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.

 

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.

 

You may want to run something smoother for street . You could even advance the cam you have to smooth it out some.

To advance my existing cam I only need to change the crankshaft sprocket position right? I don't have to tear into the engine? If I attach a degree wheel to the balancer and position it to TDC according to the tab on the cover then can I use a machinist dial to find the max lift of #1 intake valve to see what the degree wheel shows? It should be 106* if it set up correctly. Then I could remove the timing chain cover and see if I have one of those 3 key way sprockets. If so, one of those will let me set it 4 more degrees advanced? If it's not one of those I could buy a multi key sprocket that allows for 2 degree increments up to 8 degrees advance or retard.

If I advance the cam I've read that will build more low end torque while decreasing piston-intake valve clearance and increasing piston-exhaust valve clearance. Is there any worries about decreasing piston-intake valve clearance too much?

 

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.

 

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

 

X2, what he said.

 

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!

 

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.

 

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.

 

I think It is about time to change to a Hyd Flat tappet or a Hyd roller cam. https://www.summitracing.com/parts/lun-10120702k/overview/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/lun-10120702k/overview/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.

 

...
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

 

Wider LSA will give it less "chop".

Of the 3 posted, I like the bottom one

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.

 

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?

 

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.

 

Because the ramps the difference between the heel and the actual lobe differ greatly from grinder to grinder the industry standardized at measuring duration at 0.050" of valve lift.

At that point in time all slack is out of a solid lifter cam and the plunger is starting to build resistance to further compression in a hydraulic cam so you get repeatable comparison information. Of course that won't sell cams (something the grinders learned back in the early sixties during the cam wars), big numbers and bigger claims sell cams. Unfortunately no other part that you can put in an engine will have more affect on the motor's behavior than the cam. It will make or break a combination.

I used to show up on dyno day with four or five cams to try out because back then heads were hand ported and just about every head was different (sometimes the porting differed from port to port in the same head though I never believed the porters claim that he did it that way intentionally). I could obtain 20-25 horsepower difference between runs with no more than two degrees of duration. But in every case I wasn't looking at peak horsepower but the area under the curve.

So much for theory; anyway Chevy never played nice in posting their numbers. Generally it was other engine builders who degreed the cams at a bunch of lift values to get the specs to calculate the profile and posted their readings.

Don't know what the secret was other than the fact that Harvey Crane made most of Chevrolet's hot cam grinds and he was a bit squirrely when it came time to share what he knew about grinds unlike the late UD Harold.

I used to buy custom cams from him (he had a shop in Daytona Beach an hour and a half down the other end of I-4 from Tampa where I lived) and he wouldn't tell me how he ground my own cams that we had talked about: instead going for the "try it, you'll like it!" approach. If I needed another cam he had the patterns and lobe angles recorded in his work book to make another one from the number scratched on the end.

Big Dave

 

I think the way I might approach this is to first find a used Holley and rebuild it myself. With the smaller cam I want to switch to I'm thinking a 600 cfm. I'm seeing them local for less than $100 and I'd like the experience of rebuilding one. What should I look out for in a used Holley? Is there some parts that wear out such that it would not be a good candidate for rebuild?

 

Here is a local one for sale that is advertised as 600 Holley 1850 with manual choke. Can an electric choke be added to a Holley?

I'm actually looking for a 600 cfm 4160. Is this one comparable?

 

This Holley is a 4150 style with one line feed. It will probably work but you need to stay with dual feed.

You can add the electric choke but by time you do that , you could have purchased one of the Avenger carbs or a 3310.

Since you are still searching for cams , go for the Comp https://www.summitracing.com/parts/cca-12-210-2/overview/ flat tappet . These fancy names applied to basic cams don't tell you much

 

Looking back through my receipts I finally found where I ordered my Comp Cams cam from Summit. The specs for it on Summit's website are a little different than what I originally posted. I don't know if it makes much difference from what y'all have posted but here are the actual specs:

UPC: 036584640301
Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 2,000-6,000
Intake Duration at 050 inch Lift: 236
Exhaust Duration at 050 inch Lift: 236
Duration at 050 inch Lift: 236 int./236 exh.
Advertised Intake Duration: 282
Advertised Exhaust Duration: 282
Advertised Duration: 282 int./282 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.495 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.495 in.
Valve Lift with Factory Rocker Arm Ratio: 0.495 int./0.495 exh.
Lobe Separation (degrees): 110
Intake Valve Lash: 0.022 in.
Exhaust Valve Lash: 0.022 in.
Computer-Controlled Compatible: No
Grind Number: CS 282S-10

 

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)

That is a nice sounding car, but I think a lot of that is exhaust.

The 282S cam is way too big for you. I have always heard that it needs at least 11:1 compression and low gears - think 4.10's.

The Quadrajet is the best carburetor to run on a 327 or 350. Best gas mileage and street performance out there. You can also look at the Street Demon 750 as they work on the same principle. They also will bolt to a square bore intake.

For the camshaft, why not use a cam that was designed to work with your heads ? https://www.summitracing.com/parts/tfs-31401000/overview/

You could also call Trick flow and see what they recommend.

 

Agree that adding a new electric choke will kill your savings.

I am probably showing my age, but I used to regularly buy used 600 to 650 cfm 4160 style Holley carbs for $25 dollars. I have a card board box full of cores I bought at swap meets to rebuild. An 850 Double pumper used to be about a hundred and I still have two DP's and one vacuum secondary in the same box. One advantage of buying a lot of carbs is that Holleys use interchangeable parts so a used electric choke off a core will fit on a newer carb already in good repair. What you can not swap even though they bolt up are metering blocks as they are sized to a specific cfm rated carb.

