Hey all. I am running a 511 RB that is still in the short block stage. I am useing Ross flat tops with valve notches. I had the machine ship zero deck the block. I want to use Indy heads with the smallest chamber volume I can get (I thank) to raise compression to around 13:1. I have read other coments that it will not work. I need advise on head gaskets or just opinons on this set up. thanks
head gasket and deck question
- Thread starter hwp
- Start date
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Mrmopartech
Well-Known Member
Is this a race car only and do you run alcohol or VP racing fuel,and how big of a cam do you intend to use and the rpm limit of this combo,and which indy head and the CC,s of that head you intend to use.Even with a big 906 head of 85cc,s,you will have 12.5-13.0 C/R.And if the indy head is any thing smaller,its going to go into total melt down,Mrmopartech
BJR Racing
Well-Known Member
Mrmopartech,
Wheres the garage? I see you have one? I Think? Is that diesel going in your race car? Man you must have a big garage. Can I put some stills in there so we can have a drink? You know how us hillbillys are!..................lol You cant get better alcohol than what a still can make, HHHHHHHHHHUUUUUUUUUUUUUUUUMMMMMMMMMMMMMM..........maybe this is why our cars run so fast, I heard alcohol runs faster than gas. Man thats some good stuff!
BJR Racing
Wheres the garage? I see you have one? I Think? Is that diesel going in your race car? Man you must have a big garage. Can I put some stills in there so we can have a drink? You know how us hillbillys are!..................lol You cant get better alcohol than what a still can make, HHHHHHHHHHUUUUUUUUUUUUUUUUMMMMMMMMMMMMMM..........maybe this is why our cars run so fast, I heard alcohol runs faster than gas. Man thats some good stuff!
BJR Racing
Thanks for the reply. I plan on VP fuel, I have been doing the calculations with a online compression calculator. this is what I get. with 4cc valve notches, the deck heigth of "0" and 72cc chamber I get 12.884 compression. If I use 65cc heads it shows it would be 14.075. these calculations were done with a head gasket compressed of .020. I most likely am wrong. I dont know what cam to use yet. It will be in a duster.(dont know final weight) 4 speed car. will be raceing only. I have a long way to go on this project as of yet, so I am not in a hurry. This information on compression is used with The Ross information and information from indy and my machinist. Acording to Ross. The pistons sit .017 in heigth with a standard deck (what ever that is) and the compression heigth is 2.065. this if before decking the block. Given that information my research shows that with 65cc chambers that the compression would be in the 11 range. Now with all that. I realy have no idea if I am doing that right or not. I want the most power out of this with out melt down, but want a very strong motor. My over all goal over time is to get into the 10's. I still have to tub it and get the rear setup right. Thanks for all the help.
Guitar Jones
aka Angry Johnny
If you have a zero deck piston with a small quench chamber head a .020 compressed gasket will get you a pile of ruble in a hurry. You should aim for about .038 piston to head clearance with steel connecting rods. A little less is OK but no more than .040 to keep the chamber active. Get the smallest chamber you can, you can't have too much compression in a race motor unless you plan on pressurizing it with a blower or turbo or hosing it to death with nitrous. 4cc's isn't much for valve reliefs either, I think mine on the small block measured about 7 or 8 and they provide very minimal clearance, larger would be better.
The correct way to measure compression ratio is the total area of the cylinder above the piston with the piston at BDC divided by the total area above the piston with the piston at TDC. You'll need to take into account the bore diameter of the gasket as well since it is always larger than the cylinder bore.
The correct formula looks like this:
chamber cc's + gasket cc's + deck clearance cc's (in your case 0) + (displacement x 2.0483 for an 8 cylinder) + valve pocket cc's
divided by
chamber cc's + gasket cc's + deck clearance cc's + valve pocket cc's
to obtain cc's for the head gasket the formula is
bore x bore x 12.87 x compressed thickness (remember this is the head gaskets bore, not the cylinders.
formula for figuring deck clearance for those of you without zero deck pistons
bore x bore x12.87 x depth of piston in block.
The correct way to measure compression ratio is the total area of the cylinder above the piston with the piston at BDC divided by the total area above the piston with the piston at TDC. You'll need to take into account the bore diameter of the gasket as well since it is always larger than the cylinder bore.
The correct formula looks like this:
chamber cc's + gasket cc's + deck clearance cc's (in your case 0) + (displacement x 2.0483 for an 8 cylinder) + valve pocket cc's
divided by
chamber cc's + gasket cc's + deck clearance cc's + valve pocket cc's
to obtain cc's for the head gasket the formula is
bore x bore x 12.87 x compressed thickness (remember this is the head gaskets bore, not the cylinders.
formula for figuring deck clearance for those of you without zero deck pistons
bore x bore x12.87 x depth of piston in block.
moper
Well-Known Member
Guitar's dead on. Using Ross's info is misleading, because of the existing height of your factory block. The one I checked this week for a 493 was .028" taller than blueprint spec. So, saying "I have had it set to zero deck height" could mean down in the hole if the block was only decked for flatness. If the block is square decked to blueprint spec, the piston will be down in the hole .017 if I read right. If it's race only, I would run tighter than .038 unless the rpm is way high. The flat top and Indys better chamber will work very well, but there comes a level where high is too high. If this is an RB block, I would not go over 12.5:1 for longevity's sake. If it's a B block base, you can go higher. A lot depends on the work done to the lower end. A 511 doesnt need rpm to make it's power, and the lower the rpm range, the longer it will live, regardless of the static compression ratio.
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