The Stovebolt Site Forums The Shop Area Engine Shop 235 valve job

What should a valve job cost on an old (51) 235 cost? I know there are varibles but just as an average.
GEC52,

About 175.00 with no parts,valves,seats,etc.

Pete

Saw one done a few months ago with all new valves, bronze guides, seals, hardened seats amd machined flat. $350. I considered that a good price.

Here they ask almost $1000

Jianis

Chicago suburbs, bake and blast, magnaflux and pressure check, resurface head, install hard seats, install new guides, new valves, check and shim spring pressure and assemble about $450.
Had two done a couple of years ago, price is still about the same.
Denny Graham
Sandwich, IL

Q: Why do shops advise seat replacement?
A: They have rent to pay.

here is a complete engine and transmission for a good price
click here

You suppose that after a couple of valve jobs the valve could be sitting quite low in the port Panic???? If the exhaust seats are badly burned by the time they clean up again the valve can sit quite low. With the valve sitting lower in the seat you need more shims to bring the springs up to the proper pressure and it also increases the combustion chamber volume lowering the compression.
New seats bring it up to the proper height in the combustion chamber. And there is always that simple fact that the new hard seat is gonna last a lot longer than the much softer cast iron seat.
You can also skimp on the guides and knurl them, if you just want it to run, but if you want it to perform like new, plan to spend a little more and do it right.
Denny Graham
Sandwich, IL

True, a seat replacement will last longer than the original - which lasted 50,000 miles. If you expect to do another 50K, it's a good investment.
However: it's a precise operation. It's expensive because it's not easy work. New seat hole is not centered = port is ruined. Press fit is too loose = seat comes out. Press too is tight = head cracks (which may happen if overheated anyway). Been there, done that. The heat transfer from the insert to the casting is not as complete as the original. Even if the work is guaranteed, who pays you for R&R the head?
The change in chamber volume is far too small to have a significant effect.
My choice: a SBC 1.60" valve can be reduced to 1.53" or so (no larger than you need) on the re-facing machine, and permit the seat to be re-cut to the original depth and stem height at 1/3 of the cost.

Well Panic, opinions are like a certain orifice on the human torso, everybody has one. I personally have seen too many engines that didn’t perform up to expectations because the owner tried to save a buck. Replacing valve seats in engines today for a qualified auto machine shop is as common a practice as replacing guides.
Larry Carley wrote this article for Engine Builders Magazine on the subject of valve seat replacement, some people may find it interesting: http://www.enginebuildermag.com/Article/1946/valve_seat_installation_procedures.aspx
I didn’t think it was all that expensive when you figure all of the work they did on my hard for $450. After all, I got another 32 years to go so I shouldn’t have any problem getting another 50K on the old gal.
Nothing wrong with your solution but remember, “there are more ways of killing a cat than choking it with cream“.

DG

When you have a reliable method of detecting which seats will fail in advance, please let us know.
I've never heard of a shop that said "I'm sorry, we had a problem so we're not going to charge you, and here's a replacement head for free".
Nothing is more fun than choosing the most expensive method "because it's the best", and getting a free ride on the tow hook for your money.

Hey panic, YOU WIN!!!

DG

I rebuilt my 54 235 about 10 years ago. They replaced the seats, valves, guides, etc. I have not had any problems. The new seats are harder and allow the use of unleaded fuel. The expense for doing it right the first time is much less than reworking,in a few years. At least, my opinion. Make sure you have a good shop, talk to the hot rodders, they usually know the good shops. They also know the best price.

Good evening, do you have the name of the shop that did this work? I’m in Oak Forest, IL. I have a Pontiac 261 that might need all of the above.

MJDOOM.
You are responding to a 12 year old post, but I believe Denny still checks the forum regularly. With 1 post you can't send him a PM, so I will send him one for you.

Yes, I tried to send a PM. But like you said, I couldn’t. Thank you for contacting him for me.

