just wondering if anyone has experience playing with the chambers on a 4l head?
My question is, how many cc's can you easily remove from the chambers?? As part of my turbo project i want to take out roughly 8cc to decompress it, i really dont want to go with a head shim because i read bad things about detontation if you start increasing the piston to head clearance which upsets the squish/quench design, you need to retain the turbulence in the chamber.... AND changing the pistons isnt really an option since i rebuilt it 7months ago with ACL race series
just wondering if anyone has experience playing with the chambers on a 4l head?
My question is, how many cc's can you easily remove from the chambers?? As part of my turbo project i want to take out roughly 8cc to decompress it, i really dont want to go with a head shim because i read bad things about detontation if you start increasing the piston to head clearance which upsets the squish/quench design, you need to retain the turbulence in the chamber.... AND changing the pistons isnt really an option since i rebuilt it 7months ago with ACL race series
good luck you can try a grafite head gasket it is 10 thou thicker than mono torque type but not shore if you can still get them other wise rip the engine out and resize the rods to drop the piston down the bore
Did you measure it before and after?? I doubt it was anything like 3-4cc, I have really hogged the shit out of one, and only got 2cc. There is alot of metal in that amount of space!!
You need to get an EA head, the one with the protrusion, and hog out the little island thing that sticks into the chamber, this gives you 4cc more volume than any other head, if you take it a little bit further, you may get 5cc. You only need to shoot for about 8.5:1, which is plently low enough for 23-25psi, I went 32 on pump fuel with 8.2:1 and never ever had a single problem.
I was putting off cc'ing the chambers and 3 -4 cc was an (over) estimate. My head didn't have the little island in it, so I must have removed practically nothing. Excellent.
I have noticed a couple of threads where people mention the 3.9 ACL race series pistons, and that they are good for the 4.0 engines also. Do you know anything about this? I have pulled apart my EB2 motor, done the head obviously, and was considering just getting it honed and re-ringed and hopefully squeeze 50,000kms of fun out of it, but if the bores are out of round or have too much taper it will need to be overbored. In which case, are the 3.9 race pistons slightly larger, or do they come as an overbore size?
The 3.9 pistons are actually 17 thou smaller in stock form, hence the lower capacity. BUT!! riest: You can only buy the race series pistons in 20 thou over, and as they are usually 17 thou smaller, they will be 3 thou bigger than the stock 4 litre bore size. With the wear that your engine probably already has, you would probably only need a good hone, and the piston to bore clearance would be spot on, plus, as you are only taking 3 thou off the bore, not 20, you'll have the thickest walls of the block left possible.
Dremel use 1/8 shank stones and are expensive. Go to Supercheap and u can buy a 1/4 die grinder for like $30 and the stones from Crazy Clarks for like $2 for 5.
Don't use dremel, you need a die grinder. I don't use stones myself, I use a cutting tool and am very carefuel with it, then clean up with a sanding flapper wheel thing on the end. But a safe bet for your first time would be the stones.
I discovered there is an ACL distributor in an industrial area near to where I live so I can chase up on the race series pistons and then get on to having the block done.
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