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| bam | leak down test results | ||
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Senior Guru
 
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Got my leak down tester in the mail today. Here are the results, need a little help interpreting them.
Drivers side; 1-92, 3-93, 5-94, 7-94 Pass side; 2-96, 4-78 (best of 4 readings 80), 6-94, 8-94 All reading with 100 psi. Obviously something is wrong with #4, it's way lower than the rest which are pretty close together. Near as I can tell with #4 air was coming out the crank case, it obviously was not coming out the intake valve, as I have the intake off, the exhaust is a little harder to tell for sure but I listened at the tail pipe and no hissing sound, so must be the crank case. How bad is this, a tear down required? Thanks |
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Posted on: 2011/8/19 19:14
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| BrianCunningham | Re: leak down test results | ||
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Know anyone with a borescope?
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Posted on: 2011/8/19 19:18
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Polo Green 95 LT1 6-spd http://mysite.verizon.net/vzevcp74/ 383 LT1/Vortech Supercharger/AFR heads/Rod end suspension/Penske-Hardbar dual rate coilovers/Wilwood 6pot brakes NCCC Governor: http://BayStateCorvetteClub.com |
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| flyboy | Re: leak down test results | ||
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Elite Guru
 
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Squirt some oil in the cylinder and see what happens to the reading? Might tell you if it's wear or something broken/damaged. Just guessing here.
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Posted on: 2011/8/19 19:45
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'91coupe, LT4Hotcam, some other stuff. If it's too loud, you're too old. "He works on old cars, then junks 'em" |
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| BillH | Re: leak down test results | ||
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The Stig Moderator
 
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If it was the exhaust valve, you'd definitely hear it. You can amplify the sound a bit with a piece of heater hose stuck in your ear.
Valves, piston/rings, whatever, @78 it's time to dissemble. |
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Posted on: 2011/8/19 21:24
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Every man dies but not every man lives. |
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| bam | Re: leak down test results | ||
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Senior Guru
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What kind of pistons should I think about for a rebuild and what rings, am thinking of going 355 so I can reuse my crank and rods and save some money. Also thinking of going with Trick Flow 185 heads. What do I need to know about rebalancing with internal balance. Anyone know a good rebuilder in the KC Missouri area?
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Posted on: 2011/8/20 1:02
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| flyboy | Re: leak down test results | ||
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Elite Guru
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Just a thought. Don't know what your budget is. At least you know exactly what you're getting. Warranty, no waiting.
Brand new. Forged crank. GM. http://www.jegs.com/i/GM-Performance/ ... -1?parentProductId=749884 |
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Posted on: 2011/8/20 1:38
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| tjpreul | Re: leak down test results | ||
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Elite Guru
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The factory set up for balancing is internal/external. Which is internal up front, so then the balancer has a neutral balance. The external for the rear means there is a weight (on the flywheel) to balance it out. If you switch the rear to internal you won't have this weight on the flywheel. It was an extra $150 for the added slugs to make mine an internal. However I left it as external so I didn't have this cost.
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Posted on: 2011/8/20 1:42
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_________________
Vegas wasn't built on winners. '92 auto, MSD, Banski, Taylor wires, SS lines, C5 rims, 3.07 gears, white gauges, seats from a '96. Motor: Forged rotating assy, Probe pistons, CC valvetrain, AFR heads, Procharger P1SC |
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| mistaben | Re: leak down test results | ||
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Senior Guru
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ooof! that's a bit expensive for a bottom end isn't it? i mean he should be able to pull the engine, have the bottom end mains and cam bearings reground, new seals, and cylinders honed, and new rings put in for like 600 or so?
or at least that is what I think i paid to have my block cleaned up... |
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Posted on: 2011/8/20 1:43
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| bam | Re: leak down test results | ||
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Quote:
I think that short block is for the pre LT1 motors, right? I would love to just buy a short block but there aren't any for the LT1, at least from GM. |
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Posted on: 2011/8/20 1:56
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| tjpreul | Re: leak down test results | ||
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Quote:
Golen used to offer one at a decent price, but now they only have a 383 starting at $3k. http://www.golenengineservice.com/eng ... -streetstrip-short-block/ |
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Posted on: 2011/8/20 2:05
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| BillH | Re: leak down test results | ||
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The Stig Moderator
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Quote:
It's been said all over the internet that the balancer is neutral,Tyler. But it's not true. The balancer is weighted at the factory and is not neutral. |
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Posted on: 2011/8/20 2:18
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| tjpreul | Re: leak down test results | ||
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Elite Guru
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Quote:
This is why I am not using the factory one on my engine. Each one is/was suppose to be balanced to the crank. If you compare several they all have holes drilled to correct their balance. For balancing for an LT1 factory is listed as internal/external, but I do agree the factory balancer wasn't truely balanced. Why else would GM put "Rotate the balancer 90deg if there is an engine vibration". |
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Posted on: 2011/8/20 2:47
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| BillH | Re: leak down test results | ||
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The Stig Moderator
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Quote:
That's there for an engine that has had the hub pulled without marking it first. That's the suggestion to try if their indexing procedure doesn't work. Though why the hell GM didn't key the hub is betond me, The holes will have weight's inserted though it's possible that some engines required no wieghts. It's a stupid set up. |
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Posted on: 2011/8/20 12:12
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Every man dies but not every man lives. |
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| bam | Re: leak down test results | ||
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Senior Guru
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I would like to rebuild my engine and keep the stock crank and rods, that way I would have money to spend on Trick Flow heads. Has anybody used them? I am thinking that with my hot cam, a rebuild with new pistons and rings and trick flow heads I should be 400 - 425 hp at the flywheel, that would be plenty for me.
No one has commented on the oil on top of the valves, I am thinking it might be the guides, is there any other way for oil to get there besides that? I am thinking that the new hot cam and raising my rev limiter to 6200rpm was just too much for my motor with 100,000+ on it. |
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Posted on: 2011/8/20 12:36
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| flyboy | Re: leak down test results | ||
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Elite Guru
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The cam in the test is very similar to the Hotcam.
I forget what they actually dynoed. I'll look for that issue. http://www.vetteweb.com/tech/vemp_100 ... n_lt1_corvette/index.html |
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Posted on: 2011/8/20 13:24
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_________________
'91coupe, LT4Hotcam, some other stuff. If it's too loud, you're too old. "He works on old cars, then junks 'em" |
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| tjpreul | Re: leak down test results | ||
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Elite Guru
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Quote:
When you pulled the pcv hose off on the passenger side was there oil in it? With the valve seals it is hard to believe all eight failed. Plus if it was only the valve seals the oil shouldn't have made it all of the way to the tb without another issue (your leakdown test results). |
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Posted on: 2011/8/20 15:40
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| rklessdriver | Re: leak down test results | ||
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Senior Guru
 
