grantar2

Dave, because I live in California, a lot of mods are unadvisable from a smog inspection point of view. I have two seperate questions. The first is if your familiar with Mike Graycars work in porting the intake plenum and modifying SLP runners, it is worth doing if no other part of the engine is changed?

My understanding is that the stock 90 L98 Aluminum heads can be made to flow very well with port matching and unshrouding the valves, perhaps larger valves, with or without a cam change. Any cam change for me would have to be modest as not to be detected. I have enough problem with my exhaust system which leads them to question engine mods of which there have been none at this point.

grantar2

Greg, did you ever post the details of your build, parts list, thoughts, etc?

GREGGPENN

There are many examples of what shorter runners and/or larger tubes will do for stock/modified engines. When you do either, you will raise the rpm ceiling/tuning of the intake. That WILL result in a faster car especially if you can stay in a lower gear long enough to leverage the improvement. With L98, long-tube TPIs, staying in gear longer is not hard. You will go faster.

As cast, SLPs aren't very impressive. Their tube size is barely above stock and their siamesing is lame. If you go to the extent Graycar does (or go past that), they will be much more effective. Extrude honing those runners and a stock base would perform very close to a superram. If you're familiar with the results of a SR, that should help you understand this answer.

I spent hours and hours on mine, going ALL the way thru the runners and fluting out the tops of the tubes.


A specific question leads to a better answer. Notice, you didn't ask one above! If you're asking whether stock 113 heads can be improved significantly, my answer is yes. TPiS has a CNC program that will outperform anything a hand-porter can accomplish. On the track and dyno, mrcx24 has shown direct results from their porting work. He's putting down 330rwhp with a modified TPI intake and hotcam. I don't know what you're allowed to do with cam/rockers, but I will guarantee better-flowing heads will accomplish a great deal with a modest cam. That was the point I made on the previous page of this thread.

My personal guess is rwhp could go up 40-50hp -- if your intake and exhaust will support it. On paper, TPiS ported 113's look very close to AFR 180's. I bet everyone in this forum would be surprised to see what (either AFR or TPIS) 180s and 1.65 rockers on a stock cam would produce. Supporting intake/exh mods are assumed.

GREGGPENN

Here you go. Notice the link in post #1. It leads to my parts list.
http://forums.corvetteforum.com/c4-t...ahhh-live.html

As for my thoughts....People here are correct when they say shorter runner intakes will make more power. You need to understand how/where you want to make power to get results you're most happy with.

On a 350 motor for street use...or even track, a modified TPI can be fun and successful. (Again, I refer you to mrcx24's accomplishments). Anyway, I'm certain more low-rpm torque would be present which can be leveraged even in part-throttle response at every stop light. Mid-rpm power would also be maximized. There's no question a modified TPI intake will outperform it's long-runner twin if you're restricted to an rpm ceiling or air intake.

On a 383 or larger motor, the need for more torque is minimal. Though I'm certain I would have a faster car if I swapped to an HSR (or miniram), I choose to stick with my modified SLP for looks and ability to return to emissions compliance if necessary. Because VE occurs much lower with a long-runner intake, it might also be possible to get best mpg with this config.

From a practical standpoint, my psuedo super ram config is quite good for a grocery getter. Under 5k rpms (with a 383), it feels like a boosted motor....Actually better due to the immediate response. And, it will pull long enough to challenge my self-restraint and speed limit laws for it's given purpose.

GREGGPENN

I understand what you're saying Andy. I've had similar thoughts. OTOH, I've seen older tech threads pulled up just as a joke.

I'm guessing one of the reasons is to help improve odds that the original participants will continue to see/add to the thread's contents. In this forum, maybe they WANT more thread activity to encourage continued envolvement? Nah...

The thing this thread is missing is an explanation of air flow needs at 4k rpms, 5k rpms, etc.... For people building TPI applications (with longer runner intakes), I haven't seen ANYONE reasonably qualify air requirements for a given CI/rpm. OTOH, I've seen a couple of impressive TPI builds using stock or lightly modified aluminum cylinder heads. IIRC, the original reason I posted this was to figure out what level of heads/flow was "right" for a given application.

Some of the statements I made (on page 1-2, in 2007) were out of other threads at the time. As such, reading it in that timeframe may have added to it's context.

TJM

[QUOTE=GREGGPENN;1576269609]I understand what you're saying Andy. I've had similar thoughts. OTOH, I've seen older tech threads pulled up just as a joke.
................. OTOH, I've seen a couple of impressive TPI builds using stock or lightly modified aluminum cylinder heads. IIRC, the original reason I posted this was to figure out what level of heads/flow was "right" for a given application.


This will make your ears bleed, but iron Vortec heads will outperform the aluminum ones on our '89's. Painful, but true.

