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Old 07-31-2003, 12:06 PM
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Red face Help! Chevy 350 Crate: Cam and Head concerns?

Purchased a rebuilt 4-bolt 350 Chevy SB longblock (dare I say where). Heads are 462 and 993 mixed castings with metal repairs. Specs say it's 9:1 compression (I hope). Provided comp readings are between 145-160PSI. Found a bent purshrod and a stuck rocker swivel. Supposedly this motor was test run for 30mins and has 3 yr warranty?

Removing a head, I see shiny new .060 flat-top 4 relief pistons (30min test run??). Instead of returning the motor, it was in my financial interest to buy rebuilt cylinder heads (441 casting, 150/90 CFM, 76cc, from American Cylinder Head, Utah). I asked for '70 350 Z28 heads, but they didn't have the 2.02/1.6/64cc. Few more days and I'll have the heads. At least the block is a 010 high nickel casting.

I'll be using a Holley 600CFM Vac Sec/Edelbrock Performer/Accel HEI&Coil/TH350 tranny B&M Stage 2 kit installed 2000-2200 stall converter. No headers yet.

The specs of the current cam are 247 Dur .417"/.417" lift, double-roller chain, 240 HP is claimed. My local speed shop said ditch the stock cam. I said I'd like more HP but want to keep the heads stock and have vacuum for AC and Brakes.

He recommeded a Crane Blazer 284-2H (hyd, with lifters/lube), 284/294 Dur (224/234@.050) .465"/.488" lift. He said it would have a slight lopey idle and could make 300-350HP with no worries about the stock valvetrain or piston/valve collision (fel-pro 1003 .041" head gaskets).

Crane recommends 9.5:1 min compression and 2500 stall.

I'd like the 300HP, but it's got to be reliable. Is this cam going to break the stock springs and put a valve into my cylinders? Will I need a vacuum canister to use my brakes/AC?

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Last edited by 360Camaro; 07-31-2003 at 12:22 PM.
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Old 07-31-2003, 12:42 PM
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I ran a cam similar in my BBC (comp 280H). It was the biggest cam I could find with out having to do any head work or change of springs. It ran fine with no worries. Well, actually one. I broke a rocker arm, but it was just a stamped stocker. It made for good reason to get a set of rollers in it too. I think you'll be just fine and pretty pleased with it.
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Old 07-31-2003, 01:50 PM
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My opinion is that you won't like that 224/234 cam one bit in your application. You simply don't have the compression for it. Your vacuum will be on the low side forcing you to run a rich mixture so the engine will idle OK. This will result in your eyes watering at stop lights from the rich mixture. I know, I've been there. I really believe you would be very satisfied with the tried and true cheap SSI 214/224 cam. Sure there is a sea of other cams out there like the XE 252 series that I'm sure will do but they are alot more money. I run a SSI 214/224 cam in my cheaply rebuilt 9.4 compression small block. That cam is really a sleeper because it's got good vacuum and just a hint of lope at idle and most importantly, has very crisp low speed torque. One other note...I needed to replace my rocker arms so I purchased a set of cheap stamped steel 1.6 ratio rocker arms for the motor. If this woke up that cam, I don't know but I did run that very same cam in the 400 small block that was in the auto previously. The engine had 8.5 compression and the idle was smooth but had a hint of elevated tone to it but no lope. My guess is that some compression really wakes up this cam. However, the 400 small block ran exceptionally well for many years until it finally wore out. If you still insist on the 224/234 cam then I suggest that you ask around a bit more. In my opinion, that cam will need compression, low gears and a good exhaust...not just one out of the three but all three! Good luck
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Old 07-31-2003, 02:12 PM
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I'm glad the cam runs well in the BBC. I've read posts on here that state stock SBC heads can take .500" lift max. I believe my rocker studs are pressed, not screwed, in as well.

But then why does everyone say to get the matching springs for your cam? Is it because of lift (over .500" coil bind) or valve float (not enough seating pressure) or a little of both??

So I guess I can assume this cam profile is not aggressive enough to necessitate changing from stock spring/pushrods or adding valve guides.

Quote:
Originally posted by dallam1
My opinion is that you won't like that 224/234 cam one bit in your application. You simply don't have the compression for it. Your vacuum will be on the low side forcing you to run a rich mixture so the engine will idle OK. This will result in your eyes watering at stop lights from the rich mixture. If you still insist on the 224/234 cam then I suggest that you ask around a bit more. In my opinion, that cam will need compression, low gears and a good exhaust...not just one out of the three but all three! Good luck
Appreciate the advice. Last thing I want to do is overcam the engine. What if I use a .015" copper head gasket? That should boost the compression, or will this mess-up the quench and bring the valves/pistons too close?

Aren't vacuum canisters available to help maintain some vacuum like at stop lights?

I'm going out now to find out my rear gear ratio...

Last edited by 360Camaro; 07-31-2003 at 02:12 PM.
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Old 07-31-2003, 02:32 PM
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It won't hurt the quench because it's measured different (from to of cylinder, not to the heads). And the best way to tell about the valve to piston clearance is to do a clay test. I don't know if it's that different from a BBC to a SBC, but I had flat top pistons with open chamber heads (don't know the actuall cc). I had a 850 dp on it also, and it ran a little fat, but not so much to where it burned my eyes. I think if I knew then what I know now, I could have tuned the carb just right. Putting in a thinner gasket will help out, just make sure you do a clay test to see if everything clears out ok. Matching springs to your cam is a great idea, but I was on a tight budget and couldn't afford it. I bought the cam and checked for bind and it was ok. I just didn't take it over 6000 rpms to ensure no valve float. I did float them once when I got a little crazy and took it over 6300, but luckly didn't harm anything. I guess with some better springs it would have allowed a higher rev, since it still pulled nice at 6000.
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Old 07-31-2003, 03:35 PM
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Okay, this is a 92 Camaro RS 25th Anniv car. It's got granny gears, 2.73 non-posi, car weight 3198lbs.

