Critique this combo - 318!

rmchrgr said

Couple reasons. First, the 340 pretty much needs 2.02 valves which unfortunately is not in the budget at the moment, due to the extra machine work. If and when I upgrade the heads to larger valves I'll build the 340.

The 318 has already been hot tanked, has new freeze plugs and bearings.

Piston choice for the 340 is also a little bit more difficult since most everything is out of the hole and the cams that are good for my goals are a little less streetable than what they are for the 318. The 340 generally RPMs higher too, making street driving all the less fun.

Also, just wanted to see how it goes with this level of build. Can't say I've ever completed something like this from start to finish. Thought it would be best to start with the 'expendable' 'teen.

Vague reasons maybe, but oh well.

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I am not sure what you are referring to as to the cams being less streetable in a 340. I realize you have the 318 and I am okay with that. But a 340 is 22 cubic inches bigger and that will mellow out the idle and streetability a bit as well as making more power due to it being bigger. Okay enough on that.

The 318 in question sounds like it will be a fun little motor for sure. The reason that Thermoquads are slower than Holleys is due to the way that Carter rates the CFM. See there is no industry standard on rating carbs. Holley flows theirs at 3.5 inches. Carter flows theirs at 5 inches. For this reason two 850 carbs tested side by side will have very different results. Not to mention the lack of a secondary pump shot of fuel. I think you may have some trouble getting the stall speed you need since you have a short stroke engine with low compression and a lot of camshaft. Obviously 5k would be ideal for a stall speed, but the converter would have to be so loose that it will be very inefficient. I think by over gearing it you can minimize the lack of converter. The intake is another area I think you could pick up some hp with. The RPM Air Gap is an excellent intake and I think it would be very close to ideal. A single plane would make more power hands down with a slight trade on driveability. If you are going all out, which you will need to make your goal, a single plane would be best. A 750 Holley DP should be what to park on top of that intake. Good luck, I look forward to hearing how it runs.