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How much do you want to spend on pistons and rings?
Something like the KB/ICON 9929 is only $310 but uses 5/64 rings and weighs 545grams. It's a good piston for the money. http://www.cnc-motorsports.com/produc ... ?ProdID=32004&CtgID=18728 The KB/ICON 971 is $390 uses 1.5mm, 3mm rings and is only 450grams..... http://www.cnc-motorsports.com/produc ... ?ProdID=29397&CtgID=12779 The weight is important because the lighter the pison and pin the less stress on that stock crank and rods as you pump up the HP and extend the RPM range with heads and cam. Both examples I gave you will work fine at 400HP and 6200rpm like you hope for but the 971 will make slightly more power because of a better ring pack and stand more RPM. When you put it back together make sure you open the rod and main clearance up. My recomendation is .002-.0025 on the rods and mains. The factory .0012 rod clearance won't survive at that kind of HP for very long. Also I'd suggest the hotcam (or similar custom grind) and the TFS 195's. The TFS 185's are not going to get you where you want to be. Will |
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Posted on: 2011/8/20 17:37
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| BrianCunningham | Re: leak down test results | ||
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Senior Guru
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Before planning anything, 1st find out what wrong with it.
pull the cylinder head and take a look and see what's broke. |
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Posted on: 2011/8/20 20:20
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_________________
Polo Green 95 LT1 6-spd http://mysite.verizon.net/vzevcp74/ 383 LT1/Vortech Supercharger/AFR heads/Rod end suspension/Penske-Hardbar dual rate coilovers/Wilwood 6pot brakes NCCC Governor: http://BayStateCorvetteClub.com |
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| mistaben | Re: leak down test results | ||
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Senior Guru
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Quote:
this. need to know whats wrong first. |
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Posted on: 2011/8/21 6:48
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| bam | Re: leak down test results | ||
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Senior Guru
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Hopefully I can pull the heads next week and see what there is to see.
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Posted on: 2011/8/22 18:40
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| tjpreul | Re: leak down test results | ||
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Elite Guru
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What part of KC are you in. I have family on the north side. However I still couldn't recommend a builder.
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Posted on: 2011/8/23 4:06
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_________________
Vegas wasn't built on winners. '92 auto, MSD, Banski, Taylor wires, SS lines, C5 rims, 3.07 gears, white gauges, seats from a '96. Motor: Forged rotating assy, Probe pistons, CC valvetrain, AFR heads, Procharger P1SC |
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| bam | Re: leak down test results | ||
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Senior Guru
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I live in a small town 120mi from KC, but I go there often.
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Posted on: 2011/8/23 20:45
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| SpectatorRacing | Re: leak down test results | ||
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Elite Guru
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I might have some nice LTx parts for sale soon
 Pistons - I like SRP stuff, their kits include rings usually. #4 seems to be a problem spot these days. If you want, I'll send you my number 4 for free. See below. I never liked the hotcam myself, there is way better stuff out there for the same money. Unless you're trying to keep the same valvetrain, in which case I guess you can't go much more aggressive. As everyone esle already stated, see what's wrong, figure out your budget, and put a nice little plan together. Don't forget to add $300 for gaskets and lube! Check out this link. These guys are awesome but sadly nowhere near you. But the price list is sorta standard. http://www.champion-performance.com/price_list.xls Attach file:  Piston #4.JPG (0.00 KB) |
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Posted on: 2011/8/23 22:35
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aka Scaryfast |
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| bam | Re: leak down test results | ||
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Senior Guru
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Quote:
Was that a stock piston? Were you able to figure out what did that to it? How bad did it mess up your block? |
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Posted on: 2011/8/24 14:32
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| SpectatorRacing | Re: leak down test results | ||
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Elite Guru
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No, it was an SRP. The details are here, I don't want to clutter your thread:
http://www.corvette-guru.com/modules/ ... id=171123#forumpost171123 |
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Posted on: 2011/8/24 21:54
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aka Scaryfast |
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