Ported top end: Port Match or bolt it on...

[Schrade]

Jeff (batch); would you clarify / equate please your 'A', and 'B', to Leeg's options - either Option 1), or Option 2), or Option 3)???

And which Option are you favoring here? (Never mind your race regs, for the moment here).

Your 'A', looks like LeeG's Option 2), but I'd like to be clear here on what we're saying...

Originally Posted by batchman

Sincerely hoping this thread has not scared Lee off, I have a question.

My racing rules limit me to going 1" into the head ports, intake or exhaust. On the other hand if I'm going to crack open the thing (or the wallet), I want to make sure I don't leave anything on the table. After all, this is [strikethrough]war[/strikethrough] racing.

To my eye, choices appear to be A) porting IH with <=4deg taper to match the stock head or B) porting to the extent that <=4deg taper can happen within the top inch of the head.

Looking at the implements of destruction I honestly didn't think one could taper like "A" in the IH. On the other hand I figured using the 1" into the head would be the way to make sure the ports register properly between the IH and the head.

If I think between the lines a little bit it sounds like Lee's answer to my dilemma would be let the head ridge stay, but knowing myself I'd take that to mean stick with tapering in the IH.

Maybe the truth lies in the middle, taper the IH from 36 to 33 then use the last mm in that top inch of the head to be sure to align the ports?

I am still on the fence about the secondaries. Once in a while I need to leave the car with a mechanic and knowing human nature that's a great time to keep the power key in the pocket so to speak. It sounds like there's nothing to be gained there at the head other than simplification, which I do confess I like a lot...

Thanks,
- Jeff

[LGAFF]

Just facts not speculation:

*Marc Haibeck's website posts the average gain of his tune, 63mm, porting, port match to 36mm was 35hp. I think the dyno sheet listed shows a 33rwhp gain on a car with stock manifolds and Corsa

*So the prior statement that 37rwhp was low...not sure were that comes from...no dyno sheets were shown

http://zr1specialist.com/HAT%20Web/products/top%20end%20porting.htm

*Car intake I did with essentallly the same mods as Marc had, except no tune or port match..it did 37rwhp......if someone wants to see the dyno sheet search my last name in forum it will show.....same dyno same car... (again this is not some claim about my porting, point is the port match was not done and # was still in the 30s for an increase)

*When I port matched my car and Dominic did it at the same time, I recall Marc saying it was worth another 5 or so(I hate to quote other people, but it was clear port matching did not pick up another 20hp+)...and we are talking about a port match, not porting 3" down the runner....thats more than a port match, thats a ported runner....be real

*My 92 is port matched just into the top(1 inch tops, maybe not even), nothing near what Dominic did, although I wish I did, but the car put down 391 with no tune and ran 12.42 @ 117.5mph with cheap tires and a 1800 rpm launch(I am not a pro driver what can I say(This car has headers)...(this is to answer someone's question about a track car)

Again this is about a person wants to know if they have to port match a 36mm or should it be tapered from the top of the IH to the bottom to match the stock head. That was my intention for the discussion.....if you are going to spend $1K-$2800 why not go to the 36mm.....leave the door open for future mods....opening up the last few inches on the port is what takes the longest......so why pay twice????

Bringing up comparison cars with headers or full cyl head porting is not; as was said here Apples to Apples. The comparisons I made were on actual dyno results....

So if someone wants to port an intake and have it taper to a port match on a stock head and have it well outperform a 36mm ported intake; lets see it......By the claims here it should be about 50hp+ rwhp on a car with no headers....step up! Heck lets see 50+ rwhp on a 36mm with port match and no headers.

[Paul Workman]

Originally Posted by Schrade

Jeff (batch); would you clarify / equate please your 'A', and 'B', to Leeg's options - either Option 1), or Option 2), or Option 3)???

And which Option are you favoring here? (Never mind your race regs, for the moment here).

Your 'A', looks like LeeG's Option 2), but I'd like to be clear here on what we're saying...

It took me a while and lots of re-reading and intuitive unraveling (along with overcoming personal prejudices), and I'm essentially OK with everything Lee said. In fact, we're in "violent agreement" (with these caveats):

1. Dyno results for several LT5s with very similar mods, for various reasons, produce a range of hp results that exceeds that typical for the particular (port matching the head) hp gain. Its sort of like trying to measure an inch within a stick a yard long.
   
2. Therefore 'it is beyond the bounds of accepted scientific process' (there's a mouthful) to predict the absolute outcome of a test conducted under one set of variables based on results derived from a different test where some or all of the variables are independent or uncontrolled.

In short, the change in hp between porting matching the head to the same ported IH 36mm (primary side only) vs. not matching the head to the 36mm IH falls inside the range (in Lee's considerable experience) for LT5s that have been port matched, and therefore irrelevant compared to the relatively wide range of hp results for all LT5s w/ head port matching (primary side).

