Recommendations on carb and cam - Team Camaro Tech
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post #1 of 162 (permalink) Old Sep 19th, 16, 03:43 AM Thread Starter
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Recommendations on carb and cam

I finally gotta admit I've gotten too old to enjoy my 68 like I should. It's just too radical for me now. I built a stout 350 about 13 years ago and now I just don't enjoy driving it due to having to slip the clutch a little and idle issues and how loud it is and all the creaks and squeaks etc. To begin with I'm sure I over sized the cam and carb for a decent street machine. I guess I wanted to relive my glory days when I owned a 67 327/350 Vette. Anyway here are my specs. I'm looking to tame it down considerably by changing cam and carb. Maybe I'll go to a Holley. I think I'd like to stay solid lifter but maybe not.

350 .040 over
10:1 flat tops
Trick Flow aluminum heads 2.02
Comp Cams XS282S (specs below)
Edelbrock 750 on Performer RPM intake
1 3/4 Hedman headers
M20 trans
3:42 posi

Cam Specs:

RPM Range: 2400 to 6800
Valve Lash: 0.016 0.016
Valve Timing: 0.015
Duration: 282 290
Lobe Separation: 110
Duration @ .050" Lift: 244 252
Intake Centerline: 106
Valve Lift: 0.52 0.54
Lobe Lift: 0.347 0.36

My goal would be to make it sound and run as smooth as the 67 Impala on TV show Supernatural. I love the sound of the cam in that 327
(I assume)
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post #2 of 162 (permalink) Old Sep 19th, 16, 05:22 AM
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Re: Recommendations on carb and cam

Just cam it down. You don't need to buy another carb, you'll just need to tune it for the new cam. Look at this cam from Comp: 12-223-4 Solid lifter cam, 236 duration at .050 on both intake and exhaust with .495 lift on both also. This would be a nice step down without leaving too much on the table.
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post #3 of 162 (permalink) Old Sep 19th, 16, 06:57 AM Thread Starter
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Re: Recommendations on carb and cam

Quote:
Originally Posted by onefiness View Post
Just cam it down. You don't need to buy another carb, you'll just need to tune it for the new cam. Look at this cam from Comp: 12-223-4 Solid lifter cam, 236 duration at .050 on both intake and exhaust with .495 lift on both also. This would be a nice step down without leaving too much on the table.
I'm a little concerned with the Basic Operating Range on that cam being 2,000-6,000. It's the low end that really bothers me with the 282 I have. I have to slip the clutch and rev it up more than I'd like. Wouldn't I be better with one of these: Or too small for my carb and intake?

12-674-4 1,000-5,600 218/224 duration .465/.477 lift
12-675-4 1,300-5,800 224/230 duration .477/.488 lift
12-676-4 1,600-6,000 230/236 duration .488/.501 lift

Also I need to ask can the cam be swapped out with the engine still in my 68? I haven't pulled a cam like that in 50 years and that was a 59 Impala that you could put a hot tub in front of the engine.
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post #4 of 162 (permalink) Old Sep 19th, 16, 07:08 AM
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Re: Recommendations on carb and cam

Winch, The cam Onefinnes recommended is the almost the same cam grind I run but with a 112 LSA in a roller. The difference is , it doesn't idle rough and is more streetable because its lobe center. Its also the same cam you are listing.

I think since you are looking for an old HP cam Chevy sound, If you have to buy another cam, I would contact Chris Straub, on this site.
He is a cam master and could set you up with what you want. You may want to run something smoother for street . You could even advance the cam you have to smooth it out some.

You could also try more gearing.

Might send him a pm and see what he says.

Don
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Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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post #5 of 162 (permalink) Old Sep 19th, 16, 07:20 AM Thread Starter
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Re: Recommendations on carb and cam

Thanks, I'll PM him.

