Tom454

Been surfing for about 2 hours and can't dig up what I need.

Does anybody have flow rates and runner cc's etc for the old Z28 style manifold? (3932472)

DZRick

Scroll down this page and you'll find some specs that might answer your questions Tom.

http://www.hotrod.com/how-to/engine/...gine-shootout/

Auto Gear

I didn't see flow rates on the MANIFOLD just the heads? Thats a seriously cool article though, except for the Boss 351 winning LOL

(PS) DZRick; PM me sometime

Bad Bird

Before Corvettes, my previous rides were XB Falcons (like Mad Max's car) running 351 Clevelands. Those are some seriously underrated motors - they rev to the moon especially with the factory 4V heads.

DZRick

Sorry about that, I guess I wasn't paying attention.

I'll PM you in a few.

Solid LT1

I've never seen a need to calculate runner volume on a dual plane intake manifold....why are you in need of this? I have only seen this done on Individual Runner intakes on motor cycles and small displacement vintage race motors. My expirience with the LT-1 intake, it will work well on motors until about 450HP.....then you need to step up to a single plane intake.

Tom454

I'm building a stroker (383 style) and I need more info for picking the heads & cam. I have the manifold. I purchased both the Summit and Edelbrock equivalent (sent them back) and it was very clear via port size and runner volume that the GM manifold has better flow capability. Ordering the heads today. Can't decide on the cam. Trying to match the intake, heads, cam and exhaust.

redvetracr

you could always send your intake to Wilson, they cut them in half, port em and weld them back together.....

Solid LT1

The Edelbrock Performer RPM I tried on my LT-1 build back in the 90's gave about 6HP increase over the factory LT-1 intake but, since it didn't look as " cool " I replaced it with the factory intake after the dyno session, this was crankshaft HP ( both intake run with a open hole 1/2" spacer on them.) Running a RPM intake with a cut down plenum divider would pick up the HP to around the 19HP improvement over the GM hi-rise that Edelbrock claimed in their ads back then, Never believe what you read! The RPM airgap HP increase over the RPM is mainly attributed to the cut down center divider. For a good "street/strip" 383 I would go with 200cc intake runner ( or less ) heads but cam would depend on transmission/differential type/gearing and what your using the Vette for. Chevy L-82 cams were around 224 degrees@ 0.050" tappet lift ( about the minimum starting point on a nice running 383, if you had a manual trans Vette or a very loose convertor and wanted 1/4 mile performance I would go into the low 230@ 0.050" range with a 2-6 degree larger exhaust on a 110 int/exh lobe separation angle. Comp Cams has a online calculator for their cam selections. here is the download for the cam calculator:

link: http://www.compcams.com/downloads/register.asp

Tom454

This will be strictly a street 383 stump puller 1500-5000 rpm engine. Looking for torque, not hp. I suspect your peak hp numbers were up a little too high for me. Correct me if I'm wrong, but I believe it's best to stick with a dual plane in my case to keep the fuel velocity up at lower rpms. I'm trying to get the same low end torque feel of my 70 LS5 out of a 383. No racing. My 66-327 had the LT1 intake on it and I drove it... it worked very well on the 327, so I suspect it will do even better on the 383. I measured the port area of the performer (LxW) and it is substantially less than the LT1 intake. About 11 or 12%. The eye-balled internal passages of the Performer look smaller as well from the outside and the inside. Again... I'm not going to rev this thing above 4500 or 5000. I just want it to pull hard coming off idle. I don't understand why your dyno numbers were better for the Performer in any range. Any idea? Did you have different cams?

694speed350

had a '70 351 Cleveland they were underrated also had a 71 351 Cleveland. good engines.

