I'm planning on sending my head in to get shaved to pick up as much compression as possible. I dont want to get the deck done because the bottom end is freshly rebuilt, so the cost of new $#!+ would grind my gears. Whats the most I can shave off of the head? If it helps, its a '71 head with enginebuilder valves.

-Ryan

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1965 Plymouth Belvedere II Turbo Project - SOLD
2002 Subaru OBS
1995 Lexus LS400 Race Car

Do a search on this site for "dynamic compression." It is more a matter of how much you need to shave rather than how much is possible, and there are many important variables.

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Casually looking for a Clifford hyperpak intake for cheap.

Also you have to measure it to see what CC you are at now before you can even begin to think about it. And measure how far down your pistons are currently.

Without doing that you are kind of shooting in the dark and you could get lucky, or you could end up with an engine that pings all the time and isn't happy without octane booster.

The more the merrier for this engine. The cam would run well with a sc between 10:1 and 11:1. It will be run on c16 as well, so I'm not worried about octane haha.

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1965 Plymouth Belvedere II Turbo Project - SOLD
2002 Subaru OBS
1995 Lexus LS400 Race Car

C16?????

BTW polish and unshroud the valves? Then CC it. Then figure what you need to take off.

If you are going to bigger valves? (Correct me if I am wrong,) it could mean 2 trips to the machine shop. Insert big valves, unshroud, polish then CC.

edit

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

I've already advised this...especially with regards to shooting in the dark on the actual SCR.

He's running all race so he's shooting for a 9.5:1+ DCR, which is fine on 110 leaded or the race fuels (C16)...

Either way he can't go too far below 36 cc in an earlier head (I know that I have one that is 38 cc and on the thicker deck of the peanut plug head at that thick of a cut it's a less than .010 before the coolant passages start to get 'wider'/ and the deck won't be much more than paper. I've seen one head that was 32 cc in the chamber...it won't take another cut ever again...(it was being used as a door stop in the machine shop...).

Until he does the measurement on the deck height he can't tell the machine shop what to shoot for anyway...so he's stuck until he does it
so he can help us help him. (Would suck if the rebuilt block had dished pistons and his deck height would have to come down to make up for it.)

-D.Idiot

C16 will be a waste of money unless it's a high boost situation.

9.5 will make more power on 100.

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Official Cookie and Mater Tormentor.

What about using ethanol if you want high compression?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

E85 the poor man's race fuel

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

He's on a budget (otherwise he wouldn't have made his rear a demo derby locker...i.e. stick welded). For running alcohol he'd have to re-kit the carb and change the jetting to be very rich...and then work on the rest of the fuel system to bring it up to par... The expense to immediate use ratio goes down pretty fast. I've actually done my 20 minute engine break in on a 12:1 slant on street 92 without issues (no vac. adv. and limit timing to 30 total), but spike the tank at the track to make sure that it doesn't rattle at part throttle (heavy body and part throttle lug with manual tranny don't mix...)...



-D.Idiot

Just measured it, I tried to get it as close to tdc as I could. It looks to be about .180 in the hole, and the pistons are flat tops. I had a welded diff before, but changed it for a spool.

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1965 Plymouth Belvedere II Turbo Project - SOLD
2002 Subaru OBS
1995 Lexus LS400 Race Car

Bump, it's .180 in the hole. Checked with a depth micrometer. Flat top pistons, 1971 head. Sorry for not checking beforehand.

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1965 Plymouth Belvedere II Turbo Project - SOLD
2002 Subaru OBS
1995 Lexus LS400 Race Car

Time to tear down the short block and have .100" whacked off the deck. When I was blindly going for compression with stock-type pistons I had .100" taken off the block and head both. With Ford 300 valves, home porting and a relatively mild cam (Oregon 819) it ran rather well. I should have measured the combustion chamber volume so I could calculate the compression ratio. This was in my road racing '66 Dart and I burned 100 octane low lead aviation fuel. It probably would have been fine on 92 octane pump gas, but we didn't put hard seats in the head.

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Joshua

I concur with Josh...

Assuming the 1971 head is kindly 54 cc (may be a bit more), and running a victor Reinz composite head gasket...taking a .120 cut would reduce the "stock" head volume (this will change with new O/S Valves and seats)...to a 36 cc chamber...

Bringing the SCR from 8.06 to 9.9.... on your stock block (36 cc chamber...)

Keeping the chamber the stock size and taking a .100 cut off the deck bring you up to a 9.51 SCR...then reducing the chamber to a 44cc chamber brings you up to 11.21 SCR to support the AM Cam.

Which comes up to an interesting idea...

Plugging your cam into the DCR calculator at 11.21 SCR, with that cam dialed into an intake Centerline at 102...brings the DCR to a whopping 8.92:1....which means if all goes well you could possibly street drive it or run it on 92 octane once you have dialed in the timing curve (or if using a very aggressive race curve...then adding a few gallons of 100-110 to your 3/4 tank of 92 should keep it from pinging).

So if you can get that done...you should save $$$ by not having to go to full $9/gallon race gas all the time...and put that $$$ toward your entry fees.



-D.Idiot