740 B204GT-rebuild engine "stuck"

hi guys,

TLDR: thingtened crackshaft+ untightened rods turns fine/ rods tightened: does not trun what so ever


I took a B204GT appart a few years ago, it was running when i started the project, but leaking oil everywhere, woudn't idle popperly,...

I've got som more time now and I'm (re)building it. It's got new rods (had a chance to buy the cheap) and measured everything up so i got the right parts.

Had te crankshaft machined to new specs (as right in between two sizes that they recommend bearings for. Bought new bearings for the crackshaft brackets and the rods. Installed the crackshaft, tightened it to spec and was able to still turn it by hand. Installed rods with the oil rings, and tried turning it over, was a bit harder, but still easy.
Tightend my rods with the ARP 2000 bolts i got with it to the specs on the package.
Tried to turn the engine by hand, nothing, tried to do it wit my smaller wrench, still nothing.
I can set my torque wrench to 180nm and it clicks before my engine starts turning. I haven't tried to put more force onto it.

losened the rods again and it turns freely now.

I used just a bit of motor oil to lube things up (worked fine with the crankshaft alone).

any ideas. I know it's probably wrong bearings for the rods, but i measured the crackshaft and it was exactly the size it needed to be for those bearings. (don't ask me the coreect size, this was done 2-3 years ago) Bought the bearings from volvo. Any chance i got wrong bearings in my package? never measured those, but they seem to fit really nice, the stick to the shaft with a bit of oil perfectly..

Do you have access to Plastigauge in Belgium? Buy that or equal, and find out the clearance on your rods.... might as well back out completely and confirm the crank bearing clearances (the center of the redblock universe, per StealthFTi). Confirm what you have before taking the next step.

Any work done to the block?

DET17 said:

Do you have access to Plastigauge in Belgium? Buy that or equal, and find out the clearance on your rods.... might as well back out completely and confirm the crank bearing clearances (the center of the redblock universe, per StealthFTi). Confirm what you have before taking the next step.

Any work done to the block?

Click to expand...

no work on the block;

i'll buy some form amazon

Sounds like you don't have the right size rod bearings.

Btw, how hard should it be to turn a "fresh" engine without head

Fairly stiff but not to crazy, so it's the wrong bearings, caps on wrong, rods facing the wrong way, side clearance is to tight, bore in the big end of the cheap rods is off, tourqe wrench is off, the correct way to do them is specified value then x-amount of stretch,I like to use lubriplate no 105 assembly grease

There is a fair amount of friction from the rings (bores should be lightly oiled), but that should lessen as the pairs of pistons arrive at TDB/BDC at the same time, so it should be pretty easy to turn through that part of the circle, harder as the pistons are moving through the middle of their strokes.

Didn't even think of the rod caps being on backward - that could do it. They're bolted together, then machined to a specific size. If you put the cap on the wrong way, the top and bottom halves of the machined circle can be slightly uneven, causing a bind.

those crank journals where the rods go, did you measure those over the full width of the journals?


if they only measure to specs in the middle while having concave or conical shape it might cause the binding.

towz-T said:

Btw, how hard should it be to turn a "fresh" engine without head

Click to expand...

without oil seals and pistons the lubed and torqued crank in the block should turn easy using very little effort. All binding of any sorts is no bueno.

A fully assembled shortblock should still turn kinda easy but it will have some friction from pistons, rings, bearings, oilseals and oilpump drive.

Are the rod caps matched to the correct rods? Are the big end of the rods round, not oval?

It's good that you stopped now and asked for help. Something is clearly not right, and it does sound like the rod bearings are to blame, assuming the rod big ends are round and caps are matched to the right rods.

A long time ago I bought a rebuilt B23FT with new pistons for US$100 (that's 1/3 the price of the pistons alone!). The guy put it together and it would not turn with a breaker bar on the crank. He installed the engine anyway....obviously it didn't start because it wouldn't turn. He removed the engine and it sat on a stand for a few years, then I bought it.

The tell tale sign were the dirty main bearing caps (compared to the very clean block). They probably came from a different block. When the main cap bolts were loosened one by one, eventually the crank would rotate. I had the mains resized and it fixed the problem.

Found the problem, two of the endcaps of the rods where not on the correct rod. Could hardly feel it by hand but i could see the machining marks didn't line up, changed these two and it all played put nice. So previous owner of the rods probably took them appart and forgot which one belonged to the correct rod...

I can turn it over by hand now feels really smooth. Thanks for looking into it guys!

nice save!!! those are awesome motors.