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[Teg2boo]

I found this today looking for PR4 vs P75 port size.

http://www.flickr.com/photos/45424931@N05/sets/72157623070162488/

It might be useful for some you, fuckers. I was wondering if PR4-Y heads (OBD1 LS head) had bigger port than P75 (B20 head).

It's half info and half question thread  Jew

I almost finished the port and polish on the P75 head, but I noticed that the exhaust stud holes are fucked... Should I repair and tap the holes or should I use the PR4 head (need a port and polish job...)?

Here are some pics of PR4 vs P75 head I took yesterday:

PR4 intake port


P75 intake port


Pr4 intake port


P75


PR4 exhaust port


P75 exhaust port



Do you think JB weld can take care of the fucked up stud holes on the P75? I'm not sure if the thread makes sense, I'm drunk, tired and I wake up in a couple of hours 

[snm95ls]

Timesert the fucked stud holes IMO.

[Teg2boo]

You say this cause you think that the P75 is a better head?

[HiProfile]

In my unprofessional opinion, I'd say the PR4's greater cross-section area and narrower divider would lead to more flow. Given that guy tested both, it appears that is correct (dotted lines in link below).

http://www.flickr.com/photos/45424931@N05/4229804309/#sizes/o/in/set-72157623070162488/

Speaking of that, I'd have to say JD's constant ranting of non-v heads flowing around the rate of vtec heads is correct. They just need a bit of work to do so. If you cut down the spots around the valve guides to what the p75 head is like, you'd probably be better off with less work anyways. Just use the p75 cams, although it seems they don't add noticable power in his case.

[snm95ls]

You say this cause you think that the P75 is a better head?

I say it because you have already put in the extra work on the P75 head.

So if the cams seem to make little difference in power between PR4 and P75, and the PR4 seems to have better ports, then the extra power comed from the P75 intake manifold?

I dunno.  Always wanted to do a mild non-VTAK build, but never got around to it.

[Teg2boo]

In my unprofessional opinion, I'd say the PR4's greater cross-section area and narrower divider would lead to more flow. Given that guy tested both, it appears that is correct (dotted lines in link below).

http://www.flickr.com/photos/45424931@N05/4229804309/#sizes/o/in/set-72157623070162488/

Speaking of that, I'd have to say JD's constant ranting of non-v heads flowing around the rate of vtec heads is correct. They just need a bit of work to do so. If you cut down the spots around the valve guides to what the p75 head is like, you'd probably be better off with less work anyways. Just use the p75 cams, although it seems they don't add noticable power in his case.

Well, I think I'll go with the PR4 then. I have bigger cam than stock (crower turbo 2 cam) so the flow will be a bit more important.

I'll start to clean and port the head tonight since it's a lot of work...

 

[HiProfile]

So if the cams seem to make little difference in power between PR4 and P75, and the PR4 seems to have better ports, then the extra power comed from the P75 intake manifold?

No, I'm saying that guy's tests with datalogging an accelerometer & dyno tests in the same head setup indicated the cams alone don't have a noticable difference. He says it more eloquently in his captions. Regardless I'd go with delta regrinds or something. If he's doing port work, there's a good chance he wont stick with stock cams anyways.

[snm95ls]

So if the cams seem to make little difference in power between PR4 and P75, and the PR4 seems to have better ports, then the extra power comed from the P75 intake manifold?

No, I'm saying that guy's tests with datalogging an accelerometer & dyno tests in the same head setup indicated the cams alone don't have a noticable difference. He says it more eloquently in his captions. Regardless I'd go with delta regrinds or something. If he's doing port work, there's a good chance he wont stick with stock cams anyways.

I was referring to OEM vs OEM configurations.

Isn't there a 10 or 20 Hp difference between the early B18A1s and the later B18B1s?

The data presented on that site is quite interesting for sure.

[Joseph Davis]

90-91 small port heads = loldongs
92+ big port heads = win

Any permutation of the big port head casting is just a few tweaks you don't have to grind in yourself.  LS head requires a lot more work to get to the level Levi wants to go, but for near 200 whp NA, or 300-500 whp turbo streetcar goodness, they are pretty solid with a good valvejob and a set of cams.