horsepower
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
Josh,
I thought that I read somewhere that you used Aussie heads. If you used the stock 400 heads(78.4cc), you will be OK with a Crane H278-2, but if you used Aussie heads(58cc), I think that you have a problem.
I am not at my own computer now, but I will check your Dynamic Compression Ratio when I get home.
What heads did you use?
I thought that I read somewhere that you used Aussie heads. If you used the stock 400 heads(78.4cc), you will be OK with a Crane H278-2, but if you used Aussie heads(58cc), I think that you have a problem.
I am not at my own computer now, but I will check your Dynamic Compression Ratio when I get home.
What heads did you use?
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
That stroker kit uses a 400 crank offset ground to 4.2" stroke. The connecting rod is 6.25". The forged piston must be a TRW L2436F (1.947CH) to give 9.5:1 CR with a 78.4cc head. This piston had about 15cc dish/valve relief. The deck clearance is zero.
If I swap to an Aussie head with 58cc, then the Static CR becomes 11.59:1. This is quite high, but it is the Dynamic Compression Ratio that is important.
The Crane H278-2 cam has an Intake Valve Closing Angle of 72 degrees ABDC, if the cam is installed 'straight up'. This will produce a DCR of 8.76:1. This will be too high for pump fuel.
If the cam is installed 4 degrees retarded, the IVC is 76 degrees ABDC, the DCR will be 8.44:1. You should be OK with 93 Octane.
My information says that a DCR of 8.5:1 is the absolute maximum for a motor with quench. I would check these numbers with the shop that did the work, there may be some difference between the piston or combustion chamber ccs from the numbers that I used.
If I swap to an Aussie head with 58cc, then the Static CR becomes 11.59:1. This is quite high, but it is the Dynamic Compression Ratio that is important.
The Crane H278-2 cam has an Intake Valve Closing Angle of 72 degrees ABDC, if the cam is installed 'straight up'. This will produce a DCR of 8.76:1. This will be too high for pump fuel.
If the cam is installed 4 degrees retarded, the IVC is 76 degrees ABDC, the DCR will be 8.44:1. You should be OK with 93 Octane.
My information says that a DCR of 8.5:1 is the absolute maximum for a motor with quench. I would check these numbers with the shop that did the work, there may be some difference between the piston or combustion chamber ccs from the numbers that I used.
