Cylinder leakage test

[Lenny5160_v2]

While not an answer to the question, when I use a leak-down tester I'm mainly looking for consistent results from all cylinders.

[Ralph A Powell]

You can also listen for intake and exhaust valve leakage. When I tested at TDC then I would let the piston roll over to BDC and with a long beaker bar pull the piston toward TDC and watch tester to see if it is holding pressure.

[Kirk Morgan]

Here is some detail to my findings. This is a Nitrous engine which was chirping out of the left bank after a run. Iam not a Nitrous person but a N/A engine person. Ran the valves all was good. Ran a compression test not good. The compression was a roller coaster from 200 PSI to 50 PSI. Un adjusted all the valves and removed the rocker arms. The 50 PSI was a exhaust valve leak with 80% leakage and the 200 PSI is 20% leakage. I have a cylinder leakage tester and they way i use it i turn the pressure on one side to 100PSI and read the other gauge to see how much leakage there is. To me the 20% leakage on the 200 PSI cylinder is to much i was always trying to get in the 10% or less leakage range on engines i have built. I have never built a engine with gas ported pistons. BTW i always spin the engine over 5 revolutions when checking static compression.
Thanks

[Jeff Stout]

Exhaust valves leaking I wonder why, they run away from each other. Low valve spring pressure or broken spring.Any of the low

cylinders measurements next to each other? What did plugs look
like? Asking as I have had all these problems on nitrous plus more.

[Henrys Toy]

Originally Posted by Jeff Stout

Exhaust valves leaking I wonder why, they run away from each other. Low valve spring pressure or broken spring.Any of the low

cylinders measurements next to each other? What did plugs look
like? Asking as I have had all these problems on nitrous plus more.

Good morning Jeff, Kirk and all,
I'm not a nitrous user, but I'm thinking the EGT's might be on the extreme high end and could cause exhaust valve face and seat erosion. Exhaust valve guide wear or loose clearances could be contributing factors. Like a " stacking of clearances " and the possibility of the valve springs fatigue and pressure loss causing the exhaust valves to bounce once they are trying to seat I would think should all be taken into account.
What condition was the engine in when the customer started using N20?
If it was " seasoned / used " there may have been underlining conditions that were exasperated once the "bottle" was used. The quality of the exhaust valves themselves can also be a factor.
No definitive answer, just food for thought, I hope this helps.

Respectfully,
Henry Kunz 1534 H/SA

[Jeff Stout]

Originally Posted by Henrys Toy

Good morning Jeff, Kirk and all,
I'm not a nitrous user, but I'm thinking the EGT's might be on the extreme high end and could cause exhaust valve face and seat erosion. Exhaust valve guide wear or loose clearances could be contributing factors. Like a " stacking of clearances " and the possibility of the valve springs fatigue and pressure loss causing the exhaust valves to bounce once they are trying to seat I would think should all be taken into account.
What condition was the engine in when the customer started using N20?
If it was " seasoned / used " there may have been underlining conditions that were exasperated once the "bottle" was used. The quality of the exhaust valves themselves can also be a factor.
No definitive answer, just food for thought, I hope this helps.

Respectfully,
Henry Kunz 1534 H/SA

I would never read egts, they would naturally show hot. Spark plug reading is your friend. Like you said used motor and maybe had underlying issues. Nitrous always finds the weak link. Hope it's not internally.

[Jeff Stout]

Also if motor would be built for nitrous more ring gap is required and I would expect 10 or more leakage.