Top end porting examples

[Locobob]

Some of you expressed interest in seeing my porting projects so here they are.
This set is my standard port job on a 94.

Plenum


Air Horn


Injector boss close up - 93+ style, finish is from bead blasting.

[Locobob]

Set 2: standard porting job on a 91.

Plenum + Injector housing bolted together to show port alignment - looking down a secondary runner from the bottom of the injector housing.


Side by side before and after injector housing pics (90-92 style)

[Locobob]

Set 3: Partial siamese job on a 94, close to completion but lacking final finish.





Plenum + Injector housing bolted together to show port alignment.

[Locobob]

This last set is my own 368. I had the underside of the plenum and backsides of the injector housings welded up so I could go futher with the partial siamese. Finish is from bead blasting.

[A1990]

Impressive work

[Patton]

Anybody have $1000 dollars to donate to the Poor Ex-Soldier Trying To Make A Living foundation?
Its worth a shot!

But seriously, Robert thats great work! I am curious,... Does taking all this metal off have any plausible drawbacks? Does it pose any longevity/durability issues?

Also, what kind of performance would I see with your porting & headers/RTcats/B&B xpipe cat back/perf chip? This is with a 94 motor.

Now what performance increase would I see with siamesing done to that setup?

I have never had an explanation of what siamesing actually enhances... Anybody care to fill me in? I’m guessing it just combines the primary and secondary tubes and increases the overall volume dramatically. I.E. better air flow.

[Locobob]

Does taking all this metal off have any plausible drawbacks? Does it pose any longevity/durability issues?

No, these are non moving non wear parts.

Also, what kind of performance would I see with your porting & headers/RTcats/B&B xpipe cat back/perf chip? This is with a 94 motor.

Probably around a 50rwhp increase on a 94 with all of the above. The earlier cars (90-92) have more to gain from porting. The 93+ castings are much better flowing from the factory mainly due to the reduction in size of the primary injector boss.

Now what performance increase would I see with siamesing done to that setup?

Probably very little to none. I had planned on testing the difference on my own 368 which start out looking very similar to what you see in photo set 2 but I ended up doing some other things that will muddy the test so it wont be a good before and after comparison.

I have never had an explanation of what siamesing actually enhances... Anybody care to fill me in? I’m guessing it just combines the primary and secondary tubes and increases the overall volume dramatically. I.E. better air flow.

Airflow science is tricky business, not being a scientist I'll give you my basic laymans understanding of it. Think of it as going from a dual plane to a single plane carb intake. The dual plane design relies more on port velocity than volume and is better for low and mid range power. The single plane design allows a greater volume of air at high rpm but loses some port velocity and thus mid range torque. What I have done with the partial siamese would fall somewhere between these two designs. In practice on a 350 LT5 I've seen no loss of low-mid range torque from doing a partial siamese. Is it worth anything extra on the top end, maybe, maybe not. Now on a more radical/larger motor you should see some benefit just like a carbed race motor responds to a single plane intake.

[tomtom72]

[QUOTE=Patton]Anybody have $1000 dollars to donate to the Poor Ex-Soldier Trying To Make A Living foundation?
Its worth a shot!

I know this Federal Reserve bank in NYC, we could tunnel in from the subway....oh, that was a movie...yea, right. I'll go take my meds now!

That stuff looks sweet Bob! I'm saving my nickles because I think my 90 really deserves a present. Gotta keep up with those damn C5's & C6's!

Happy Thanksgiving everyone!! Hope everyone has a nice day with their family!


Tom

[Aurora40]

I don't know jack about jack. But just wanted to toss in, the SLP siamesed runners I put on my '87 L98 were what you are talking about. They were only partially siamesed at the top and bottom. Of course, those were runners to two different cylinders, so only one would be on intake at a time, thus I guess allowing more air volume into each cylinder. They were designed to be well-rounded, not a top-end gain with a bottom-end hurting. I thought they seemed fine, the car seemed a little more peppy, though it actually wasn't that dramatic, I was expecting more.

Edit: Oh, and that bead-blasting finish looks How much would you say you are widening the openings?

[cuisinartvette]

Looks good, Bob! Awful lot of time spent there. I remember browsing that thread a long time ago, one of the things that really set off the bug for a Z. Now I'm ruined, thanks a lot