81 computer. cam suggestions?
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81 computer. cam suggestions?
im rebuilding an 81 for a fella my father works with and I cannot get him to remove the electronic type carb and dizzy so I was wondering what cams would work best on this set up? im open for suggestions. also, he wants to use the original heads(ughh) so the compression will still be like 8.2 or whatever it is. can I run flat top pistons as opposed to the factory dished pistons and get away with it?
Burning Brakes
Joined: Apr 2013
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From: Castle Rock CO
Without major adjustments to everything else you can install a mild cam with stock everything else to get the engine to breath a little more and have slightly higher lift in the valves. Such as this one at summit racing. A stage one cam will provide more performance while keeping everything else close to stock. It is when you go into higher stage performance parts that you need to replace the intake manifold, carb and go to headers.
You would accually want to go to Dome Pistions to increase compression with stock heads but you will have to do the research some require boring the piston walls
The L48 engines are able to be modified but going into high compression they need the 4 bolt main of the L82 engines.
http://www.summitracing.com/search?k...0pistons&dds=1
http://www.summitracing.com/parts/cro-00462/overview/
You would accually want to go to Dome Pistions to increase compression with stock heads but you will have to do the research some require boring the piston walls
The L48 engines are able to be modified but going into high compression they need the 4 bolt main of the L82 engines.
http://www.summitracing.com/search?k...0pistons&dds=1
http://www.summitracing.com/parts/cro-00462/overview/
Last edited by MakoJoe; Jun 29, 2013 at 12:26 AM.
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thanks for the advice. I will most likely stick with a comp cam as I have built many a strong sbf without a problem with them. im happy to know I can do something with the engine since in stock form it is a gutless wonder. do you have any comp cam suggestions? I was looking at the extreme 4x4 line since they should make good man vac
or like an xe262h or the 4x4 X4262h? the only difference between these two is higher exhaust lift ijust need a little bit of cam music out of it or im going to feel like im wronging this vette build.
or like an xe262h or the 4x4 X4262h? the only difference between these two is higher exhaust lift ijust need a little bit of cam music out of it or im going to feel like im wronging this vette build.
Last edited by 81vettehelp; Jun 29, 2013 at 12:39 AM.
Race Director
Joined: Jan 2000
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From: San Jose CA
I'd probably go with a 112 LSA cam, not a 110 LSA, it'll help the computer out with figuring out the idle.
I'd also keep duration under 220, especially if you're not raising the CR. Try to get CR to at least 9:1.
If you're sticking with stock heads, don't worry about a 4 bolt main. The 2 bolt will hold up just fine. This thing will likely not pull much past 5k anyways.
I'd also keep duration under 220, especially if you're not raising the CR. Try to get CR to at least 9:1.
If you're sticking with stock heads, don't worry about a 4 bolt main. The 2 bolt will hold up just fine. This thing will likely not pull much past 5k anyways.
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
You can use flat-top pistons with no problems. They should get you up to about the 9:1 CR that shark Racer mentioned. Here's a cam that should have a little more oomph than the stock cam, shouldn't overpower the computer, has old-skool ramps that should break in nicely, and won't break the bank:
http://www.summitracing.com/parts/sum-k1102/overview/
It won't be a dragstrip terror, but it should at least be able to get out of it's own way. You could maybe even go up to the k1103 cam, it's just big enough to give a little rumpity-rump to the idle, I don't know if the computer would like it, though.
Scott
http://www.summitracing.com/parts/sum-k1102/overview/
It won't be a dragstrip terror, but it should at least be able to get out of it's own way. You could maybe even go up to the k1103 cam, it's just big enough to give a little rumpity-rump to the idle, I don't know if the computer would like it, though.
Scott
Last edited by scottyp99; Jun 29, 2013 at 12:58 AM.
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220 duration huh? jeez you cant get any lift out of these babies can you. LSA? lobe separation is that what this means?
im going to run it with flat tops. I wish I felt comfortable with dome pistons but I just don't care for the flame travel efficiency of dome pistons. iv always just used good heads except im not allowed to on this build. what kind of a cam runs less than 220 duration?
im going to run it with flat tops. I wish I felt comfortable with dome pistons but I just don't care for the flame travel efficiency of dome pistons. iv always just used good heads except im not allowed to on this build. what kind of a cam runs less than 220 duration?
