Another cam / intake poll

[MaineShark]

Okay, I just heard back from the body shop, and they can't take the car before the third week in September, to do the hood.

So, I have some more time than I thought, before I can get the car back together. While I have it apart, anyway, should I just take the plunge and swap the cam and intake, right now?

If so, I'm going to ask for cam recommendations, again (not that I distrust the earlier recommendations - I've just refined my other part choices a bit better).

The basics are small-block 350, dual exhausts (but no headers in the near future), TH350, and other than that pretty much of a mystery. It's a replacement engine, so I don't know what it's actual compression ratio is, but it does make approximately 250 hp, which is pretty close to what an L82 with dual exhausts should make, so it's probably pretty similar to the L82, internally.

I'm going to go with an Edelbrock RPM Air-Gap intake, with a 3/4" spacer/adapter (necessary to mount the Q-Jet to the RPM manifold).

Any cam will still have to be a hydraulic flat tappet - I'm not spending money on roller lifters, right now.

So, the big question is: do I replace only the intake, or do I replace the cam, as well?

Then, the second question is: if I replace the cam, what cam do I use?

I would, of course, like to do as little work as possible, but I don't want to end up putting the new intake on, and not being able to get much improvement, because the cam is restricting things...

Joe

 

[iron cross]

The best bet on a cam would be the GM 151 cam available through Federal Mogul. It`s the 327/350 hp cam and works very well. You may have others suggesting some off the wall brands COMP CAMS for example, but this one works and is hydraulic. Just use new lifters and springs. It don`t have all the hype associated with the so called racing brands, but it works.

 

[Crickett]

I say replace em both! :cool

 

[waterboy1976]

I have a 73 with a 350 also and have the Edelbrock RPM Air Gap manifold and looked at multiple camoptions with the heads I have (920 castings 1.94 intake 1.50 exhaust screwed in studs and guideplates)carb setup (Holley 4160) and exhaust set up (Hooker SuperComp Headers, H pipe and stock mufflers) and the 327/350 cam grind is a little too steep unless youre gonna go put a higher lift valve spring on it. Ive worked for GM for 7 years now and ended up going with a Edelbrock RPM Cam for that set up. The 327/350 Cam from GM is a hell of a cam ( NOT knocking you Iron Cross!!!!!) but there are some nicer grinds out there for those of you who dont want to pull a complete motor set up. Remember with Cams to get a lot of TORQUE ( which is seat of your pants) you need a higher lift cam and less duration.. Youll end up sacrificing a little horsepower but gaining torque in the RPM range you run. The old LT1 Cams and the old .30/.30 cams were great on the proving grounds at GM because thats where Duntov wanted them...turning over 6000 RPM for long periods of time. Thats not where you want your car or where IT wants to run....You could write a book on Cams bigger than the bible itself.... Good luck....

 

[MaineShark]

Something I forgot to add: I still need some vacuum for the headlights and the climate control systems. (but not the brakes - the booster is now hydraulic)

Here's the kicker: if I get a cam now, it needs to have some vacuum to it. But I should be eliminating the headlight vacuum system this winter, and the climate control vacuum system within a year or two.

So, this is really a question of whether I should replace the cam with something a little bit better than stock, now, then replace it again after I scrap all the vacuum components, or if I should just wait and do it only once?

Joe

 

[waterboy1976]

the performer RPM Cam Kit that Im running......... (.510 lift exhaust .488 intake lift) does create enough vacumn for my lights as well as my brakes however if that were a problem (which for you shouldnt be) you could always add a canister to boost it up a little......

 

[MaineShark]

Hmm... isn't .510 lift a little much for stock heads?

Joe

 

[Classicvette63]

Without headers, it doesn't much matter. Whatever you do, you will not be getting the most from it. Headers are first and foremost.

I have the edelbrock air gap, cam and heads and have been impressed, to say the least. Classic

 

[Bob_K]

Unless you can find out what your compression ration is, I'd only replace the intake.

 

[clar2001]

If your considering a cam headers are a must other wise your running backwartz.
I here bad things about the RV cams have to many dead spots.
The air intake is really nice and a carb spacer, Hood clearence could be a major issue.
what about a curve kit for the distrubtor .
I allways said need to match all your equipment front to rear it's not how big, but how you build it that matters !

 

[waterboy1976]

Hmm... isn't .510 lift a little much for stock heads?

Joe

Hmm.....did I SAY "STOCK"....????:duh :duh :duh :duh

 

[MaineShark]

Hmm.....did I SAY "STOCK"....????:duh :duh :duh :duh

Nope. But I did

Joe

 

[Hib Halverson]

The Performer RPM Air Gap manifold is way too much for a 250 hp "replacement" engine with no headers and a stock cam.

Actually, it's probably too much for a replacement engine with no hearders AND a cam.

The Perf. RPM Air Gap with the spacer and the Quadrajet will not fit under a stock hood.

If you want to run the engine you have, with no hood change, use the Edelbrock Performer Manifold and Camshaft kit. It will work well with low compression and no headers.

 

[MaineShark]

I'm already changing the hood (the original got crunched), so that's not an issue. I plan on doing some more extensive modifications to the engine, so I'd like not to buy two intakes...

But the real question is, if I use that manifold, is it simply excessive for my current needs, or will I actually lose performance because of it?

Joe

 

[Glensgages]

The best bet on a cam would be the GM 151 cam available through Federal Mogul. It`s the 327/350 hp cam and works very well. You may have others suggesting some off the wall brands COMP CAMS for example, but this one works and is hydraulic. Just use new lifters and springs. It don`t have all the hype associated with the so called racing brands, but it works.

20 years ago, my buddy & I both rebuilt the motors in our Z28s (mine a '79, his an '80; both identical 20,000-mile LM-1s) we'd bought with-in months of each other.
In stock form, his smoked me fairly good (identical THM350, 3.42 gears, UNIROYALS, etc.).
For the rebuild, we used identical 'double-hump' heads to raise the CR, identical headers {Black Jack}, intake {Chevy dual-plane}, carb {650 dbl-pump Holley}, ignition (we used the 'as-is' short-blocks), shift-kits, etc., buying most of this stuff at the same time, from the same vendor.

The ONLY difference between these cars (besides his functioning 'air-intake-scoop' on the '80; he ALSO added a 10" 'Hole-Shot' converter, too!) was the camshafts: he chose the #151 cam; I used an 'on-sale' SUMMIT-'house' brand {GENERAL KINETICS}.
Altho the 'specs' (lift & duration) were VERY similar, I out-ran him by .3-.4 (14.40s to 14.70+) every time we went racing. We'd swap carbs, with NO change in the result. Keep in mind, he had a BETTER torque converter, too!

I'd think a COMP-CAM grind with approx .450" lift, short duration @ .050" (216*-220*?), and a tight LSA (110*-112*) will give you good power to 5500-5800 RPM, yet give no piston-to-valve problems.
When you no-longer need the vacuum, swap-out the rockers to 1.6:1 ratio (stock is 1.5:1 ratio) to produce .480" lift....
Just a thought.......

 

[macx]

You GOTTA read this!

Here's an amazing story of what can be
done with a lo comp stock 350 and at a reasonable price, and remains very streetable.

http://www.corvettefaq.com/c3/goodwrench/GM Goodwrench 350 test part 1.htm

Then take a look at these big bunch of dyno tests - also amazing power at streetable rpms

http://ryanscarpage.50megs.com/combos2.html
http://www.geocities.com/MotorCity/7610/dyno.htm

I'm currently headed down the path of the first one with my "new" 81.