So we are finishing my friend's MGB with a Z28 LT1 and T56. The engine was running fine, we pulled it, cleaned and detailed it and replaced all the maintenance items (water pump, Opti, etc...). Reinstalled the front harmonic balancer (from an LT4) as we are using a kit to mount a small C130 alternator and removed the AC and PS. Engine still turned fine. We installed a flywheel and new clutch from Summit (again everything seemed fine. Installed the engine and then installed the transmission. The build as taken months as we had to build headers, and do a ton of other work. We got to the point of finishing up the loose ends and today decided to crank the engine to make sure we had oil pressure. Starter clicks but engine does not turn, pulled the starter, nothing obvious. Pulled the plugs and tried to rotate it but did not budge.
The T56 was from an Camaro with an LT1 motor, not an LS later car, so that should be fine. So something is locking it up, any ideas what could be causing this? Based on our assembly timing, I don't think it is anything we did on the front of the motor, unless we have the wrong bolt somewhere where it is hitting something (too long). Or is the transmission or clutch/flywheel somehow locking it up? Transmission and drive shaft turn fine when out of gear.
Need help, any ideas for where to look?
If the clutch is now working have someone disengage it while someone #2 tries to turn the engine. My thought is gearbox stuck in 2 gears at once. If it is still stuck, did it get moisture into one or two bores from condensation? I have seen that lock an MGA up solid in 2 weeks. from running to siezed so tight we had to chop one pistons out.
It makes sense that it’s stuck in gear. That motor is GM dumb and tough. Doubtful that it would just lock up from some moisture or overnight internal breakage like that. A Subaru it is not.
Is the belt drive on it? I would check to see if the alternator or a pulley locked up before pulling the transmission out.
Did you try turning it over by the crank bolt or just the starter?
if it won't turn manually Id guess an error with the clutch/flywheel or trans is locked up. Try turning the rear wheels with the clutch depressed and see if it will rotate.
if you just used your starter I'd start there
First don't force it.
From your story it sounds like the motor turned until you mounted the trans.
Release the clutch and see if it turns. easy button.
Did the trans mount up to the motor nice or did you pull it on with the bolts?
Loosen the trans and see if the motor will rock?
All very good suggestions esp the flywheel bolts. How bad is it to pull the trans all the way out?
LT1s take special clutches. No SB1 or LS clutches allowed! So make sure you've got one of those.
What bellhousing are you using? I had a lightweight flywheel interfere and lock up an sbc swap one time.
Thanks guys, just got back from Import Carlisle, so just catching up. Answers below:
1: not the alternator, that is new and turns freely
2: bellhousing is what came with the T56 from an LT1 Camaro
3: Clutch kit is from Summit, supposedly for an 95 LT1.
4: Flywheel bolts, now that is a good question just looked at my receipts and they say they are for an LT1 86-97 Camaro or Firebird ARP kit. Same with the clutch cover bolts.
5: Flywheel. I thought it came with the clutch kit, but turns out it came with the transmission, so perhapsit is LS and not LT1?
I am thinking it is something to do with the transmission, flywheel or clutch, so that is what we will pull next as we troubleshoot.
In reply to dherr (Forum Supporter) :
Side note, how was Carlisle? Im thinking of heading out tomorrow but dont want to make an 8hr round trip if its a bust...
The SBC and LT1 flywheels look the same at a glance, but a close look shows they are different heights. They do not interchange.
In reply to TR7 (Forum Supporter) :
Carlisle was decent considering Covid. I am goiing back tomorrow, hoping for many more cars and people. The vendors were like last year, but I got a few good deals today. So I won't tell you to make a 4 hour trip unless you but I can tell you there will be some of us diehards there! The Triumph club had probably 15 cars there today.
Trans seems fine if it turns. Motor likely fine. They don't just lock up like that. Even if it were a valve stuck open it would spin one way or the other until it hit the valve. The Optispark can cause trouble if it's not installed correctly. Usually it just munches the Opti when you turn it, but they can be a bugger to get right.
They're a lot like a torque converter. Then need to seat all the way on their own. You can't use the bolts to draw it in. Basically, if you didn't get it seated properly, the rotor is smashed against the cap.
Outside possibility... bad water pump? Since they are driven off the cam you can't just take the belt off and check, but worth a glance.
Post the part number for the flywheel and clutch combination. The LT1 T56 uses a pull style clutch instead of a push style and getting the fork engaged correctly can be a bit tricky too. I've got an LT1 T56 swapped behind a 1st gen SBC the flywheel is taller than a normal flywheel and the slave and fork faces the wrong way compared to traditional transmissions.
We will be working on it tomorrow morning, will be checking the Opti, water pump and then the clutch fork. Thanks for all ideas hopefully it will be something simple!
I can understand checking the flywheel bolts, but the clutch shouldn't matter. If it's in neutral, you could weld it together and still turn the engine over. He mentioned that in neutral he could turn the driveshaft, so the trans isn't holding it from turning - with or without a clutch engaged.
Plus, even if the clutch were engaged and in gear, it would just cause the car to lurch forward when you hit the starter. Not lock it up.
Flywheel bolts SHOULD not matter because it's a one piece seal engine. Clutch bolts should not matter unless they are four inches long.
I had a bolt peripheral to the bellhousing once lock a flywheel in place like a set screw.
Likewise, make sure you didn't use the wrong length bolts for the harmonic damper. It's the kind that bolts to a little spider that presses on the crank, to make distributor servicing easier, right?
Also, can it rotate backwards?
Pilot bearing incorrect/too thick/stuck before seating all the way?
Thanks for all the suggestions. We pulled the radiator so we could turn the engine with a socket wrench off the balancer. Turns out it turned fine (thank God), so after checking a few other things we went back to the starter. Turns out the starter was bad. It spins for a second, makes a "clank" sound and then seizes up. After we tested it on a bench and it did the same thing we are quite happy it was not the engine. The clearances on this V8 swapped MGB make things hard to diagnose despite our efforts to make it all serviceable, so very happy we don't have to pull the engine or transmission.
jfryjfry (Forum Supporter) said:
Did you try turning it over by the crank bolt or just the starter?
if it won't turn manually Id guess an error with the clutch/flywheel or trans is locked up. Try turning the rear wheels with the clutch depressed and see if it will rotate.
if you just used your starter I'd start there
Nice when the problem is easy and relatively cheap! (Hmm, accidentally quoted someone there from days ago... not sure how that happened.... haha)
Easy fixes are the best. I had terrible luck with LT1 starters, but I suspect it may have been a flexplate issue in mine.
Yes, easy and cheap really made my day as this a project for a friend where I have a ton of time invested and it needs to get finished this month. Now we are back on track. Thanks again for all your help, should have the new starter in tonight and back to finishing it all up!