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You can use flat-top pistons with no problems. They should get you up to about the 9:1 CR that shark Racer mentioned. Here's a cam that should have a little more oomph than the stock cam, shouldn't overpower the computer, has old-skool ramps that should break in nicely, and won't break the bank:
http://www.summitracing.com/parts/sum-k1102/overview/
It won't be a dragstrip terror, but it should at least be able to get out of it's own way. You could maybe even go up to the k1103 cam, it's just big enough to give a little rumpity-rump to the idle, I don't know if the computer would like it, though.
Scott
http://www.summitracing.com/parts/sum-k1102/overview/
It won't be a dragstrip terror, but it should at least be able to get out of it's own way. You could maybe even go up to the k1103 cam, it's just big enough to give a little rumpity-rump to the idle, I don't know if the computer would like it, though.
Scott
I realize this car wont be all that spunky especially with the auto but I just would like to get a little sound if not something different for the guy as he is on dialysis and has a broken leg currently.
I appreciate the responses I just personally feel the most comfortable with the comp line
Race Director
Joined: Jan 2000
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From: San Jose CA
220 duration huh? jeez you cant get any lift out of these babies can you. LSA? lobe separation is that what this means?
im going to run it with flat tops. I wish I felt comfortable with dome pistons but I just don't care for the flame travel efficiency of dome pistons. iv always just used good heads except im not allowed to on this build. what kind of a cam runs less than 220 duration?
im going to run it with flat tops. I wish I felt comfortable with dome pistons but I just don't care for the flame travel efficiency of dome pistons. iv always just used good heads except im not allowed to on this build. what kind of a cam runs less than 220 duration?
You can put a giant cam in if you want, but you're limited to the stock heads so there's not a lot of point. I'd go with the K1102 Scotty recommended.
If you were going up on heads and intake, along with static CR, I'd say to go up more on cam. Throwing a big cam at heads that can't support it is a recipe for disappointment.
If you can get the XE262H ground on a 112LSA you'd probably be OK. I'd rather run a smaller cam given the heads frankly suck.
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Lots of cams do. The 500 hp LS7 engine runs a 211/230.
You can put a giant cam in if you want, but you're limited to the stock heads so there's not a lot of point. I'd go with the K1102 Scotty recommended.
If you were going up on heads and intake, along with static CR, I'd say to go up more on cam. Throwing a big cam at heads that can't support it is a recipe for disappointment.
If you can get the XE262H ground on a 112LSA you'd probably be OK. I'd rather run a smaller cam given the heads frankly suck.
You can put a giant cam in if you want, but you're limited to the stock heads so there's not a lot of point. I'd go with the K1102 Scotty recommended.
If you were going up on heads and intake, along with static CR, I'd say to go up more on cam. Throwing a big cam at heads that can't support it is a recipe for disappointment.
If you can get the XE262H ground on a 112LSA you'd probably be OK. I'd rather run a smaller cam given the heads frankly suck.
mild ford cams and mild chevy cams must be different. I run a cam in my 289 with 11 to1 at something like 498 lift. iv always considered this mild.
im obviously chevy ignorant. I didn't think the cams I listed were big enough to bleed off enough compression at low rpm to be a problem.
if neither of these cams have a chance at working I guess il just go with the stock cam as id rather be sure it runs well since the vette engine bay is pretty tight and id rather not have to change things.
Last edited by 81vettehelp; Jun 29, 2013 at 09:50 AM.
Melting Slicks
Joined: Apr 2001
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From: Lubbock Texas
You can also have the heads milled to reduce the size of the combustion chambers.
DC
Team Owner
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From: Crossville TN
It is apparent that you really don't want to do what the car's owner wants you to do (with his car!). You obviously have lots of knowledge about getting more power out of a SBC engine.
What you must understand is that he doesn't really care about power...he wants his engine refreshed. Why not try to do what he wants for his car so that he will be pleased with it?
What you must understand is that he doesn't really care about power...he wants his engine refreshed. Why not try to do what he wants for his car so that he will be pleased with it?
