consaka
Active Member
I am pretty sure shims would fix it. Shims would bring the precup out flush with the surface of the head so the gasket can press on it. That would hold it steady.
I am 90% positive.
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4x4 Chevy 6.5 turbo diesel van project.
- Thread starter consaka
- Start date
I am pretty sure shims would fix it. Shims would bring the precup out flush with the surface of the head so the gasket can press on it. That would hold it steady.
I am 90% positive.
ak diesel driver
6.5 driver
so where are you going to find inconel shims?
consaka
Active Member
Because they are heat sinked directly to the block they should not need to be inconel. The center part that gets super hot needs to be inconel.
Will L.
Well-Known Member
Because the inconel is a tight fit and expands more than the cast iron under its heat, the fit becomes very tight. I am wondering what material you would want inbetween the two that the heat difference doesn't cause issues.
consaka
Active Member
You still have the iconel pressing against the sides. Since the sides do the majority of the heat sinking I don't think you would want any other material there.
The quote I have right now is for stainless shims. .06mm $330 for 40 of them. Heat of the precup probably doesn't increase pressure where those shims would go. Least not much. If it did it would be lifting the head off the deck. Pretty sure about that. That area where the precup rests against the lip in the head is really small.
The quote I have right now is for stainless shims. .06mm $330 for 40 of them. Heat of the precup probably doesn't increase pressure where those shims would go. Least not much. If it did it would be lifting the head off the deck. Pretty sure about that. That area where the precup rests against the lip in the head is really small.
consaka
Active Member
Got a question for you guys that build engines. You ever notice the difference when torquing heads when they are hot versus cold? I never thought about it till I read that some guys heat them a bit somewhere. 90 foot lbs suddenly turns into 60. But if you were to torque them hot that would seem like torquing them to 120 cold. When they cool down they tighten up? Or is it just better to heat cycle them a few times and then retorque when they are cool?
Not clear on:
1) The machine shop FUBARED the precups by grinding the heads with them in. The grinding wheel will "suck" the precups into the wheel...
2) Machined the precup recess in the head too deep.
WHEN you find out if they destroyed the precups, the heads, or both: ASK yourself if you want to pull the engine back out when the red-neck duck tape and bailing wire shim idea fails? @Will L. can tell you what the precups are made of to resist the blow torch in the combustion chamber and we just had a pic of a flame cut precup on here. Glow plugs are on the razors' edge of failure and they are bolted into the head. Shims with contact cooling to the head doesn't sound like something that will last especially if you are building it for power like the rockers etc. indicate. Would the shims flat out melt, soften up and deform becoming thinner, or would their extreme expansion and contraction all work the gasket into a quick failure? Just saying risk of do it right or take the time to do it over.
Set of heads or just a set of precups? My luck would be both... (The shim cost is half that of new precups.)
I have never had to re-torque a head as this is the point of TTY head bolts. I haven't re-torqued the ARP studs either. Cold is relative as I have torqued them when it's 110 out.
consaka
Active Member
They machined the recess too deep. Then they red threadlocker on the precups to hold them up in place.
They provided some precups but I had my own I wanted to use. That is how I found out what they did.
Precups are in contact with the head in two places. The main heat sink area is the sides of the precup. When it gets hot and expands it expands sideways into the head. That additional pressure makes the heat sink effect that much better. The lip inside that keeps the precup from falling into the injector and not seal against the head gasket is really small and not really an effective heat sink source. The only pressure pushing on it to encourage contact is the head gasket on less then half the surface. You should be able to shim up the depth of the precup without issues. Stainless steel shims smashed flat would still transfer heat on that narrow ledge a little. I'd do it with no reservations in a second if I had the shims.
Sure a hell of a lot better then threadlocker.
consaka
Active Member
I am not sure the actual depth Thickness of a piece of paper or two. The danger with machining with the precups in is catching them in the bit and tearing things up since they can move. Now I have had other machinist say they know about that problem but still do it after pining the cup in place. In this case I have no idea what the hell they were thinking. Guy must have been green. All I know is my T-cups were longer than theirs so it wasn't as bad with mine. couple shims would hold it up against the gasket just fine. Sure was a pain cleaning out that thread locker.
consaka
Active Member
Hot diggity! Steve at Harland Sharp sent me new 1:6 rockers next day. I am stoked now. Except for that head issue I'd be confident again.
