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DIY coolant tubes in heads

n8in8or

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I am attempting to install brass tubes in the coolant passages between the valve bowls in my heads. I'm working on a pair of heads that don't have cracks yet, so it's more of a proactive thing. In an unrelated conversation @Will L. sent me this video that showed how to do it.


I purchased an extended 9.7mm drill bit from MSC and some 10mm OD, 1mm wall brass tubing off of Amazon. Last night was my first attempt at trying it in a junk head I had laying around. The first thing I noticed was that the 9.7mm drill bit didn't really remove any material, it just kind of cleaned the hole up. The first brass tube that I started driving in got kind of mushroomed while I was driving it in and turned into junk before it even got all the way into the hole. After that I tried making a better driver using some bolts that I turned down using a grinder and then cutting a square shoulder using my bandsaw (this is the best I could do without having access to a lathe). I got further this time, but progress stopped about 1.5" from getting the tube installed all the way. Oh and I also ground a slight chamfer on the outside of the second tube to help it install.

head1.jpghead2.jpg

I'm wondering what the appropriate interference fit should be between this tube and the coolant passage. I feel like this is too tight and that's why I can't get it to install. Since the drill bit isn't really drilling a hole, I'm not sure what the ID of the passage is exactly all the way down, however if I use the drill size and the known tube OD I theoretically have .3mm (.0118') of interference. I did a quick Google search last night and didn't find much helpful info. I did find some info on McMaster-Carr for bronze bushings and for a 10mm OD bronze sleeve bushing they spec an interference fit of .03mm (.00118")…..significantly less interference. I'm wondering if I should be shooting for a hole size somewhere between those 2 values. I'm hoping someone on here has some first-hand experience with this or something similar and has some guidance on what the interference fit should be.

BTW, Lock n Stitch does sell a kit to do this job with their own inserts and reamer and driver, but it's a $400 kit.

 

WarWagon

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Sometimes renting $600 worth of experience from a diesel head shop for two heads to be completely redone including this mod may be money ahead by not ruining a good head and the mod working as intended.
 

n8in8or

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I like the heating and freezing ideas. I was already thinking I’d get an oven for the barn so I could preheat heads before filling the EGR runners and doing other handy things out here like baking pies.... Problem is, with 3 trucks currently torn down in here space is at a premium so I’m going to hold off on that for now. It’s looking like I should put this idea on hold for the time being as well. I’m not so worried about ruining good heads - I have a few junk heads to practice on and some I could repair and test, but as far as a preventive measure, it would be good to figure out the proper fitment because there may even be a chance that adding the extra tubing in there could help stabilize that area and actually help prevent cracks. The fact that even Optimizer heads crack between the valves disgusts me and I’d like to figure out how to avoid that altogether. Forget fixing cracks, I want to prevent them. To be continued I guess.
 

Twisted Steel Performance

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n8in8or

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I noticed both Goodson and Lock n Stitch used reamers to finalize the bore before inserting their tubes. That makes sense to me, you'd want it to be very smooth so the tube is best able to seal against the wall of the casting. That would also help installation as well I suppose.

I think I know what you're saying about the other passage. I've seen pictures of the passage between the valves being 2 ways - a long passage that dead-ends at the outer wall of the pre-combustion chamber and then the pics you shared where it had that bolt cast into the passage, blocking it. So far any heads I have looked at here are the first type, with the long passage that dead-ends. I toyed with the idea in my head of tying the passage between the valves into that other coolant cavity above it. I have some ideas on the method of doing that, but nowhere near having an idea on the orifice size to use. The brass tube has an ID of about 5/16", it seems like that would large enough for plenty of coolant flow. This is all stuff I was thinking I would play with in the future, certainly not on this set of heads. That may be the trick that stops the cracking though....
 

n8in8or

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Yesterday I emailed Goodson to see if they would send the instructions for the kit they used to sell. They actually did, so that's cool. Attached are the Goodson as well as the Lock n Stitch instructions. Interestingly both kits use a sealant around the insert to make sure they seal to the bore. The Goodson insert apparently had a split in it because the instructions say to orient that away from the crack. The LnS inserts have seals on them in addition to the sealing compound. So the two companies used slightly different approaches to do the same thing. I was hoping the Goodson instructions would have the size of the reamer, but no dice. The LnS instructions say .400" for the reamer, which is larger than the 10mm brass tube, but their inserts also have the seals so no way to know the basic diameter of their inserts.
 

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MrMarty51

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Is the head tube repair kit for the 6.5 heads too ? Just curious if the 6.5 had the cracking problem. It says the kit is for the 6.2, whay I asked.
They sure a secretive about their prices, have to send them an message or email them to get the prices.
 

n8in8or

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Is the head tube repair kit for the 6.5 heads too ? Just curious if the 6.5 had the cracking problem. It says the kit is for the 6.2, whay I asked.
They sure a secretive about their prices, have to send them an message or email them to get the prices.
Yeah, that's interesting the Goodson instructions only say 6.2L. They must have made their kit when only the 6.2 existed. The 6.2 and 6.5 heads all seem to have this problem - even some Optimizer heads.
 

Will L.

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Yuppers all of them. The only one that has a chance is the p400 heads with the improvements they made there.

I spoke to a machinist that I used years back and he laughed at me- said he installed the tube in heads he did for me. I never even knew. I went back and looked at a couple old pics and sure enough they had the screws in there instead of the plugs.
 

Husker6.5

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IIRC, didn't NAPA sell a kit for that? Or were they just carrying someone else's kit? Yes to sticking the tubes in the deep freeze and possibly warming the head for easier fitment and a shmear of Permatex #2 sealant to ensure things stay coolant tight.
 

n8in8or

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Just a "friendly" reminder every time you start a new project. You don't even want to know how many projects around the house/on vehicles that I started and still have hanging. Hell, around the house, there's some from 29 years ago!
Good thing I don't share all of my projects 😁

My oldest is 24 years now.
 
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