two79rx7's

How can you tell if a 2nd gen engine is 86-88NA or 89-91NA once out of car?
other than looking for leaks around the housings
or how dirty the engine is (not such a good indicator) is there a way to judge the condition of the engine once on the ground with tranny off.

2ndGen.rocket

look at the intake manifold

NCGNETO90

iTrader: (3)

Indeed. The UIM is what will tell you.

two79rx7's

be spacific guys \
what about the UIM
what will I see that will tell me which version?

NCGNETO90

iTrader: (3)

The S4 will look like the exhaust manifold. The S5 will have like this...

NCGNETO90

iTrader: (3)

OH. I forgot that i owned a couple S4 as well. Here is a S4 one.

two79rx7's

supose no throttle body or intake on engine
just the short block core on the ground
how do I tell the early vs late version

theloudroom

Maybe there's a casting # on some part of it? <shrug>

Hot_Dog

The 86-88 NA came with an EGR whereas the 89-91 NA did not have an EGR. The EGR is bolted to the housings just below the dynamic chamber. If the EGR has been removed, than the only other way to determine if it early or late would be to disassemble and compare rotors. The 89-91 rotors are lighter than the 86-88 rotors.

If I remember correctly, that Atkins website once mentioned something about distinguishing between early and late model engines using the numbers which are stamped on the engine block. You should check out the Atkins website for more information.

Larry Mizerka
90 RX7 GXL
02 Acura RSX-S

NoPistons4Chris

what he said, plus you can tell by the intake manifold right off the back

Wicked_razor

you can also tell by the front cover of the engine the S4 has 2 bolt holes for the OMP and the S5 has 3 holes

wozzoom

The EGR valve is a dead giveaway. The S4 motor will have the 2 holes for the EGR even if the valve it removed. S5 blocks don't have the holes.

Electronic Oil Metering Pump on the S5.

The water pump outlet on the S4 is aluminum, the S5 is plastic.

The intake ports on the engine are also different. S5 blocks have a third port (for the port air injection) located directly below two main intake ports in the center housing. On the outer housings, the S5 blocks only have 2 ports each. On the S4 engines, the port air is moved from the center housing to the outer housings.

Digi7ech

iTrader: (1)

The Biggest and easist one other than manifolds.

THE Oil Metering Pump.

On S4 it is mechanical. On S5 they are electrical.
The electrical one will have a plug going to it the S4 won't.

I had to check this out when ripping apart my S5 Jspec(They were supposed to send me a S4).