Solid LT1

Back in the 80's I had a 65 ElCamino with a PAW sourced 383 stroker Kit. I topped it off with a 72 LT-1 top end.....487 open chamber heads and the LT-1 hi-rise with the Holley 4801 carb.....as I recall I had a Crower hydraulic cam around 224@ 0.050 int/exh on 110 lobe separation. That combo was a good running combo with a TH350 and 3.31 twelve bolt Posi it did 13.50's at 108MPH and returned about 18-20 MPG on long freeway trips. If your truly not going to rev the motor past 6000RPM.....you won't see any big performance gain over the Quadrajet intake. My 383 was shifted at 6500RPM on its drag strip passes ( using the column shift gear lever!....some concentration and skill required! ) That 383 has the 5.65" 400 small block rods inside it....next to my DuraMax it was one of the best tow vehicles I ever owned. If I were building a 383 for a Vette, I would want it to be able to pull through 6K RPMs why such a low RPM goal?

Tom454

I sent the two q-jet manifolds back so that part is history. I have a 6211 spread bore Holley that was earmarked for the 383. I just can't see how the Performer could work better than the LT1. Anyhow... I don't "race" (anymore) and I am interested only in an occasional burst of enthusiasm.. probably from streetlight to streetlight. I won't even get an opportunity to rev past 4K or 4.5K. I don't need it, and my main concern is longevity of the parts. I just want an engine in my C2 that will pull hard like my LS5 (500ft-lbs) without making a lot of noise through the side pipes to attract unnecessary attention. I want to have fun, but stay under the radar.

The list of parts to convert to a BB in the C2 is too long (radiator support, accessory brackets, pulleys, wiring harness etc) and expensive. So a 383 it is.

Solid LT1

You keep on referring to a Edelbrock " Performer " intake manifold, yes this is a more restrictive intake than the Chevy Z/28-LT-1 Hi-Rise intake but, a Performer RPM is a comparable intake in runner volume and performance plus has far better intake gasket sealing than a Chevy Hi-Rise intake. There is a Performer RPM Q-jet pattern intake available but, if your intending to keep RPMS below 6000.......your wasting your $$$$ on any intake over a factory Q-jet.

Tom454

Sorry ... I had the Performer stuck in my head and that's the one I purchased & returned. The lit says the RPM "Will not clear stock Corvette hood." so I discounted it. The LT1 fits under my stock 327 hood.

I picked up the LT1 manifold 30 years ago for the cost of a cup of coffee. As I mentioned... it worked really well with 327, so I'm guessing it will work well on the 383.

In retrospect, I perhaps should have ordered the Performer RPM, but the hood issue scared me away.

ignatz

I don't have the benefit of horsepower measurements but only seat-of-the pants feel, but I've used the Z28 manifold with my 383 and an aggressive cam and it pulled really hard. This was with a 650 Holley carb where I could tell the motor was getting a little starved at high RPM. But the mid range torque was great. The only problem I had was a misfit area with some Pro TopLine heads. There was a small gap which led directly into the crankcase and I'd get mystery oil deposits. No problem with stock hood fitment either.

I really think you will be happy with it.

Torqued Off

Lt1 - SO, if I am understanding what you are saying, below 6000 RPM, a Performer RPM will produce no more HP or torque than a straight Performer? Another way to ask this is, if for example an engine produces 400 ft lbs of torque at 3000 RPM with a Performer RPM intake manifold, it will produce 400 ft lbs of torque at 3000 RPM with a straight Performer manifold.

This matters to me because I have read many times that a Performer RPM actually produces more torque across the entire RPM range, not just at the very top end. If an RPM manifold truly only adds power above even 5500, then its not worth the issues with hood clearance, etc....

If I am misunderstanding you, can you please clarify. You may be comparing the LT1 manifold to the Performer RPM??

Solid LT1

What I am saying is that if you don't intend to rev your motor over 5500RPM, then there are lots better ways to spend money on performance. As far as intake selection and power there are lots of factors ( camshaft, gears, transmission, car weight, engine displacement, cylinder heads, carburetor )....on a 383 the RPM would be my choice over the Performer intake for a 350 below 6K RPMS you probably wont see a great difference between the 2 ( if a Z/28 Hi-rise fits, the RPM intake should fit too ) On the other-hand if I was building a low budget 283/327 Chevy, I wouldn't waste money on a Performer intake if I had a Q-jet intake around. If you have some talent, an air compressor, die grinder, carbide burrs ( I own several hundred dollars worth of those! ) and time, you can rework a Q-jet intake to perform quite well.

