minimun piston compression height?

Posted By: brownout

minimun piston compression height? - 10/19/13 05:22 AM

Hey I am building a low deck motor with aluminum rods what do you guys think the minimum piston compression height should be with a 1.094 pin size? The application is going to be a low deck block with 4.5 inch bore and valve pockets for b1 heads and a decent size cam with some duration plus there is going to be a lot of nitrous run through the motor say 500-600 total. I should have room for a 1.20-1.23 compression height hopefully that is enough. Thanks for any advice or experience.

Posted By: LSP

Re: minimun piston compression height? - 10/19/13 05:47 AM

It will need to be closer to 1.350"-1.400" depending on the valve pocket depths.

Posted By: brownout

Re: minimun piston compression height? - 10/19/13 06:24 AM

cam card says duration at .050 is 282 on the intake and 294 on the exhaust. lobe lift is 4.850 on the intake and 4.8 on the exhaust so with 1.7 rockers it should be 824/816 before lash and a lsa of 115.

The pistons will probably nee a slight dome to bring the compression up to a desired range.

Posted By: viperblue72

Re: minimun piston compression height? - 10/19/13 09:06 AM

Don't know if I should weigh in on this, but I like the 1.32ch. Light piston, but pin isn't into the rings.

Posted By: Performance Only

Re: minimun piston compression height? - 10/19/13 10:47 AM

A short compression height, 1.094 pin and aluminum rods that leave little room above the pin for valve reliefs all stuffed into a low deck? Why? It sounds like the perfect beginning for a debacle in the making.

Change that to a good steel rod and .990 pin (or smaller) and make things a lot easier on yourself.

Posted By: 80fbody

Re: minimun piston compression height? - 10/19/13 12:32 PM

Quote:

Don't know if I should weigh in on this, but I like the 1.32ch. Light piston, but pin isn't into the rings.

The pin is into the oil rings on my 1.32ch KB280 pistons. Not sure if forged would be different.

Posted By: JohnRR

Re: minimun piston compression height? - 10/19/13 01:25 PM

Quote:

Quote:

Don't know if I should weigh in on this, but I like the 1.32ch. Light piston, but pin isn't into the rings.

The pin is into the oil rings on my 1.32ch KB280 pistons. Not sure if forged would be different.

Forged would be very different if that KB is a hyper piston, though the 1.094 doesn't help. None of the forged .990pin pistons I've had have the pin in the oil ring.

Posted By: fbs63

Re: minimun piston compression height? - 10/19/13 02:49 PM

I was told by two different piston manufacturers that 1.300 was the minimum CH with B1 valve pockets.

Posted By: brownout

Re: minimun piston compression height? - 10/21/13 07:49 PM

Ok thanks for the infromation I spoke to Koffels and was recommended to keep the compression height to around 1.300
I also told him the application and he said still keep the 1.094 pin vs the .990 pin what do you guys think.

At this point I have the option to change the combo around I was thinking of running a 2.2 rod journal with a piston compression height of 1.3 and some aluminum rods at 6.535 with a .990 pin to lighten things up. Once again this is a nitrous motor that will see a lot of spray.

Thanks

Posted By: Cab_Burge

Re: minimun piston compression height? - 10/21/13 07:54 PM

Quote:

Ok thanks for the infromation Once again this is a nitrous motor that will see a lot of spray.

Thanks

Make sure and buy a tool steel wrist pin that is thick

Maybe the 1.094 size pin will be better also to start with also

Posted By: mac56

Re: minimun piston compression height? - 10/21/13 11:15 PM

Quote:

Ok thanks for the infromation I spoke to Koffels and was recommended to keep the compression height to around 1.300
I also told him the application and he said still keep the 1.094 pin vs the .990 pin what do you guys think.

At this point I have the option to change the combo around I was thinking of running a 2.2 rod journal with a piston compression height of 1.3 and some aluminum rods at 6.535 with a .990 pin to lighten things up. Once again this is a nitrous motor that will see a lot of spray.

Thanks

Dan at performance only helped me pick my B1 pistons and spent a lot of time going over the details of my combo. I also run a 6.535 chev aluminum rod. I think if I remember right the compression height came in at 1.35 and I still ended up with a support rail with 990 pin. Because of Dan's relationship with Diamond he was able to get me what I felt was a great deal for superior parts.