Exhaust valve to piston interference.......

Go down

Exhaust valve to piston interference.......

Post  Race Ready Fabrications on April 23rd 2012, 8:38 pm

I'm trying to finish things up with this new motor and figured I'd better check valve clearance good. I'm having issues with the exhaust valve just barely tagging the piston. So little in fact I didn't notice it at first. Had to pull the head back off and confim it with the small mark on the piston. I've advanced the cam as far as I can and still hit. I'm trying to get at least .090 clearance on the exhaust side. My questions are:
What is the minimum exhaust valve to piston clearance?
Will a thicker head gasket resolve my issue?
There's no exhaust valve relief, Do I need to have the pistons fly cut?

This cam is .798 lift on the exhaust side and 284 @.050. I'm headed out now to check what the least amount of clearance I have is. Thanks!!! Brian
avatar
Race Ready Fabrications

Posts : 617
Join date : 2010-04-19
Age : 37
Location : Chandler, IN

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  ustahava67 on April 23rd 2012, 9:05 pm

I set up for .080 -.090 vertical clearance with .025 - .030 radial clearance. I have run as close as .035 vertical ( customer didn't want to spend any more and took the risk) but... if the valves float bad things happen fast
avatar
ustahava67

Posts : 53
Join date : 2009-11-30
Age : 56
Location : Caldwell, Idaho USA

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  cool40 on April 23rd 2012, 9:10 pm

are you checking with checker springs or "the"springs your gona run? did you figure valve lash in? Arrow
avatar
cool40
BBF CONTRIBUTOR
BBF CONTRIBUTOR

Posts : 7161
Join date : 2009-08-31
Age : 47
Location : on the 1/8 mile dyno

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  Lem Evans on April 23rd 2012, 9:13 pm

Cyl. head is?

Lem Evans

Posts : 7102
Join date : 2008-12-03
Location : Livermore , Ky

View user profile http://bfevansraceparts.com

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  Race Ready Fabrications on April 23rd 2012, 9:13 pm

Just checked mine to see what the minimum is, .060 is where I'm at. This is with a .041 compressed head gasket. So a .060 gasket would give me .079???
avatar
Race Ready Fabrications

Posts : 617
Join date : 2010-04-19
Age : 37
Location : Chandler, IN

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  Race Ready Fabrications on April 23rd 2012, 9:14 pm

cool40 wrote:are you checking with checker springs or "the"springs your gona run? did you figure valve lash in? Arrow

I'm using the springs I'm gonna use and not figuring it accounting for lash.
avatar
Race Ready Fabrications

Posts : 617
Join date : 2010-04-19
Age : 37
Location : Chandler, IN

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  Race Ready Fabrications on April 23rd 2012, 9:15 pm

Lem Evans wrote:Cyl. head is?

TFS streets that Charlie did with the raised intake runners
avatar
Race Ready Fabrications

Posts : 617
Join date : 2010-04-19
Age : 37
Location : Chandler, IN

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  Lem Evans on April 23rd 2012, 9:18 pm

An exh. valve relief is needed i.m.o.

Lem Evans

Posts : 7102
Join date : 2008-12-03
Location : Livermore , Ky

View user profile http://bfevansraceparts.com

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  56Tbird on April 23rd 2012, 9:26 pm

I had that same problem with my .060 460 in my Mustang..I took die grinder and cut a relief in the pistons while still in the engine...I don't recommend it ,and it ain't the prettiest thing I've ever seen,but it's been together since 2004 without being apart. I think if I ever pull it apart I'll have JetBoat Bob to cut the reliefs the same ...if I pull it before it comes apart??
avatar
56Tbird
BBF CONTRIBUTOR
BBF CONTRIBUTOR

Posts : 5255
Join date : 2008-12-02
Age : 59
Location : Hawesville,Ky.

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  bbf-falcon on April 23rd 2012, 9:30 pm

Lem Evans wrote:An exh. valve relief is needed i.m.o.

X2. Don't take THAT chance. Sad

bbf-falcon

Posts : 8992
Join date : 2008-12-03
Location : Jackson, Ohio

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  cool40 on April 23rd 2012, 9:53 pm

Race Ready Fabrications wrote:
cool40 wrote:are you checking with checker springs or "the"springs your gona run? did you figure valve lash in? Arrow

I'm using the springs I'm gonna use and not figuring it accounting for lash.
so your not counting lash? if not then you have more room than you think. how are you checking it? most of the time i check ex 10*btdc,int 10*after tdc.set the rockers up with lash,as youd run it,set an indicator on the retainer and turn it to 10*btdc. now run your lock down with a short wrench,dont use your good arm Smile thats how i do it anyway.works for me.lol
avatar
cool40
BBF CONTRIBUTOR
BBF CONTRIBUTOR

Posts : 7161
Join date : 2009-08-31
Age : 47
Location : on the 1/8 mile dyno

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  Lem Evans on April 23rd 2012, 9:58 pm

Please do not find a reason to do the wrong thing........put an exh. relief in the piston. Wink

Lem Evans

Posts : 7102
Join date : 2008-12-03
Location : Livermore , Ky

View user profile http://bfevansraceparts.com

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  c.evans on April 23rd 2012, 10:23 pm

Brian,

PLEASE,,,X 10 on what Lem said. Aren't those pistons Sealed Power/TRW with a stock diameter pin? Those pistons need an exhaust valve relief with that much lift and duration. If not, you'll be bending exhaust valves and tearing the engine down again really soon. Get the pistons out of it and do the job the right way. That's why you mocked up and checked clearance anyway. If you go with a thicker head gasket, you'll be losing compression.

