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Old 12-21-2007, 08:44 AM
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Chev Small Block Cam Question...

Hi Members,

I am rebuilding a 1970 Corvette LT-1 (350cu, 370hp) that I have owned for 20 years.

The block is original. I have refreshed the stock heads (2.02 & 1.60).

When I purchased the car, 20 years ago, it had a Chambers Max One camshaft in it.

I am considering changing it to either the originial Chev cam (P/N 3972182) or a cam from a Corvette, 327cu, 365/375 h.p.(P/N 3849346) that the specs seem to indicate has a bit more intake duration but a slightly different overlap.

I will be using the prescribed Holley 4555 carb on either a '69 Z28 Alum. HiRise intake manifold, or on a Chev. replacement 1970 LT-1 Alum. HiRise intake manifold.

Question - Which camshaft should I use? Which intake manifold should I use?

I would appreciate you thoughts on these questions and the basis in which you base your recommendations.

Also, do you have any recommendations as to where I can obtain those original, new camshafts?

Thank you,

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Old 12-21-2007, 08:59 AM
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moving this to the engine forum.
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Old 12-21-2007, 11:00 AM
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Quote:
Originally Posted by Corvette70LT-1
Hi Members,

I am rebuilding a 1970 Corvette LT-1 (350cu, 370hp) that I have owned for 20 years.

The block is original. I have refreshed the stock heads (2.02 & 1.60).

When I purchased the car, 20 years ago, it had a Chambers Max One camshaft in it.

I am considering changing it to either the originial Chev cam (P/N 3972182) or a cam from a Corvette, 327cu, 365/375 h.p.(P/N 3849346) that the specs seem to indicate has a bit more intake duration but a slightly different overlap.

I will be using the prescribed Holley 4555 carb on either a '69 Z28 Alum. HiRise intake manifold, or on a Chev. replacement 1970 LT-1 Alum. HiRise intake manifold.

Question - Which camshaft should I use? Which intake manifold should I use?

I would appreciate you thoughts on these questions and the basis in which you base your recommendations.

Also, do you have any recommendations as to where I can obtain those original, new camshafts?

Thank you,
Try Performance Chevrolet in Phoenix,AZ usually have good prices too, phone # is (602)254-9586
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Old 12-21-2007, 11:43 AM
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Quote:
Originally Posted by Corvette70LT-1
Hi Members,

I am rebuilding a 1970 Corvette LT-1 (350cu, 370hp) that I have owned for 20 years.

The block is original. I have refreshed the stock heads (2.02 & 1.60).

When I purchased the car, 20 years ago, it had a Chambers Max One camshaft in it.

I am considering changing it to either the originial Chev cam (P/N 3972182) or a cam from a Corvette, 327cu, 365/375 h.p.(P/N 3849346) that the specs seem to indicate has a bit more intake duration but a slightly different overlap.

I will be using the prescribed Holley 4555 carb on either a '69 Z28 Alum. HiRise intake manifold, or on a Chev. replacement 1970 LT-1 Alum. HiRise intake manifold.

Question - Which camshaft should I use? Which intake manifold should I use?

I would appreciate you thoughts on these questions and the basis in which you base your recommendations.

Also, do you have any recommendations as to where I can obtain those original, new camshafts?

Thank you,
The Chevy 1970 LT-1 intake is a very nice piece.

I know nothing about the Chambers cam, but if your happy with it and it doesn't exhibit wear, I be tempted to stick with it. The factory cams tend to be quite rampy so out if their apparent long durations, when measured from .050 lift really are fairly mild. Lobe Separation Angle (LSA) greatly influences idle and manifold vacuum. Long LSAs say 112 degrees and up tend to reduce over lap which improves idle quality and manifold vacuum. Short LSAs under 112 increase overlap giving the engine more of a staccato idle and reduces manifold vacuum. These are easier to live with when the car has a manual transmission and no vacuum assisted brake. Long LSAs tend to boost bottom end torque, which is good with an automatic and can be well used to get more duration and lift into the cam without forcing a high stall converter into the equation. The LT4 Gen II HOT cam is an excellent example
of this where you have pretty aggressive lobes but overall a decent idle, high manifold vacuum with high torque and a pretty darn good top end.

