[Dragncar]

Originally Posted by blueghoast

What is the torqe spec on the outer bolts on the 4-bolt mains.?

GT

Some have 1/2" out mains, some have 7/16"
7/16 is preferable, especially on a stock block.

What do you have ?

[Tim Corcoran]

My block is at the machinist and he finally got the thrust surface cut. This was a challenge as it is very difficult to measure how much to cut off the new thrust cap. He is currently doing the line hone. The new 4 bolt caps are much harder to machine than the cast saddles in the block so this is also a challenge to prevent cutting to much off the block side during the line hone. To further complicate this process the front and rear caps are the original cast caps. The steel caps came about .050 too small compared to the correct bore size. The steel caps were put in a mill and the bore was rough cut to reduce the amount to be honed during the line hone. After line hone then it will move to boring the cylinders and moving one bank over about .015" to get more material on the thrust side.

[Mr Twister]

I don't understand why steel caps are used instead of ductile iron. It seems the ductile would machine easier. Is the iron cap a lot weaker than steel? I have a block headed to the shop for 4 bolt caps and was planning to use ductile caps.

[Tim Corcoran]

Do you have cast iron caps? Have you talked to your machinist yet about the thrust register will need to be machined on the new thrust cap? A lot of machinists won't even take the job, they are used to chevy main caps that don't have dowel pins and the process is much easier. Some say that going to 4 bolt mains doesn't do much unless they are splayed and that two bolt mains are stronger than most believe. I personally don't have the expertise to weigh in on that. I can tell you I'm going to have a big bill for putting these new four bolt steel caps and the line hone. He won't be able to give me a price until he knows how many hours he has into it.

[Dragncar]

Well, if one has a 2 bolt non drilled block IMO it makes no sense to run straight 4 bolt caps.
Few things, the front cap is cheap, might as well run a steel front cap. If a IA2 has 7/16 splayed caps we know they are better. And there would be no reason to run a 1/2 outer bolt and its greater torque pulling on the weaker stock block.
I bought my 400 block from Dan W. I thought it was a drilled and tapped 400 block and sent him straight PE caps. In conversation I found out it was a non drilled block. Even though Dan was partway through with the straight caps, thrust was cut, I called KRE and had them send him splayed caps. And it cost me a extra 200$ for Dan to do splayed. Lot more Fing around. But he did have the jig for drilling the splayed caps.
Dan had another customer who could used the straight caps as they fit his block even though cut.
Splayed id the way to go. They help out with cap walk. Bolts pulling from 2 directions.

Milodon makes ductile iron for Pontiac,s in 3" and 3.25" mains, straight and splayed. You only have to cut .030 off a Mildon cap and they are ductile iron so the line bore has to be much easier for the machinist.

https://www.milodon.com/main-caps/main-caps.php

[BB70]

Sounds like you have a great guy doing the work for you. Had the same done to mine except I had splayed put on, what a mess when its not done right. Best of luck to you this coming season.

John

[hurryinhoosier62]

Originally Posted by Tim Corcoran

Do you have cast iron caps? Have you talked to your machinist yet about the thrust register will need to be machined on the new thrust cap? A lot of machinists won't even take the job, they are used to chevy main caps that don't have dowel pins and the process is much easier. Some say that going to 4 bolt mains doesn't do much unless they are splayed and that two bolt mains are stronger than most believe. I personally don't have the expertise to weigh in on that. I can tell you I'm going to have a big bill for putting these new four bolt steel caps and the line hone. He won't be able to give me a price until he knows how many hours he has into it.

I’m trying to understand WHY cutting the thrust to the proper thickness has been such an issue. All the align bore machines I’m familiar with have a thrust cutting fixture that attaches to the cutting bar. I’ve used this cutting fixture a few hundred times over the years. You just have to be aware of how much material you are removing from the block side of the thrust, as to no machine the thrust surface too narrow.

[Tim Corcoran]

Originally Posted by hurryinhoosier62

I’m trying to understand WHY cutting the thrust to the proper thickness has been such an issue. All the align bore machines I’m familiar with have a thrust cutting fixture that attaches to the cutting bar. I’ve used this cutting fixture a few hundred times over the years. You just have to be aware of how much material you are removing from the block side of the thrust, as to no machine the thrust surface too narrow.

Are you a machinist? Can you tell me how you can measure the amount to remove from the thrust surface? The difficulty is not cutting the register, it's how to get a measurement. If you can explain this to me I will forward this info to my machinist this will help him on future jobs.

[blueghoast]

Originally Posted by Dragncar

Some have 1/2" out mains, some have 7/16"
7/16 is preferable, especially on a stock block.

What do you have ?

Mine are 1/2 inch, same as the inner bolts.

GT

[Tim Corcoran]

I am not installing splayed caps, the block is pre drilled for 4 bolts. All pre-drilled outer bolts are 1/2"

[chiefbigb]

I would imagine he is cutting with the cap installed on the block to the factory one already there matching them up. That would create a correct fit .

[Tom63LeMans]

Originally Posted by Dragncar

Milodon makes ductile iron for Pontiac,s in 3" and 3.25" mains, straight and splayed. You only have to cut .030 off a Mildon cap and they are ductile iron so the line bore has to be much easier for the machinist.

https://www.milodon.com/main-caps/main-caps.php

I’m trying to locate a set of these for 3” main 400 block. Anyone know of somewhere they might be available? Butler, Summit and Milodon do not have any in stock. Milodon says none will be available until end of February at the earliest.

