I am installing 2.02 int./1.600ex. manley valves in my stock ported 95 lt1 aluminum castings. I just ordered new hardened valve seats to press in. How much interference fit would i want to figure in when I bore the heads for the new seats? I run a vertical mazak v655b and bore tight tolerances on a regular basis. I have access to liquid nitrogen. I also have a home made fixture to set the heads up to bore and to press the seats in. I was wondering if i should replace the valve guides since I can do it all in the same set up. They still feel pretty tight. I believe I have the resources to do the whole job, including grinding the new seats in. Anyone who has done this before or has first hand knowledge, you help would be appreciated. thanks.

 

I guess everyone must pay to have all there work done.

 

Alright - you should change out to bronze guides, or have a shop install bronze liners first, stainless and cast iron tend to cause galling. I understand that swapping the guide inserts is within your capabilities, but you need to hone the ID to a clearance of approx .0015" INT/.0019" EXH. - this takes a special guide hone tool made by Sunnen - guides don't come pre-fit out of the box. Guide press into the head should be .0015" minimum - .0023"

Then for the seat inserts you need to use ones that are ~ .025" per side larger than the valve head diameter, so for a 2.02" valve you will use a 2062 seat. Seats are marked with the number that you cut the counter bore to, there are iron and aluminum specific seats that have the press fit built into them, and the aluminum specific seats have a nicer radius on the bottom to keep from pulling aluminum on insertion. So if you have a iron specific seat SB2062-1 for example, if you cut the bore to 2.062" the seat will actually measure with your mic at 2.0665" for a press fit of .0045". An aluminum specific seat will read the same on the seat (SB2062-55 for example) but will actually measure at 2.068" for a press fit of .006"

I always add some a little more on top of that and put my seats in iron heads at .005-.0055", and for aluminum at .0065"-.007"

What are the specific seat numbers that you ordered?


Let me know if you have any other questions.

 

First of all......you are just the kind of person I had hoped would respond to my post. My seats just came in. The numbers on the intake seats are sb2062-23. (and also have a nice chamfer on one side of the o.d., and the o.d. measures 2.068, just like you said it should) and the ext. seats say sb1625-0. Does the (-23 ) mean I should counter bore .230 dp. for the intake seats? Does that sound deep enough? The ext seats say(-0) but they measure .375 thick. How deep should I bore for these ext seats? I want the guides and seats to be to "true" to each other. What would you do? The guides including honing first, then press in and grind the new seats 'piloted' off of a ground shaft placed through the new guides? Is this worth the effort?

 

SB2062-23 : 1.687"ID X .375" tall
SB1625-0 : 1.375"ID X .375" tall

The -0/-23 just designates which seat out of ~75 possibilities you are holding with different combinations of ID's and heights. For aluminum heads you don't cut the counter bore any deeper than it already is, you will bore the hole to size and just cut enough out of the bottom step to make it square to the wall. So if you remove the original seats, and are left with a bore that is .341"(11/32") deep, you would cut whatever is necessary out of the bottom (.005" maybe) to allow the new seat to fit square in the hole and flush with the bottom step. Then you would cut down whatever is left at the top of the new seat to make it flush with the chamber.

That is what you do to make everything concentric, but the guides are honed after they are pressed into the head. If your probe tip on the VMC is small enough I would use the guide as the G54 offset or use a center less ground pilot to probe off of. Then interpolate the hole with a 1/2" end mill.

 

Here's how we cut seats - a carbide pilot is put into the guide for the cutter body to spin on concentrically, the form tool that slides in/out of the body has the seat profile on it. With a setup fixture we set the seat placement where we want it, and the elaborate drill press machine(sunnen vgs-20) cuts the seat.

 

My mill is pretty old (r32b controller). I have a tool eye only. No actual probe. And If I circle mill a hole, it will tram .0012 out of round. But, We have some grayflex boring heads I will probly use. I will tickle the existing casting floor depth. (I already popped out the old seats). I will have precision ground pilots made to tram for location. Should I indicate every guide? Or zero off one, and offset shift my program? It holds location pretty well. You have been very helpful. Thanks. _nick

 

I wouldn't trust the guides in a production head to be close enough for a fixed shift on the offsets, it's best to setup your offsets individually for each hole. But you could go ahead and measure the center-center distances, and if they are close run the offset program for the seat bores.

How are you going to do the valve job? Do you have a souix grinder setup?

 

great advice on hole locations. Unfortunatley my father has passed away recently. But, he has a valve grinder and lots of goodsen seating equipment in his shop. I have not personaly used this eqipment, but have seen him use it. I am confident my heads will turn out good. I really sucks not to be able to ask him questions anymore. But, you have answered a lot of them for me. thanks again._ NICK