Bogie

Last edited by oldbogie; 12-21-2007 at 02:25 PM.
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Old 12-21-2007, 02:18 PM
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I have an LT-1 In my '68 Vette. My machinist ordered an LT-1 cam from Dema Elgin at Elgin Cams. It' a duplicate of the original although probably more true to the design specs. It idles at 800 RPM with 16.5 inches of vacuum. The specs on this cam are 316/336 at lash point and 242/254 at .050. Lift at the valve is .459/.485 and LSA is 116. Like Bogie says this wide lobe seperation angle makes for better manners at idle. My vette has an M-21 with a 3.70 axle and this cam works well with that set up. It can pull up a rather steep grade in 4th at 1200 RPM with no bucks, shudders or clatters. Cruise vacuum is about 25 inches and I have to really get on it to drop the vacuum below 8 inches.
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Old 12-21-2007, 02:38 PM
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The two intakes you mention are identical. I am running a 9.5:1 350 with the 182 cam and the Z-28 Intake. Not a bad cam, a little lazy, but has a nice choppy idle.

tom
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Old 12-21-2007, 05:23 PM
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Duplicate Cams

All the big name Cam companies make Duplicates of the LTI/L79/Z28 cam and other muscle car cams. Comp, Crane, Elgin etc. There easy to find now. Comps Part # for GM3849346-LTI/L79/Z28 is 12-107-3 and some others for 302-350ci / 300-350HP cams are 12-105-3, 12-106-3.

Last edited by SSedan64; 12-21-2007 at 05:24 PM. Reason: spelling
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Old 12-21-2007, 06:11 PM
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You seem to be lumping the LT-1,L-79 & Z-28 together as if the cams are the same.
This is incorrect. The L-79 is hydraulic, and as mentioned in an earlier post, the LT-1 cam has a different PN from the Z-28/327-365HP cam.
To Corvette70LT-1:
My opinion is: Since it's a numbers matching car, I would use the original cam & manifold.
JA
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Old 12-21-2007, 06:46 PM
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Quote:
Originally Posted by johnnya
You seem to be lumping the LT-1,L-79 & Z-28 together as if the cams are the same.
This is incorrect. The L-79 is hydraulic, and as mentioned in an earlier post, the LT-1 cam has a different PN from the Z-28/327-365HP cam.
To Corvette70LT-1:
My opinion is: Since it's a numbers matching car, I would use the original cam & manifold.
JA
I thought something was odd. I"m looking at CompCams catalog that's the way they have them listed Solid Cam GM3849346, CC12-107-3, 67-69 302ci 290HP, 64-65 327ci 365/275HP,70-71LTI 350ci 370HP == Lift-.485/.485, Dur-254*/254* L/S-114* (It's actuallyL84 327ci 365HP Cam)
They have 2 other #'s for Hydraulic for 327ci & 350ci
GM3896929,CC12-105-3, Lift-.390/.410, Dur-195*/202* L/S-112*
GM3863151,CC12-106-3, Lift-.447/.447, Dur-222*/222* L/S-114*

Last edited by SSedan64; 12-21-2007 at 06:56 PM. Reason: correction
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Old 12-21-2007, 07:16 PM
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If that's what Comp is selling as a '70 LT-1/Z28 cam then they are wrong. The original cam has the specs that I quoted in my earlier post. Here are the specs on the original again: At .050 lift, 242/254, Lobe centers 110 int,/122 exh, LSA 116, intake opens 10 btdc, closes 52 abdc, Exhaust opens 68 bbdc, closes 6 atdc. The last cam you listed looks like the 327 L-79. It was a hyd. lifter cam and I think that the duration was222/222 The lifts on the LT-1/Z28 cam are .459/.485 not .485/.485