And by the way,...... those Intake Runners of yours are ... Genius!! Brilliant!! Inspired !! [ a bigger ROTUNDA for your now shorter corridors!!! ].

and Merry Christmas,

TJM

ddahlgren

I see a couple of things wrong with the TPI setup personally. First there is very little if any taper in the runners. Between 2 and 4 degrees incuded angle will broaden the torque range without hurting anywhere in most cases. Second the whole thing is just too small in cross section from begining to end so anything you can legally do there is a plus. If a First system is legal in CA i think it is the best bang for the buck if you add up buying larger runners then have them and the manifold ported and selling what you have for a couple hundred bucks I think the dollars work out the same or very close.

The same goes for the heads by the time you get the heads ported bigger valves and seats a valve job and new spings you might as well buy new ones even if not the latest and greatest and sell your cores for a few hundred bucks I think you come out close to even again. BTW there is no such thing as too big a valve unless it is shrouding on the cylinder wall. Without haveing the guides shifted 2.050 I and 1.0 E is a pretty good combination as bigger valves act like high ratio rockers with no added valve train loads. It is all about the flow at between 70 and 80 degrees after TDC as that is the largest demand for airflow.These thoughts all balance on the idea that you have having someone else to all the porting rather than do it yourslf.

I am planning on putting a ZZ4 cam in my car this winter if time allows along with 1.6 rockers on the intake and 1.5 on the exhaust as this cam has a lot of exhaust lobe and not nearly as much intake.

If was completley rebuilding the engine i am positive I would go for a set of 6 inch rods. These will change the relationship between peak and mean airspeed in the intake and buy you an additional 500 or so rpm without the torque faling off with occasional slight penalty at peak torque but always add area under the curve.

I know what I am proposing may not be a popular view but I am egually confidant it would work just fine.
Dave

ch@0s

I think this is an interesting topic that needs to be discussed. We often tell noobs to use the search but when the find an old topic we flame them.

ch@0s

I have a question .. something that has been bothering me about my modified
HSR. If you think this is to far of topic just tell me or PM the answer please.

I have modified 2 HSR intakes one was for my stock heads the one i have now is a vortec version. I basically cut the bottom out of the HSR and shoved the runners into the intake and had it welded. I also reshaped the first two runners in order to get better air flow to the rears. My fear is what I have done will just make matters worse. In other words by modifying the front two runners they will now flow better than the others. What is you opinion?

ddahlgren

Without trying to be rude so please don't take it that way. The original design was about 1" lower on the top and had the throttle body section extended about 2 1/2 inches forward and angled down approximately 5 or 6 degrees so the air aimed at the roof of the plenum rather than blow across the runners. Maybe i will look at casting some correct tops as previously they were all done in sheet matal and rather expensive and time consuming. There would sure have to be some interest level to make core boxes etc. and have them poured. Break even would be around 15 or 20 pieces at 200 or so for the tops. They were also wider and overhung the rails sort of like an oval shaped piece of tubing. I know the fit a Corvette as Calloway used one in the first shoot out car as I built it for them while working for another company before I went into business for myself.
Dave

ch@0s

That was not an aswer was it? I really just wanted an opinion. All you said is yours was different. I am also running a 1" spacer at the front of the plenum. one of these.

1989TransAm

"I am also running a 1" spacer at the front of the plenum"

Interesting as I just made up a .750" extension to go on the front of my factory TPI plenum. Going to do what I can to increase the plenum volume of my new long tube runner set up that I am in the process of building. I think I can get it up to around 45% of the engine cubic inch.

ddahlgren

I did my very best to be polite. the short answer is you screwed the pooch with your answer to the problem. You made it fit and made it worse than what it was. this is the conversation I was avoiding.. Problems with the Stealth Ram lets all get a soda /pop bottle of our choice blow across the top because the air flows over the top 90 degrees to the runners. Here that noise it is a low pressure area making a whistling sound enough said. 99% of the time physics can be expalained in very simple terms and this is one of them. OK better if I was polite??? Whenever you send the air 90 degrees to a runner you have lost. This is a better answer though bot what you were looking for I suspect and not politically correct eiter.
Dave
Dave

ch@0s

Never mind.. you still don't get the actual question.
You are saying what we all ready know about the HSR and similar intakes.

pologreen1

Exactly, so tired of hearing people cry that someone dug up a thread that had content they need, or when they don't people cry to use the search function.

It's supposed to be a database of knowledge, and the way this place works now many of the people that have the knowledge or experience don't post or don't come here any more.

Most of the great informative posts were made back years ago when people were researching and experimenting with these cars.

grantar2 it's nice to see it worked for you.

GREGGPENN

What? Where? I still didn't catch the "results".

ddahlgren

Ok If I don't get the question make it clearer. If it was does angle milling it mater the answer is yes but not in comparison to the other short comings of the design. Making a new plenum with the mods I originally listed is the fix. If you had to flat mill a half inch or so off all of it that would be fine as long as you have radiused inlets at the top. The clearance on the sides of the runners is a big deal as the air does not just drop in vertically something that is ost on the original verson.

ch@0s

Thanks, so what I did will help. That was the question.
I don't have the resource to make another plenum. I just wanted to know if what I did hurt or helped.