Ad Radar
Car Craft
Click here to find out more!

1989 Chevy K2500 TBI Setup - What's Your Problem?

Olds Rocket Science
Nolan Malone, River Falls, WI: I have a few questions about building an Olds 350 Rocket. The engine is a second-generation motor from my '72 Cutlass. Do you know how far I could bore it out and how great a stroke I could get? Can you tell me a few companies that make aluminum cylinder heads besides Edelbrock? A list of performance parts and where to find them would also be extremely helpful. I'm only 16 and all I really know is Chevy (I have a 355 SBC in the Olds right now). It's hard to find good forged cranks/rods/pistons and nice heads. All the websites I seem to find look sketchy. Can you point me in a good direction for building a naturally aspirated engine that makes 400 to maybe 500 lb-ft (that may be pushing it without a longer stroke)? I don't care much for big horsepower numbers because this will be mainly a street engine. If you know of a good cam to help with that torque, I would love that, too. I have been reading Car Craft for almost three years, and I love every issue.

Jeff Smith: I particularly enjoy receiving tech letters from younger readers. They are the next generation car crafters who will keep this whole industry going. Since you're only 16 years old, Nolan, I'll assume this is a budget project, which means you probably can't afford stroker cranks, aftermarket heads, and all the rest of that expensive stuff that we all would love to build. I called Dick Miller at Dick Miller Racing (DMR) to get his take on your request. Dick's first question mirrored mine: "Why doesn't he just build a bigger motor? A 403 Olds will bolt right in to that Cutlass, and even the brackets for the alternator and power steering are the same." Dick's point is that the easiest way to make more torque and horsepower is with a larger-displacement engine. He gave us an example of a pump gas 403 he built for a customer with fully ported factory iron heads and a 240/246 degrees at 0.050-inch tappet lift cam with 0.541/0.544-inch valve lift that made 476 lb-ft at 4,200 rpm and 482 hp at 6,000. This was with an Edelbrock Performer RPM intake manifold and a 780-cfm Holley Street Avenger carburetor. Another point worth considering is that buying a camshaft or cylinder heads for a smaller engine like the 350 costs the same as for a 403, but the potential to make more power will always be with the larger engine. The 403 sports a massive 4.351-inch bore and a relatively short 3.385-inch stroke. The 350 uses a much smaller 4.057-inch bore and the same 3.385-inch stroke. If there is one limit to the 403, it has to be that it was available only in GM passenger cars between '77 and '79 and some motorhomes and other applications. That limits the number of engines that are out there for retrieval.

Since you asked about the 350, Dick also gave us some specs on one of his engines that made 431 hp at 5,700 rpm and 434 lb-ft at 4,900 rpm. It was equipped with production No. 5 iron heads that he ported and fitted with larger 2.07/1.71-inch stainless valves. Compression was 10.25:1 using a set of forged, flat-top TRW pistons. The camshaft Dick used was a DMR-1441 hydraulic roller with 236/240 degrees of duration installed 5 degrees advanced and produces 0.553/0.544-inch lift.

Dick says your '72 350 is probably fitted with a set of No. 7 heads, which are just as good as the heads he used on his customer's engine, but you will need to use a flat-top piston to create more compression because stock, your engine is rated at 8.5:1. This is a good step, as porting the heads may be more than you can afford, but that can wait as long as the short-block is in good shape. As a budget alternative to the hydraulic roller setup, he offers a similar-spec flat-tappet hydraulic camshaft (PN DMR-1530) with specs of 230/236 degrees of duration at 0.050-inch tappet lift with 0.522/0.522-inch lift. Combine that with an Edelbrock Performer RPM dual-plane intake and a good 750-cfm carburetor and you're on your way. If your engine is still equipped with the stock Quadrajet, that's a great carburetor for this engine. Rebuild it (if it needs it) and learn how to tune it because it will offer outstanding part-throttle response. Did you know a stock Q-jet will flow at least 750 cfm? Most guys don't realize that.

Here's our take on this: If you can find a 403 motor, we'd suggest going that route instead of the Olds 350. It will make more power. But if you want to get going, you can always buy bolt-on parts for the Olds 350 like headers, an intake, a cam, and even cylinder heads, and then if you find a 403 at a later date, you can use those parts on the new 403.

Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
0 comments
Car Craft