Main Caps

[VETTE_50_TH]

So i called the machine shop i think im going with, and he said that i should try to find the main caps off of the block i got, or buy a new block. The block and crank were given to me for free and crank, but he forgot to give me the caps. Hopefully he has them, but what if he doesnt. I've read people line hone the block, but he said more than likely, they still will not work. What have you guys experienced with these blocks and main caps off of different blocks? Should i worry about it, or what should i do? I dont want to pay for a block when i got a perfectly good one in my shed.

James

 

[1992awdlaser]

I would find a machine shop that can properly line hone it. I have never heard of somebody not being able to use main or cam caps off another engine after being line honed.

 

[cruisintalonawd]

get the billet steel ones from slowboy or ckeck the junkyard. just make sure they line bore it

 

[absolute_DSM]

If your machinist says it wont work, then listen to him. He may not be able to properly do it for some reason which may comprimise your block.

Cant afford another $100 block?

 

[VETTE_50_TH]

Well, i can afford $100 bucks. But not if i dont have to. He kept saying, we probably cant do it, plus he doesnt do it anyway, he must send them out. It just made me a little worried. I've heard of people doing it. I might just buy some caps off another car, like im going to, and say they are the originals, and ask to line bore and hone it anyway. Other than that, his prices are good. I had another thread open talking about how much to do the engine work. He would want 450 to do everything. Degrease, install fresh freeze plugs. Bore and hone, deck, assemble short block, and some minor things. To give you an idea, there is a place in reading that charges 400 just to bore and hone. Place is called Hyde Villa, aka, rape your checking account villa. I think i will just ask to line hone it anyway.

James

 

[JamiesTSI]

Mains from another block will be fine. Line honeing the block is a must. Are there any other machine shops in your area you could price compare? Line honeing is a pretty common item for most machine shops.

 

[outkastracing]

thats cheap if hes going to assemble the bottom end i just 240 and got my block bored, the head surfaced,pistons mounted to my rods,and put my springs in for me so thats a good deal hope hes good!

 

[VETTE_50_TH]

There are other ones, but either not as good, or way to overpriced. He seems pretty reputable.

James

 

[turboglenn]

Just give him some caps and some ARP main studs, He will HAVE to line bore it because the main studs change the actual clamp and distort the caps slightly to where they have to be line honed/bored either way. If he doesn't line bore, make sure he know at least that it HAS TO BE DONE to put the ARP's in.

Then you've got a stronger bottom end and you know it's right

 

[VETTE_50_TH]

I was planning on using arp's. So if i say, listen, im using stronger studs, the main caps must be honed anyway to use these, then im in good shape?

James

 

[VETTE_50_TH]

Wanna send me your mains? I think the guy who gave me the block has them. If he doesn't, i'll keep that in mind.

James

 

[Big Woo]

If you do not end up with the original main caps from the block, then you are more likely to need align boring than align honing. This is because the main housing bore halves (upper in block & lower in the main cap) are aligned by the main cap register I.E. the machined verticle portion on the outside edges of the main caps, and the machined verticle edges on the block where just outside of where the main bolt hole are. The register acts as an alignment method (left to right, when the engine is viewed alogn its cylinder axis), this ensures that the two halves of the main bores precisely align.

When differnt caps are installed the relationship of the register to the center of the main bearing housing bore change for the cap and not for the block. Therefore this creates a misalignment of the two halves of the main bearing housing.


Align honing is less expensive (less set up time, but it can only correct a small amount miss alignment). This method is generally used to straighten the axis of all of the main bores. This process does remove a small amount of material from the mating surfaces of the main caps, therefore when align honing is complete it does move the crankshaft centerling up in the block, in relation to the deck surface. It is importaint to have all machining done at a high quality machine shop. Misalignment, machinest knowledge, and other factors can cause the crankshaft centerline to shift left to right, up and down, and yes both, thereby destroying an otherwise good block.

Align boring is more epensive, due to set up time and the level of expierence required to do the job right. This process uses a cutter to remove material, and therefore is capible of removing more marteial, and has the ability straighten, correct cap to block misalignments, and match new caps to exhisting block main bores. On the down side there is alot more that can go wrong here, so expierence is key, additionally this operation generally removes more material than align honing, thereby having a greater effect on the end crank centerline to deck height measurement. In extreme cases pistons with differnt than stock pin heights might need to be used for a given rod length.

 

[VETTE_50_TH]

Good information Big Woo. I will makes sure i ask for align bore if they look extremely off.

James

 

[turboglenn]

I was planning on using arp's. So if i say, listen, im using stronger studs, the main caps must be honed anyway to use these, then im in good shape?

James

Correct, as long as the main caps you get are close enough to the blocks journal areas that it can be align bored. Most times they should be fine, my machinist says he rarely sees a block that can't be line bored a few times, so you may have to take it out to the max bore you can get, but it should work. He will have to line bore it no matter what if you're using ARP studs, if he doesn't know that, pick another machinist!