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

[LGAFF]

Results speak for themselves......I would also note Mr. Haibeck sells his porting as a bolt on...maybe he can weigh in.....again, I am not proclaiming it to be superior, just that the 36mm will flow as well as a runner that tapers down to a stock head port......

*37 rear wheel upmatched....
*Marcs average is 35
*Locobobs average is about the same and he tapers to 34


I am not an engineer, but obviously what works, works, alot of things in play here, the angle of the entry into the heads, size of runner, air speed, etc.....Peter Brock was laughed at for his Daytona Coupe design, was told it did not conform to the "rules".....guess who was right.

Theory and practical application can produce two different results...show me proof of a dramtic difference in hp and I will agree....

again, broken rcord, someone go out and port an intake to the stock head port and show the improvement of 45 or 50 rwhp.....we can talk all day about theories, but someone show a result!

Originally Posted by 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).

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.

[mike100]

Originally Posted by USAZR1

...
If you could only do one mod,what would you do; headers or ported plenum & IH's?

Yes, that one mod.

I think my factory catalysts may have been a little plugged up because seat-of-the-pants wise, I liked the headers the most (and I'm still running cats). But like I described before- I had ported the top end previously so I can't really comment on what just headers alone would feel like. If one had to compromise because of emissions inspection, it would be interesting to slap a 93-95 set of catted manifolds to see what improvement you could get over the early units.

Quite honestly, I pretty much assume everybody has a chip too...if nothing else to fix the power key default and to make the fans come on sooner.

[ZZZZZR1]

Lee,

You seem to be jack of all trades!

Porting

Cams

Engine building

Have you dyno'd anything?

Before / after?

How many cars have you worked on!

Great stuff!




David

[Schrade]

Originally Posted by LGAFF

Results speak for themselves......I would also note Mr. Haibeck sells his porting as a bolt on...maybe he can weigh in.....again, I am not proclaiming it to be superior, just that the 36mm will flow as well as a runner that tapers down to a stock head port......

*37 rear wheel upmatched....
*Marcs average is 35
*Locobobs average is about the same and he tapers to 34


I am not an engineer, but obviously what works, works, alot of things in play here, the angle of the entry into the heads, size of runner, air speed, etc.....Peter Brock was laughed at for his Daytona Coupe design, was told it did not conform to the "rules".....guess who was right.

Theory and practical application can produce two different results...show me proof of a dramtic difference in hp and I will agree....

again, broken rcord, someone go out and port an intake to the stock head port and show the improvement of 45 or 50 rwhp.....we can talk all day about theories, but someone show a result!

I'm pretty sure that the cut in those heads - on that '90, is pretty generous - perhaps to halfway between 36 and 32? Maybe 34?. And I'm bettin' that however 'deep' they are, that they're always cut @ 45'.

You didn't happen to mic the cut, or angle it, did you there Lee?

And still glad that you decided to re-join discussion there..............

Now if we could get F/B from others???

[LGAFF]

This is the old school porting that my 92 came with....the DRM ported intake was 34-35mm(primary) and necked down to stock at the IH. This was done with Extrude hone; Dyno test of an Extrude Hone in Vette Magazine(Dec 1997) showed a peak power increase of 18rwhp; more under the curve(20+ at 5K) but 18 peak. Car was untuned with and exhaust

The DRM package came with more..tune and 63mm TB...mine also had headers.....

DRM 500/415
1990-92 ZR-1 Corvette
(50-state legal E.O.# D-323-2)
415 horsepower/390 ft-lbs.
350 cubic inches
Ported plenum and injector housings
K&N air filter
Modified air filter lid
63mm throttle body
Custom computer calibration

[LGAFF]

This was the Doug Rippie plenum extrude honed with 35mm ball....some ports were larger and alomost the entire top of the ball was hidden







Narrowed to stock

[Paul Workman]

Dom said he went with the GVD heads he already had rather than risk perforating the head runners. That decision makes a lot of sense, financially. Before I finished porting and relieving my heads, it ended up costing me just over $137/hp gained to go from about 395 (using Dom's numbers for top end pnp) to 432 ≈ 37 hp gain. (almost $2000 of that was the cost of my "education", and I have one of my original 90 heads sitting right here beside me as I type this.)

This explains why the "seat of the pants" meter felt like doing the full Monte on the heads was somewhat anticlimactic: 2/3 of my total wheel HP came from the plenum/IH/<4º taper almost 3" into both ports of the head/SW headers/SW X-pipe/tune.

For the same money I spent DIY, I could have had "Magic Marc" or Pete's CNC heads AND cams; sans all the fun I had learning where the thin spots are and how to fix 'em later.

Whatever dyno Lee is using...I want to do my next tune on that one!

