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Old 09-07-2015, 10:57 AM
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New Engine Leak Down Numbers Question

I recently had an engine built buy a well know local builder. It is a small block 434 with AFR heads and Titan intake. I thought I would perform a cold leak down test and compression test before installing the engine. I don't know how much break in time the engine saw on the dyno but we did run it to 7000 rpm where it made close to 700 hp. The numbers below were obtained using an OTC tester set to 80 psi on a cold engine I also included cold compression test values:

Leakage Cold Compression
Cyl #
1: 18.0% 170 psi
8: 12.5% 180 psi
4: 8.8% 185 psi
3: 12.5% 180 psi
6: 6.3% 180 psi
5: 8.8% 175 psi
7: 12.5% 175 psi
2: 10.0% 180 psi

Solid Roller Cam, 257/263 @ .05, Lift .731/.736, T&D 1.7 Shaft Rockers

Should I be concerned about these numbers on a new engine? All the leakage appears to be past the rings.

Thanks!

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Old 09-07-2015, 02:28 PM
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That's quite a bit of leakdown. However I would want to do that test on a warm engine. Also, might need some more breakin time for the rings to seal 100%
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Old 09-07-2015, 03:01 PM
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X2 with richieHD.
Run it , break it in, redo the test in 1000 miles
Sooner if Moly rings as they seat much faster
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Old 09-07-2015, 04:06 PM
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That is what I was thinking. I doubt the engine spent much time on the dyno for break in. The part number on the bill of sale for the rings is J.E. 4155-5
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Old 09-07-2015, 10:53 PM
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are you using the AFR 345s? You are making more power than me,,,Run the engine an hour or drive the car and retest,,,double recheck that 18% leaker?
Make sure your headers are big enough!
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Old 09-08-2015, 07:07 AM
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Quote:
Originally Posted by vinniekq2 View Post
are you using the AFR 345s? You are making more power than me,,,Run the engine an hour or drive the car and retest,,,double recheck that 18% leaker?
Make sure your headers are big enough!
Here are more details of my build, the actual HP was 695.

434 Dart Sportsman Small block, Forged 4340 crank, Oliver Billet Rods, JE pistons, Holley Modified 950 cfm, AFR 245cc Tony Mamo Ported Heads, AFR Titan Intake, 11.0 CR, Solid Roller Cam, 257/263 @ .05, Lift .731/.736, T&D 1.7 Shaft Rockers, Isky EZ Roll Lifters w/forced Oiling, TKO 600, Rebuilt Rearend w/ HD Bearing Caps & Bolts, Tuned and Polished Eaton Posi, Carbon Fiber Clutches & Yukon 3.73 gear, Spicer U-Joints, Kooks 1-7/8 Headers Thru 3" pipes & Super 40's. 695hp/600ft-lbs (Engine Dyno)

I build the engine about 10 years ago as a 427 small block. At the time, information was hard to come by regarding large displacement small blocks. I spent many hours on desk top dyno, searching the web and car magazines to select the best combo for the car. I ended up with a power plant that produced 450hp/485ft-ibs at the rear wheels. I decided to freshen the engine up but may have gone a little to far with over-boring, solid roller lifters, shaft mounted rockers.....
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Old 09-08-2015, 10:15 AM
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you have the (almost) exact build to mine.CORRECTION AFR 245s,sorry.not 345s.
I used the 227 Dart heads. and almost identical cam with 1.6/1.5 split ratio rockers.
headers I used are Stahl 1 7/8 stepped 2".

run the engine and recheck leak down.

Im due for an engine freshen and Im interested in your results. My engine peaked at 6500 rpm
cam is 256/264 on 108 square

what LSA/ICL did you use?
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Old 09-08-2015, 05:51 PM
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112/108.

Did you chassis or engine dyno your combination? I have kind of a funky dyno curve.

The jump in HP at 6000 rpm is very strange to me.
Attached Files
File Type: pdf PDI_0003.pdf (568.9 KB, 40 views)
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Old 09-08-2015, 05:54 PM
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it was an engine dyno. I was meaning to chassis dyno once before I freshen it to see what to change if anything
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Old 09-09-2015, 01:59 PM
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Quote:
Originally Posted by kjlavall View Post
I recently had an engine built buy a well know local builder. It is a small block 434 with AFR heads and Titan intake. I thought I would perform a cold leak down test and compression test before installing the engine. I don't know how much break in time the engine saw on the dyno but we did run it to 7000 rpm where it made close to 700 hp. The numbers below were obtained using an OTC tester set to 80 psi on a cold engine I also included cold compression test values:

Leakage Cold Compression
Cyl #
1: 18.0% 170 psi
8: 12.5% 180 psi
4: 8.8% 185 psi
3: 12.5% 180 psi
6: 6.3% 180 psi
5: 8.8% 175 psi
7: 12.5% 175 psi
2: 10.0% 180 psi

Solid Roller Cam, 257/263 @ .05, Lift .731/.736, T&D 1.7 Shaft Rockers

Should I be concerned about these numbers on a new engine? All the leakage appears to be past the rings.

Thanks!
I certainly wouldn't like these figures, both excessive in at least 4 cylinders but also all over the place in respect to each other.

I'd spend some time on the high leakers just listening for the leakage to determine if it's past the valves or rings. Ring leakage is a big problem to fix but if it's valves simply compouding the seats to improve the seal may get those cylinders in line with something more like 10% or less.

Bogie
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Old 09-09-2015, 06:33 PM
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I believe they were all ring leaks. Kept blowing the tape of my valve cover breather grommets. Plus it was easy to hear. I am going to check one more time but squirt some oil into each cylinder first. It is very frustrating but i don't think the numbers are bad enough to tear down the engine. There is very little run time on the engine and these numbers are cold values. If the numbers still look bad after some miles, then I will need to decide what to do. I will need to find a trust worthy builder in the Georgia area. I am not to happy with the builder. I decided to check the valve lash (cold) as well and they were all over the place. I would have thought after some break in runs they would have made a final pass to make sure they were good to go. I adjusted them including the recommended compensation for a cold adjustment on aluminum heads. I will recheck when hot.
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Old 09-10-2015, 11:23 AM
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anything past 10% is not great as mentioned by OLDBOGIE. When the engine is brand new is when it makes the most power and leaks the least.Blue printing is very time consuming and expensive! If the engine was not meticulously assembled then little things could have been missed,A big "for example" is bolting on new aluminum heads without taking them apart and measuring everything,,,especially the valve grind performed on them. Hand fitting the pistons in each bore,,,,,

As the Germans would say,"perfection is acceptable"!
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Old 09-10-2015, 11:43 AM
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"perfektion ist akzeptabel"
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Old 09-10-2015, 11:45 AM
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Gents;

If the surface finish on the cylinder wall wasn't matched to the ring pack selection; would this yield similar results?
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Old 09-10-2015, 11:54 AM
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Autogear,I appreciate the German translation. I used an old German machinist,the only person I met that measured to 1/10000 of an inch. Of course we checked his work with a tape measure and told him it was good enough,(from a very safe distance)!
Note: German machinists can throw things a long way and have loud voices.Not many people were allowed in the shop.
We played so many pranks on the L7 . Always,always,always got a reaction. An he had the nerve to drive a Porsche,,, of course we all called it a Volkswagen
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