jeremyferguson

Im putting a 96 lt1 and t56 into an rx7. The chassis is about ready for the transplant. The motor was already pulled from the donor car when i bought it. Suposed to be 96,000 miles and ran good when pulled.

I can see that the opti is not original and the intake manifold gasket has been redone atleast once, without leaks since done. I am going to hook up the starter and run a compression test on all cylinders while its still on the stand. Everything i can see with the oil pan off "looks" o.k. and it rotates smoothly with the spark plugs out.

Im just looking for any little pointers i can go through before i set it in there and start with wiring.....i know either way it will still be a gamble on whether it will need a full rebuild but im hoping to get it running good this summer before i pull it apart for lloyd elliott package next winter.....thanks! Jeremy

Fatdog2

I think you can do a compression check without the starter if the engine rotates smoothly by hand,but I'm no mechanic.
Might take the opti off and look for issues.New water pump and egr valve while the engine is out of the car.This is all I can think of for now unless you want to redo the famous intake manifold leak while you are there just for piece of mind.Hope this helps.

jeremyferguson

Thanks for those recommendations. Ive never done a compression test using the hand (breaker bar) method but that would definitely be less hassle if its still accurate.

It looks like whoever did the last intake gasket on it did a pretty good job with the rtv in the back and there is no evidence of any leaks there so i'll probably leave that until the either the full rebuild or h&c in the fall/winter.....

I was thinking about trying to check the condition of the main bearings....can i just pop the main caps off and put them back on or is that a big no-no?

shoebox

Don't think it is possible to do a real compression test without the starter cranking it. It takes several quick revolutions to build up testing pressure.

If you want to inspect bearings, do one at a time, put them back exactly as they came out and torque the fasteners back to spec.

jeremyferguson

Thanks for the info about checking the bearings! I think i'll throw a rear main seal in too.

If there are any other recommendations for checks i can perform to gauge the condition i'm all ears! I've also been looking for a tutorial to check/set valve lash on a non running LT1 if anyone knows of a good one....

Thanks again all!

gaedbo

Maybe going to shbox.com website will help you on the valve check/lash, among many other helpful things.

Here is the link

4th Gen LT1 F-body Tech Articles

Chimera96

The way I have checked compression is using the starter. just 3 revolutions. I always have done it with motor in car so I pull coil wire and injector fuse

Mount the motor on engine stand so FW is clear and bolt a starter on. Car battery and bump button should work

Buying a used motor with very little if any history about it...you can roll the dice but since the motor is not installed it only takes a few min to pull some crank or rod caps, Do as Shoebox notes and one at a time. The pan gasket is re-useable or you can replace it

If it has a AC delco Opti on it and there is no signs of oil leak around it I would leave it and go. I would have more faith with a used OEM opti and WP vs a new WTF brand one

You can pull the cap on the Opti and check condition of it & rotor. MSD C&R is a recommended replacement. Use blue loc tite on rotor screws.

If you want to replace the Timing cover and rear main seal fine...although if timing cover shows no leaks and has a Opti WP installed I would leave it alone. Rear main is simple to replace with motor out although not while bolted to engine stand. Hanging from a hoist you can get to it. I prefer the Felpro rubber one. Some like the Teflon one

One of those video bore scopes from Harbor Freight you can look down each plug hole and check out piston top, cyl walls and even valves. Easy with engine on a stand and likely cheaper than having to buy new head and intake gaskets and faster....or course if the video cam shows issues...you can make decisions on how to proceed from there

jeremyferguson

Awesome advice! Thanks everybody. I'll post some results and progress pics once I get my "build thread" going. I finally have the engine compartment all cleaned up, primed, and painted, in the rx7 so I'll be getting into the motor pretty soon.

Thanks again!

jeremyferguson

I finally got around to doing the compression test today. It was on the engine stand with the starter hooked up and a jump starter helping. I was super excited when I was getting numbers all in the 180's and 190's......until I got to cylinder #5. It was down around 40 psi with a few drops of atf it went up to 80. Cylinder #7 was also a little lower than the rest at 165 psi. #7 jumped to 190 with a few drops of atf.

I was super bummed because a couple weeks ago I pulled the main caps (one at a time) and checked with "plastic-gauge" and was getting .002" across the board.

So with #5 at TDC, and compressed air going in the spark plug hole, there was a good bit of air coming out of the exhaust port. Backing the crank a few degrees seemed to send the air into the intake, which I thought was wierd because that should be compression stroke, right (both valves closed).

I guess the next step is to pull the head, but is there a way to narrow it down further between a head gasket and valve issue? Should I do rings too, since the number on that cylinder jumped with oil added, or can that happen with head gaskets too?

As always thanks for the input!

bw_hunter

I think you've already gotten your answer. The hissing you hear in the exhaust is from a leaking exhaust valve and requires you to have a valve job done. Also have the shop test for a warped head while you're it just to be safe.

Since all the other cylinders are good on compression, I don't think you have a ring issue...your compression loss is very likely due to the bad valve.

So, I recommend you have both heads done, replacing all valve seals. It might be a good time to replace/upgrade the springs. They're cheap and easy with the heads on the bench...

jeremyferguson

Spot-on my friend! I was in a bit of denial about it when I posted after the compression test. I ended up pulling the heads and found the cause of the problem (I think). It looks like after the engine was pulled from the donor car by the guy I bought the engine from, he stripped the spark plug threads for #5. They drilled out the hole and put a thread insert into the head, but during the process they nicked that exhaust valve with the drill, and also left all the metal shavings in that cylinder. Some of those metal shavings got sucked through the exhaust valve during my compression testing and managed to bugger-up the exhaust valve seat just enough to keep it from sealing completely The shavings that didn't get shot-out of the exhaust valve had a joyride up and down the cylinder wall and left some decent scratches.

Looks like I'm just going to do the full rebuild now. I got a pretty decent quote from a local engine builder to fully machine the block and heads and assemble the long block with me supplying the LT4 cam kit. Thanks all for the input!!

jeremyferguson

Here's some carnage....

jeremyferguson

Did some shopping...

jeremyferguson

Not sure why the pics are upside down. Sorry bout that!

GaryDoug

Did you use an iPhone to take the photos? If so, that is the problem. The iPhone can tell how the phone was held while taking the photo, stores the info in the photo file, and always reads that information when displaying the photo so that it always looks ok. Windows, Unix and other operating systems usually do not use that information. To make sure the photos will appear right side up on other systems, you would have to either get an app for the iPhone that does that correction, or use an pc app to fix them.
And I believe that some Android phones use that method also.