I'm building a fairly stock super six with a late model block and was wondering if there are any gains from decking the block and bumping the compression in such a mild motor. It just seems wrong that the pistons sit so low in the cylinders. Will this mod give any performance gains and will running regular still be possible? Sorry if this topic has been asked 100 times already. The motor is for my '64 wagon that we haul lots of heavy food and equipment in if that makes any difference....probably not, I just like giving too much info.

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Well I would advise that some measuring should be done before hand, chances are you will find the current compression isn't even close to what the engine was originally rated. Milling enough to bring it to "spec" shouldn't create any issuses, but milling it a bit more would likely make an aftermarket cam respond a bit better. Keep it 8.5-9.0 or so and regular should be OK, maybe plus.

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225 .030
.020 off the block .100 from head
Comp 264
904 Tranny
New Ebre-ting

http://s78.photobucket.com/albums/j103/edrod01/

Go ahead and deck it and buy a new cam while its apart.

I run a Comp 264 and 9.25 CR and run on regular fuel.

Decking the block 50 with a stock cam is prolly not a bad idea either (Ive never done it)

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I've already got everything for the build including a stock cam (thanks Dave) so I probably won't get a new cam. We do have a turbo slant in the works for another car though but that's for another day. While we're on the topic, what's the equation for calculating CR. I assume stock slants come in somewhere around 7 1/2-8.

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Here's a CR Calculator

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Yes, a stock 225 Slant comes in around 7.5-8:1. I would go 0.060"-0.080" with a stock cam and you should have no issues.

Lou

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Home of Slant6-powered fun machines since 1988

What kind of performance gains can be expected from this simple task?

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If you have everything working properly, I would expect a bit better mileage, and probably 4-12 HP gain (~5%).

FWIW, degreeing your cam properly and optimizing your ign advance curve will likely net you the same sort of gains, since they (cams/tchains, or adv curves) are often not right.

Lou

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Home of Slant6-powered fun machines since 1988

I just went through this same process not wanting to be crazy about HP but wanted more torque to pull the 2.76 gears and get good mileage.
Advancing the cam 4 to 6 degrees helps, milling off a .100 helped alot. I have lots more snap with only mild work done on the head.
2.25" exhaust all the way back helped allot too.

Those three things are a must for a hauler like a wagon or a truck.
THere are several other items that can help, like a distributor recurve, carb rebuild, etc. I kept it pretty basic and am very happy with the outcome.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I just had .100 taken off the top of my 62 block, and after asembly, my slugs are still .100 in the hole. To get a CR in the 9.0-9.5 range, I'll have to get head volumed in teh 52-55cc range.

hi, i took .060 off a 68 225 and ended up -.115 in the hole. wish i had taken off more. also took .100 off a 69 225 and ended up .070 in the hole. i also found that my new .030 pistons were .025 to .030 shorter than my stock originals from center of piston pin to top of piston. ron