piston height at TDC?
Postmaster
Joined: Aug 2001
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From: Delaware
With 0.010 milled off the heads, and 0.088" deck clearance, your static compression ratio is a 8.2:1. If you have an H272-2 Crane cam with an IVC of 67 degrees, the dynamic compression ratio is only 6.5:1.
The peak torque is 406 ft-lbs @ 3500 RPM, and the peak HP is 325 @ 4500 RPM.
You could advance the cam by 4 degrees to get a little more torque at low RPM, but your HP will drop slightly.
I think that you have both the wrong pistons and the wrong cam. The pistons give you low compression and the cam makes it worse with late intake valve closing.
A set of flattop pistons and a Comp Cams 265DEH cam will give you 450 ft-lbs torque @2500 RPM and 337 HP@ 4500 RPM.
The peak torque is 406 ft-lbs @ 3500 RPM, and the peak HP is 325 @ 4500 RPM.
You could advance the cam by 4 degrees to get a little more torque at low RPM, but your HP will drop slightly.
I think that you have both the wrong pistons and the wrong cam. The pistons give you low compression and the cam makes it worse with late intake valve closing.
A set of flattop pistons and a Comp Cams 265DEH cam will give you 450 ft-lbs torque @2500 RPM and 337 HP@ 4500 RPM.
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Posting Guru
Joined: Jan 2001
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From: Nebraska
Are those 406 torque and 325 horsepower figures with what I have now? I don't think both a different cam and pistons are in the budget. I've already been screwed by the machine shop and am spending way more than I planned.
Most pistons I'm seeing mentioned here are for a 9 or 9.5 to 1 compresson ratio. I'd like to still be able to run 87 or 89 gas without problems. Will that be a problem if I went with these pistons?
Sorry for so many questions, this is my first engine build. And of course, nothing's going the way I planned. Thanks for all the help so far.
Most pistons I'm seeing mentioned here are for a 9 or 9.5 to 1 compresson ratio. I'd like to still be able to run 87 or 89 gas without problems. Will that be a problem if I went with these pistons?
Sorry for so many questions, this is my first engine build. And of course, nothing's going the way I planned. Thanks for all the help so far.
Last edited by brown 4x4; Feb 10, 2005 at 10:22 AM.
Elder User
Joined: Jan 2004
Posts: 867
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From: Eastern Pa
Danlee the measurement fo rthe intake closing on that cam should be 35 abdc @.050 lift. That would bring the static to 8.07 and dynamic 7.12. Still not enough to run that cam.
Brown I know your'e over budget, I did the same thing but trust me you need to address this somehow and I think the best thing to do here is to get your cr up. You should be able to run 9:1 on pump gas with that cam. if you got the block decked .020 and swithched to a badger piston it would get you in the 8.8:1 static and 7.8:1 dynamic range which should run on pump gas. I'm not sure whic would be the least expensive things to do to achieve that but I do know you'll kick yourself for quite awhile after your build for having done all that work and not finishing it off right.
Brown I know your'e over budget, I did the same thing but trust me you need to address this somehow and I think the best thing to do here is to get your cr up. You should be able to run 9:1 on pump gas with that cam. if you got the block decked .020 and swithched to a badger piston it would get you in the 8.8:1 static and 7.8:1 dynamic range which should run on pump gas. I'm not sure whic would be the least expensive things to do to achieve that but I do know you'll kick yourself for quite awhile after your build for having done all that work and not finishing it off right.
Postmaster
Joined: Aug 2001
Posts: 4,270
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From: Delaware
Yes 406 torque and 325 Horsepower is with the cam and pistons that you have. You might have to run a higher octane fuel than 87, if you changed the cam and pistons. There are others who are running badger flattops on 87 octane on this forum.
The Badger pistons will give you about 9.2:1 Static CR. With the H272-2 cam the DCR is 7.27:1. With the pistons that you have now, the Static CR is 8.2:1 and with a 265DEH cam your DCR would be 6.9:1. This combo will give you 426 ft-lbs torque @2500 RPM and 312 HP@4500 RPM.
You probably cannot change pistons without some more machine work, because the clearance may be different between your current pistons and the Badgers. You should be able to replace the Crane H272-2 cam with a Comp Cams 265DEH. The Crane springs are probably OK for the lower lift Comp cam.
The Badger pistons will give you about 9.2:1 Static CR. With the H272-2 cam the DCR is 7.27:1. With the pistons that you have now, the Static CR is 8.2:1 and with a 265DEH cam your DCR would be 6.9:1. This combo will give you 426 ft-lbs torque @2500 RPM and 312 HP@4500 RPM.
You probably cannot change pistons without some more machine work, because the clearance may be different between your current pistons and the Badgers. You should be able to replace the Crane H272-2 cam with a Comp Cams 265DEH. The Crane springs are probably OK for the lower lift Comp cam.
Posting Guru
Joined: Dec 2002
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From: chicago burbs
brown 4x4, i got that you had the recommended springs for the cam, but did you have them set-up and checked for coil bind? i think your 272-2 is way past the limit for stock retainers and unmachined spring seats. you could be looking at a lot of bent pushrods and worse if the springs coil bind.
Elder User
Joined: Jan 2004
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From: Eastern Pa
That cam and kit should not give any problems with coil bind, it didn't with mine. Neither did I need to machine the spring seats, but making sure you get the proper lifter preload will be important.
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Posting Guru
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From: Nebraska
I had new exhaust valve seats installed. Right now my exhaust valves sit about .020" too low in the head and the seats will need to be ground down some in order for the installed spring height to be right with no coil bind. The intakes are fine (they have been ground).
So...how do these sound for options?
I keep everything I have and live with the low cr. I think I can get the seats ground down enough to make the springs not bind.
I can get new Badger pistons, and keep the cam and do the necessary head work so the cam will work. This will give me what for a cr?
Or I can keep my current pistons and switch to the 265 DEH cam. This would give me an 8.2:1 static cr and a 6.9:1 dynamic cr, correct? The dynamic ratio would be better than with the 272-2 and I probably wouldn't have to worry about coil bind.
I just don't think I can afford new pistons and a new cam, or any more machine work. What do you recommend?
So...how do these sound for options?
I keep everything I have and live with the low cr. I think I can get the seats ground down enough to make the springs not bind.
I can get new Badger pistons, and keep the cam and do the necessary head work so the cam will work. This will give me what for a cr?
Or I can keep my current pistons and switch to the 265 DEH cam. This would give me an 8.2:1 static cr and a 6.9:1 dynamic cr, correct? The dynamic ratio would be better than with the 272-2 and I probably wouldn't have to worry about coil bind.
I just don't think I can afford new pistons and a new cam, or any more machine work. What do you recommend?
Postmaster
Joined: Aug 2001
Posts: 4,270
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From: Delaware
Keep the pistons that you have, get the head work done and go with the 265DEH cam.
If you do some porting work on the exhaust port, you can pick up a few extra HP. This is something that you can do yourself in a few days without a lot of expense.
If you do some porting work on the exhaust port, you can pick up a few extra HP. This is something that you can do yourself in a few days without a lot of expense.
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Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
Yes, the 265DEH has less lift than the Crane cam. The specs for the recommended springs are close. The Comp springs have seat higher pressure, but they are specified at lower installed height, they will have similar pressure at the same installed height. The coil bind spec is better for the Crane springs at 1.08" vs 1.15"
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