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  Raising compression

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Author Topic:   Raising compression
CRB
Gearhead

Posts: 119
From: Raritan NJ
Registered: Jul 2000

posted 04-08-2001 09:31 PM     Click Here to See the Profile for CRB   Click Here to Email CRB     Edit/Delete Message   Reply w/Quote
I am getting ready to put my 351 heads on a 289. The current compression ratio calculates to 8.5. I want to raise that up a bit. Does anyone know how much is requiered to take off of the 351 heads (currently 64cc) to drop 1 compression point?

If not what is the best way to determine the amount be milled off?

thanks
chip

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sigtauenus
Gearhead

Posts: 3295
From: Va Beach
Registered: Jun 2000

posted 04-08-2001 10:01 PM     Click Here to See the Profile for sigtauenus   Click Here to Email sigtauenus     Edit/Delete Message   Reply w/Quote
I think Alex has some super secret super thin super strong head gaskets that will do that trick for you and only costs like $30.

He'll be along shortly to toot his own horn though.

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kcode
Gearhead

Posts: 3296
From: alvaton,ky,usa Suburb of Bowling Green, M&M #79, MCA #29208
Registered: Jun 99

posted 04-08-2001 10:45 PM     Click Here to See the Profile for kcode   Click Here to Email kcode     Edit/Delete Message   Reply w/Quote
CRB
I doing this from memory so my number might not be correct, it will take about .040" off to reduce the chamber about 7 cc. then you are back to where you started. To take that much off you will problably have to mill the bottom of the intake also to match the ports.

Good luck,

Mike

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steve'66
Gearhead

Posts: 9555
From: Sonoma,CA,USA
Registered: Mar 2000

posted 04-09-2001 12:12 AM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
You can do the math, but I'm not up to it tonight. LOL I took .040 off the DO heads on the 289 to bump the compression to about 10-1. But they were about 60cc heads if I remember correctly. Your machinist will know for sure. Good luck,

SteveW

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CRB
Gearhead

Posts: 119
From: Raritan NJ
Registered: Jul 2000

posted 04-09-2001 06:38 PM     Click Here to See the Profile for CRB   Click Here to Email CRB     Edit/Delete Message   Reply w/Quote
I spoke with the machine shop today and they suggested that I should mill the block so that the deck clearance is closer to the recommended. It is currently at .025 and the piston manufacture lists the minimum as .0015. Does this mean I will have to mill both the block and the heads?

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Moneymaker
Administrator

Posts: 27660
From: Lyons, IL, USA
Registered: May 99

posted 04-10-2001 11:26 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Toot toot! You can install steel shim head gaskets and save a bunch of time and money for a .1 increase in compression.

------------------
Alex Denysenko Co-Administrator and Moderator NHRA/IHRA/SRA member
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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CRB
Gearhead

Posts: 119
From: Raritan NJ
Registered: Jul 2000

posted 04-11-2001 09:12 AM     Click Here to See the Profile for CRB   Click Here to Email CRB     Edit/Delete Message   Reply w/Quote
Alex,
In your post you said that using the steel shim gasket would raise the compression .1 points. Did you actually mean 1 point? If not then that would only raise my compression to 8.6. I am hoping to get above 9.5. Based on the other information posted above and my compression calculations if I take about .020 off the heads that should bring the chamber volume to about 59-60, which will give me a compression of about 9.6/9.7. Does that sound right?

OR
Will the steel shim raise the compression 1 full point. In which case that would work perfect. Is there a down side to using this set up?

Thanks
chip

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