I have an imported JDM block I bought a while ago that came with the big 16g turbo so always assumed it was from an RS model.

The CR is the same as 7.8:1 from the compression test, but the pistons have a designation I am unfamiliar with. Does the R mean anything special?

Thanks in advance.

I bet Phillip (fuel) would know the answer to this.

Fuel does seem to know the answer to any non USDM question. Its damn impressive really.

this is probably one thing I don't know haha. Have never seen the TR pistons before. The crown looks the same as the regular T pistons. I'm thinking they are replacement OEM pistons in oversize.

Generally from what I have found -

T = turbo
D = DOHC
M - MIVEC or High compression N/A
L - Low compression N/A

Interesting read here: click

Best estimate by the thread was they are VR4-RS pistons. If so back to fuel, what are the motor deltas in the non vs RS VR4 lumps?!?

I'll have to do some digging in CAPS tonight with std/early RS/late RS/Evolution VR-4s and see if the piston part numbers are the same across the board.

As for the rest of the core engine (ie head, block, rods, crank, cams, supposedly pistons etc) they are all the same through all the models - only diff are the bolt ons like the injectors, turbo, inlet + exhaust manifolds, oil filter housing and water pipe.

Without measuring the exact piston crown dimensions and wrist pin size it is hard to determine the difference. Does the OP have some original 63DT slugs that they can be compared against?

also I feel it's worth pointing out yet again that the RS and Evolution models are being mixed up.

The Evolution model (August 1990 to May 1992) are the ones with the 510cc injectors, big16G turbo, 3.909 driveline, hood vents etc - regardless if it's an RS, Monte Carlo or plain jane VR-4. Any RS before July 1990 will still have the 450cc injectors, 14B turbo, non-vented hood etc, but it is worth noting from October 1989 the RS did move to 3.909 driveline ahead of the Evolution. All RS models prior to October 1989 will have 3.545 driveline.

Thanks for the link. I thought that most of the comments seemed to be rather loose opinions with the exception of the person that said they inspected it and saw a wrist pin difference.

Fuel, good info on the evolution/RS terminology, thanks. The engine came with the yellow top 510 injectors as well as the dual runner intake. I measured the bore at the top of the cylinder and it appears to be a standard bore, not oversized. I have a person interested in purchasing the block from me and they want to know the internals. They may come over this Saturday we might pull the piston to do a better inspection. I will post in the Info archive if we pull it and I see anything interesting.

all JDM VR-4 engines have the dual runner cyclone intake. Non-Evolution models will say 'CYCLONE TURBO INTERCOOLER' while the Evolution models say 'ECI-MULTI TURBO INTERCOOLER'. The manifolds other than the writing are identical.

If you could pull out the piston and take lots of photos and measurements if possible that would be good. Do you have a standard VR-4 piston to compare it with?

Some more info about the JDM models here too if you haven't seen it already - click

Yes the Evo Zeros I have checked all have the R on the piston crown. Always wondered if they are any different to the standard VR4 piston.

I wonder if Kris has any pictures of the pistons from the build of my engine.

Purchaser of the shortblock didn't want to remove a rod and piston from the bore so no pictures or observations. Sorry.

Quoting fuel:
I'll have to do some digging in CAPS tonight with std/early RS/late RS/Evolution VR-4s and see if the piston part numbers are the same across the board.

As for the rest of the core engine (ie head, block, rods, crank, cams, supposedly pistons etc) they are all the same through all the models - only diff are the bolt ons like the injectors, turbo, inlet + exhaust manifolds, oil filter housing and water pipe.

Without measuring the exact piston crown dimensions and wrist pin size it is hard to determine the difference. Does the OP have some original 63DT slugs that they can be compared against?



Fuel, just bought the engine and brought it home. It's on a stand, and the standard pistons are on the floor next to it. Will measure and let you know, and also check the wrist pins.

Liane (of Liane and Bruce)

Hi Had a look in the tech manuals:

87.10:

Lists 7.8:1 CR for T/C and 9.0:1 for DOHC N/A
89.10:

Lists 7.8:1 CR for T/C (both MT and At), 9.0:1 for DOHC N/A and 10.4:1 for the AMG
90.10

Looks like was a die change. Can't see if the P/N rolled as the original parts book was not released with a P/N for the pistons
Lists 7.8:1 CR for T/C (both MT doesn't mention AT), 10.4:1 for all DOHC N/A

Does this solve the mystery?

Rich

Thanks misterfixit. I see the 63DTR

revised. Anyone ever tried weighing the two?

Quoting 467:
Thanks misterfixit. I see the 63DTR

yeah I'm wondering if R denotes the change in piston ring groove depth - I know that the DOHC engines of that era changed from a deeper groove to a shallower groove.

i think it also says wrist pin is different to

I would doubt that - they wouldn't be a different diameter anyhow!