Valve seats - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DanoDMano · 11-17-2003, 08:59 PM

I have a question for you motor guys who have been giving me a hand through my project.Today I started replacing my valve seals with the umbrella type. I have the engine on a stand, and the heads are still on the block.
When I pressurize the cylinder to hold the valve up so I can remove the spring I am getting alot of blow by from where the valve seats. On a couple of the cylinders it has been bad enough to make my compressor (5 gal) cycle constantly.On one cylinder in particular I could not hold sufficient pressure to force the valve to stay up!
I am contemplatin pulling the heads and lapping in some new valves.

What do you think? Should I just remove the heads and replace the valves? Should I have the heads machined, if so what kind of cost am I looking at?

I did not plan on going through the lower end, and am also wondering what to expect if the heads are done and not the lower end what may happen to the rings?

Any help would be greatly appreciated as usual!!!

*redbowtie* · 11-17-2003, 09:10 PM

I think you already know the answer.......

If the seats are that bad, yes, you need a valve job.

*racedvl* · 11-17-2003, 09:41 PM

And guides!

JimKshortstep4x4 · 11-17-2003, 09:44 PM

Before I would condemn the valves I would pressurize the cylinder with the springs still in place on the valves and smack the valve straight on with a compothane hammer. It is possible to have dirt or carbon between the valve and seat and this will usually dislodge anything and let the valve seat. If that does not cure the leaking then definately you will have to pull the heads.

Jim

DanoDMano · 11-17-2003, 09:53 PM

Thats a good idea JimKshortstep4x4 , I'll try it. They do look pretty cruddy, with alot of buildup!! Can I just tap out the guides with the heads removed?

DanoDMano · 11-17-2003, 10:34 PM

How much can a guy expect to pay for a rebuilt set of heads?

*racedvl* · 11-17-2003, 11:52 PM

I just had the heads done on my 88, and it cost me $250 for 8 exhaust guides and a valve job.

DanoDMano · 11-18-2003, 12:52 AM

Did you just take your heads into a machine shop and tell them what you wanted?? IO guess I need to find a good local machine shop.

Hooter · 11-18-2003, 03:55 AM

I f you are getting that much air through, you valve guide have got to be toast, and plus its just better to get the heads done, because it it pretty embarassing to have a brand new motor that blows blue

*racedvl* · 11-18-2003, 10:28 AM

I took them to the machine shop, and they told me what it needed. I knew that was what it was gonna need. And the nice thing is, is that now, I have no more smoke at start up.

11-17-2003, 08:59 PM	#1
DanoDMano Pronounced "Pew-al-up" Join Date: Oct 2002 Location: Puyallup, Washington Posts: 845	Valve seats I have a question for you motor guys who have been giving me a hand through my project.Today I started replacing my valve seals with the umbrella type. I have the engine on a stand, and the heads are still on the block. When I pressurize the cylinder to hold the valve up so I can remove the spring I am getting alot of blow by from where the valve seats. On a couple of the cylinders it has been bad enough to make my compressor (5 gal) cycle constantly.On one cylinder in particular I could not hold sufficient pressure to force the valve to stay up! I am contemplatin pulling the heads and lapping in some new valves. What do you think? Should I just remove the heads and replace the valves? Should I have the heads machined, if so what kind of cost am I looking at? I did not plan on going through the lower end, and am also wondering what to expect if the heads are done and not the lower end what may happen to the rings? Any help would be greatly appreciated as usual!!! __________________ Classic GM Trucks of Washington Club Member 1970 FS chevy,350/350, Edelbrock cam and intake. Holley 650 carb,HEI,AT,Tangier Orange, 18's, Power Locks, Truck Photos

11-17-2003, 09:53 PM	#5
DanoDMano Pronounced "Pew-al-up" Join Date: Oct 2002 Location: Puyallup, Washington Posts: 845	Thats a good idea JimKshortstep4x4 , I'll try it. They do look pretty cruddy, with alot of buildup!! Can I just tap out the guides with the heads removed? __________________ Classic GM Trucks of Washington Club Member 1970 FS chevy,350/350, Edelbrock cam and intake. Holley 650 carb,HEI,AT,Tangier Orange, 18's, Power Locks, Truck Photos

11-17-2003, 10:34 PM	#6
DanoDMano Pronounced "Pew-al-up" Join Date: Oct 2002 Location: Puyallup, Washington Posts: 845	How much can a guy expect to pay for a rebuilt set of heads? __________________ Classic GM Trucks of Washington Club Member 1970 FS chevy,350/350, Edelbrock cam and intake. Holley 650 carb,HEI,AT,Tangier Orange, 18's, Power Locks, Truck Photos

11-18-2003, 12:52 AM	#8
DanoDMano Pronounced "Pew-al-up" Join Date: Oct 2002 Location: Puyallup, Washington Posts: 845	Did you just take your heads into a machine shop and tell them what you wanted?? IO guess I need to find a good local machine shop. __________________ Classic GM Trucks of Washington Club Member 1970 FS chevy,350/350, Edelbrock cam and intake. Holley 650 carb,HEI,AT,Tangier Orange, 18's, Power Locks, Truck Photos

11-18-2003, 03:55 AM	#9
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,078	I f you are getting that much air through, you valve guide have got to be toast, and plus its just better to get the heads done, because it it pretty embarassing to have a brand new motor that blows blue __________________ MEMBER DISCS UP FRONT CLUB 69 custom camper/cst 10 70 monte carlo 383 stroker with a 700r4 77 fully loaded silverado (back in the backyard for a little while longer) 1980 BMW 320i (back in the garage finally) 1981 f@*d f150 4x4 (Robert red ford) tried to kill me 1972 Honda ct 90 trailbike Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com AC/DC RULES!!! First generation Monte Carlo club pictures of my life

11-17-2003, 09:10 PM	#2
redbowtie Account Suspended Join Date: Nov 2003 Location: Fort Worth, Texas Posts: 0	I think you already know the answer....... If the seats are that bad, yes, you need a valve job.

11-17-2003, 09:41 PM	#3
racedvl Account Suspended Join Date: Jan 2000 Location: Woodstock, IL Posts: 7,020	And guides!

11-17-2003, 09:44 PM	#4
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Before I would condemn the valves I would pressurize the cylinder with the springs still in place on the valves and smack the valve straight on with a compothane hammer. It is possible to have dirt or carbon between the valve and seat and this will usually dislodge anything and let the valve seat. If that does not cure the leaking then definately you will have to pull the heads. Jim

11-17-2003, 11:52 PM	#7
racedvl Account Suspended Join Date: Jan 2000 Location: Woodstock, IL Posts: 7,020	I just had the heads done on my 88, and it cost me $250 for 8 exhaust guides and a valve job.

11-18-2003, 10:28 AM	#10
racedvl Account Suspended Join Date: Jan 2000 Location: Woodstock, IL Posts: 7,020	I took them to the machine shop, and they told me what it needed. I knew that was what it was gonna need. And the nice thing is, is that now, I have no more smoke at start up.



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