Race Director
Joined: Jan 2000
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From: San Jose CA
we can all agree that these heads are aweful with 76 combustion chambers and poor flow rates , but unfortunately iv been instructed to reuse these heads
mild ford cams and mild chevy cams must be different. I run a cam in my 289 with 11 to1 at something like 498 lift. iv always considered this mild.
im obviously chevy ignorant. I didn't think the cams I listed were big enough to bleed off enough compression at low rpm to be a problem.
if neither of these cams have a chance at working I guess il just go with the stock cam as id rather be sure it runs well since the vette engine bay is pretty tight and id rather not have to change things.
mild ford cams and mild chevy cams must be different. I run a cam in my 289 with 11 to1 at something like 498 lift. iv always considered this mild.
im obviously chevy ignorant. I didn't think the cams I listed were big enough to bleed off enough compression at low rpm to be a problem.
if neither of these cams have a chance at working I guess il just go with the stock cam as id rather be sure it runs well since the vette engine bay is pretty tight and id rather not have to change things.
And yes, as mentioned you could port the heads and that would help a little.
These engines are actually quite fun with the stock heads and cam, as long as they're in good tune. Around town they scoot pretty well, they just run out of steam around 3500-4k.
7T1Vette's point is pretty spot on as well.
Melting Slicks
Joined: Dec 2004
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From: Palo Alto CA
Why in God's name is anybody letting you rebuild their engine?
-TJ
Race Director
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From: Scottsdale Arizona
When selecting a cam for an 81 you have to be very cognoscent of the computer system, as it's very primitive and easy to upset. Lift doesn't bother it, nor compression. The whole system works well with increased flow too. You have to be careful with duration and overlap will kill you. If you get it wrong, the carb will fight the cam and it'll run worse than it did before the rebuild. It'll also throw codes and fail smog.
Last edited by CA-Legal-Vette; Jun 29, 2013 at 09:01 PM.
Burning Brakes
Joined: Aug 2006
Posts: 1,058
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From: Eastern North Carolina
When I rebuilt my 81 I put in Flat top pistons and went with a Melling MTC-1 cam which is very close to the Summit 1102. Motor is much stronger then stock and very smooth. I did change the junk 624 heads to a set of modified 487x Early 70's chevy heads, true dual exhaust and headers.
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
Yes, your 11:1 289 is going to like a big cam. An 8:1 350 will not, especially with the 2.87 diff gear and the stock converter. And, too big of a cam will make the crude, ancient computer puke. It only has Read Only Memory, you can't program it. You have to deal with it's parameters, or chuck it, one or the other. Also, IMHO, a Comp Cams cam is a waste of money on a build at this level, the summit K1102 will do just fine, and save some coin.
So, here's my advice: flat top pistons, Summit k1102 cam, pocket port the stock heads. Take it or leave it. If the guy complains that it doesn't make that much more power, say "I tried, but you wouldn't let me."
Have you thought about just telling the guy that the heads are cracked between the middle exhaust ports, and he needs new ones? I know, I know, it's dishonest, but ya know, the greater good, and all that?
Scott
Last edited by scottyp99; Jun 29, 2013 at 07:56 PM.
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anywho thanks for the replies. I ended up going with flat top pistons and the stock cam is being sent with the kit but I plan to upgrade it.
im not trying to do anything he didn't want. originally he told me he wanted 300 ponies out of it, but obviously he is dreaming with this stock head design and with keeping the system. . .
like everything in life, you get what you pay for.
Burning Brakes
Joined: Apr 2013
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From: Castle Rock CO
your not all too friendly. I mentioned earlier lobe separation, then it was referred to as LSA by another individual. where I live we just refer to it as lobe separation as in Lobe Seperation Angle.
anywho thanks for the replies. I ended up going with flat top pistons and the stock cam is being sent with the kit but I plan to upgrade it.
im not trying to do anything he didn't want. originally he told me he wanted 300 ponies out of it, but obviously he is dreaming with this stock head design and with keeping the system. . .
like everything in life, you get what you pay for.
anywho thanks for the replies. I ended up going with flat top pistons and the stock cam is being sent with the kit but I plan to upgrade it.
im not trying to do anything he didn't want. originally he told me he wanted 300 ponies out of it, but obviously he is dreaming with this stock head design and with keeping the system. . .
like everything in life, you get what you pay for.
The 383 Stroker Kits are from different manufactures and can be priced from between $600 to $1000 bucks depending on the kit and who is the manufacture.