Last edited by Will H; 12-21-2007 at 07:19 PM. Reason: add lift
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Old 12-21-2007, 07:26 PM
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Quote:
Originally Posted by Will H
If that's what Comp is selling as a '70 LT-1/Z28 cam then they are wrong. The original cam has the specs that I quoted in my earlier post. Here are the specs on the original again: At .050 lift, 242/254, Lobe centers 110 int,/122 exh, LSA 116, intake opens 10 btdc, closes 52 abdc, Exhaust opens 68 bbdc, closes 6 atdc. The last cam you listed looks like the 327 L-79. It was a hyd. lifter cam and I think that the duration was222/222 The lifts on the LT-1/Z28 cam are .459/.485 not .485/.485
Yes there passing them off incorrectly. I goggled and found specs you quoted. I think there saving themselves $$.
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Old 12-21-2007, 07:49 PM
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Quote:
Originally Posted by Corvette70LT-1
Hi Members,

I am rebuilding a 1970 Corvette LT-1 (350cu, 370hp) that I have owned for 20 years.

The block is original. I have refreshed the stock heads (2.02 & 1.60).

When I purchased the car, 20 years ago, it had a Chambers Max One camshaft in it.

I am considering changing it to either the originial Chev cam (P/N 3972182) or a cam from a Corvette, 327cu, 365/375 h.p.(P/N 3849346) that the specs seem to indicate has a bit more intake duration but a slightly different overlap.

I will be using the prescribed Holley 4555 carb on either a '69 Z28 Alum. HiRise intake manifold, or on a Chev. replacement 1970 LT-1 Alum. HiRise intake manifold.

Question - Which camshaft should I use? Which intake manifold should I use?

I would appreciate you thoughts on these questions and the basis in which you base your recommendations.

Also, do you have any recommendations as to where I can obtain those original, new camshafts?

Thank you,
you have a nice engine and I agree with some here that staying with the GM grinds might be the way to go. As far as hydraulic cams go I love the old 3896962 350 horse cam I think it was the RPO L-48. If you really want to improve performance I would also suggest considering a hydraulic roller...they are unreal.
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Old 12-22-2007, 02:54 AM
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Kinda wonder what your intentions really are. Offering opinions on this really depends on that. You wanna be original, go with the gm grind and intake and be done. You wanna step it up a bit I'd go with a comp cams nostalgia cam. There close but the lift versus duration isn't as screwed up as the old grinds. and the opening closing rates really do make a different animal, just dont forget to match new springs, they get old and tired. As for intakes, vettes kinda limit your picks, hood clearance and all, but when your not hunting for max perf. any good dual plane that'll fit under should fit the cause. Sory, kinda vague, again, goes back to what YOU want.
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Old 12-22-2007, 08:52 PM
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Quote:
Originally Posted by Will H
If that's what Comp is selling as a '70 LT-1/Z28 cam then they are wrong. The original cam has the specs that I quoted in my earlier post. Here are the specs on the original again: At .050 lift, 242/254, Lobe centers 110 int,/122 exh, LSA 116, intake opens 10 btdc, closes 52 abdc, Exhaust opens 68 bbdc, closes 6 atdc. The last cam you listed looks like the 327 L-79. It was a hyd. lifter cam and I think that the duration was222/222 The lifts on the LT-1/Z28 cam are .459/.485 not .485/.485
The first design LT-1 cam was .485/.485 but later revised to .459/.485. The earlier 327/365 cam was called a 30-30 cam. I have an original LT-1 short block in my '62 but I changed the heads to Dart Iron Eagle Platinum 200 runners and 72 cc to lower the compression to use regular H/T pump gas. The combo works great. I would quiz Comp cams again and also Crane.
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Old 12-23-2007, 09:18 PM
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Quote:
Originally Posted by GCD1962
The first design LT-1 cam was .485/.485 but later revised to .459/.485. The earlier 327/365 cam was called a 30-30 cam. I have an original LT-1 short block in my '62 but I changed the heads to Dart Iron Eagle Platinum 200 runners and 72 cc to lower the compression to use regular H/T pump gas. The combo works great. I would quiz Comp cams again and also Crane.
You may be correct, but i think what you are refering to is the first design short track cam. My 1984 edition of the Chevrolet Power Book lists this cam at .481/.485. The LT-1 cam was .459/.485. I've measured mine and this is what I get.
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