Leakdown and HP loss
Leakdown and HP loss The engine in my 10K mile Y2K Z28 seems to leak badly - best is 12% and wost 43%, with an average of 20%. All (or at least most) of the leakage is into the crank case - lots of noise at the oil fill cap, none at the TB or exhaust.
Back in the day, we didn't have leakdown testers, so I'm in the dark on this. I've searched here and found conflicting info - everyone suggests a leakdown test when engine are down on power, but then I saw a post where fixing 50-90% leakdown made a 10 HP difference. So what's the deal? How much HP wil I gain with good rings?
It isn't worth pulling it down for 10 HP, but assuming leakdown really makes a difference, can you just bust the glaze (I could see the origional cross hatch when I had the heads off) or should I go 5 over with new pistons?
I just remembered that back in the day one of the local engine builders liked to set the block out in the rain so the rings would seat quicker
Back in the day, we didn't have leakdown testers, so I'm in the dark on this. I've searched here and found conflicting info - everyone suggests a leakdown test when engine are down on power, but then I saw a post where fixing 50-90% leakdown made a 10 HP difference. So what's the deal? How much HP wil I gain with good rings?
It isn't worth pulling it down for 10 HP, but assuming leakdown really makes a difference, can you just bust the glaze (I could see the origional cross hatch when I had the heads off) or should I go 5 over with new pistons?
I just remembered that back in the day one of the local engine builders liked to set the block out in the rain so the rings would seat quicker
Originally Posted by critter
It isn't worth pulling it down for 10 HP, but assuming leakdown really makes a difference, can you just bust the glaze (I could see the origional cross hatch when I had the heads off) or should I go 5 over with new pistons?
I just remembered that back in the day one of the local engine builders liked to set the block out in the rain so the rings would seat quicker
I just remembered that back in the day one of the local engine builders liked to set the block out in the rain so the rings would seat quicker
Originally Posted by sawedoff
If you can see the OEM finishing on the cylinder walls, then I wouldn't mess with it. I'd just replace the rings all the way around, and go with a tension that's as close to stock as you can get.
Have you checked the heads? That's another problem spot. I'd freshen up the heads, by checking the valves, guides, seals, seats and such.
Your block is more than seasoned, so there's no need to lay it out in the elements.
Deck plate hone
Balance assembly
Recon rods w/arp bolts
Polish crank
Forged piston
FM file fits
FM bearings
Arp Main cap studs
This will go 7K all day long and with the right H/C make an easy 450RW+
I'd call Futral/Ape/Hpe for one of there killer shortblocks
Balance assembly
Recon rods w/arp bolts
Polish crank
Forged piston
FM file fits
FM bearings
Arp Main cap studs
This will go 7K all day long and with the right H/C make an easy 450RW+
I'd call Futral/Ape/Hpe for one of there killer shortblocks
Originally Posted by critter
Thanks! Any choice on brand? OEM?
As I said, all the leakage is into the crankcase - you can't hear a thing at the TB or header.
LOL! Didn't plan to, just thought everyone could use a laugh
As I said, all the leakage is into the crankcase - you can't hear a thing at the TB or header.
LOL! Didn't plan to, just thought everyone could use a laugh
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