Go .21 inboard head clearance

[Jeremy Linney]

Asking for input as what seems to work well for head squish clearance. Recently bought a 7port to install into a Phil Thomas SS21 and will be using 3280 pipe and 50% nitro. Installed a turbo head button in place of standard plug button in which original head clearance measured .026" with standard button. I installed turbo head button and shimmed for .009" head clearance. Will this be a safe starting point or do I need more clearance?

 

[RodneyPierce]

thats perfectly fine.

 

[dave roach]

On 50% I would go .006 on head clearance.

Dave Roach

 

[RodneyPierce]

I personally run .005-.006, but not knowing anything else, or what he is planning on doing, .009 sounds just fine to me. I can tell you from experience with the GO. Its very very tight if new. And you will take plug after plug if its not broken in, at .005-.006 clearance. Keep it at .009-.010 until its broken in, then drop the clearance (if you so wish too)

 

[Jeremy Linney]

Thanks for the info guys. Brand new everything so I will leave at .009" and then play with it a little after broken in. Thanks again.

As far as being tight this engine is not what I would consider tight. Every other new engine I have disassembled would push sleeve out of case when piston nears TDC with head off and this one does not? Not much pinch for a new engine if you ask me.

 

[tom galdys]

If my GO 5 port OB has anything less than .009 clearence I burn through OD blue heads in seconds. .009-.011 would be right. Tom

 

[RodneyPierce]

Tom, I run .005-.006 on my inboard GO motors. Its many vcariables. When they are super tight, you cant go that low, but once broken in, they are fine.

 

[Kevin Krogness]

Mark "Lights" set my 7 port turbo at .008 right out of the box... The pinch was tight but not what I was expexting from what everyone was telling me... Exact set up as you also Jeremy...

 

[RodneyPierce]

My 5 port here, was so tight, you had to use a wrench to turn it over at TDC if there is no heat in the motor.

 

[moparbarn]

If my GO 5 port OB has anything less than .009 clearence I burn through OD blue heads in seconds. .009-.011 would be right. Tom

Blue's man thats a cold pulg for a .21

jmho

Greg

kinda dependant on nitro %, imho. i have run blues sucessfully in my .21's on 65%. also has a lot to do with head/squish clearance & amount of water cooling/engine temp. i also think manufacturer's "specs" as to hot & cold aren't set by any common "standard". o'donnell says a od-9 is a medium to medium cold plug, equalivent to a mc-9, which mccoy lists as cold :huh: .........but i do agree that a blue is a cold plug by anyone's "standard"