"Thick Wall" 92mm and big valves?

live4power · Posted: Mon Sep 17, 2012 8:11 am Post subject: "Thick Wall" 92mm and big valves?

Sorry in advance if this has been covered, but I tried searching and I haven't found the information I was looking for.

I assume it is because 92mm pistons have had such a bad rep with having such thin cylinder walls and there isn't much info about them. But now that the "Thick Wall" 92mm cylinders are available, it has got me thinking. With the "thick wall" cylinders the heads and case would be cut to a 94mm bore, and there are plenty of big valve heads to choose from with this bore. But the piston would actually be 92mm....so

Can anyone tell me what the largest valve spread is for a 92mm piston without any issues or interference? I would assume 44x37 would be easily doable. But can you stuff 46x37 inside and not have any shrouding? Or even go larger?

Sorry for such a Noob question, but any info would be appreciated.

Glenn · Posted: Mon Sep 17, 2012 10:30 am Post subject:

You're still limited by the 92mm bore.

The wall thickness won't change that.
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live4power · Posted: Mon Sep 17, 2012 10:40 am Post subject:

NJ John · Posted: Mon Sep 17, 2012 11:37 am Post subject:

I know 42x37 fits. Not sure beyond that.
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live4power · Posted: Mon Sep 17, 2012 11:54 am Post subject:

I know CB Comp Elim's can fit a 48x40 in a 94 bore. So would it be possible to run 46x37 in a 92? Only a 2mm difference in the two bores. Unless the Comp Elim's have had their valves moved???
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stoneloco808 · Posted: Mon Sep 17, 2012 3:35 pm Post subject:

IMO the answer would be just about anything is possible, one will have to sacrifice money. I say call a head porter willing to take that challenge, either it be Jeff Denham, Clyde Berg, etc... Explain to them what you want. From the top of my head 46mm valve + 37.5mm valve = to 83.5mm. So that leaves 8.5mm to space out the 2 valves and cylinder wall. If someone could stuff a 48x40 valves in a 94 bore with 2mm between each valve and cylinder wall, I am sure they could stuff a 46x37.5 in a 92 bore. IMO a head porter would have to start with a blank head, and machine it. I would not doubt one of the valve seats would be bored into the other. Like I mentioned earlier it just costs money, how bad do you really want it?

lostinbaja · Posted: Mon Sep 17, 2012 3:51 pm Post subject:

With the smaller 92mm bore there is a point of diminishing returns when it comes to valve diameter. Larger valves screw up the flow because they are so close to the cylinder wall.
I went through all of this on a flow bench years ago but I don't remember the specifics. I'm sure a current quality head porter can enlighten you.
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live4power · Posted: Mon Sep 17, 2012 4:05 pm Post subject:

Alright guys, I appreciate your time and info. I will keep this stuff in mind.
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fuguboy · Samba Member Joined: December 14, 2004 Posts: 218

stealth67vw · Posted: Mon Mar 10, 2014 10:27 pm Post subject:

fuguboy · Samba Member Joined: December 14, 2004 Posts: 218

Is a Super pro 44x37 too much for a 92 bore ? Better with a Tims stage 2 ? Don't want to go too big and shroud valve .

Glenn · Posted: Tue Mar 11, 2014 6:44 am Post subject:

I have 92TW with Steve Tims Stage 2 42x37.
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[email protected] · Posted: Tue Mar 11, 2014 8:35 am Post subject:

as has been the case for 100 years, the port job is more important than the valve size.
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bugguy1967 · Posted: Tue Mar 11, 2014 6:24 pm Post subject:

I guess that depends on what you want to build. Like mentioned, a 44x37 would fit, but you'll have to make power in a 2180 to 7500-8000 rpm to take full advantage. You could do a 2213 and rev a bit lower, but with the added problems of assembling a 2213 (84x92).
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fuguboy · Samba Member Joined: December 14, 2004 Posts: 218

I was thinking ACN L-5 heads and K-10 cam 84x92 , got a 1 5/8 exhaust and IDAs . Good porting with smaller valves for better control and more port velocity .

bugguy1967 · Posted: Wed Mar 12, 2014 6:11 pm Post subject:

For that much cam, I'd suggest larger valves. Run a 42x37 head or choose a lower RPM cam.
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MURZI · Posted: Wed Mar 12, 2014 7:24 pm Post subject:

K10, IDAS, and Tims stage II's. 9.6:1 compression.....Killer. Just get vw 650 springs.
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do you have your carbs and exhaust yet? If so, what are they? There is no point getting a 7500 RPM cam if you have 6k RPM carbs.
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fuguboy · Samba Member Joined: December 14, 2004 Posts: 218

Got 48 idas and 1 5/8 exhaust , stock gears 3.88 rp 24.5 " tires weekend car .Thanks for replies still learning and planning my build .

[email protected] · Posted: Wed Mar 12, 2014 9:34 pm Post subject:

FK8 or 86B, and a 42 x 37.5mm head.

More cam than this would require more exhaust than 1 5/8".
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