Checking deck height on M8
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Road Captain
Joined: Sep 2012
Posts: 625
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From: Mo
Ok, after making a few phone calls I was not comfortable with the figures I came up with on deck height. Its kind of hard trying to hold a straight edge, feeler gauges and keep the piston at TDC. With no rings it wanted to back off TDC a couple thousands... Anyway I ordered a deck bridge. That made the job easier and more accurate.I also used a new base gasket and torqued the cylinder down. My original measurements were incorrect. The measurements with the deck gauge are .013 in the hole rear and .011 in the hole front. Just goes to show its best to have the right tool for the job.
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Joined: Aug 2011
Posts: 64
Likes: 15
From: New Mexico
Having the right tools is so important specially when we are talking fractions of an inch. Man, even .013/.011 still seems pretty far down in the hole. What size head gasket are you planning on using? I would want to see no more than .005 in the hole before adding headgasket thickness. At that I would slap an ideal .030 HG on it and have a quench of .035. For you with a .013/.011 youd be at .043/.041, thats not horrible but it isnt ideal either for a performance build.
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Joined: Jun 2006
Posts: 12,763
Likes: 2,597
From: san antonio
I debated posting a comment similar to what Colvinb just posted but backed off remembering that the TC OEM head gasket is .045" thick and in stock configuration the later models, not sure on the M8, it was not unusual for the piston to be done mas o menos .007" below deck which the OP may have considered. Many stockers running around like that with no issues. Just sayin.
I would still trim to zero deck and use a .030" head gasket but that's just me.
I would still trim to zero deck and use a .030" head gasket but that's just me.Last edited by djl; Nov 23, 2022 at 02:50 PM.
Advanced
Joined: Aug 2011
Posts: 64
Likes: 15
From: New Mexico
I debated posting a comment similar to what Colvinb just posted but backed off remembering that the TC OEM head gasket is .045" thick and in stock configuration the later models, not sure on the M8, it was not unusual for the piston to be done mas o menos .007" below deck which the OP may have considered. Many stockers running around like that with no issues. Just sayin. I would still trim to zero deck and use a .030" head gasket but that's just me.
I would still trim to zero deck and use a .030" head gasket but that's just me.Last edited by Colvinb; Nov 23, 2022 at 03:50 PM.
Road Master
Joined: Mar 2013
Posts: 817
Likes: 380
From: Central Ohio
Ok, after making a few phone calls I was not comfortable with the figures I came up with on deck height. Its kind of hard trying to hold a straight edge, feeler gauges and keep the piston at TDC. With no rings it wanted to back off TDC a couple thousands... Anyway I ordered a deck bridge. That made the job easier and more accurate.I also used a new base gasket and torqued the cylinder down. My original measurements were incorrect. The measurements with the deck gauge are .013 in the hole rear and .011 in the hole front. Just goes to show its best to have the right tool for the job.
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Road Captain
Joined: Sep 2012
Posts: 625
Likes: 509
From: Mo
I am using .030 Cometic head gaskets and .014 base. The cylinders are getting shipped out Monday to be trimmed down. Big Boys calculator shows right at 11:1 with a 89 cc chamber after the cylinders are trimmed. I sent my heads out to be freshened up and cc'd.
This is actually the second time around for this 124 deal. First time around it had a piston slap sound in the front cyl after a couple of startups. I tore it back down and did some checking and found some taper in the front cylinder. I sent the piston and cylinder in and they sent me a new cylinder. First time around I used some .010 base gaskets to get the deck height a bit closer. This time around I'm trimming the cylinders, freshing up the heads with some bowel work and cc/mill and having the pistons Line2Line coated. I have used Line2Line several times on some of my big block Chevy builds and it works slick.
This is actually the second time around for this 124 deal. First time around it had a piston slap sound in the front cyl after a couple of startups. I tore it back down and did some checking and found some taper in the front cylinder. I sent the piston and cylinder in and they sent me a new cylinder. First time around I used some .010 base gaskets to get the deck height a bit closer. This time around I'm trimming the cylinders, freshing up the heads with some bowel work and cc/mill and having the pistons Line2Line coated. I have used Line2Line several times on some of my big block Chevy builds and it works slick.
Last edited by wilburbill; Nov 24, 2022 at 09:42 AM.
Advanced
Joined: Aug 2011
Posts: 64
Likes: 15
From: New Mexico
I am using .030 Cometic head gaskets and .014 base. The cylinders are getting shipped out Monday to be trimmed down. Big Boys calculator shows right at 11:1 with a 89 cc chamber after the cylinders are trimmed. I sent my heads out to be freshened up and cc'd.
This is actually the second time around for this 124 deal. First time around it had a piston slap sound in the front cyl after a couple of startups. I tore it back down and did some checking and found some taper in the front cylinder. I sent the piston and cylinder in and they sent me a new cylinder. First time around I used some .010 base gaskets to get the deck height a bit closer. This time around I'm trimming the cylinders, freshing up the heads with some bowel work and cc/mill and having the pistons Line2Line coated. I have used Line2Line several times on some of my big block Chevy builds and it works slick.
This is actually the second time around for this 124 deal. First time around it had a piston slap sound in the front cyl after a couple of startups. I tore it back down and did some checking and found some taper in the front cylinder. I sent the piston and cylinder in and they sent me a new cylinder. First time around I used some .010 base gaskets to get the deck height a bit closer. This time around I'm trimming the cylinders, freshing up the heads with some bowel work and cc/mill and having the pistons Line2Line coated. I have used Line2Line several times on some of my big block Chevy builds and it works slick.
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