Performance Q&A Questions - Performance Q&A

Kevin McClelland Jan 1, 2009 0 Comment(s)
0901chp_01_z Performance_qa_questions Illustration_by_tom_truty 1/2

The General Makes Them Right
OK, I'm probably going to hear about this one. For many years I've been preaching the good word that GM's parts are designed and tested for 100,000 miles and over. I use factory components, like starters, on my race cars and have never had a failure. One other benefit from using factory-designed and -manufactured parts is that they fit! Many of the generic auto parts you buy today are a hodgepodge of designs to make one part fit as many vehicles and engines as possible. This will lower the cost and make the parts house very happy, since it only has to carry one part for many applications.

Several months ago I wrote about my buddy Phil Doyle's vacation to Disneyland, when his serpentine belt broke, wrapped itself around the water pump shaft, and pulled the water pump apart, driving the cooling fan through the radiator core. All this 450 miles from home.

Since then Phil's been ordering parts for the Suburban. Yes, a '93 2500 4x4 Suburban is 15 years old, but you'd think most parts would be OK. He started with our good friend Ken Casey at Burt Chevy for the water pump, clutch fan, fan blade, and the serpentine belt. Another local pal here by the name of Mike Eling had a great contact for radiators. It was a beautiful plastic-tank/aluminum-core radiator. We buttoned everything up on the engine and dropped in the radiator. This is where the trouble started. Phil's 'Burb was equipped with heavy-duty cooling and a tow package. This option gives his truck an integral engine-oil cooler in the return tank of the radiator. Everything was going fine; the trans cooler bolted right up, but when he went to connect the oil lines from the engine to the rad, the upper hose was 2 inches too short! After trying to reroute the line to gain a couple of inches, there was no way. For now, Phil bypassed the cooler by removing the oil lines and plugging the block. So he's not planning to use the truck for towing anytime soon.

After checking back with the radiator manufacturer, this was the proper radiator for Phil's application ... and about 10 other trucks. Maybe some of the other truck models or a different year had a longer hose, but not his. This is back to the proper-factory-designed part for the vehicle. Now, I'm not trying to get you guys to spend more money, but when the parts don't work, they're not really a bargain.

What Do You Want From a Mouse?
Q

I've built up a 283 with a 270 Magnum Comp Cam with matching valvetrain, springs, retainers, locks, and roller-tip rockers. Heads are Camel Backs with 1.94/1.50-inch valves, ported. It has an RPM intake with a 600-cfm Edelbrock Performer carb and is fired by a Mallory Unilite ignition with an ACCEL Super coil. I was told to use the 8-inch harmonic damper over the smaller one. It just doesn't seem to have the high rpm like it should. I have a BorgWarner Super T-10 trans with the 2.88 First gear and a 3.42:1 posi with big 31-inch Pro Trac tires. I have a 3.70:1 9-inch rearend that I'll be putting into it, but I still wonder if the balancer is right for this engine.

I also have a 350 on the stand with a Comp Cams High Energy 268 cam and valvetrain with World Products 76cc heads and the same intake and carb. I know the 350 puts out more torque, but I like the whine from the short stroke in the 283. Both engines have the forged flat-top pistons and the 8-inch damper. Should I switch the one on the 283 to a smaller one or just drop in the 350? The 283 is better on gas, or so it seems, since it has a smaller bore. I'm retired and on a fixed income now, so anything to save dollars will help. I also have a 400 small-block to rebuild, but not sure which way I want to go yet. Thanks for your help.Daryl Brooks
Via e-mail

A
We were all for the 283 until you said you were pulling around 31-inch Pro Trac tires. Those tires probably weigh more than the rotating assembly of your engine! The 270 Comp Cams Magnum camshaft is a pretty big stick for a 283. With your buildup, you're probably only making around 300 lb-ft of torque out of your little Mouse. Gears are the only answer. With that tall a tire and 3.70:1 gears, it's like having 3.08s with a normal 26-inch performance tire. You're going to need more like 4.30-4.56 gears to get that thing going.

Yes, the 8-inch damper is larger and heavier; however, I don't think it's affecting the way your motor revs. The larger damper will slow the acceleration rate slightly but won't hurt the horsepower at steady state, nor will it limit rpm potential.

Finally, working with a fixed income, the 283 is going to get the best mileage out of all the engines you mentioned. If you wish to kick the mileage up a little more and pick up some torque to help move better (truck, car, or whatever you have those 31s on!), you could swap out the camshaft for a smaller one. Your 270 Magnum comes in at 270 advertised duration, 224 degrees duration at 0.050 inch tappet lift, 0.470 inch max lift, and is ground on 110 centers. We'd drop the camshaft down to an Xtreme Energy 256. This cam specs out at 256/268 degrees advertised, 212/218 degrees duration at 0.050 inch tappet lift, 0.447/0.454 inch max lift, and is ground on 110 centers. Yes, this is a much smaller camshaft, but with your ported Camel Backs on the 283, it will still make good power upstairs and you'll like the whine! Good luck with your projects and enjoy retirement!

Source: compcams.com

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