MJ

Tks Gord. Yeah, couldn't tell ya what it would cost you today with the price of everything going
thru the roof. I had one shop here in Sandwich take a stab at it and he flunked the head saying
that he Magnafluxed it and it was cracked. Did an extensive cleaning a spot check here in the shop
and couldn't find a crack so I took it to Auto Machine in St. Charles and they did the valve job on it.
Old Blue's been running for 15 years and 18,000 miles now and is just as sweet today as she was
back in 1950.
With the time that's past, I wouldn't be surprised if they're getting at least around $700 to $800
for a 6cyl valve job now. Bordering on WWIII and still dealing with Covid all around the world has
really brought the economy to it's knees......all around the world. Besides that, ya just can't find
anyone that wants to work anymore.
dg

Nice to hear from you, Denny

Just had a valve job done on my 302's head. Price was around $800 including both a magnaflux and pressure test.

Where did the myth originate that "hard seats are needed for unleaded fuel"? While an engine that runs max RPM and full load for hours on end on LP or CNG needs hard seats and possibly stainless steel exhaust valves, I'd like to see some statistics on how many heads actually wear out valve seats in normal use on a low compression toy like a restored stovebolt. I'll wait patiently while somebody dreams up some numbers or pulls them out of his third point of contact.
Jerry

I have a 235 motor that I built in 85 sitting in the back of my garage. I beat on that motor unmercifully for many many years. Unleaded gas, no hardened seats. I have had that head off and on a couple of times over the years and not one hint of the valves pounding themselves into the seat.

On my 261, same deal, no hardened seats and that motor will rev to 6000 rpm. No issues. I have always been of the opinion that unless you are going to put 100,000 highway miles on your motor, probably don’t reallly need them.

Now my biggest reason for not using them, when unleaded became the only fuel available I rebuilt a couple of heads with hardened seats. Right up to the point that I discovered accidentally that one of my heads had core shifted really really bad. Did not affect the usefulness of the head at all. But when we went to machine the head for hardened seats, we unexpectedly hit water. Turned a perfectly good 848 head into an instant boat anchor. That was my last, has to be 25 years or better.

Unleaded fuel has been around longer than these Stovebolt engines. There is absolutely no noticeable increased wear on the valve seats of vehicle engines under normal conditions.

AMOCO introduced its famous Super Unleaded White Gas in 1923. It didn't harm engines then and doesn't harm them today.

That myth probably originated at the same time whale oil was removed as a friction modifier from ATF and every mechanic said that no automatic transmission ever shifted right since. That was around 1972 - 2 years before the unleaded gas mandate.

Exhaust Valve Hard Seats, copied from my blog.

There is some confusion about when hard seats are needed.

If an engine is run at full throttle for extended periods, with unleaded fuel as in pulling a heavy load over a pass, or a tractor pulling a plow for extended periods, the exhaust valves will become red hot. At this point when the valve closes it welds it's self to the valve seat. Then the next time the valve opens it breaks the weld and a little bit of metal is removed from the seat. Over time this causes the valve and seat to become recessed in the head. On a mechanical lifter engine this causes the rocker arm to valve clearance to go away so the valve can not close completely and eventually the valve will burn. On a hydraulic lifter engine the lifter will compensate for this wear for a while but over time the same thing will happen.

Another time a problem can arise is when an engine is timed too slow (retarded). In this case the air fuel mixture does not have enough time to burn in the power stroke so it is still burning as it is going out past the exhaust valves on the exhaust stroke. This will also super heat them and cause welding.

The lead additive in the past acted as a barrier between the valve and the seat preventing this welding action from taking place.

Valves do not like to weld to hard seats, being a dissimilar metal, so that is why they are sometimes used.

One other option that I use just for cheap insurance during a rebuild is to use stainless steel exhaust valves. Stainless steel being a dissimilar metal does not like to weld to cast iron either.

Chevrolet six cylinders from 1950 on use the same exhaust valve as the small block Chevrolet so stainless valves are cheap and easy to find. In most other cases stainless valves are available from places like Egge Machine.

There is one occasion where hard seats are needed and that is when the seats are eroded away from this welding action or from repeated grinding. This will leave the valves recessed in the head causing restricted flow in or out of the engine. This will effect engine performance.

I do not like using hard seats unless absolutely necessary as I have seen them come loose and damage an engine and they are fairly expensive to have installed.

The bottom line is if the engine is timed correctly and running fine and the engine is not loaded heavy nothing special needs to be done.

Small block V8 stainless exhaust valves are available on Ebay for dirt cheap prices, in sets of eight, not six. After doing a valve job on three heads, stainless exhaust valves for the next one are free!
Jerry

Thanks DG.