Way back in my misspent youth I spent time on the back roads of the SF Bay area late at night, my buddy had a 65 ChevyII that we pulled the 283/PG out of it and put in a wrecking yard 1970 400SBC/THM350 with a 4bbl Q-jet intake, we reworked parts until it was a mid/low 12 second ride......we made lots of " beer money " with that Deuce.....yeah....its some old 327 we found at his uncles ranch......The bottom end of the 400 was completely stock except for cam/lifters/timing chain, the 400 heads were reworked ( 186 castings same as a LT-1 even had 1.6 exhaust valves but, with 1.94 intakes ) and the Q-jet was re-jetted for the better exhaust system. That car was a sleeper

What I don't get is people building motors and then saying they don't plan on running over 6000RPM.....every good running SBC and most big blocks will make decent power to 6500RPM with a little reworking/tuning on a tight budget.

As far as the choice between a Z/28 LT-1 Hi-rise VS Performer RPM, the Edelbrock does make a slight amount of more power but, nothing near the 19HP that was claimed for this intake ( about 6HP in my testing.) The RPM Air-Gap makes even more power ( say 15-20HP over a Chevy intake ) but, sacrifices some bottom end with its cut down plenum divider, if you do the same removal on a RPM intake then you have just about caught back up to the Air-gap......

There was a street racer back in my time than had a 302 Z/28 with a factory intake on it but, the center divider was cut down 3/4" on that car....it was pretty fast 12.20's with a 5.57 gear set in it. We used to joke as the owner rowed the Muncie to 4th gear by the time he crossed an intersection by his house.

Torqued Off

[QUOTE=
What I don't get is people building motors and then saying they don't plan on running over 6000RPM.....every good running SBC and most big blocks will make decent power to 6500RPM with a little reworking/tuning on a tight budget.[/QUOTE]

Thanks for the response, I have built a fairly high quality 350, with AFR heads, etc. I don't want to hijack the thread, as I posted a thread a few weeks ago on intakes, trying to make a decision. The question is below 5500 RPM, does a Performer RPM really improve anything over a Performer? I seem to read mixed responses, some say a RPM improves the torque across the whole range, and if true, then seems like it would be worth it given it matches my AFR 180 port dimensions and flow more so than the Performer. And the Comp Cam XR270HR cam I have is advertised at 1600-5400 RPM operating range.

Anyway, I wanted to respond to part of your quote...why nobody wants to go to 6500 RPM. When I drove the car the two years before the body off restoration, it was as stock L48 with 66,000 miles on it, stock four speed. Even if I really got on it, my normal shift points would be 2500-3000 RPM, and even with the anemic L48, I could be at 60 mph in no time. So, when I think about shifting at 6000 RPM, that would mean I would stay in first gear till 6000 RPM....!!!!, then shift to second gear, stay in that till 6000 RPM, and so on. Here is the part I cannot figure out.....I probably would be at 50 mph in FIRST GEAR if I did that, even though I never tried it as it seems like unnecessary thrashing and abuse of an engine. Certainly by second gear at 6500 RPM I would have been at 50. Obviously by fourth gear I would be going far faster than is safe or reasonable on the streets and highways of Pennsylvania.

So, I respect your racing background, maybe even street racing background, but to drive a car on the streets, and try to somewhat obey the speed limits and be responsible and safe, 6500 RPM is useless. So there has to be some reality in this. I wanted performance, mostly torque for acceleration, to shift through the gears, feel the push and power that a sports car should have but high RPM Horsepower is not really something I care about, especially given that I have no desire to drive this car 150 mph anytime, anywhere. SO, to respond to your statement I really don't know why any street car need to have a 5500 Plus capability. I have stated this before, and gots lots of toughguy bragging B.S. about how people shift at 5000 RPM, but it really sounds ridiculous and nothing but barstool crap.

Tom454

That's the same mindset that I have and the primary design factor of my 383.