Reply With Quote8.5:1 all around good just change pulley if needed
Fixing to purchase a BBC 555 or 565 shortblock to be run on alky, what would be the ideal static compression ratio to order ??? Builder said any comp. for same cost ....what you guy's think is best ?? would like to still keep it somewhat lakeable if possible :idea:
Enderle Bird w/8-71 , ProTopline 320 Alum. Heads
8.5:1 all around good just change pulley if needed
If you are gonna run alky I would go more than 8.5:1. For a lake boat/sometimes bracket boat deal I would put it somewhere between
10.5:1 and 11.1:1. If you go as low as 8.5:1 you will probably be seeing more alcohol in the oil.
12.5 works for me.
If you were straight all out drag racing, and with a big blower, I would say lower compression. But if this is to be lake-able, then we need to re-think. The higher the compression that you run, the better the thing will run down low and more important, the better it will idle. The low compression alcohol engines are the ones that continuosly give that lurching 'whump, whump, whump' at idle. Tough to get the fuel exactly right at adle, etc. Fine for drag racing, but difficult for driving around, without setting the idle at 2400. With higher compression, you really just take a little more blower out of it, and run it that way. And with that little blower, that would be perfect. If you were on gas, the window would be verrry narrow, but on alcohol, let any old thing fly. I would say that you are safe to run to 12.5:1 without any difficulty. The optimum in my mind would be between 10.5:1 and 12:1.
Not going to be used for all out racing , might only hit 1 or 2 races a year ?
But since this will be a completely new shortblock I want to get the most bang for the buck
Will probably get C.Straub to line up a cam for it, and it will not be anything really wild ...just trying to make great power and still be fairly easy on the engine....if that's possible
we were looking at about 11.5 or 12.5 ? just wanted alot of opinions and why so before I made the decision
Let's hear some more :argue:
Wannbe...it's on gas now with about 5 seasons on it with only rolling in bearings .... std GM 3/8" rotating parts,she's getting tired and I can sell my shortblock hopefully to re-coup a little $$
for the curious....this is what I'm leaning towards
http://www.shafiroff.com/shortblocks.../468_sbkit.jpg
The 540 seems to be popular for alky...good bore/stroke combination. I agree on the higher compression, less blower approach. I had a hard time finding 11:1 pistons off the shelf, so I'm going with plain ol' SRP (JE) 12.5:1's with Brooks alum. rods. The alum. rods aren't a bad idea either if you don't mind spending the $$. They help absorb some of the shock in the bottom end. CStraub will set you straight on a cam, that's for sure. No matter who you get the short block from, take it apart, inspect everything, check all your tolerances, and then run it. There isn't a crate motor or "package" deal out there that I would trust. GM, Ford, none of them.
edited to add...just noticed that's a Shafiroff deal in your pic...probably OK there, but I bet it's not cheap! (I'd still take it apart and check everything, but that's just me)
Not going to be used for all out racing , might only hit 1 or 2 races a year ?
But since this will be a completely new shortblock I want to get the most bang for the buck
Will probably get C.Straub to line up a cam for it, and it will not be anything really wild ...just trying to make great power and still be fairly easy on the engine....if that's possible
we were looking at about 11.5 or 12.5 ? just wanted alot of opinions and why so before I made the decision
Let's hear some more :argue:
Wannbe...it's on gas now with about 5 seasons on it with only rolling in bearings .... std GM 3/8" rotating parts
for the curious....this is what I'm leaning towards
http://www.shafiroff.com/shortblocks.../468_sbkit.jpg
Steel, could you elaborate a little more on aluminum rods and a lake
boat.....not sure about that.......Steve
Sure. What do you want to know?
Always considered Aluminum rods for 1/8 and 1/4 mile drags, not leggin it on a
river or lake. Thought maybe I needed to be updated......Steve
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