[hurryinhoosier62]

Originally Posted by Tim Corcoran

Are you a machinist? Can you tell me how you can measure the amount to remove from the thrust surface? The difficulty is not cutting the register, it's how to get a measurement. If you can explain this to me I will forward this info to my machinist this will help him on future jobs.

ASE certified master engine machinist. I have cut the thrusts on a couple of hundred two stroke Detroit blocks. This isn’t rocket science. Most thrust bearings use interference fit to secure them in the cap and in the block; usually around .001-.0015. Measure the inside of the thrust bearing you are going to use( flange to flange); what is that measurement? You are going to want the finish size of the thrust surface to be .001-.0015 thicker than the inside measurement of the thrust bearing. If you will refer to a bearing catalog of the OE of the thrust bearing you are using the thrust surface specs are listed. Any other questions? Try working on your reading comprehension. WHY would I have technical familiarity with align boring equipment unless I was a machinist?

[chiefbigb]

Allot of good experienced people on this board in many different trades. Sometimes people assume they are knowledgeable in areas they play in part time and don't know they are communicating with someone that's knowledge on the subject is based on real life experience from many years hands on. Keyboard has more than likely never installed aftermarket main caps on a block. It can make you seem like you have though.

[hurryinhoosier62]

Originally Posted by chiefbigb

Allot of good experienced people on this board in many different trades. Sometimes people assume they are knowledgeable in areas they play in part time and don't know they are communicating with someone that's knowledge on the subject is based on real life experience from many years hands on. Keyboard has more than likely never installed aftermarket main caps on a block. It can make you seem like you have though.

It really isn’t a difficult task IF you have the proper equipment and experience. Several years ago, OE semi-finished thrust caps for 6V53 Detroits became nonexistent; semi-finished main caps were still available, so we produced our own using the thrust cutter supplied with our Berco BC-5 align bore machine. The critical issue with Detroit thrust bearings is they consist of three elements; two thrust washers and the main saddle bearing insert. ALL must be on spec or you will not have proper crank endplay or gear lash.

[Tim Corcoran]

Originally Posted by hurryinhoosier62

ASE certified master engine machinist. I have cut the thrusts on a couple of hundred two stroke Detroit blocks. This isn’t rocket science. Most thrust bearings use interference fit to secure them in the cap and in the block; usually around .001-.0015. Measure the inside of the thrust bearing you are going to use( flange to flange); what is that measurement? You are going to want the finish size of the thrust surface to be .001-.0015 thicker than the inside measurement of the thrust bearing. If you will refer to a bearing catalog of the OE of the thrust bearing you are using the thrust surface specs are listed. Any other questions? Try working on your reading comprehension. WHY would I have technical familiarity with align boring equipment unless I was a machinist?

Have you ever cut the thrust register for new caps on a Pontiac engine? My machinist does not have a cutter that can be used to cut the thrust register with the caps installed installed using a line hone. He used a fly cutter on a milling machine. Getting the new cap cut to match up with the block is the difficult part. You could have the thickness correct and be way off from the block. Once you have one side cut to match the block then all you need to do is cut the other side to the correct thickness, better to measure the thrust register on the block or the old factory 2 bolt cap than to measure the bearing. The new cap needs to match up the the register on the block.

[242177P]

Originally Posted by Tim Corcoran

Have you ever cut the thrust register for new caps on a Pontiac engine? My machinist does not have a cutter that can be used to cut the thrust register with the caps installed installed using a line hone. He used a fly cutter on a milling machine. Getting the new cap cut to match up with the block is the difficult part. You could have the thickness correct and be way off from the block. Once you have one side cut to match the block then all you need to do is cut the other side to the correct thickness, better to measure the thrust register on the block or the old factory 2 bolt cap than to measure the bearing. The new cap needs to match up the the register on the block.

Any chance fitting it with oversized dowels would
get it close enough for one face to match? Then it
gets cut for the right thickness?

[Tim Corcoran]

The thrust register on the new cap is done and the line hone is complete. Next up is boring and honing the block for the new Ross pistons.

[hurryinhoosier62]

Originally Posted by Tim Corcoran

Have you ever cut the thrust register for new caps on a Pontiac engine? My machinist does not have a cutter that can be used to cut the thrust register with the caps installed installed using a line hone. He used a fly cutter on a milling machine. Getting the new cap cut to match up with the block is the difficult part. You could have the thickness correct and be way off from the block. Once you have one side cut to match the block then all you need to do is cut the other side to the correct thickness, better to measure the thrust register on the block or the old factory 2 bolt cap than to measure the bearing. The new cap needs to match up the the register on the block.

Tim, it doesn’t matter what marque the block is; the process is the same. I have cut the thrusts on aftermarket Ford SVO blocks. A fly cutter will work; you just have to make certain that ALL the facets of cutting the thrust are taken into account. In a couple of instances we bolted the new “thrust” cap in its position after confirming that it was in the correct position, then used a fly cutter in one of our F90 Rottler machining centers to make the initial cuts. Once the first side was completed, we reversed the block, re-positioned the “thrust” cap and made the initial cut on the other side.

[chiefbigb]

I am a Cummins and caterpillar master machinist. Worked for dealers and oems since 1990. Mostly did deck repair at remote locations. Not allot gets fixed anymore just swing engines in long block form. I do more wiring and emissions work these days. Still play with the Pontiac engines. There are a couple in progress similar to what Tim is working on out there now.