Bearing/ ring clearances for forced induction??

NOGEN 3 · 16-08-2009, 03:55 PM

Hey all, about to start on the build up of a 355 purposely built for supercharging/ turbo charging. What sort of ring gap is ideal and what sort of clearance should I see on the plastiguage as This is pretty much a 1 off investment and I don't want ring butting together and destroying themselves and possibly the pistons/ bores or spinning a bearing??

alain · 10-01-2010, 05:50 AM

Doesn't matter what kind of block, it does matter what type of fuel and or power adder.

For blown petrol, bore X .0055 and round up to thousands. For example: bore is 4.605 X .0055=.02532, so then gap to .026. That will be for top and second ring. Turbo would be the same.

If your adding nitrous to your blown petrol deal you're asking for trouble. Nitrous has a higher percentage of oxygen than atmospere. So you're adding to an unknow mixture. Generally for nitrous you would gap bore X .008. So you can see that it burns much hotter than anything else including nitro.

For blown alcohol you can reduce the gap a little. That would be bore X .0045 top and second.

The bearing clearance: http://mahleclevite.com/techbulletins/CL77-1-205R.pdf

Also, I wouldn't use plastigage to set the clearance. Use proper measuring equipment.

Dynoryder · 10-01-2010, 06:49 PM

you need a good set of vernire micrometers in an out prob set you back a lot so go to a good builder the above is good info but differnt setups need differnt clearances example a ls1 is differnt to a cast 350 its all got to do with expansion really the only was is to go to a guy that races in the field cuz the nos guys know ther stuff and the alco guys know there stuff so get a bit more specific

MCEcomp · 04-02-2010, 12:39 PM

Its best to go on the loose side especially with your top ring gap.
If the rings butt together you will be sorry

16-08-2009, 03:55 PM	#1 (permalink)
NOGEN 3 Newby Join Date: Jan 2007 Location: Adelaide, SA Posts: 41	Bearing/ ring clearances for forced induction?? Hey all, about to start on the build up of a 355 purposely built for supercharging/ turbo charging. What sort of ring gap is ideal and what sort of clearance should I see on the plastiguage as This is pretty much a 1 off investment and I don't want ring butting together and destroying themselves and possibly the pistons/ bores or spinning a bearing?? __________________ Ashley *BAN LOW PERFORMANCE DRIVERS, NOT HIGH* *PERFORMANCE CARS. Crush the hoons, not the cars...*

10-01-2010, 05:50 AM	#2 (permalink)
alain Clutch Popper Join Date: Jun 2008 Location: Holland for now, Qld next year Ride: '69 Chevy Camaro RS, '69 Dodge Dart, '77 W200 Posts: 99	Doesn't matter what kind of block, it does matter what type of fuel and or power adder. For blown petrol, bore X .0055 and round up to thousands. For example: bore is 4.605 X .0055=.02532, so then gap to .026. That will be for top and second ring. Turbo would be the same. If your adding nitrous to your blown petrol deal you're asking for trouble. Nitrous has a higher percentage of oxygen than atmospere. So you're adding to an unknow mixture. Generally for nitrous you would gap bore X .008. So you can see that it burns much hotter than anything else including nitro. For blown alcohol you can reduce the gap a little. That would be bore X .0045 top and second. The bearing clearance: http://mahleclevite.com/techbulletins/CL77-1-205R.pdf Also, I wouldn't use plastigage to set the clearance. Use proper measuring equipment. __________________ Later, ~Alain~ Forced Induction:"You'll run outta tire, before you run outta horsepower"

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10-01-2010, 06:49 PM	#3 (permalink)
Dynoryder Banned because i am a retard Join Date: Oct 2009 Location: A.C.T. Ride: vr commy Posts: 1,002	you need a good set of vernire micrometers in an out prob set you back a lot so go to a good builder the above is good info but differnt setups need differnt clearances example a ls1 is differnt to a cast 350 its all got to do with expansion really the only was is to go to a guy that races in the field cuz the nos guys know ther stuff and the alco guys know there stuff so get a bit more specific

04-02-2010, 12:39 PM	#4 (permalink)
MCEcomp Newby Join Date: Sep 2009 Location: melb australia Posts: 8	Its best to go on the loose side especially with your top ring gap. If the rings butt together you will be sorry