I had 3.73 gears behind it and it wasn't as bad but there was a problem with that rear end and when I got it fixed I dropped down to 3.42. It is worse than with 3.73 but not near as bad as when I first dropped the 350 in and had the 3.08 peg leg original rear end in it. I thought I'd burn up the clutch trying to drive that combo.
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post #6 of 162 (permalink) Old Sep 19th, 16, 07:38 AM
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Re: Recommendations on carb and cam

If you want actual performance you can use with a 350 sized engine (what all cam companies use in their description of behavior, even if you are installing it in a 500+ cube Chrysler SC Hemi) keep the duration at 0.050" under 224 degrees.

For a street driven car keep the carb and cam small. If you are building to impress your friends by how loud it is or how rough the idle is then don't expect to be able to drive the car. Duration increases with displacement for the same reason race cars use a longer duration cam. It takes time to move air (it is a fluid and responds to all of the laws of fluid dynamics that apply to a compressible fluid). A bigger motor needs more air, a smaller motor needs les so a 305 wants less cam than a 454 to get the same idle.

Everyone wants a motor that sounds like John Force's Peak Camaro that idles (if you can call it that) at 2,400 RPM and revs to 9,000 RPM while pumping the cylinders full of air at 60 psi of pressure. I must mention John doesn't drive his Camaro on the street, and would probably be arrested if he tried, but people still want a car that has a rough idle.

A rough idle is the sound of lost power (an engineer defines noise as lost power). It was better in the old days when kids jacked up the rear end of their cars and stuff the biggest tires they could find (an L60 or a tire 9.15 inches wide that is 265 in metric speak) to look like their favorite racer rather than sound like it.

Just an old farts opinion.

Big Dave
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post #7 of 162 (permalink) Old Sep 19th, 16, 07:47 AM
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Re: Recommendations on carb and cam

X2, what he said.

Don
TC # 349
Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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post #8 of 162 (permalink) Old Sep 19th, 16, 07:52 AM Thread Starter
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Re: Recommendations on carb and cam

It sounds like of those cams I listed you would recommend the 12-674-4?

I don't want to impress anyone and I'd prefer it be as smooth and quiet as I can get it. I've even considered swapping out that entire drive train. If I had it to do over again I'd shoot for a stock 327/275 with an automatic! But that would be quite an expense at this point so I'm thinking of swapping cam and maybe carb/intake this winter. I would really like to get this car back to something I can enjoy. At this point in life I'm keeping it mostly as an heirloom to pass on to one of my kids. I hate to admit this but I recently bought a 62 Nova vert 6 cyl auto and after putting PS & PB on it I love driving it way more than the Camaro. They both turn heads but the Camaro gets more whiplash!
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post #9 of 162 (permalink) Old Sep 19th, 16, 08:08 AM Thread Starter
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Re: Recommendations on carb and cam

OK let me ask this: If I go with a smaller cam like the 12-674-4 will it work with the Edelbrock 750 on Performer RPM or do I need to downsize that combo; If so can I just drop to a 600 cfm Edelbrock on that manifold or do I need to drop to say a Performer (not RPM). Then what if I go with Holley 4160. Can I keep that manifold or downgrade it as well?

Lot of decisions.
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post #10 of 162 (permalink) Old Sep 19th, 16, 08:22 AM
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Re: Recommendations on carb and cam

If you decide to go with a different carburetor, my recommendation would be to pass on the Edelbrock and the Holley carburetor and go with a Quick Fuel carburetor instead. As far as Carburetor size goes, it depends on the rpm operating range of the engine and the displacement so you can't really figure that out until you lock down the actual cam you decide to go with. A dual plane intake manifold would be of benefit with the direction you are planning to go as well. And yes you can swap cams in a first gen small block with the engine in the car, you will spend time bent over the front of the car which will probably leave your back a bit unhappy, but it can be done without issue. You will want/need to remove the radiator though.

