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From: Bishop CA
ok i missed that in the first couple of posts.....Scott i am on the same page as you.....i think the advance is coming in earlier now then it did before and the advanced timing is smoothing out the idle.....i wonder if he put the cannistor to ported vacuum if it would give him his lope back?
Thread Starter
Racer
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From: Bishop CA
If I have an adjustable vacuum can does that take the place of putting in a curve kit, springs and weights?
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Le Mans Master
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From: Oxford MA-----You just lost the game!!!!
Curve kit, springs and weights affect mechanical advance, vacuum can affects vacuum advance, two separate systems. Do yourself a favor and read this thread, it should get ya headed in the right direction.
http://forums.corvetteforum.com/c3-t...long-post.html
Scott
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
there are three types of timing....base. mechanical and vacuum...
and they work sometimes together and sometimes not together....the base is always there and the mechanical caused by weights and springs comes in based on rpm...the weights get thrown out by spinning and the springs slow down the centrifugal force outwards.
the vacuum comes in when there is no load.....so when you stomp on it the vacuum drops and the vacuum advance cuts out....this allows the engine to run on a higher level of advacne under a no load situation like cruising down the highway....while allowing just the right amount under a load situation....clear as mud eh
Le Mans Master
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From: Seattle Area WA
Nope. Since it has an adjustable can it may already be set up for a faster curve. If you can back off (turn) the distributor so that you are 36 degrees at 3K your weights and springs are fine. The can brings in more advance with vacuum.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
i tossed my adjustable cannister and went with a fixed unit, it is possible to hook a mity vac up to the vacuum cannister and to measure exactly what it is doing....this may help in figuring out the puzzle.....i did it with mine then tossed the adjustable one for a fixed one
i would probably like to know exactly how much vaccum advance i was getting
i would probably like to know exactly how much vaccum advance i was getting
Last edited by bobs77vet; Jul 3, 2011 at 10:18 PM.
Le Mans Master
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From: Oxford MA-----You just lost the game!!!!
i tossed my adjustable cannister and went with a fixed unit, it is possible to hook a mity vac up to the vacuum cannister and to measure exactly what it is doing....this may help in figuring out the puzzle.....i did it with mine then tossed the adjustable one for a fixed one
i would probably like to know exactly how much vaccum advance i was getting
i would probably like to know exactly how much vaccum advance i was getting
Scott
Le Mans Master
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From: Livonia MI
Hard to tell, as the technologies been around for awhile, and like many modern electronics, dirt cheap now, so most modules probably have it. Only a few lighter pulses before/after the main spark at low rpm to help with emissions/idle quality, so hard to pick up with a timing light. If a newer module, could be what you've got though.