Piston to valve Clearence?!?!?

kenneth kimble · 02-28-2001, 04:16 PM

What is the correct way to check piston to valve clearence? Can this check be made without ruining a new head gasket?

Z28EATR · 02-28-2001, 04:37 PM

ive heard some crazy ideas and one including playdoh but dont quote me on that, anyone else??

Tom351 · 02-28-2001, 04:59 PM

You can use modeling clay if you have the heads off. When you say without ruining a head gasket do you mean by taking the heads off or torquing them down on it? If the heads are off, you can check with no head gasket, just remember that the valves are .040" closer without one. So if you are ok without a gasket, you will be fine with one.

I use a light tesion spring in place of the valve spring to check clearance. Replace the valve spring with a light tension spring from the hardware store. Adjust the rockers to proper preload. While turning the engine over you will now be able to push the valve down until it touches the piston. Find the point of least clearance (generally as the exh is closing and int is opening) and measure the distance that the valve moves before hitting the piston. You should have minimum .080" intake .100" exhaust. Let me know if you have any other questions.

------------------
67 Fastback - Arctic White Pearl paint
351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Carter 750 CFM, Comp. Cam 477/510 219/233@.050, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars.

My 351W Fastback

kenneth kimble · 02-28-2001, 10:44 PM

Thanks guy's after talking to a TFS tech I was alittle concerned about the advice he gave me - torque the heads with out the gasket to take a clay reading, with out a head gasket, just wanted to make sure it was the right advice. DO I torque to normal head bolt value?!?!?!

Tom351 · 03-01-2001, 09:04 AM

I would only snug them down to make sure that they are flush. If would not torque them more than hand tight. While checking mine, I just set the heads on with no gasket because I now the gasket will increase clearance.

------------------
67 Fastback - Arctic White Pearl paint
351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Carter 750 CFM, Comp. Cam 477/510 219/233@.050, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars.

My 351W Fastback

Smokedawg · 03-01-2001, 11:27 AM

Ok..Go to your nearest auto dealer and ask for plastigage. Its less that 2 bucks..it looks like a piece of fishing string but different colors for different sizes. You use that to check your piston to valve clearance.

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347 Stroker Motor: Balanced, 30lb Bosch Injectors, Cobra Computer, Cobra Transmission, GT40 Ported and Polished Upper and Lower, GT40 Milled Ported and Polished Heads, B303 Cam, BBK 1 5/8 Headers, March Underdrive Pulleys, Electric Fan, Accel Performance Coil, Accel 300+ Racing Wires, NGK Plugs, Ram Air, K&N Filter, 77mm Mass Air Unit, FlowMaster Exhaust w/offroad H-Pipe, Hurst Short Throw Shifter, 3:55 Gears, Ram Clutch, Cross Drilled Rotors, High Tolerant Painted Calipers and Drums.

Rick 91GT · 03-01-2001, 09:41 PM

Quote:

Originally posted by Smokedawg:
Ok..Go to your nearest auto dealer and ask for plastigage. Its less that 2 bucks..it looks like a piece of fishing string but different colors for different sizes. You use that to check your piston to valve clearance.

HUH? I don't want to start a pissing battle but....He isn't checking bearing clearances he need to check PTV clearance. I have never seen plastiguge thats .100" thick?

I use modeling clay. Put some WD-40 on the piston and valves so the modeling clay will not stick to them and put the modeling clay on the notch or relieved areas. Bolt the head down snug then turn the motor over using a strong arm on the crank bolt, if you feel any strong resistance STOP!!! that may mean your valve is hitting the piston. After you turn the motor over take the heads off and use a set of calipers to mic the depth of the relief through the lowest part in the clay add your compressed thickness of you heads gasket and then you have your PTV, .100 is a perferred minimum.

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My Ride Check Out My Site 91GT, Holley SysteMAX II Kit-Heads 2.02" x 1.60",Full MAC exhaust 1-5/8" Long tubes, 2-1/2" O.R H-Pipe, 2 1/2" cat back, 12" K&N Filter, RNH PERFORMANCE Ram Air, Ron Davis Radiator, Full Suspension,3:73's, Welds, Best on new motor-12.60 @ 108, no traction 1.98

[This message has been edited by Rick 91GT (edited 03-01-2001).]

02-28-2001, 04:16 PM	#1
kenneth kimble Registered Member Join Date: Apr 1999 Location: chesapeake va. Posts: 89	Piston to valve Clearence?!?!? What is the correct way to check piston to valve clearence? Can this check be made without ruining a new head gasket?

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02-28-2001, 04:37 PM	#2
Z28EATR Registered Member Join Date: Jun 2000 Location: Florence, KY,USA Posts: 210	ive heard some crazy ideas and one including playdoh but dont quote me on that, anyone else??

02-28-2001, 04:59 PM	#3
Tom351 Registered Member Join Date: Oct 2000 Location: Atlanta,GA,USA Posts: 278	You can use modeling clay if you have the heads off. When you say without ruining a head gasket do you mean by taking the heads off or torquing them down on it? If the heads are off, you can check with no head gasket, just remember that the valves are .040" closer without one. So if you are ok without a gasket, you will be fine with one. I use a light tesion spring in place of the valve spring to check clearance. Replace the valve spring with a light tension spring from the hardware store. Adjust the rockers to proper preload. While turning the engine over you will now be able to push the valve down until it touches the piston. Find the point of least clearance (generally as the exh is closing and int is opening) and measure the distance that the valve moves before hitting the piston. You should have minimum .080" intake .100" exhaust. Let me know if you have any other questions. ------------------ 67 Fastback - Arctic White Pearl paint 351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Carter 750 CFM, Comp. Cam 477/510 219/233@.050, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars. My 351W Fastback

02-28-2001, 10:44 PM	#4
kenneth kimble Registered Member Join Date: Apr 1999 Location: chesapeake va. Posts: 89	Thanks guy's after talking to a TFS tech I was alittle concerned about the advice he gave me - torque the heads with out the gasket to take a clay reading, with out a head gasket, just wanted to make sure it was the right advice. DO I torque to normal head bolt value?!?!?!

03-01-2001, 09:04 AM	#5
Tom351 Registered Member Join Date: Oct 2000 Location: Atlanta,GA,USA Posts: 278	I would only snug them down to make sure that they are flush. If would not torque them more than hand tight. While checking mine, I just set the heads on with no gasket because I now the gasket will increase clearance. ------------------ 67 Fastback - Arctic White Pearl paint 351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Carter 750 CFM, Comp. Cam 477/510 219/233@.050, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars. My 351W Fastback

03-01-2001, 11:27 AM	#6
Smokedawg Tires Fear Me... Join Date: Jan 2001 Posts: 867	Ok..Go to your nearest auto dealer and ask for plastigage. Its less that 2 bucks..it looks like a piece of fishing string but different colors for different sizes. You use that to check your piston to valve clearance. ------------------ 347 Stroker Motor: Balanced, 30lb Bosch Injectors, Cobra Computer, Cobra Transmission, GT40 Ported and Polished Upper and Lower, GT40 Milled Ported and Polished Heads, B303 Cam, BBK 1 5/8 Headers, March Underdrive Pulleys, Electric Fan, Accel Performance Coil, Accel 300+ Racing Wires, NGK Plugs, Ram Air, K&N Filter, 77mm Mass Air Unit, FlowMaster Exhaust w/offroad H-Pipe, Hurst Short Throw Shifter, 3:55 Gears, Ram Clutch, Cross Drilled Rotors, High Tolerant Painted Calipers and Drums.