Well I have an oppurtunity to buy a 10:1 JDM engine (claims the pistons are flat-tops) with a broken rocker arm for very cheap (no cams) for $150. From my search here, the extra bump in compression is worth about an extra 2~3whp.

While searching here on what involves changing from a OBDII lowport to JDM highport, I came across this interesting fact that I knew about but never thought about...

The lowport motors are rated at 140 even though it has the milder cam and "crappier" head. (duh)

Since most - if not all- claims the highport is the better designed head, what differences between the motors account for the "gain" the lowport got? Did the shorter IM of the lowport make up the losses? Someone mentioned that there is better lubrication in the lowport that makes up the hp loss, is this a valid claim? If so wouldn't it be best to swap the jdm top-end with the USDM top-end?

Is the top-end of the highport noticeably different than the lowport? If there is that's what I'm looking for.

Before getting this post any longer, would I experience more HP with the lowport w/91 cam and the 10:1 CR than just swapping the highport JDM?

edit: also does the lack of emissions parts (egr) add any more power?

i doubt it is only broken rocker arm usually it could be more

that's what i would have thought. I assume that it was over-revved, but he's giving me a gurantee that it'll run/start when I replace the rocker arm. I was planning on rebuilding if I got it anyway.

anyway, thanks though

get that in writing.....;)

Originally posted by hurddawg
Well I have an oppurtunity to buy a 10:1 JDM engine (claims the pistons are flat-tops) with a broken rocker arm for very cheap (no cams) for $150. From my search here, the extra bump in compression is worth about an extra 2~3whp.

While searching here on what involves changing from a OBDII lowport to JDM highport, I came across this interesting fact that I knew about but never thought about...

The lowport motors are rated at 140 even though it has the milder cam and "crappier" head. (duh)

Since most - if not all- claims the highport is the better designed head, what differences between the motors account for the "gain" the lowport got? Did the shorter IM of the lowport make up the losses? Someone mentioned that there is better lubrication in the lowport that makes up the hp loss, is this a valid claim? If so wouldn't it be best to swap the jdm top-end with the USDM top-end?

Is the top-end of the highport noticeably different than the lowport? If there is that's what I'm looking for.

Before getting this post any longer, would I experience more HP with the lowport w/91 cam and the 10:1 CR than just swapping the highport JDM?

edit: also does the lack of emissions parts (egr) add any more power?

Yeah from what I have heard, the chance that is a 10:1 JDM is pretty slim, those motors are hard to come by.

thanks for the heads up.

I'm actually more interested in the second part of my post than anything else.

Originally posted by hurddawg

I'm actually more interested in the second part of my post than anything else.
So am I. I have also heard about it being due to better lubrication. I'd really like to know.

I think I heard the highport head will not work on a lowport block, I might be wrong.

bump