Thread: Possible ways to tell if you have a JDM 10:1

Hey guys. I just picked a up a JDM highport DE from a local parts warehouse. I chose it based on the head code information. The 3L stamp is on the head and from information on both forums this pointed to a 10:1 motor. Upon further research I think the head code is possibly meaningless.

I'm pretty sure I have a U13 Sr20de on my hands indicating that the compression ratio is a 9.5:1 so not what I was looking for. Here are several reasons that point me to a U13 Sr20de.

Passenger side engine mount bracket is totally different than a B13 or P10. I mistakenly put on a P10 bracket on the engine thinking it was a b13 unit. The bracket that came with the engine is thicker in shape than the P10 bracket.

Second clue is the build date. From what I can see my engine was built 09/95. So the year gives you an idea of what possible models it came from.

Third clue is the distributor that came with the engine. Part number 22100-0M810. The distributor part number points to R10, P10, or U13 models.

Fourth clue is the IACV-AAC valve. On my JDM the part number is 23781-33Y10. This points to P10, R10, U13 models.

Based on engine build date the only candidate left from the information I gathered is the U13 since production went until 11/95. There could have been a small chance that I had a P10 engine because production ended in 08/95 and maybe the stamp on the water neck was an 8 and not a 9. The fact that a USDM motor mount bracket is not the same shape as to what came with my JDM I'm thinking the Primera engine is ruled out.

Somebody with a complete FAST could for sure put all the pieces together. The FAST that I have might not have all the models that had FWD Sr20de's in 1995.

Google hits on the IACV-AAC part number also turned up the M11 Prairie as a user of this part. I don't have M11 data on my FAST so I cannot tell if it came with the 65J pistons (10:1).

A resource that I found useful was CAR DIRECTORY - Forums, Picture Galleries and Specifications. It has spec info on different JDM models. Once you narrow down what vehicle the engine came from you can use this website to see if the compression ratio is 10:1 or 9.5:1 .


All this stuff I just talked about will only be useful if you have FAST, are for sure the engine is from a Japanese market vehicle, and assuming that the components on the engine are the originals that came with the engine.

hhhmmmm strange , i guess the most obvious would be the " 101" on the head..

when i bought my UKDM SR a few years back it had that stamped on the head.

i posted it on the old forum and Miko told me it had sodium filled valves and the cam duration and lift were close to JWT S3 cams...i could be wrong since this was a few years back, at least 7 years

UK made engines seem to be marked different. The engine I purchased is from Japan. You are right though if the 101 really means 10:1 then yes that would be a super easy way to tell.

the biggest factor in visibly identifying a 10:1 i do Believe is the intake manifold, if its a highport style its not a 10:1 but i could be wrong.. dont think so tho since i've yet to see a 10:1 with a highport intake, all the ones i've seen had the low port style intake..

Highport 10:1s do exist. The P10 Primeras were equipped with 10:1 motors. If you check FAST the cars with 65J pistons are the ones that have the 10:1 compression.

The 9.5:1 pistons have 63J in their part number.

guess ya learn n something every day

oh highport 10:1's exist all right. On the old forum there is an engine identifyer but alot of the head numbers on there ive had in the last 3 years of buying my motors and motors for friends cars were not 10:1 motors when on the chart they were listed as 10:1. Ive had 2 highport 10:1 motors out of the 8 or 9 highports ive purchased over the past 3 years from Soko. The only way ive been able to know for sure is pulling the head off. Flat top pistons. That and the feel of the car when it was turbo was a bit more responsive and made more power. One of my jdm motors back when i had a t25 was a 10:1 and one of my buddies motors was a 10:1. They both ran very strong on 8-9psi of boost.

You could compression check it. If you have more than 185psi of compression across the board then its a good chance its a 10:1

All the other 9.5:1 motors i got came in around 175-180 across. If i remember right one of the 10:1 motors compression checked at 190psi

I like this method best personally.

The UK ones have UK parts from a company called "Lucas" like water pump and distributor. That's what mine had and it was a highport from early 90s.

cant you just check the head code?