Final check and questions before it goes together

[ctdthrasher]

Hey all
Been on here a while, lots on the other forum, but came here to ask some higher end questions that perhaps won’t get as much feedback over there. Here’s the build:
6.7 block, 5.9 crank, .080 longer Carrillo rods, oem 6.7 coated pistons, Colt stage 4 cam (similar to Hamilton 188/220), ported head (stock intake shelf) 7x13, 13mm ppump, 64.5/485 compounds. Looks for 10s and 1000hp or bust. No nitrous planned yet

Short block specs (checked them all myself):
Mains clearance - .0035
Rod bearing clearance - .002 plastigauge on each side, .004 micrometer, so I say good
PTW- .0065
D+J tool steel wrist pin clearance - .0015
Connecting rod side clearance - .009. Machine reliefs in rod caps? If yes just at the bottom or the whole cap and would it need a rebalance?
Top rings - .016-.018
Second rings - .043-.046
Oil rings - .021

Does that look good for the bottom end? Truck is a hot street truck, daily driver, casual drag, set up to handle 5000 rpm.

Thanks in advance guys

[Cflanery88]

Can do caps either way but they will need re-balanced. Top ring looks good, 2nd ring is a bit loose which is expected with a wider PTW. I doubt you’d notice any difference with what it’s at now and would run fine. My PTW was .0075 and I file fit .020 over rings to get the gaps I wanted which were .020 top, .030 2nd, and .018 oil control.

[Cflanery88]

Definitely a solid setup you have.

[Cflanery88]

This is how Wagler does the caps on there rods.


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[9724VF350]

Machine the caps. They won't need re-balanced afterwards unless the guy machining them is a complete hack.

[zfaylor]

This^^

An inline engine isn't balanced like a v engine. The rods are all the same. As long as the caps are machined even remotely the same everything will be well.

[Cflanery88]

If the complete rotating assembly (crank, rods, pistons, rings, wrist pin, crank dampener, and flexplate) have already been balanced then me personally would have them re-check it as an assembly if you decide to clearance the caps. Mine was completely balanced on a CWT balancer which the weight of the piston/rod assemblies directly correlated with the crankshaft balance on how much material needed removed or bob weight added to maintain a percentage of balance to 8k rpm. If your not balancing the rotating assembly it doesn’t matter. As far as rods go aftermarket Billet rods are usually within a gram of one another. Using stock pistons weight can vary due to casting and that’s where material will need removed to match balance a set of rods if going that route. Most machine shops can make sure each rod weighs the same if machining the caps.

[Big Blue24]

Double check your top ring gap, I've butted rings on the Junker at similar power level with stock 12v pistons with 030" top ring gap on a standard bore. I've also scuffed pistons at 007" piston to wall. Admittedly I don't run a pyrometer, nor do I focus on EGT management with water injection, better charge air cooling, etc.

[ctdthrasher]

Cflannery88. I just read your 6.4 build thread, great read. Thanks for the pic of the machined rod cap. I’ll end up getting mine machined. I’ll just weigh them before and after. Helps to have an experienced machinist working in house, machines at my fingertips

Now on to the ring gaps. All the 2nd rings came in at .030-.032. Factory calls for .032-.047. I filed them all to the top end since scuffing walls is not high on my list of things to do. This is expensive enough as it is lol
Will, the factory spec for a 6.7 top ring is .013-.018. I believe the factory 12v spec for the top ring is ~.015-.030. Not sure on how far I would take it now. Take them all to .020? I don’t want a ton of blowby or crank pressure. Food for thought.....
My PTW is ~.0015 tighter than I wanted but I do have Teflon coating on the skirts, if that helps. I’m just past stock clearances and lots of guys take these motors to 1k hp on a stock bottom end so hopefully that won’t be an issue. I do have and egt gauge and I do watch it...watch it hit 2000 degrees, that’s about it haha

[Cflanery88]

Originally Posted by ctdthrasher

Cflannery88. I just read your 6.4 build thread, great read. Thanks for the pic of the machined rod cap. I’ll end up getting mine machined. I’ll just weigh them before and after. Helps to have an experienced machinist working in house, machines at my fingertips

Now on to the ring gaps. All the 2nd rings came in at .030-.032. Factory calls for .032-.047. I filed them all to the top end since scuffing walls is not high on my list of things to do. This is expensive enough as it is lol
Will, the factory spec for a 6.7 top ring is .013-.018. I believe the factory 12v spec for the top ring is ~.015-.030. Not sure on how far I would take it now. Take them all to .020? I don’t want a ton of blowby or crank pressure. Food for thought.....
My PTW is ~.0015 tighter than I wanted but I do have Teflon coating on the skirts, if that helps. I’m just past stock clearances and lots of guys take these motors to 1k hp on a stock bottom end so hopefully that won’t be an issue. I do have and egt gauge and I do watch it...watch it hit 2000 degrees, that’s about it haha

Thank you and your welcome.

I say run it. I don’t see you having an issue sticking a piston or kissing rings. Blow by I say little to none. Break the cam in, then go give it hell.

[ctdthrasher]

Sounds good. Hopefully the short block will be done in a week or two. Then it’s time to port the head. Fun times

[Red Sleeper]

Good info to read here. Thanks for sharing.

Good luck with the assembly.

[jasonc]

Ptw and ring gap are the most important things if your gonna run it hard. I'd go .009

[ctdthrasher]

.009 on a daily driver not going to be an issue?

[jasonc]

No sir, and will be your downfall if you go tighter. Along with ring gap. They run just fine with a little loose ring gap and ptw, they don't run long tight.

[biggy238]

Can someone go in to detail on the failures with the rod caps that has everyone machining the caps? I didn't machine mine and I'm not going back and don't it now.


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[jasonc]

It's a relief cut to shed oil.

[ctdthrasher]

Well hmmmm. Crank is already in. Rings are gapped to max, and these are already .020 over rings and pistons so I can’t buy any larger ones and file to fit. Not sure how far out the gaps will be if I go to a larger bore.

[ctdthrasher]

Originally Posted by biggy238

Can someone go in to detail on the failures with the rod caps that has everyone machining the caps? I didn't machine mine and I'm not going back and don't it now.


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I guess the failure that can happen is under high rpm the oil won’t evacuate the bearing fast enough, create heat/pressure and you might spin a bearing? Once you look at it there really isn’t that much clearance on the rod sidewall to clear out the oil

[kleann]

Originally Posted by biggy238

Can someone go in to detail on the failures with the rod caps that has everyone machining the caps? I didn't machine mine and I'm not going back and don't it now.


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I want to say I first heard of it probably 6 or so years ago. Some pro street guys where trashing bearings and they found this to be the cause.