[rkreigh]

great stuff Lee, don't get discouraged.

I'm reminded of an "accident" back in my C3 days a buddy of mine put a square port intake on an oval port head on a big block chevy

worse port mismatch in the world with a HUGE ridge of the oval ports not lining up with the square port intake

made a ton more power and picked up 30 hp becuase the square port intake was so much better flowing and he got better mix from the air fuel turbulence I would have thought it would be horrible, but it worked.

sure the mismatch induced huge turbulence and was far less than optimal, but it worked

so he port matched to try it out . couldn't really get all that close due to the casting limitations and it really didn't do too much

then he "rounded" the edge of the head port so it's not such a sharp ridge

it again helped. so things that "shouldn't work" often do.

it's all about finding the flow choke point, optimizing flow "velocity and quality" and getting the air fuel mixture to be as homogenous (well mixed) to burn as much as possible. a lot of folks were shocked this year at engine masters when the "little ford modular" built by Jon Kasse pulled 720 hp ouf of a long stroke small bore coyote motor. tuned for top end it pulled over 800 *(albeit with a much less desireable "average torq" which is the numbers we should be focused on)

the lt5 has some pretty small ports in the heads. a very well ported LT5 head flows around 350 cfm which is about where a modern stock LS3 head flows

the big doggie LS7 has HUGE ports and flows 370+ out of the box.

Back to the LT5, Todd has shown me about the upper limit that the LT5 castings do with a max effort port and cam to flow enough for over 700 HP. I'm not really sure what the "upper limit" in CFM is for the LT5 head, Pete probably knows more than most on the best head porting

what we really need is a billet head for the LT5 with the MY95 port or updated head design

maybe we can talk graham and nelson racing into doing it together

it would be amazing to build a "modern LT5"

looking at what Mercury marine did would be a good start to see how they updated their cyl head and manifold port designs. they might be interested too, who knows

great discussion, let's keep it going

[Paul Workman]

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

For what it's worth, like Mike 100, I found tapering (from 36+mm) down the length of the head runners (<4º) to be easy enough while the heads were on the motor, and still be quite safe if done right*. I did both primary and secondary runners, making them identical, all said and done, and it took less than 90 minutes avg, start to finish per port. My top end, (36+mm for plenum and IHs) including that long matching taper into the head, was total DIY without doing anything I would consider anything risky.

Even at ≈ 390-400 wheel hp, the reward is it turns the Z into another animal - even before installing an aluminum FW for a bit more ZAP (especially in the first couple gears!)

Having BTDT, I see no reason to shy away from maxing out the top end P&P by complementing it with porting the heads at the same time.

[Schrade]

I venture that turbulence in a carburetted induction motor is a little different that turbulence in a fuel injected motor...

Was there no bevelling in the OEM heads already?

Originally Posted by rkreigh

great stuff Lee, don't get discouraged.

I'm reminded of an "accident" back in my C3 days a buddy of mine put a square port intake on an oval port head on a big block chevy

worse port mismatch in the world with a HUGE ridge of the oval ports not lining up with the square port intake

made a ton more power and picked up 30 hp becuase the square port intake was so much better flowing and he got better mix from the air fuel turbulence I would have thought it would be horrible, but it worked.

sure the mismatch induced huge turbulence and was far less than optimal, but it worked

so he port matched to try it out . couldn't really get all that close due to the casting limitations and it really didn't do too much

then he "rounded" the edge of the head port so it's not such a sharp ridge

it again helped. so things that "shouldn't work" often do.

it's all about finding the flow choke point, optimizing flow "velocity and quality" and getting the air fuel mixture to be as homogenous (well mixed) to burn as much as possible. a lot of folks were shocked this year at engine masters when the "little ford modular" built by Jon Kasse pulled 720 hp ouf of a long stroke small bore coyote motor. tuned for top end it pulled over 800 *(albeit with a much less desireable "average torq" which is the numbers we should be focused on)

the lt5 has some pretty small ports in the heads. a very well ported LT5 head flows around 350 cfm which is about where a modern stock LS3 head flows

the big doggie LS7 has HUGE ports and flows 370+ out of the box.

Back to the LT5, Todd has shown me about the upper limit that the LT5 castings do with a max effort port and cam to flow enough for over 700 HP. I'm not really sure what the "upper limit" in CFM is for the LT5 head, Pete probably knows more than most on the best head porting

what we really need is a billet head for the LT5 with the MY95 port or updated head design

maybe we can talk graham and nelson racing into doing it together

it would be amazing to build a "modern LT5"

looking at what Mercury marine did would be a good start to see how they updated their cyl head and manifold port designs. they might be interested too, who knows

great discussion, let's keep it going