[hobbygto65]

I have a 4 bolt main block with 2 bolt caps. Which 4 bolt caps would you recommend?

[Dragncar]

You can buy Program billet steel. Milodon makes set of ductile iron caps.
But remember, a 2 bolt block with studs are good to 600 HP. You only gain 100-150 HP more reliability going to billet caps.
And 600HP is a very stout street engine.

[Scott Stoneburg]

With any aftermarket 4 bolt cap you will need to line hone. If you're set on 4 bolt I would go With Program Caps. What is your HP goal for the engine?

[mgarblik]

Originally Posted by Scott Stoneburg

With any aftermarket 4 bolt cap you will need to line hone. If you're set on 4 bolt I would go With Program Caps. What is your HP goal for the engine?

Knowing your goals would be important. Honestly, installing billet caps is quite a process. You are locked into the straight caps because your block is already drilled and tapped. You need the caps and a set of longer pins. Then the short, almost useless pins need to be removed, which can be difficult. Then new pins installed, the caps bolted up and torqued. Then the three new ones need to be line bored next. Then the Thrust surfaces need to be machined perfectly. Then the front and rear cap need to be cut and the set of 5 caps line honed to the finished size. I just did a 1967 400 block a month ago. If your having a shop do all this work, caps, pins and machining will easily eat up $1000.00. Worth it if you need it. A waste if you don't IMO.

[hobbygto65]

Yes I realize all this, I've been driving Pontiacs since I was 18, I'm 71 now. Its an extra block that I was thinking about selling and thought it would be more desirable with the 4 bolt caps on it. I thought I read that the extra holes made the block weaker?

[steve25]

Sell it as is!

Whoever buys it if they are not going to add 4 bolt caps all they need to do if they need added strength while retaining the 2 bolt caps is to run studs and use locktighted in Allen head bolts in the unused holes.

[ho428]

I've added 4 bolt caps to several blocks, I always find undrilled 2 bolt blocks and add splayed caps. IMO, adding 4 bolt caps to factory straight drilled blocks aren't worth the effort/cost for a build that needs 4 bolt.

[steve25]

Please note that in my above post in regards to installing Allen head bolts into the six unused bolt holes that it important to NOT use long enough bolts that they bottom out!
The bolts are not to be tightened down , just the use of the Loctite and then being no more then sung on the top of the main web is all that's needed.

If they bottom out in the hole and you tighten them down you had better check the line Bore to confirm that nothing has shifted.

[PAUL K]

Originally Posted by hobbygto65

Yes I realize all this, I've been driving Pontiacs since I was 18, I'm 71 now. Its an extra block that I was thinking about selling and thought it would be more desirable with the 4 bolt caps on it. I thought I read that the extra holes made the block weaker?

The unused extra holes for the four bolt caps does weaken that area of the block a bit. However if four bolt caps are added the block now is better off than a solid block with two bolt caps. If it is something you are looking to sell I think you are better off selling it "as is" then the new buyer can build it the way he wants.

[Will]

Originally Posted by PAUL K

The unused extra holes for the four bolt caps does weaken that area of the block a bit. However if four bolt caps are added the block now is better off than a solid block with two bolt caps. If it is something you are looking to sell I think you are better off selling it "as is" then the new buyer can build it the way he wants.

This.

You'll never get the money back out that you spend to have the 4 bolt caps installed.

I wouldn't pay extra for that because just studding a 2-bolt block is good enough for any engine I'm ever likely to build, and I think 90% of the people building engines don't need any more than that either.