Pull an exhaust valve out of the head and then put the head back on without the valve. Use a center finding punch through the guide to punch mark the piston when it's at TDC,, or you can take an old junk valve, cut the head off of it and sharpen it to a point on a lathe. Then drop the old valve through the guide and punch the piston. Any good machine shop with a piston vise ought to be able to take it from there and flycut your valve reliefs.

Charlie

c.evans
BBF VENDOR SPONSOR
BBF VENDOR SPONSOR

Posts : 2209
Join date : 2008-12-03

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  rmcomprandy on April 23rd 2012, 10:36 pm

Race Ready Fabrications wrote:I'm trying to finish things up with this new motor and figured I'd better check valve clearance good. I'm having issues with the exhaust valve just barely tagging the piston. So little in fact I didn't notice it at first. Had to pull the head back off and confim it with the small mark on the piston. I've advanced the cam as far as I can and still hit. I'm trying to get at least .090 clearance on the exhaust side. My questions are:
What is the minimum exhaust valve to piston clearance?
Will a thicker head gasket resolve my issue?
There's no exhaust valve relief, Do I need to have the pistons fly cut?

This cam is .798 lift on the exhaust side and 284 @.050. I'm headed out now to check what the least amount of clearance I have is. Thanks!!! Brian

Other than notching the pistons ... Your best option is advancing the cam till you have .050" intake piston to valve clearance and getting exhaust rocker arms of less ratio than what you have.

rmcomprandy

Posts : 5093
Join date : 2008-12-02
Location : Roseville, Michigan

View user profile http://www.rmcompetition.com

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  Race Ready Fabrications on April 24th 2012, 11:48 am

Lem Evans wrote:An exh. valve relief is needed i.m.o.

bbf-falcon wrote:
Lem Evans wrote:An exh. valve relief is needed i.m.o.

X2. Don't take THAT chance. Sad

c.evans wrote:Brian,

PLEASE,,,X 10 on what Lem said. Aren't those pistons Sealed Power/TRW with a stock diameter pin? Those pistons need an exhaust valve relief with that much lift and duration. If not, you'll be bending exhaust valves and tearing the engine down again really soon. Get the pistons out of it and do the job the right way. That's why you mocked up and checked clearance anyway. If you go with a thicker head gasket, you'll be losing compression.

Pull an exhaust valve out of the head and then put the head back on without the valve. Use a center finding punch through the guide to punch mark the piston when it's at TDC,, or you can take an old junk valve, cut the head off of it and sharpen it to a point on a lathe. Then drop the old valve through the guide and punch the piston. Any good machine shop with a piston vise ought to be able to take it from there and flycut your valve reliefs.

Charlie

I appreciate the concern and the advice from everybody. These are probe pistons, I'll get one marked tonight and get them over to Mat Wright and let him fly cut them for me. Just another set back that's all Evil or Very Mad
avatar
Race Ready Fabrications

Posts : 617
Join date : 2010-04-19
Age : 37
Location : Chandler, IN

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  Maxx Levell on April 24th 2012, 1:15 pm

Here is a piston cutter if anyone ever has a need ... go to http://www.lindytools.com/ click on the tools drop down...and you will see the in head piston notcher...
avatar
Maxx Levell

Posts : 87
Join date : 2010-05-24
Age : 51
Location : Henderson KY

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  maverick532 on April 24th 2012, 1:50 pm

I'ved used that tool and the tool from Isky imo the Isky is much better .
avatar
maverick532

Posts : 165
Join date : 2010-11-25
Age : 56
Location : orlando fla.

View user profile

Back to top Go down

Re: Exhaust valve to piston interference.......

Post  dfree383 on April 25th 2012, 12:40 am

Race Ready Fabrications wrote:
Lem Evans wrote:An exh. valve relief is needed i.m.o.

bbf-falcon wrote:
Lem Evans wrote:An exh. valve relief is needed i.m.o.

X2. Don't take THAT chance. Sad

c.evans wrote:Brian,

PLEASE,,,X 10 on what Lem said. Aren't those pistons Sealed Power/TRW with a stock diameter pin? Those pistons need an exhaust valve relief with that much lift and duration. If not, you'll be bending exhaust valves and tearing the engine down again really soon. Get the pistons out of it and do the job the right way. That's why you mocked up and checked clearance anyway. If you go with a thicker head gasket, you'll be losing compression.

Pull an exhaust valve out of the head and then put the head back on without the valve. Use a center finding punch through the guide to punch mark the piston when it's at TDC,, or you can take an old junk valve, cut the head off of it and sharpen it to a point on a lathe. Then drop the old valve through the guide and punch the piston. Any good machine shop with a piston vise ought to be able to take it from there and flycut your valve reliefs.

Charlie

I appreciate the concern and the advice from everybody. These are probe pistons, I'll get one marked tonight and get them over to Mat Wright and let him fly cut them for me. Just another set back that's all Evil or Very Mad

Its not a set back.... It Race Engine Building..... Its required to put one together properly.
avatar
dfree383
BBF CONTRIBUTOR
BBF CONTRIBUTOR

Posts : 14130
Join date : 2009-07-09
Location : Home Wif Da Wife.....

View user profile

Back to top Go down

Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum