Thread: Another Cam Suggestion

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Originally Posted by kool

Thanks Lynn!
I'm going to look into the XE 268 H (CL12-242-2).
I was reading this article that was using this cam. Anything you might want to point out for me?
REALLY appreciate this help Lynn.
http://www.compcams.com/information/...HP0401-001.asp

Just a couple of points to help with your education.
Since the reformulation of motor oils and the removal of extreme pressure lubricants, it is an extremely iffy proposition to run a flat tappet cam. Howards has some acceptable hydraulic roller grinds that will retrofit into an early block for less than $500. If you think $500 sounds expensive, just wait until you frag a flat tappet cam and have to yank the motor all the way down to a bare block again to remove all the shrapnel from the oil galleys.

Of course, a much better alternative is to begin with a roller block. '96-'00 Chevy trucks and vans used a Vortec 5700 350, regular production order number L31. The heavier duty models of these motors used a 4-bolt main, but you won't need 4 bolts at the power level you're considering with this build. I have found short blocks here in Phoenix for $200, although they are beginning to get a little pricey as the word on them gets around. You can re-use (in most cases) the factory roller tappets, dog bones and spider, rods and crank, having to purchase only the cam of your choice, pistons, oil pump and gaskets.

Use only 1.5 rockers on a street build. 1.6 rockers will add less than 10 hp, but will add considerable stress to the entire valvetrain.

You didn't say what pistons you will be using, but you should pay particular attention to the article you linked about using the D-cup pistons. If the pistons you are using have this configuration, then you are good to go. If they have a full circular dish with very little flat area on the crown to mate up with the underside of the head, then you will not be building the optimum motor and may experience some difficulty running on lesser grades of fuel when using optimal ignition timing. I have included photos of a less-than-optimum crown design dished pistons using a circular dish and a very thin flat area around the perimeter of the crown. Compare these photos with the one in the article and you can see that they used a piston with a considerable amount of flat surface to accomplish a good squish (D-Cup piston).

I have run the XE268H cam in a 9.00:1 350. It is not a lumpy cam and you will more than likely have to drop the idle down pretty low to get any lump-lump at all. It is a great street cam though. Makes good torque to move a heavy car. Now here's the thing. All you guys who are building your first or one of your first motors want the lumpy sound of a race motor. Street motors don't sound like that. Race motors sound like that. If you're building a race motor, then build it 10.5-11.0 to 1 and use a 290 degree cam (240 @ 0.050") and put up with its ill street manners, high stall torque converter, stiff rear gears, transmission cooler and crummy fuel mileage on premium pump gas. You'll be sick of it in a few weeks, but boy oh boy, it'll sound good to the geeks down at the drive-in who don't know any better.

Dump the intake and use a Edelbrock RPM or Weiand Stealth. Either of them will be worth 40 hp over the manifold you have now. You didn't say about the headers, but use only full length, tuned headers. Block huggers and other shorty headers are a waste of money in my opinion. You might just as well use those fosdick OEM cast iron manifolds.

12cc pistons with zero deck, 64cc heads and 9cc gasket will yield 9.55:1 SCR. 18cc pistons with zero deck, 64cc heads and 9cc gasket will yield 8.99:1 SCR.

Oh, and I use "fosdick" a lot. It is synonymous with bogus or lame. Fosdick was a character in the Dick Tracy comic strips.

Oh yeah, about heads. Here is a great head for the money. 0.550" max valve lift (street friendly). Will make 400 hp, 450 ft/lbs @ 9.5:1 SCR with a mild cam.
http://www.summitracing.com/parts/EDL-5089/

Scorpion makes a high-quality roller rocker arm with roller tip and roller fulcrum that is affordable. Don't be fooled by the Comp rockers that us a roller tip and ball/socket fulcrum. Fosdick.

The motor will be much easier to drive with a vacuum-secondaries carb. The rule of thumb is....vacuum secondaries if the converter stalls at less than 3000. Double pumper if the converter stalls at over 3000 or if the trans is a stick.