So I have a bit of a problem. I've been dealing with a guy here on the Bonneville Forum regarding the purchase of an engine for parts. I was going to drive up to Philips, Wisconsin, from New Lenox, IL (a ~400 mile drive) to pull the parts off of the engine myself. Instead, he needed to scrap the block so he pulled the parts off for me.

I needed the heads in particular for my 95 L27 as I have a burned valve and figured it would be cheaper and easier to get these heads with 85k miles on them, which I was told are from a 93 or 94 Park Avenue or Lesabre (I forget which), than it would be to have my 214k mile heads rebuilt by a machine shop.

I went and picked up the heads on Saturday, brought them home, and today I started cleaning them. I noticed while cleaning them that the factory rocker arms weren't roller rockers as they were on the later year heads. This also meant that the rocker arms use 3/8" bolts instead of the 5/16" bolts that my heads use.

This is a bit of a problem for me because I have Yella Terra 1.9 ratio roller rockers, which I need to transfer over to the new heads. I need to know if, aside from the thread size in the heads, if there is ANY difference between the 3/8" bolt heads and the 5/16" bolt heads.

If there isn't a difference, I'd appreciate it if anyone could tell me what my options are. I could obviously drill out the rocker bracket and the rocker arms to fit 3/8" bolts and find some allen head 3/8" bolts, but I need a second opinion. It would be 1/8" of a difference to drill out.

Any advice would be appreciated. If I bought these heads, I'd like to try to make them work, as I spent a good deal of money on them and the rest of the parts off that engine, and another $80 in gas to pick them up.

Well since nobody'* replied so far, I figure I'll give you all an update. I found studs that would work at lowes. The head of the studs fits perfectly inside the roller rocker arm, so all I have left to do is drill out the rocker seats and the rocker arms themselves and they *should* fit. This is of course, assuming that aside from the thread size in these heads, everything is 100% identical.

Some times you need to give a little time for a reply. Many of us work. Try asking Billboost, he might have a answer.

Before you do any drilling and or threading, definitely ask Bill his thoughts. Sometimes removing just 1/8" of material is enough to cause a failure point!

I know, but its either this or I find new heads and I've wasted all this money.

At this point, I don't think drilling 1/8" into the material will cause a failure point, as I'm only drilling into the rocker arm pivot mount, not the arm itself. Therefore, I'm not weakening the parts that experience the most stress. The pivot mount never moves. Here are some photos that should help.

Roller rocker with factory bolt:


Pivot mount I need to drill 1/8" larger (its that part in the middle):


Rocker base I also need to drill 1/8" larger. Comparison of 3/8" bolt and 5/16" bolt:


3/8" bolt on top of the rocker base:


Comparison of rocker, base, and both bolts:

I'm sorry for that. I did pull that motor from a 94 buick lesabre. I'm not sure why the studs aren't what you wanted. The door tag says 02/94. I have that wrote on the paper tag I had put on the engine alone with the 85,000 miles. Please accept my apology as I'm not sure on all the internal parts that may or may not cross over.
thanks
craig

Sorry..I don't have much info other that what we can search/find.

It may be only 1/8" But how can you be sure you have that dead center. We've see HS roller rockers with bad wear because the pedistals were not perfect. Will you have the same problem here? You may be better adding a helicoil in the head and use the proper rocker bolt.

I would have a machine shop do the drilling, and I'm not quite sure if I want to mess with a helicoil. I'm wondering how secure those things really are when I really need those things to stay put permanently. Where can I get a helicoil kit?

I'll be damned. I wonder if the engine you had was a completely different design for some strange reason.

I can't just tap out the threads in the block, as they are bigger than the bolts I need for the roller rockers. My option is now to either have the rockers professionally drilled, or to get a heli coil kit.