consaka
Active Member
Ok I found some bare heads on amazon. BUT I am suspicious they are any good.
https://www.amazon.com/dp/B0176LF0PK/?tag=jhdiesel-20
What do you guys think?
https://www.amazon.com/dp/B0176LF0PK/?tag=jhdiesel-20
What do you guys think?
consaka
Active Member
Actually I am looking into it. The head has been shaved before so not sure how much more they can shave. The shop that did the work is 60 miles away through downtown Portland. Pain to get to. I'm thinking maybe a local shop could shave just a little more. I need to measure all of them and see if the depths are all the same. Getting the precups out is a pain. I don't have any brass punches so I have to use wood. wood doesnt last long with stubborn precups.
n8in8or
I never met a project I didn’t like
I've used an aluminum rod before and it seemed to work ok. Yeah I wonder how much more you could shave them and not risk cracks. Good luck, I hope they're all the same depth so you at least have the option.
Will L.
Well-Known Member
What happens is when the cut the head because of warpage or gouging: they can either cut the precup down separately, or the can cut inside the recess where the cup sits. The second is what his shop did, but they cut a hair to deep.
I've been thinking about this shim. Iirc @sctrailrider -did his precups with a thermal barrier to separate the heat of the precup from going into the head (Is that correct?)
It really seemed counterintuitive to me- but I am still mulling it over, and have shifted from 100% against to nuetral. The precup is inconel not just so it can withstand the heat, but maintain it on purpose.
If this is correct -that our friend from South Carolina has had success with isolating the precup heat wise, you may be able to get away with the shim provided you thermally coat the precup and the shim, maybe even the recess in the head. Less heat transfer means slower change in growth and may not cause the expansion from the recess.
My concearn is having a shim in there to take up the space is subject to expansion/ contraction from temperature swings. And as the cast iron heats and cools more rapidly than the inconel, the inconel remains almost unaffected by the temperature changes.
Surely anything so thin, and ajacent to the psycho hot inconel is going to be affected by the heat. It would want to not just expand, but any disc of metal I have ever worked with, when heated it warps into a wavey pattern where 12:00 and 6:00 flex upward and 3:00 and 9:00 flex downward causing growth in height much greater than the metal itself could normally expand. That expansion is my concearn.
I've been thinking about this shim. Iirc @sctrailrider -did his precups with a thermal barrier to separate the heat of the precup from going into the head (Is that correct?)
It really seemed counterintuitive to me- but I am still mulling it over, and have shifted from 100% against to nuetral. The precup is inconel not just so it can withstand the heat, but maintain it on purpose.
If this is correct -that our friend from South Carolina has had success with isolating the precup heat wise, you may be able to get away with the shim provided you thermally coat the precup and the shim, maybe even the recess in the head. Less heat transfer means slower change in growth and may not cause the expansion from the recess.
My concearn is having a shim in there to take up the space is subject to expansion/ contraction from temperature swings. And as the cast iron heats and cools more rapidly than the inconel, the inconel remains almost unaffected by the temperature changes.
Surely anything so thin, and ajacent to the psycho hot inconel is going to be affected by the heat. It would want to not just expand, but any disc of metal I have ever worked with, when heated it warps into a wavey pattern where 12:00 and 6:00 flex upward and 3:00 and 9:00 flex downward causing growth in height much greater than the metal itself could normally expand. That expansion is my concearn.
consaka
Active Member
well to make the precups flush after a shave they machine out the relief. If they machine too far then they really screwed it up.
Of course if they machined with the cups in then that wouldn't be the case. Some machine shops will do it without and some will do it with. because the cups can move the rule is to remove them first. but I know at least one machine shop that will peen them in so they can machine with them in place.
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consaka
Active Member
I coated my precups but my objective is or was to insulate the heated air from the block. My thinking was to keep the precup heatsinked to minimize cracking on it. I see a problem with trying to insulate the precup from the block. Doing that is going to allow the precup temps to go really high since it isn't heatsinked to the block anymore. However the expansion is going to be a lot more then normal without the block pulling heat out of it. That expansion is either going to compress the precup or put extreme stress on the head. In the end I don't know that it is even possible to keep that much pressure from heatsinking. My main fear would be the precups getting loose in the head, start rattling around and we all know what will happen if a precup breaks in half. Even if it doesn't that rattling around would ruin the head and possible the block if it does it long enough.
Chinese heads. Will they work as well or better then OEM?