Rebuilt RB25DET - Cylinders 2 & 5 low compression won't start

[radianation]

We have fully rebuilt an RB25DET and now that everything is in the car we want to try and get it running using MAF (temporarily) while we wait a few more days for the AEM EMS so that we can run MAP. However, cylinders 2 & 5 are showing compression numbers in the 30's. All other cylinders are good, but they had to build up compression over a series of cranks and attempts to start the vehicle. They are now in the 130's range and climbing. Any ideas why cylinders 2 & 5 would not have compression?

The vehicle attempts to start on the first crank, but then it never really grabs. We're a little concerned that one of the valves that was previously bent and allegedly repaired by the machine shop was not repaired with respect to the camshaft to make sure the motion was perfect, thus it might not be opening correctly?

I'm at a loss on this one and a lot of my searches regarding engine not starting are not mentioning this specific compression issue.

[Shocker]

Do a leak down test to find out where the pressure is escaping. You can get a leak down tester through JEGS. Summit might have one as well, possibly a local auto parts store might as well.

With a fresh build there should be solid compression. Did you/he test the valves for leaks before putting the head on?

[radianation]

The machine shop tested the valves and repaired one of them that had a small bend. Also, the engine did ok on the leakdown test overall. There is some question about the lifters possible not working on those two cylinders. I'm a little out of my league here, but reading as much as I can to try and think of a solution. I'm getting used to the roadblocks after 9 months of downtime.

[BoostFab]

dont repair a bent valve, replace it.

obviously the your head are not sealed

[radianation]

Yeah, I'm kind of agreeing with you at this point. Not sure if that's the issue or not, but 20/20 hindsight. Any other ideas before we dive into that?

[radianation]

The left cam was on incorrectly. Once that was adjusted the engine started up like a champ and sounds like a beast.

[Shocker]

good to hear.