400 Build Compression Help
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Joined: May 2011
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400 Build Compression Help
Hello all, new to the forums. Just picked up a 1979 f150 and planing a complete restoration. Working on the power plant now. I just cant figure out the compression ratio route (looking for close to 10:1 & 92 octane). Here are the current build specs.
Swap out stock pistons for 8cc dome pistons (Keith Black)
No machine work on heads or block (decking / shaving)
This combo yeilds 9.8:1 CR assuming standard boar.
Compression option 2
Swap out stock pistons for flat top pistons
Deck the block 0.020"
Shave 0.025" off the heads
This combo yeilds 9.9:1 CR assuming standard boar.
I know option 2 would yeild a better squish. Would option 1 have detonation problems since it would be stock compression height?
Im at the end of my budget so im trying to find the best/cheapest way out... worried that the block / heads machine work would add $ up.
Open to any sugestions / help thanks
- Comp Cams 276 thumper cam kit, timing chain, springs, retainers, ect
- All new engine accesories
- stock crank and rods
- Edelbrock performer intake
- 750cfm eldelbrock carb
- Port and polised stock D5AE heads
- Headman headers
- OEM C.R. = 8.4:1 as far as i know
- Heads =78cc combustion chamber
- Compressed head gasket thickness = 0.041" (8.4cc)
- Stock top of piston to deck height = 0.07" = (14.4cc)
- Stock piston dish 8cc
Swap out stock pistons for 8cc dome pistons (Keith Black)
No machine work on heads or block (decking / shaving)
This combo yeilds 9.8:1 CR assuming standard boar.
Compression option 2
Swap out stock pistons for flat top pistons
Deck the block 0.020"
Shave 0.025" off the heads
This combo yeilds 9.9:1 CR assuming standard boar.
I know option 2 would yeild a better squish. Would option 1 have detonation problems since it would be stock compression height?
Im at the end of my budget so im trying to find the best/cheapest way out... worried that the block / heads machine work would add $ up.
Open to any sugestions / help thanks
Posting Guru
Joined: Nov 2008
Posts: 1,937
Likes: 2
From: wyoming
dome stuff?
If running OEM heads open chamber. The dome piston needs to fill in the dead areas of the open chamber. not familiar with this piston. Meaning the open chamber piston has a tendency for preignition they say. I have ran a dome piston in a cleveland with openchamber and it wasn't a issue. 750 holley. Not a fan of edelbrock! installed pistons only block stock and heads stock. Just upgraded the valves and springs and ran a 268 hi energy comp cam. great little combo.. One of the tricks is to fill in the dead areas of the open chamber or atleast tighten up the combustion chamber as much as possible. But I would build the engine to at least run on 88 octane because some fuels are not created equal no matter what they say at the pump. Not familar with the thumper cams. So the intake/exhaust valve opening/closing will change your compression also. www.wallaceracing.com check out their auto calculators to kinda give you a idea of whats gonna happen. Need some info from your cam to get the best guestimation you can get. Good luck!
I personally think it will work but need more info on the piston.
I personally think it will work but need more info on the piston.
