Thread: 350 sbc build need advise

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Originally Posted by Travlin55

Ok so, after much pondering and considering the great information you have provided I think I'm going to have simons machine here in charelston hopefully give me a thumbs up on the bore as is at .040 as it was built only 3000 miles ago.I'm now considering a 383 kit with wiseco Pistons as suggested and having the block decked as suggested.
I will then possibly go with skip whites aluminum heads, maybe still use the air gap intake? and possibly a 750 Holley? Still not sure about the cam but feel a roller would be a nice touch? By the way what's the difference between a regular 383 crank and a scat crank?
So, what do you think? Please keep in mind this has been a learning curve for me.

Forged pistons generally require a little more piston to bore clearance than a cast piston, so you could be in good shape if the walls are relatively straight and the bores are round. The shop might be able to put the extra clearance in the block for you with just a precision hone job using the proper grit stones to match up with the piston ring material being used. I don't know if you knew that different piston ring materials require different roughness on the walls, but yeah, they do. Then, there is plateau honing. Read through the process here, the more you learn, the better you will be prepared to go head to head with the guy at the machine shop.
https://www.enginebuildermag.com/200...e-refinishing/

Although some fellows will tell you that you don't need the pistons in hand for the machine shop to finish hone the block, I will caution you that we are dealing with human beings here, and human beings make mistakes. MY VERY BEST ADVICE TO YOU IS TO TAKE THE PISTONS AND RINGS TO THE MACHINE SHOP BEFORE THEY BEGIN HONING ON THE BLOCK.

The rings will have to be gapped according to the piston manufacturer's instructions. Wiseco calls for the top ring on a 2618 (this is the piston alloy designation) "piston to be used in a hot street application" to be gapped at 0.005" per inch for each inch of bore. So, a bore of 4.040" times 0.005" equals 0.0202". I would be OK with dropping the two ten-thousandths off the end and gapping the top rings at 0.020" (twenty thousandths). Wiseco calls for the second rings to be gapped at 0.0055" per inch for each inch of bore. So, a bore of 4.040" times 0.0055" equals 0.02222". Again, I would be fine with using only 3 places past the decimal point and calling the second ring gaps at 0.022" (twenty two thousandths). The idea behind this is that any blowby that gets past the top ring will be vented past the second ring because of the wider gap in the second ring. The top compression ring and the second oil control ring do their jobs by closely fitting the bottom of the rings to the bottom of the piston grooves, so any high pressure area between the first and second rings could upset this arrangement. The third set of oil rings, the expander and rails, will be in a low heat area, so whatever gap is on them from the factory will probably be OK. Pow-Wow with the machine shop about this. You can pay them to gap the rings or you can purchase a ring gapping machine and do them yourself. HINT: I would rather do them myself. It adds another skill to your engine-building knowledge.
https://www.youtube.com/watch?v=uAguO3EPzcI
Here's a hand-turned model where a buddy would turn the crank while you manipulate the ring on the tool.....
https://www.summitracing.com/parts/pro-66785

You'll find that there is more to aluminum heads than just being aluminum heads. While I would have no problem recommending the Wiseco taller compression height pistons and piston rings from Skip White Engines, I would have to pull my recommendation on aluminum heads from them. Unless I am mistaken, all of their offerings are cast in China or other offshore location where everyone copies everyone else and nobody seems concerned in the actual flow capability of the heads. You buy cylinder heads for the flow that they are capable of, not for the money you're going to save because the Chinesium heads are cheaper than the heads that flow correctly. Currently, there are only two manufacturers that I would call on for heads, Airflow Research and Pro-Filer. AFR casts up the Rolls Royce of heads and charges for them commensurate with their quality. There is another head, the All-American by Pro-Filer that flows nearly as well as the AFR head, but is about $400 cheaper for the pair.

Here's the Pro-Filer, you'll end up with a total investment of about $1200 into the pair of heads. That will be complete with screw-in studs (I'd opt for the 7/16" studs instead of the 3/8" which come standard on 350 heads), guide plates, valves, seals, locks, springs and retainers, ready to bolt on and go. Use ONLY valve springs that are recommended by the cam manufacturer for the cam you will use. These heads, bolted onto a 383 with 10.0:1 to 10.5:1 static compression ratio, 230 degree intake duration @0.050" roller tappet cam, 850 CFM carb on a dual-plane, high-rise intake manifold and a set of 3/4" diameter primary, equal-length headers, H-pipe immediately after the collectors, will generate 500+ horsepower and 500+ lbs/ft of torque. Your current differential would last about 5 minutes.
https://www.profilerperformance.com/...ree-heads.html

There is no regular 383 crank. Chevrolet never made a 383. It's a hybrid that was concocted by hot rodders by turning down the main journals on a 400 crank so that it would bolt into a 350 block. The 400 crank has the same rod journal size as the 350, but has a 3.750" stroke instead of the standard 3.480" stroke of the 350.

Scat is an aftermarket manufacturer that has been making hot rod parts for Volkswagens for decades now....and has morphed into a new business model by casting up 3.750" cranks to fit into 350 blocks. Journalist and hot rod guru expert David Vizard has written that he has used Scat cranks for the past few years, taking as much as 550 horsepower out of a 383, without a single failure. When you put a 383 together with stock 5.7" rods, there is interference at some points with the cam lobes. To fix this, you grind on the rod at the big end to make clearance. I will not recommend using stock type rods in such a build though, and would strongly recommend using Scat 6.000" rods instead. They are manufactured to clear the cam lobes and will also allow a larger diameter crank so that balancing doesn't cost you an arm and a leg for Mallory Metal. Internal balancing is far superior to using a damper with offset weight and flexplate with offset weight.

Pro-Filer casts up the All American heads with 64, 70 or 72cc chambers, it is pretty easy to get to the static compression ratio that you want by juggling the chamber volume with various piston crown configurations.

I can appreciate that this has been a learning experience for you........and I expect for a few other fellows as well. There are others in the hobby who could make me look stupid though, and I really wish they would show up and share themselves.

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