Now, THAT SAID, on and individual basis, Lee is NOT saying hp would not be improved at least some amount when the head is later port matched to the IH.

So, if you send a plenum and IH to Lee for 36mm PNP, but don't want to DIY port match your heads, chances are your LT5 hp will still fall within the established range of LT5s performance that have had the heads port matched.

How-some-ever, there also is some future "low hanging fruit" hp available when the head ports are matched to the IHs. (I don't believe I'm speaking out of school if I tell you that part of the reason Marc's 500 hp upgrade is now up to 510 is in part due to some changes in porting.) And, when you consider spending several 100s of $$ to have a TB opened up to 63mm, then a couple hours or so using a burr and a die grinder is pretty cheap for nearly the same amount of improvement.



EDIT: Ah, Lee, your post beat me to "what you said".

[Paul Workman]

Originally Posted by LGAFF

*So the prior statement that 37rwhp was low...not sure were that comes from...no dyno sheets were shown

Lee, I think that was essentially my initial position. I apologize for misunderstanding; taking 37 hp out of the context of the full top end pnp, short of full porting of the heads. Only using my stock 337 and Dom's 395* the net is 58 for "a top end upgrade", but of course that also includes the tuning, headers, etc, etc, etc, (i.e., the "full Monte"). So, taken by itself, 37 hp gain for the pnp plenum/IHs, is very respectable. So, please forgive me. My bad.

[mike100]

I would have guessed that port matching would have been worth more than 15% of a top end port (5 extra hp). If you think about the head port itself being the real restriction once you open up the plenum, just up-sizing the plenum gains what it gains and further improvements would have to be more internal the the cylinder head.

Still, I thought it was worth my time while the thing was taken apart to blend out the stupid core shift bevel and blend it to my I/H. I didn't go too deep- it was about a 35mm hole at most.

[LGAFF]

Port match might be worth ten on some, those with headers, etc maybe more...there is alot fo variables on hp from car to car.....

Cam timing

Variances in compression...some due to the above...

Its strange some stock LT-5s test out at 335-some even say 350 rear wheel stock...while other show 310-315...its all over the place. Dyno variances come into play...but its seems there are some really good stocker engines out there...

[Locobob]

I think everyone needs to remember that dynos are a tuning tool. Comparing one dyno test to the next, even if its run on the same dyno, is fraught with problems. Variations of 5-10hp are common with even the same car on the same dyno with back to back tests. You'd have to do an awful lot of tests to establish a meaningful trend when you are talking about the kind of subtle changes that result in 5-10hp. I don't see how anything could be gained airflow wise by a sudden change from 36 to 32mm - except that you may expose some area that was previously shrouded do to port misalignment. This is why I go 34mm at the base of the IH primarys, its enough to capture the port skew area but leaves material to work with if the heads end up being ported some day.

[LGAFF]

When you measure the primary runner mating surface on the head and if you include the bevelled portion of the opening it measures 33-33.5MM.

On the other hand a stock IH at the bottom of the runner can be as small as 30.3-30.5mm but most are 31-31.5. (90-92) IH

[Schrade]

Glad you decided to re-join the DISCUSSION. If MY posts were what made you call the exchange a 'PISSING MATCH', sorry.

-------------------------------------
"if anyone wants to see dyno sheets..."

hmm... I didn't see anyone asking for proof of anything.

OTOH, I am EXTREMELY interested in exceptions to rules.

In this case, the exception is your result:

(and it doesn't need re-wording; I understand the syntax COMPLETELY).

Option 1)Port to 36mm to bottom of IH, no port match, head primary stays at 32mm
Option 2)Port top of IH to 36mm and taper to 32mm
Option 3)Port to 36mm port match head 36mm primary

What I am saying is.....Option 1 is as good or better than Option2 and option 1

The RULE (NOT your exception to the rule, Mr. G, but the RULE) is laminar flow into a cylinder (no, NOT the combustion chamber) beats turbulent flow into a cylinder, EVERY TIME, all factors being equal.

If in the LT5 case, there's some waveform resonance that overcomes the abrupt bore diameter change from 36mm, to 32mm (inclusive of the bevel in the head inlet), I'm listening. And I have a pretty GOOD grasp of String Theory, and String Harmonics, so fear not going over my head.

[USAZR1]

Originally Posted by LGAFF

Port match might be worth ten on some, those with headers, etc maybe more...there is alot fo variables on hp from car to car.....

Cam timing

Variances in compression...some due to the above...

Its strange some stock LT-5s test out at 335-some even say 350 rear wheel stock...while other show 310-315...its all over the place. Dyno variances come into play...but its seems there are some really good stocker engines out there...

Cam timing would be my first guess as to why some LT5's make more power. IIRC,Paul Smith's Admiral Blue made over 385rwhp,stock.

What kind of ballpark hp numbers would I see by just porting the plenum & injector housings on our 94 with stock header cats? If you could only do one mod,what would you do; headers or ported plenum & IH's?