I am assembling an 87 T-type engine, using heads I bought from a local engine shop; they had come out of another T-Type. I bought ARP head studs, but when I inserted the studs and placed a gasket and head over them, they were too long. The biggest problem was the upper outer studs (the ones on the ends of the head under the valve cover) were obviously too long by about 1/4 inch. I contacted ARP; they said 4.25" (total length) was the length called for at those positions on a 8445 casting head, which I have, but they agreed to switch them for shorter ones, and they sent me 4.00" studs.
When I screwed all the studs into the block and placed a gasket and the head over the studs, they were just about right, but some were long enough that when I placed one of the ARP washers and a nut on the stud, it bottomed out on the threads before it seated.
I removed the head and measured the depth of the head bolt holes with my depth caliper. The short holes, along the bottom, are 1.60" to 1.65". The upper outer ones are 1.81", and the upper center ones are 2.61" and 2.62".
I then screwed down a nut all the way on the studs, with the head/gasket off, and measured the heights from the block to the bottom of the nut, and the heights were about the same as the (head thickness+washer+gasket), but in a couple cases the stud height was a little more than that, maybe by about .03".
Does anyone have a good head that could tell me what the depth of the head bolt holes should be, compared to my measurements? Do I have some heads that were milled down a lot? Do I have some potential problems with high compression if I put these headas on my T-Type? Can I possibly get a thick gasket that would add back some space? I haven't found a thicker gasket yet, so I bought some extra washers to put under the nuts, to make sure they torque down, but am hesitant to assemble the engine till I know I am OK.
Sorry for the long-winded message, but any help would be greatly appreciated.
I can't help you with dimensions, but I do want to applaud your approach to getting your parts to fit correctly.
A couple of thoughts on your situation.
Make sure there is no garbage packed in the bottom of the short holes. Sometimes there are chips packed down by the old bolt. The factory doesn't always get the holes clean.
Buy a bottoming tap and use it to assure that the full thread is cut to the bottom of the hole. You can buy the tap at a machine supply house. If you imagine the machining process that taps the holes in the block, the tap is driven to a predetermined depth and it reverses for removal before it gets to the bottom of the hole. Otherwise, the tap would bind and break. Sometimes the drill and tap depths are not maintained correctly. It seems like they would use a slip clutch and drive it to the bottom, but since that would be a high maintenance item, they don't use that type of machine.
Thanks for the feedback, especially on a holiday weekend. I chased all the holes before installing the studs, and all studs bottomed out in the block, so I know that's not a problem. I will wait and hope someone can tell me if my heads are still useable.
What block are you using??
The 84 to 87 3.8 block's holes don't bottom out. They go right into the water jacket.
The 4.1 block's 2 lower outer most holes do have a bottom but the other 6 are bottomless.
Chris, I failed to mention that all the holes do go into the water jacket on my block, none bottom out. I did chase them all just to be sure they were clean before screwing in the studs. I do have a 3.8 block. Any help in assessing my head condition would be appreciated. Thanks
I went out and measured what I believe is a totally stock head. I put it on a reasonably straight cement floor.
Top row....left to right.
1.848 2.660 2.662 1.841
Bottom row....left to right
1.658 1.660 1.665 1.637
Chris
Looks like my heads have been milled about .040" compared to yours. I will have to find out what impact that might have on performance, both good and bad. If the engine will still be OK with these heads, I will probably add some extra washers under the stud nuts to take up the reduced head thickness so I can torque them down.
Anyone who would like to comment on using these heads, I will welcome the input. I'm sure others have used heads that have been worked, but I don't know if .040" is a problem with the turbo engine.
Your compression would go way up. You'd have to cc the combustion chamber yourself and do the math. Some people like higher compression, saying the car is faster off the line. Then they run lower boost. But yours may be too high ...40 thou seems like a lot.
You would also have to buy shorter pushrods...$75 or so from Smith Brothers. The valve train geometry would be off but I'm not sure if 40 thou is enough to affect it negatively.
Your manifold may not bolt on since the head holes are going to be out of whack with the manifold bolt holes. People who have milled heads sometimes have to have the mounting flanges on the manifold milled to match.
Stock heads are really cheap. Why not see if you can get a refund since the ones you got have been milled so much then get a stock set.