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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| High compression build with cast pistons? https://slantsix.org/forum/viewtopic.php?t=50846 |
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| Author: | Sprag [ Thu Jan 17, 2013 5:58 am ] |
| Post subject: | High compression build with cast pistons? |
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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| Author: | madmax/6 [ Thu Jan 17, 2013 9:18 am ] |
| Post subject: | |
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 |
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| Author: | DusterIdiot [ Thu Jan 17, 2013 10:10 am ] |
| Post subject: | No problem... |
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 |
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| Author: | Sprag [ Thu Jan 17, 2013 11:26 am ] |
| Post subject: | |
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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| Author: | DusterIdiot [ Thu Jan 17, 2013 5:29 pm ] |
| Post subject: | If stock... |
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 |
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| Author: | Dart270 [ Fri Jan 18, 2013 1:17 am ] |
| Post subject: | |
I have run up to 11:1 on stock type cast pistons. Lots of abuse and no trouble. Lou |
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| Author: | Sprag [ Fri Jan 18, 2013 5:08 am ] |
| Post subject: | |
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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| Author: | Dart270 [ Fri Jan 18, 2013 7:37 am ] |
| Post subject: | |
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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| Author: | DusterIdiot [ Fri Jan 18, 2013 9:37 am ] |
| Post subject: | But... |
Quote: For a NA motor, I would not bother with head studs until you are over 12:1.
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 |
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| Author: | Dart270 [ Fri Jan 18, 2013 12:55 pm ] |
| Post subject: | |
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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| Author: | 66aCUDA [ Fri Jan 18, 2013 1:31 pm ] |
| Post subject: | |
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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| Author: | Sprag [ Fri Jan 18, 2013 2:53 pm ] |
| Post subject: | |
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! Quote: 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, 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 Lou   Could you elaborate?
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| Author: | Sprag [ Fri Jan 18, 2013 3:12 pm ] |
| Post subject: | |
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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| Author: | Rick Covalt [ Fri Jan 18, 2013 3:20 pm ] |
| Post subject: | |
Quote: 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?
Or just add a hardened washer under each head bolt.Rick |
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| Author: | Sprag [ Fri Jan 18, 2013 4:55 pm ] |
| Post subject: | |
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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