Can anyone tell me the standard volume when using a burette to measure the head combustion chamber capacity on a Sprint?
I'm trying to determine how much more head gasket i need to prevent my head (skimmed to 188.4mm) from binding the valves (currently binding with std head gasket)
Head stud holes have been enlarged to prevent the head from binding on the studs which it used to do.
Thanks,
Garth
Head ccs?
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SPRINTPARTS
Re: Head ccs?
Hi Garth,
Combustion chamber volume (std) is 56.5 to 61.25 cc. I am surprised a head at 118.4mm is allowing the pistons to touch the valves. I am sure my last race engine the head was 117mm and the only reason I had to put a thick head gasket on it was to stop the darn thing detonating pistons!!! Sure the cam timing is correct? The other option is to increase the depth of the flycuts in the pistons and add extra flycuts for the other valves.
Cheers
Philip
Combustion chamber volume (std) is 56.5 to 61.25 cc. I am surprised a head at 118.4mm is allowing the pistons to touch the valves. I am sure my last race engine the head was 117mm and the only reason I had to put a thick head gasket on it was to stop the darn thing detonating pistons!!! Sure the cam timing is correct? The other option is to increase the depth of the flycuts in the pistons and add extra flycuts for the other valves.
Cheers
Philip
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grelley
Re: Head ccs?
I have run around 46 cc chambers. To acheive this I removed approximately .060 from the head, and I also run a Cosworth BD4 grind on the cam which has fairly early opening inlets. When I ground the head I inclined the head upwards on the exhaust side and lowered the inlet side so that more material was taken off the exhaust side of the head. This was because there is a lot more clearance around the valves on the exhaust side. To date I have not had any problems with this arrangement.
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speedracer
Re: Head ccs?
Hmmm, see now i'm wondering ... when rotating the engine by hand one of the cam bolts wasn't in (thus allowing the sprocket to move more than it should have)
I'm going to have another go this weekend - will do both cam sprocket bolts up then try turning the motor (by hand) ...
I'm going to have another go this weekend - will do both cam sprocket bolts up then try turning the motor (by hand) ...
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speedracer
Re: Head ccs? - cam won't turn
Ok, refitted head again and proceeded to attach cam to cam gear.
Tightened up one cam bolt until the gear popped into place.
Kept turning motor over to get to other cam bolt and part of the way round it stopped turning.
Bugger, i thought - so the clearances must be too small, went to wind motor back to TDC but the cam won't turn.
Loosened off head bolts/studs assuming that something is binding, cam still won't turn.
Removed head, placed on bench, got large spanner - cannot turn cam?!?
Should i be able to turn the cam on a bench with a large spanner?
Tightened up one cam bolt until the gear popped into place.
Kept turning motor over to get to other cam bolt and part of the way round it stopped turning.
Bugger, i thought - so the clearances must be too small, went to wind motor back to TDC but the cam won't turn.
Loosened off head bolts/studs assuming that something is binding, cam still won't turn.
Removed head, placed on bench, got large spanner - cannot turn cam?!?
Should i be able to turn the cam on a bench with a large spanner?
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SPRINTPARTS
Re: Head ccs?
Hi Garth,
Yes you should- even with the huge cams we run you can turn it over on the bench, You need a big effort but it can be done.
What is the history of the cam and head? It sounds to me as though you have either a bent cam or the cam journals in the head are out of alignment. Look for something stupid in the valve train before you panic though.
I have just raced home from Oran Park after practice to replace a clutch ready for tomorrow. Cant see anything wrong with the original, but put another in and it is fixed. so not sure what is going on!!!
The annoying part is we are racing in a combined field of over and under 2 litre cars, I qualified 31 out of 41 and didn't get to start this afternoon's race so will have to start from the back tomorrow!!
Cheers
Philip
Yes you should- even with the huge cams we run you can turn it over on the bench, You need a big effort but it can be done.
What is the history of the cam and head? It sounds to me as though you have either a bent cam or the cam journals in the head are out of alignment. Look for something stupid in the valve train before you panic though.
I have just raced home from Oran Park after practice to replace a clutch ready for tomorrow. Cant see anything wrong with the original, but put another in and it is fixed. so not sure what is going on!!!
The annoying part is we are racing in a combined field of over and under 2 litre cars, I qualified 31 out of 41 and didn't get to start this afternoon's race so will have to start from the back tomorrow!!
Cheers
Philip