When I start the car it has to be up to temperature or it will not accept the gas, and it still has a flat spot. I have 58 jets in the primaries and 64 jets in the secondaries of the 3310 Holley. What do I need to do with the carb? I have the floats set at the bottom of the sight hole with the engine running.

Also, do you think the S-10 rearend will hold up behind this engine, being it is for street driving? I have 12 inches of rubber under the fender skirts, which is why I went to a shorter rearend.

From reading your Q&A, I think I’m around 400 hp. Would you put your pen to it for me, please? I know you get tired of the same old questions, but I don’t know how to figure it. Thanks.

Jim Palmour
Tennessee Ridge, TN

We old guys have to stick together. Keep building those old-school engines, as they power around many a nice street car.

We believe you’re very close with your estimate of 400 ponies. With the Dart heads, 10.5:1 squeeze, RPM intake, and RPM camshaft we’d give you around another 20 horses. At this point, it really doesn’t matter if you’re happy with the performance of your engine. Sometimes we have to laugh a little about how wrapped up people on the Internet get talking about horsepower.

The remedy for your flat spot is to add more fuel. The factory calibration for the early 3310 vacuum-secondary Holley is a 72 jet on the primary side and 76 jets on the secondary. We’re surprised you don’t have a surging problem even when the engine is warm and cruising down the road. And you’ll love this: increasing the jet to the factory settings will probably pick you up 20-30 hp at wide-open throttle! Then you will be making the estimated ponies listed above. To find any of the original calibration specifications, check out the Holley website and look under Tech Help, then Numerical Listings.

Your S-10 rear will be just fine for street rod applications. If you try to go out and drag-race the car, you may run into some complications. The early S-10 rearends were equipped with a 71/2-inch ring gear. You can upgrade this case with the 75/8-inch gears, and the 28-spline axles and carrier. Down the road, if you wish to really step on it, you could look into a complete rearend from the ’95-and-up S-10. Some of these trucks came equipped with the larger 8.5/8.625-inch ring gear. These were the strongest 10-bolts GM built. Unfortunately, there isn’t an easy way to spec one out from model years and options. The best way is to check out the differential itself. The easiest way we know of identifying an 8.5 10-bolt is by the two casting ears at the bottom of the case by the rearend cover. The 8.5s have two ears that are parallel with the ground and squared off. The 7.5s have a semicircle machined into these two casting ears. They are easy to spot by just looking under any late 10-bolt-equipped vehicle.