69 Camaro Z/28 RS, original Azure Turquoise, M21 & 3.73 12-bolt posi. NOM 406ci, AFR 210 heads, Straub hyd. roller cam & Dynatech 1-3/4" > 1-7/8" headers, QuickFuel 750 Annular. Photos at:
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post #11 of 162 (permalink) Old Sep 19th, 16, 08:41 AM
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Re: Recommendations on carb and cam

I think It is about time to change to a Hyd Flat tappet or a Hyd roller cam. https://www.summitracing.com/parts/l...make/chevrolet This kit has everything you need Cam, lifters and valve springs. This is the Hyd roller camshaft kit that includes everything needed to change cams. https://www.summitracing.com/parts/l...make/chevrolet I think you will be satisfied with one of these hyd cam now with the smoother idle. Btw that is a beautiful Nova. The intake and 750 carb will not have to be changed but you may have to install smaller jets in the carburetor. If you want a 600 holley by all means just bolt it to your Performer Rpm intake.
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post #12 of 162 (permalink) Old Sep 19th, 16, 02:06 PM
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Re: Recommendations on carb and cam

Quote:
Originally Posted by camarodriver67 View Post
...
If you want a 600 holley by all means just bolt it to your Performer Rpm intake.
Changing jet sizes doesn't make a carb smaller or behave like a smaller carb, it just makes it run richer or leaner than Holley intended (and they are all set fat from the factory to protect your engine from running lean which can destroy it). The metering blocks mix the ratio of air to fuel based upon the cfm rating not the jet size. You may want to knock a set of jets down if you are running rich, but that is to achieve a leaner mixture closer to stoichiometric.

For a street/strip Camaro a 750 is perfectly sized, for a street only driven car a 600 to 650 cfm is ideal. Chevrolet engineers placed a 630 cfm Rochester QuadraJet on top of most 350 motors for a reason.

If you look in the parts bin of Chevrolet's high performance catalog

Chevy Parts: Performance Parts Catalog | Chevrolet

they list several grinds that were not installed in Granny's go to church on Sunday Impala. Chevy offered a hydraulic flat tappet cam that made 350 horsepower in a 327 (RPO L-79), because of a wider LSA than p[eople who demand peak horsepower numbers it idles smoothly but will rev to 6,400 RPM with the correct lifters and springs. Any cam listed for EFI will have more lift and a smoother idle than a carburetored version (because EFI rolls over and dies with any reversion in the intake manifold not knowing how to deal with valve overlap). Unfortunately the EFI fueled reverse cooled SBC2 (LT-1 and LT-4) was discontinued in favor of the LS-x series of motors before it had a chance to see what the aftermarket could offer so cam choices are few.

I have my cams custom ground because I consider valve train to be a consumable so I spend as much as needed to buy the best (half inch in diameter Manton push rods for example). I run as little duration as needed to meet engine size and intended RPM range then throw as much lift as needed to maximize air velocity in my ports. I don't follow trends or fads I use the skills I learned in engineering college to design my parts. then have them fabricated.

Big Dave
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post #13 of 162 (permalink) Old Sep 19th, 16, 03:14 PM
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Re: Recommendations on carb and cam

Wider LSA will give it less "chop".

Of the 3 posted, I like the bottom one
Quote:
12-676-4 1,600-6,000 230/236 duration .488/.501 lift
but maybe on a 114 LSA ?


I really did like my 230H CompCam (230/230~.486 I/E 110 LSA) which did pretty good in my low comp 400 as well as my 10.5:1 406...just a good all around cam IMO. But if you went that route on a roller and with a wider LSA.....I'm sure it could work well.
My buddy did just that in a ZZ4 and can't believe how good it feels.


Your intake and carb will work fine with this also, or a 650 since its only going to be on the street.

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #14 of 162 (permalink) Old Sep 19th, 16, 04:05 PM Thread Starter
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Re: Recommendations on carb and cam

Just for comparison purposes what would be the specs of an original 327/300 or maybe 350/295 cam? I know they were hydraulic but looking up the specs in my 68 Service Manual and its says they are for Lobe Lift +- .002". That's kind of apples an oranges when compare to .050" right?
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post #15 of 162 (permalink) Old Sep 19th, 16, 04:49 PM
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Re: Recommendations on carb and cam

Ken, I believe you are getting too much information from the team on what is best for need. What works or sounds well with one person may not suite the next.

Save yourself the decisions, Contact Chris Straub on this site.

Don
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Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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