So this 224/234 cam is not a great match for this gear. Looks like a step down to 214/224 (.442"/.465") is a closer match even if I boost compression with the copper head gasket.

The 2000-2200 stall decision is finalized (want fluid temps low, it's hot here) as are Energy Suspension poly mounts throughout the car.

I really don't want to go under 300HP, that's no fun.

How much HP did I just lose with the cam step down?? I mean the engine is going in the car in the next few days, but if I install the .015" copper head gaskets with the 224/234 cam, I could always buy a 3.42/3.55 gearset. Except for the exhaust (basically a single large pipe & glasspack at this point), this combo should move down the 1/4 fairly decent right?

I'll gladly take low 14's, with a preference to high 13's.
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Old 07-31-2003, 03:57 PM
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You should be close to 300 hp even with the smaller cam. By the way, where did you buy the motor. Just curious
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Old 07-31-2003, 04:13 PM
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With those gears and no posi, I don't know if you're going to make your goal. Traction is going to hurt your 60 ft time. Going down one step isn't going to make that big of a diff like USA said, but those gears will. I would throw on the thinner gasket, cam of choice (you already know which one I would use), and look into a posi unit and a set of gears (I like 3.73's). With that, high 13's should be easy.
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Old 07-31-2003, 04:18 PM
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Motor was special ordered from Pep Boys. It's built by "ProBuilt" www.atk-engines.com. Engine code is DC42 (search on the net, it's everywhere). Next time I need a complete engine, I'll be smarter and order it in kit form, so I know it goes together right.
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Old 08-01-2003, 08:45 AM
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I'm told there's not really usuable vacuum on the 224/234 cam. Also being told stock SBC springs can coil bind higher than .450" lift. And it really wants 10:1 comp and 3.73's.

In my quest to use completely stock heads/valvetrain and get 300HP I found that CompCams makes a "Nostalgia Plus Series" of grinds aimed at producing classic 60's musclecar sound (higher intake valve lift).

I found a 300HP+ (hyd) listing for SBC with 258/265 Adv Dur and (211/218 @.050") .426"/.420" valve lift. This duration should give me usable vacuum right? And I don't think that lift will be break any stock valve springs. Am I on the right track with this cam?

My (calculated) 60MPH cruise RPM is 2100. My 2000-2200 stall converter choice is concerning me. Is my TH350 going to overheat at 60MPH because the converter is slipping too much?
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Old 08-01-2003, 09:14 AM
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I wouldn't worry about the 60mph rpm reading since that's not a real cruising speed on the highway anyways. Plus, with a good tranny cooler, that rpm should fine. But like I said, you'll probably be more around 2400 since most people cruise 65-70.
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Old 08-01-2003, 09:41 AM
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Check out Crane's "Energizer" series. They're single pattern cams and are inexpensive - you'd probably want the 217dur. and .454" lift. I'm putting one in my 9:1 350 right now (after I fix the busted-*** main cap threads).
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Old 08-01-2003, 09:56 AM
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Quote:
Originally posted by gt2betubbed
I wouldn't worry about the 60mph rpm reading since that's not a real cruising speed on the highway anyways. Plus, with a good tranny cooler, that rpm should fine. But like I said, you'll probably be more around 2400 since most people cruise 65-70.
Good deal then. I'll definately use a tranny cooler.

The stock 240HP setup is 247/247 Adv Dur, .050" dur unknown, .417"/.417" lift.

The CompCams 300HP+ ($119) is 258/265 Adv Dur, 211/218@.050", .426"/420" lift.

Assuming good intake/exhaust, it sounds to good to be true to get another 60HP and 60's musclecar sound from just a cam swap (with very similar valve lifts). Is it all in the cam duration and ramping profile?
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Old 08-01-2003, 09:37 PM
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Went back to the speed shop today. Owner would have happily "downgraded" my (224/236) cam but he said I wouldn't even notice it in the car. He says he constantly puts this cam in trucks used for towing, boats, etc... he seems to consider any lesser cams RV-type cams.

The cam has a 114 LSA which he says promotes a smoother idle, enough vacuum for accessories, and is more streetable with a wider power band than 112 or lower LSA's. Crane specs this cam's RPM range @ 2200-5200.

I decided to keep this 350HP cam/lifter combo ($109). I also bought the Crane springs ($30). And a large tranny cooler $30.

My wife's 89 Firebird has a 3.08 rear. Is it worth the effort to swap rear-ends to ditch my 2.73 gear into her car? Can 3.08's and 300HP+ push this car into the 14's at least??
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Old 08-04-2003, 07:57 AM
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I'm glad I kept the 224/236, .465/.488, LSA 114 cam. I found a comparison of this cam vs 2 smaller ones on a cheap low (<8.5 compression) 355 chevy.

http://www.carcraft.com/techarticles/1057/

This "big" cam produced over 300HP, and maintained good streetability and low-end, plus 12.5in-Hg Vacuum at 800 RPM idle. It should work great with my 9.25 compression 360 chevy.

When I get the heads I'll pop in the Crane valvesprings and let you guys know how it runs with the 2200 stall and 3.08 gears.
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