Valve seat concentricity issues

General engine tech -- Drag Racing to Circle Track

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SBC
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Post by SBC »

Hi guys

I've wondered how large of a temperature gradient there is circling the intake seat (being next to the exhaust seat) on a running engine? Does this raise one side of the seat? Can the effects be seen upon dissassembly? Torque plating head much more of a factor?

Thanks Gary
Gary 540
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Post by Gary 540 »

Hi All
I would like to know what sort of movement is seen when checking runout with and without head plate bolted up ??
Is it half a thou ? 1 or 2 thou ? More ? Less.
Say for example Big Block Chevy alloy head.
I am going to buy a run out gauge but can tell I’m not going to be happy with results, from what you guys post.

Gary..
n2xlr8n
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Post by n2xlr8n »

Sad that this issue remains, given the cost of "good" cylinder heads nowdays.

Back in 2000, I purchased a set of Track 1s for my SBC brand new, my machinist almost choked me. Later that year, I built a 540 for the same car (with new Dart Pro 1 heads this time), he told me next time I brought him this "junk", I was going to get his "special" pricing. :lol: Persnickety, but he does a wonderful job.

I can't understand how manufacturers can stay in business that way. One would be better off buying used heads at times, I guess.
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let r eat

Post by let r eat »

I have seen the same things as mentioned above. You have to stone em in to get them right. No cutter is going to suffice. When I see a head that has cutter seats with no stone marks I just get to work!!!
Joe Mendelis

Post by Joe Mendelis »

let r eat wrote:I have seen the same things as mentioned above. You have to stone em in to get them right. No cutter is going to suffice. When I see a head that has cutter seats with no stone marks I just get to work!!!
I don't necessarily agree with that. 2.180 Copper Byrillium seat on a Serdi 100 will cut under .001. With a VGS I have used the K62 material and that cuts hard seat round, the other stuff won't. Stones are a pain in the ass and take too long.
Mike Rogers
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Post by Mike Rogers »

I just got done doing a set of norstar heads.I don,t know how many of you do heads with valve stems 5.5mm but what a pain in the ass.

I bought the taper carbide piolits from kwik way because that is the machine i have and i did some checking on flexing you can push the piolit .003 with no problem.

Most of the aluminum heads today from the factory use powder metal seats and any one that has tryed to cut these seat knows what i,am talking about they are rock hard so the cutter has to be sharpened every seat and the speed will very from seat to seat.

I jump thru hoops trying to get seat run out to .001 or less out of 32 valves i have 8 that are .0005 10 that are .001 and the rest being .0015 to .002 i have done everything i can to get this run out thing under controll and i have come to a conclushion that with cutters its almost impossible and you would go broke trying to get every head that way.

I spent 2 days on the heads cutting seats.I have bought tooling from other companys adapted bridge port stuff to my machine i also made a piolet with a ground flat plate that sets on top to tram the guide level all to no improvment to cut seats .0005 all the time.

I have a stress plate also for sbc heads to help with it.I did a test in the early 80s on heads and gasket thickness to see what effect it had on seats and let me tell you the end ex. seats move as much as .003 with light casting and thick gaskets .040 so the thicker the deck serface the better off you are.

You also need to realize that the water and pressure and heat in the heads and little steam pockets that will form will take your nice .0005 seat run out that you just spent 10 hours on and and raise the heck out of them on one side or another.

So lets say you have your seat run out down to .0005 on your late model head now you put it on the engine with that .040 gasket and wear your seat is .0005 out of round now becomes .0035 then the steam pocket forms in the same loction and raise it another .003 or more and now you have a seat that is .0065 to more out of round.It could also happen the opposet of it and equale it out but i think its a 50 50 shot that will happen either way.

I also dyno and engine 18 busch engine from a well know builder out in wissconsen and when we did a leak down we found a cylinder that was 20% leakage so we took the head off to find that the seat cooper was out of round by .007 so we sent it back to him and we figued that we would have picked up power it made appsolootly no diffrents in power.

Now i,am not saying i say seats should be sent out at .007 or even .004 and god knows i worry about every head i send out that has .002 if it is going to fail or not but i,am begining to beleave we are driving our selfs nuts trying to get this under control with the seat and guide machines that are out there.Most of us that are on theis board that do this for a living i would have no problem with there work because we are all trying to get our shops to a standard of what regular machine shops are at least i know i do.

The only way i see around this is to have cutters made with .020 seat width and then go in with a hall toledo grinder and get the seat to what you need.

Grinding is far more accurate then cutting with an insert but we all have to make money also not every one can pay for a $2000 valve job.
Mike Rogers
215-674-5240
EQ Cylinder Heads
http://www.rogersperformance.com
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