We wouldn’t be afraid of reconfiguring your 383 to run on Chevron’s finest. I would recommend going with a slightly smaller inlet runner than the 220 cc you’re currently running. Pump-gas engines are like tractors. They like to run between 5,000 to 7,000 rpm. Tim Wusz of Rockett Brand Racing Fuels taught us years ago, when he was the chief fuel engineer at Union 76, that pump gas isn’t very stable above 7,000 rpm. We’ve always respected his advice, kept the combinations within these limits, and have been very successful. Look into a set of aluminum cylinder heads with 210cc inlet runners, and 76cc combustion chambers; these chambers will drop your current short-block’s compression ratio down to 10.5:1. You will want to keep the engine temperature under control and not run it at high loads much over 170 degrees coolant temp. Start with the total spark timing in the 28-30 degree range. After you’re comfortable and not experiencing any spark knock, you can advance the timing in 2-degree increments until you don’t gain any miles per hour at the dragstrip. We’d even recommend when you find the best mile per hour drop the timing 2 degrees for added level of safety margin.
Back to the 1.35 hp per cube. Your 383 comes in at 517 hp at 1.35 per cube. If you take the LT4 small-block at 1.32 you’re still producing 505 ponies. Again, this shouldn’t be a problem. Good luck with your little Chevy II and let us know how it comes out.
Sources: airflowresearch.com, dartheads.com, rockettbrand.com
Q. I am trying to find the right spark plugs for my car. It is a ’69 Nova 307, bored 0.030 inch over, with a Torker intake with a Holley 750 and headers. The cam is just a little above stock, and the heads are ’80-85 305, cast number 14014416. Can you help me with this?
A. The production AC spark plug for your small-block with the later-model cylinder heads would be an R45TS. This is a moderately hot plug that will keep clean and shouldn’t give you any issues with your mild build. If you wish to run a slightly colder-range plug that would be a R44TS. Again, these are ACDelco spark plug numbers. You can convert these plugs into any flavor you wish. We’re partial to NGK plugs as they are relatively inexpensive yet very well made. The NGK cross-reference for the R45TS and the R44TS is covered by one plug: an NGK UR4. You can pick these up at any of your local chain auto parts stores. If you watch the Sunday paper for ads you’ll find one of the big boxes with them on sale. Happy hunting.
Q. I just read the header shootout from the Feb. ’09 issue. I am building a 0.030-inch-over 400 small-block for 5,500 rpm and below, with Edelbrock E200 heads, an RPM Air-Gap intake, a 650HP Holley DP carb, a COMP Cams 264H hydraulic roller cam, and 1.6 roller rockers. This will be backed up with a 700-R4 trans with a 2,600- to 2,800-stall vigilante lockup converter. I bought the 11/2-inch Flowtech mid-length headers but am having second thoughts that the diameter and collector are too small. Any new thoughts since the article? Do you have any thoughts on header selection?
A. I agree with you that the 11/2-inch primary mid-length headers wouldn’t be the best choice for your engine build. The mild 400 small-block builds we’ve been involved with always ran the best with 15/8-inch primary long-tube headers. You really need to have a pretty substantial build before the 13/4-inch primary tube headers give you enough horsepower gain upstairs to make up for the torque gains made in the meat of the torque curve with the 15/8-inch headers.
Not knowing the chassis you’re dropping your small-block in, please go and check out the Holley/Flowtech website and pick out a set of long-tubes for your build. You’ll be much happier with the finished product.