Any thoughts on where I can safely go with compression?
I'm getting close with my block and thinking about where to go with (static) compression ratio for a heavy ('66 post B Body) that's a dedicated street car. I'm using new, Made In USA, Enginetech cast pistons @ .040" over with new/old stock Perfect Circle moly rings and fresh 10/10 grind forged crank. The idea is to build a sound short block now with a .100" cut on the deck with hopes to upgrade later with a worked/milled peanut plug head and E85 fuel conversion (4 barrel, header, etc, etc). I would skip the upgrade and E85 if this requires the good rods and forged pistons, this car will get V8 upgrade before going that route. Your thoughts, please?

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1966 Coronet Deluxe

My other engine had over 350 13 second passes on it with 10.5 compression.Was running perfect when pulled for full race engine.I did have to run premium with about a gal of 110 to stop pinging under hard loads.Guzzi Mark

I've run up to 12:1 on stock Sealed Power pistons and stock rods, NA motor in a heavy duster.

Just pay attention to prep work and check all your tolerances and gaps.
Once you settle on a build, you will need to follow with a custom timing curve to support it.

-D.Idiot

That's the type of feedback I was hoping for thanks. I would be leaning more towards 12 to1 if I do the E85 thing which I'd try to get from the head cut. That leads me to the next question...

After taking the .100" cut on the block deck, is there a ballpark number for compression with only knowing it will be the peanut plug style head (1983) and (most likely) a steel shim head gasket? I know it's impossible to say without all the numbers but any rough ideas if I were to take .080" or .0100" off the head also? (my cast pistons are listed as a 1.74" comp ht). THANKS

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1966 Coronet Deluxe

So far my 1980's engines have had a stock deck heght in the .175-.190 range making it hard to make a 'guess' without actual measurements. The peanut plug head has seen a range of about 56-52 cc at the chamber after taken off the engine without modification...the 1976-1978 head are a bit tighter in the 53-54 cc range stock...

To get 12:1 out of a 1963 block and 1978 head I ended up cutting .120 off the block and about .100 out of the head....(you will need ARP head studs after this...)

FYI,

-D.Idiot

I have run up to 11:1 on stock type cast pistons. Lots of abuse and no trouble.

Lou

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Home of Slant6-powered fun machines since 1988

Thanks again, this helps. My plan from the git-go was to try to get as much as possible from compression rather than expensive trickery The head studs sure sound like a great idea though, I'll start looking for those.

DusterIdiot - PM sent.

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1966 Coronet Deluxe

For a NA motor, I would not bother with head studs until you are over 12:1. The stock bolts are plenty strong. I usually run mine up just above 80 ft-lbs and have never broken/stripped one.

Lou

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Home of Slant6-powered fun machines since 1988

It's not the bolts it's the thread depth left after an 1/8 cut off the deck and a similar cut off the head if he goes with stock head bolts he'll need to use washers on the head bolts to retain the clamping force...so far I have had to do this on 1963 truck block, 1967 car block, and 1976 car block as the headbolts bottomout with about .010-.020 between the bolt head and the head itself.

Just letting you know where I'm coming from...



-D.Idiot

OK, I have never cut that much off. Max I have done is 0.110" on manifold side and 0.210" on plug side and 0.010" of the block. Gives around 11:1 depending on valve/seat heights.

Lou

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Home of Slant6-powered fun machines since 1988

Im with DI on this ARP studs is the clear choice. I have 2 motors with .200 or more off total and the bolts wont clamp.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Well heck, I'm really glad you brought that up about the extra free length using studs, I'm sure that would have been an "uh-oh" moment for sure!
Lou, I'm a little miffed here when you say you took xx off manifold side and xx off plug side, it sounds like you mean you had your head angle milled, like a super wedgie or something? I'm not being a smartarse, I've heard of angle milling but I thought was reserved for NASA/NASCAR etc Could you elaborate?

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1966 Coronet Deluxe

OK, hear me out on this please:

I'm a believer in having the studs in the block if machining with a torque plate, but that ain't happening at my machine shop, so would it be a crime to use the stock head bolts now and just add the studs later when I drop on the milled head? I realize this is a bit silly but this allows me to spread the cost a little and just-in-case I decide NOT to add the milled head later, I simply carry on as usual?

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1966 Coronet Deluxe

Or just add a hardened washer under each head bolt.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

I like that idea. I recall some time back I used some nice hardened washers (Milodon?) that had a slight chamfer/relief on the ID on one side to clear the slight bump or flare under the bolt head. These were used on my 440 and wonder if you guys might now if the S6 head bolts are the same size (OD)?

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1966 Coronet Deluxe