Torque to turn over Engine

[n2omike]

Hey guys
Building a Ford 400M for a friend. Pistons are a weak point for these, but I found some custom Race Tec pistons offered by Clegg Machine for a good price that have a good compression height. They have 1.5mm, 1.5mm, 3.0mm rings. I noticed just how EASY it was to spin the short block over. Using a torque wrench, it only takes 15ft-lb to roll it over.

I would have a name brand and part number (just went to the garage to look) but he was here helping, and I think he also helped 'clean up'... so it's not there. They weren't a top name brand, but seemed decent. They came with the pistons. They were not file fit, and had a 0.018" gap that we opened a little for a moderate shot of nitrous. Pistons/rings are 0.040".

Anyway, any comments on the rings? We wouldn't have gotten any rings that require a vacuum pump, would we?

Thanks!

[mt-engines]

Hey guys
Building a Ford 400M for a friend. Pistons are a weak point for these, but I found some custom Race Tec pistons offered by Clegg Machine for a good price that have a good compression height. They have 1.5mm, 1.5mm, 3.0mm rings. I noticed just how EASY it was to spin the short block over. Using a torque wrench, it only takes 15ft-lb to roll it over.

I would have a name brand and part number (just went to the garage to look) but he was here helping, and I think he also helped 'clean up'... so it's not there. They weren't a top name brand, but seemed decent. They came with the pistons. They were not file fit, and had a 0.018" gap that we opened a little for a moderate shot of nitrous. Pistons/rings are 0.040".

Anyway, any comments on the rings? We wouldn't have gotten any rings that require a vacuum pump, would we?

Thanks!

Even many file fit rings have standard oil rings.
Id say youre good. 3mm ring will have less drag than a 3/16 etc
is 15 the breakaway torque? Is the rear main seal in?

[CGT]

15 is about what I'd expect on that. Ive seen that or less with that ring package in a sbc with rear main, the 400m is gonna have some more drag.

[BillK]

Mike,
If you are used to old school pistons and rings it is amazing at how much easier the new stuff turns. Especially if the bores were finished properly with a plateau brush.

[ProPower engines]

Just be sure to check the radial depth of the ring groove and compare to the top ring for back clearance.
i did a 400 M a while back and found I needed to space the top ring with ring shim stock to correct the issue.
Otherwise you can be in a situation where there is too much room behind the ring and the compression does no properly
excite the ring to seal good enough and the result was extra cylinder leakage.
And now since all the stock type ring sets are using a much narrower top ring while they say its not an issue but if you talk
to the boys at Total Seal about this they will recommend shimming the extra space. Talk to Kevin or Keith about it.
It will be worth the call

[gmrocket]

Just be sure to check the radial depth of the ring groove and compare to the top ring for back clearance.
i did a 400 M a while back and found I needed to space the top ring with ring shim stock to correct the issue.
Otherwise you can be in a situation where there is too much room behind the ring and the compression does no properly
excite the ring to seal good enough and the result was extra cylinder leakage.
And now since all the stock type ring sets are using a much narrower top ring while they say its not an issue but if you talk
to the boys at Total Seal about this they will recommend shimming the extra space. Talk to Kevin or Keith about it.
It will be worth the call

Yup, that’s why total seal sells spacers for old school fat rings

If your forced to use the big lands, it’s your only option..or get a new piston because the cost of the rings and spacers are not justified

[ProPower engines]

Even the narrow ring type pistons.
I just went through this with a name brand piston set but the rings supplied as it turned out were too shallow in the groove.
After some shim stock was used behind the top ring it closed up the gap and leakage showed 0 on the blow by meter
Not trying to hijack the thread but thought it was worth mentioning based on the build choice.

[MadBill]

Since the test is steady state, excess back clearance shouldn't affect leak down

[cpmotors]

Pretty typical for that bore/stroke. Assembled engine with HR is usual 28-32lbs in my testing.

[Kevin Johnson]

Since the test is steady state, excess back clearance shouldn't affect leak down

I am guessing that to the extent that the diameter of the back clearance wall is greater or lesser than the manufactured inner diameter of the shim stock coil/helix, a varying radial force will be exerted on the back side of the ring (undulations).


http://www.totalseal.com/pdf/totalsealCatalog.pdf

shim_stock.gif