The difference between the 4160 and the 4150 is more than just the single feed as you state it. The principle difference is the lack of a secondary metering block using a non-adjustable machined flat aluminum plate instead. Other characteristics are a center hung dual feed fuel line are used normally only on a 4150 series as is the full adjustable secondary metering block; but some one like me may have modified one in the past as those parts are interchangeable. What can not be changed easily (or better stated cheaply) is converting a vacuum secondary to a mechanical double pumper. Better to buy the right core up front than think you can change it later.

You can buy a rebuildable 4160 Holley 650 for as little as $37 plus shipping on flea-Bay. Or a HP Series 650 double pumper for $107 according to what I just saw with a quick look. (the HP series has adjustable air bleeds and no air horn which means no choke). Recommend you steer clear of the HP Series just yet till you get a little more experience tuning carbs (the fewer things to adjust the easier it is to tune when your just staring out). All you will need is a bucket of carb cleaner (how that has changed over the years is a shame, but some people think storm drains or back yards are made for dumping chemicals, so we all now must suffer), and a gasket set.

You should have no difficulty rebuilding the Holley as they were designed to fall apart in the pits for tune-ups between rounds. If you do have a problem any Holley book (your public library probably has one) or a post here will get you sorted out.

Big Dave

 

Both of those are 750 cfm. I have a 750 Edelbrock on it now. I'm dropping down to a 600 and a milder cam.

 

https://www.summitracing.com/parts/hly-0-80457s/overview/

Sounds like you had it right the first time. 600 cfm, vac secondary and electric choke, single feed. I was looking to get you away from the ford kickdown .

 

What is a Ford kick-down? Does the carb in my pic have one?

 

Ford kick down lever on between the accelerator and carb body, they attach to transmission rods. When you have universal carbs , this kick down lever is attached and if my memory serves me, they are not removable .
If you will use that link in the last message, open up the picture of the carb and enlarge it. You should see that lever.
There are more dedicated carbs that don't have that lever , but they cost more.

 

Ken, I think one of the common mistakes we make is over camming a engine, myself included. You really have to consider where most of your driving/ rpm range is and select from there. That said a roller cam is better than a flat tappet but cost enters the equation for most of us.
You originally mention Trick Flow heads, RPM intake, 750 carb......this probably works good for your existing cam, are the head intake runners 180cc of larger like 195cc? What's the combustion chamber size? Do the springs need to be changed? All considerations when upgrading.
A 600/ 670 CFM carb in that range sounds about right for a less radical cam that you may be considering. Holley has a chart that helps determining what works best for your engine parameters.
http://documents.holley.com/techlibrary_selecting_a_carburetor.pdf
For consideration maybe try this cam from Lunati:
Voodoo Hydraulic Flat Tappet Cam & Lifter Kit - Chevrolet Small Block 262/268 - Lunati Power

 

The Trick Flow heads are TFS-30400002 with these specs:

Cylinder Heads, Super 23® 195, Fast As Cast®, Assembled, 62cc Chambers, 1.470" Springs

 

Does your block have a matching hole for coolant passage between clys 3 &5 , 2 & 4 . My felpro gasket , 1010 came with instructions to drill the block where the head and gasket had the hole. This allowed more cooling between 3/5 & 2/4 as there was no water passage and created a hot spot. Might look into this .
I see this hole on your Trickflow head selection.

 

I can't find any pics I should have taken of the block before assembly. That is something to keep in mind when I pull the intake. Thanks for the info.

One other thing I should make sure about a 4160 to replace my Edelbrock 750 is the various vacuum connections. I use 4 vacuum connections now. On the carb are PCV, a rear connection that I have hooked up to my RS headlights, and a manifold vac to distributor. I have capped off the ported vac. Then there is a connection on the intake manifold itself that I hooked to the power brake booster. I assume since that rear connection comes off the throttle plate ( I think that's what it is called, it's under the carb), that it would be full time (manifold) vacuum? I don't see as many connections on a Holley 4160. I see a ported vac and a full time vac and a PCV. If there are no others then I will need to Tee into either the PCV or the brake booster for my RS headlights. Also will there possibly be a clearance problem with the fitting in the manifold behind the carb when I switch to a Holley? (see pic)

Oh, and lets not get into a debate on manifold vs ported timing. That horse has been beat to death

 

You can not use the brake booster line beyond the plastic one way valve in the vacuum ;line or you have no power brakes. A Vacuum T is easy to use.

Big Dave

 

I see what you have on the manifold now. Get you one of these manifold fittings and put where that elbow going to your booster. Search Term: Vacuum Fittings - Ricks Camaro Parts

You can also find these in parts stores, . If you get one with 3 or 4 ports, one will go to brake booster. One will go to the head lights. You can cap the rest.

On the front of your new holley carb, there should be at least one port that is manifold vac. Use it for the distrib if vac is needed. If you have mechanical, just leave it capped.
Like Dave said, the large hose goes to booster only.
A carb base port can go to the pcv . As for the clearance, just find a thick carb spacer , maybe 1/4 or 3/8th. That should get the back carb bowl away from the fittings.

What did I miss?

 

Here's a pic of a 4160 setting on a Performer RPM manifold. Looks like plenty of clearance.

So putting a Tee in either manifold or carb PCV connection is OK for my headlights?

 

NO, these are not vac ports to run other stuff. You have one port below the fuel bowl, I see it, that is manifold vac or your dist . Other can be plugged. Might as well plug those extra ports you circled if not needed.
Get a tee like the ones in the link I sent you. The largest port goes to brake booster.
If there is a vac port at the base of this holley carb, use it for pcv.

Other ports off that multi port behind carb, you can use one for your head lamps. Others can be capped if not needed.