Wobble

I'm going off the 80lbs compression test figure and assuming that he means the leak down test was good.

Either way, this is not a problem that should hold up an engine builder for long...

dean51267

yes, leak down test was good, no air lost at all, so it was a very good sign.

I am confident the motors were in good shape because they were running well, the new dart heads were vacume tested and all, the cam is a comp cams 11-451-8, a pretty standard deal there, it was part of a kit, springs were matched carefully, distributor is orginal HEI, intake is new dual plane air gap, and carb is a new elderbrock, cam was timed dead on, of course new lifters with the kit, so nothing funny on the hard parts. The guys doing the work have all got decades of doing this stuff, so it "should" be a no brainer, that leaves me to think it unlikely they adjusted valves wrong, there are two motors being done, identical set ups, the other holds strong compression, oil pressure is good and all lifters were flooded with oil before starting motors, so I doubt the people are simply making the same mistake across several different guys. Everyone involved is a CPA/Tax/Investment client and I am very close friends to all, so no one has the "it's not mine so who cares" attitude.........

Which gets me back to just a plain old lifter failure...... I think...

stevesxm

exactly.

re the leakdown, i have seen some bizzare things occur where the leak down is good but the cylinder itself is bad. the leak down puts pressure in very slowly thru a very small orfice and often people don't use high pressure to do it... ie 100 psi... they just put in 30 or 40 and if both gages say the same they assume zero leak... my experience is that the higher pressures are nec to get good readings and even at that i have had cracked piston tops and mis machined valve eybrows that only manifest the no compression/low compression issue dynamically. also have seen small rocking of the piston while leaking go from zero leak to 40 - 50 % because of ring issue...

bottom line is that is the valves are opening at all...i.e you can see the rockers move then there is enough opening to pump compression and if you have 80 then thats no good and really ought to be obvious problem for your builder...

think horses..not zebras

dean51267

okay, I just figured out I was mistaken, 80#'s of pressure on ALL cylinders, not just the one, and #8 cylinder will not fire.

All leak down test are good.

Points to cam?

Wobble

dean, you stated that other cylinders same motor were 200lbs compression.

Are you saying that the leakdown was done at 80psi? and all cylinders were good on leakdown.

all cylinders except #1 were 200lbs cranking compression except #1 which was 80lbs?

dean51267

no, the other MOTOR was at 200#'s, there are two motors.

My earlier statement was incorrect, I misunderstood what the tech said. One motor is fine, doing its thing. The second is where the problem is.

On the second mtor ALL cylinders show weak compression but leak down is negligable or non-existant. 1 to 7 will fire and run, #8 cylinder will not fire at all...

Sorry for the earlier error....... I think it is still monday here...

44MTI

Sounds like you need to have a talk with you builder and have them explain EXACTLY what a compression test and leak down are and how they perform them.
These should give you the answers your asking for.

Your last post makes no sense to me. I don't see how you could have such a poor compression and have no leakdown.

dean51267

If the valves are seating good, and rings are good, then the leak down would be fine, but if the cam is not opening and closing the valves at proper timing then the compression stroke does not generate sufficent pressure to get to usable compression numbers.

I agree my earleir post was confusing, if it sounded that way to you consider the hair pulling I am doing!

Once John said the other cylinders were weak on compression it made more sense..... it looks more like cam, or ALL lifters, meaning cam is ground wrong or the rear is mis-alligned or something....

Still looking for the horse, that answer sounds to much like a zebra...

44MTI

Must be very frustrating, however the shop should have little trouble fixing it. I can't imagine the cam being that far off but I guess anything is possible. But a quick check of the pushrod movement should confirm or deny valve train issues. Good luck
Michael

stevesxm

if ALL bad cyls then easily could be cam timing issue. watched mechanic do that exact same thing here on dock. changed cam, put gear on wrong mark. very low comp very hard to start , ran on 7.... and they did ALL they same stuff you are doing... until they took the front cover off , in the boat discovered the mistake and fixed it.

exactly as someone above suggested