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KyleG 03-06-2013 06:57 PM

Effective volume on piston
 
http://i1088.photobucket.com/albums/...902_143814.jpg

I am trying to come up with an around about cr. These are the flat tops in my 355. I think the deck clearance is around .030. The guy at the machine shop said it is very possibly, he did not measure though. He also said with the 64cc Double hump heads, it is probably around 10.1 to 11.1. The motor is all the way together, running. So to late to measure now..lol What IS effective volume? And What do these look to you? Of course, you guys wont be able to give me exact numbers, just wanting around abouts.

ap72 03-06-2013 07:42 PM

You're probably closer to 9:1. What part number is on the pistons?

KyleG 03-06-2013 07:45 PM

No idea man. Its already thrown together.. /: And I was thinking it was that low.. Hoping it was haha Cheaper gas. Been running 93, because I thought it was higher than 10:5

BOBCRMAN@aol.com 03-06-2013 07:50 PM

Nowhere near 10-1. Those pistons look like rebuilders pistons, note the large double valve reliefs and front large notch. All bleed off compression. Plus most rebuilders pistons are .020" short

KyleG 03-06-2013 07:54 PM

Goood! Soo regular gas is goood to run??

ap72 03-06-2013 07:57 PM

Maybe. Maybe not. The joys of messing with a "mystery engine"

KyleG 03-06-2013 08:08 PM

Quote:

Originally Posted by ap72 (Post 1654290)
Maybe. Maybe not. The joys of messing with a "mystery engine"

Very true!

painted jester 03-07-2013 08:45 PM

that #3 piston (2nd one back) looks like its got a bad spot above the ring land at 2 o clock is it damaged or just a bad photo? These eyes are old!!! :drunk:

Jester

KyleG 03-07-2013 08:53 PM

Its just a real bad photo, it was a little carbon build up..

BigMo 03-08-2013 04:57 AM

Yeah, youre like 9-1 or so....those 4-brow pistons have like 6 to 7.5 cc loss of volume....and with that large of a deck (.030) you are down quite a bit......unless the heads are shaved to the max and the chambers are like 62 or something w a really thin head gasket.....

KyleG 03-08-2013 07:09 PM

I dont think the heads are shaved any, and stock spec head gasket. Filled up on regular and can't tell a difference. So probably around 9:1 thankfully lol

cobalt327 03-09-2013 10:44 PM

Quote:

Originally Posted by KyleG (Post 1654895)
I dont think the heads are shaved any, and stock spec head gasket. Filled up on regular and can't tell a difference. So probably around 9:1 thankfully lol

You have a 1 point range of between about 9.2 and 10.2:1 depending on the block deck, gasket thickness and whether the pistons are 1.56" or 1.54" compression height.

The problem at the low end of the CR shown is the quench distance will be VERY wide (as much as 0.086" w/a 0.045 piston deck caused by a rebuilder piston combined w/an unmilled deck along w/a 0.041" gasket thickness).

As long as it'd not detonating, at least it shouldn't beat the bearings out of it or pinch a ring.

KyleG 03-13-2013 05:43 PM

Hard to say. Its running fine though. I'm just gonna drive it lol Drives smooth, pulls smooth. Sometimes may have a little bog. But thats part of it I guess

lg1969 03-14-2013 10:07 AM

1 Attachment(s)
I use this cal

hcompton 03-14-2013 01:14 PM

Most four vavle reliefs without the dish are 6 to 12 cc's But the deck hieght is the most important here. Zero deck or .045 in the hole makes a big difference.


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