Ported IH, non-ported IH.. have some questions

[-=Jeff=-]

let's for a moment assume we have ONE specific LT5 that these scenarios would be on, Same conditions for each dyno run.. for the discussion it will be a n early model, 90-92 all should be relatively the same. Now within my scenario my HP numbers might be off but this is just a discussion (bench racing if you will)

Okay lets begin..

Scenario 1:
Stock LT5, Stock Exhaust
Assume 350RWHP (karterdon's Z has these #s)

Scenario 2:
Stock LT5, Headers and B&B with X-pipe

Scenario 3:
36mm Ported IH and Plenum, Stock Exhaust

Scenario 4:
36mm Ported IH and Plenum, Headers with B&B and X-pipe

Scenario 5:
Late model IH and Plenum, Stock Exhaust

Scenario 6:
Late model IH and Plenum, Headers with B&B and X-pipe

Scenario 7:
36mm Late Model Ported IH and Plenum, Stock Exhaust

Scenario 8:
36mm Late Model Ported IH and Plenum, Headers with B&B and X-pipe

Not sure how much the ported TB will truly give for #s.. for now assume the Stock TB,

SO what would each dyno at, going by the 350 RWHP of Scenario 1

I am curious what gains are had by what..

Discuss....

[LGAFF]

Stock LT5, Stock Exhaust
Assume 350RWHP (karterdon's Z has these #s)

**This should be about 330hp/Don had flowmasters

Scenario 2:
Stock LT5, Headers and B&B with X-pipe

360hp

Scenario 3:
36mm Ported IH and Plenum, Stock Exhaust

350hp

Scenario 4:
36mm Ported IH and Plenum, Headers with B&B and X-pipe

390HP

Scenario 5:
Late model IH and Plenum, Stock Exhaust

350
Scenario 6:
Late model IH and Plenum, Headers with B&B and X-pipe

375

Scenario 7:
36mm Late Model Ported IH and Plenum, Stock Exhaust

370hp
Scenario 8:

36mm Late Model Ported IH and Plenum, Headers with B&B and X-pipe

410hp

[-=Jeff=-]

Where are you getting your # from? ( not the 330 stock one, but the rest?)

[LGAFF]

Why do I feel like we have suddenly crossed the line between auto enthusiasts into some sort of role playing Dungeons and Dragons cult.

My #s are just from glancing at some of the Dyno #s over the years, actually there is alot of info in the registry performance section.

My car with P&P, Watson's, XPipe and Borlas, and no CATs is 390hp.

Just saw a 91 with Headers and Xpipe, exhaust put down 360hp

**Just guesstimating from there.

LGAFF
92 ZR1
#234

[Aurora40]

Wow, 350whp from a stock '90-92 is pretty dang stout.

FWIW, my car on the same dyno put down 325whp with ported IH, plenum.

Added a cat-back exhaust and went to 350whp.

Added headers and went to 370whp.

All on a SuperFlow dyno.

My guess is doing the exhaust first makes more sense than doing porting first.

[-=Jeff=-]

Originally Posted by LGAFF

Why do I feel like we have suddenly crossed the line between auto enthusiasts into some sort of role playing Dungeons and Dragons cult.

My #s are just from glancing at some of the Dyno #s over the years, actually there is alot of info in the registry performance section.

My car with P&P, Watson's, XPipe and Borlas, and no CATs is 390hp.

Just saw a 91 with Headers and Xpipe, exhaust put down 360hp

**Just guesstimating from there.

LGAFF
92 ZR1
#234

no still auto enthusiasts, but I always wondered what the differences are.

Honestly what I really want to know is this:

if 90-92 IH is ~33mm and the 93-95 IH is ~34-35mm and guys say they get more out of a ported 90-92 IH

then when the day is done, what is the HP difference of the following only

90-92 IH vs 93-95 IH both Stock

90-92 IH vs 93-95 IH both Ported

90-92 IH (Ported) vs 93-95 IH (Stock)


just trying to understand best bang for my buck. ( yeah I know.. Headers)

[Aurora40]

I believe the gain is simply that the primary injector bump can be completely removed on the early IH's. It's hard to imagine that being worth a large amount of horsepower. I don't think I've heard of '93+ guys swapping in the earlier housings due to it?

[Locobob]

Originally Posted by -=Jeff=-

no still auto enthusiasts, but I always wondered what the differences are.

Honestly what I really want to know is this:

if 90-92 IH is ~33mm and the 93-95 IH is ~34-35mm and guys say they get more out of a ported 90-92 IH

then when the day is done, what is the HP difference of the following only

90-92 IH vs 93-95 IH both Stock

90-92 IH vs 93-95 IH both Ported

90-92 IH (Ported) vs 93-95 IH (Stock)

About 10hp

Not much - you can work around the boss and get similar results.

About 10hp



A couple of old threads you might find interesting:

http://www.zr1netregistry.com/forum/...hlight=porting

http://www.zr1netregistry.com/forum/...hlight=porting

[cuisinartvette]

Fomer owner of mine claimed 345 or 355rwhp dynoed, cant remember.(Im guessing 345) Runs like it.
Stock w/ 3" duals.

[Pete]

I would say the 90-92 are worth maybe 5-10hp more.
Here's my reasoning
Like Locobob said you can work around the boss, basicly you can port the later (93-95) IH's work the outside walls of the IH to say 36.5+mm and the injector boss side to say 35.5mm which will make the overall 36mm.
Still have a bump that will disturb airflow a bit,the question remains what would HP loss be from this.

This is why i say 5-10hp or aprox.4-8rwhp which i don't think anyone will see down the 1/4.

If you all wanna really find out pitch in dyno/gasket money and i will test a friends 1994 IH's that i have ported against my 1991 IH's in my Z.
My Z goes on the dyno tomorrow with my 1991 IH's if you guys are willing we can test the 1994 IH's anytime after,let me know.
I would not bet on either of them,i think it will be withen dyno tolerance.

Pete