intake manifolds on a xe 268 cammed 305 headed 327? is it worth it to change my manifold from a regular perf. to a perf. RPM?
Thanks.

 

It depends on what it does now, and what you want it to do. I'm not sure what exactly makes the RPM a higher performance manifold, but it uses a square bore flange (unless you get the Qjet version), and is noticeably taller than the regular performer. The RPM air gap is the tallest of the 'RPM' manifolds, and IMO the best one... untill you spill some coolant or fuel on the intake, and have to clean it up

 

i HATE that!! I've gotten to the point whenever I work on one, I stuff rags in there before I do anything lol

The performer RPM air-gap is the best one for street/strip in my opinion. The performance difference between the two intakes is the upper rpm airflow. Down low it won't make much difference, but if your motor wants to rev I'd recommend the perf. rpm air-gap manifold. It's very streetable, stays nice and cool and delivers lower end torque with a good high end charge. IIRC it's powerband is about 1500-6000, probably right where you want to be.

 

Oh I know that, but I mean the design of the intake... aside from being a little taller and having a different carb flange, I don't know what the difference is between them (if there are any other differences).

The Air Gap manifolds are a whole different animal all together. All the runners are raised off the 'lifter valley cover' part of the intake, sorta like a TPI manifold, so the runners stay cooler. This, by design, makes the intake a bit taller than a std RPM, but not much. It still fit under my stock Z28 hood with a dual-feed 750 Holley and 14x3 drop-base air cleaner.

 

right now i don't rev the motor over 5k though i probably would gain some if i did. is there anywhere i can get the dimensions of all three?
Thanks.

 

yeah I don't know the exact differences either, edelbrock probably has a cross section picture of them somewhere.

You can get the dimensions of all three on edelbrock's website.

 

the rpm is .7" higher and has slightly larger ports, i think if i can find a deal somewhere i might buy one.

 

there are some other intakes out there you can nab cheeper and perform better... hop on ebay and look for a holly contender... it doesnt look like much just a big dual plane intake but its rated from idle to 7,500rpm and between the two i would never go back to an air gap... i buy everyone i see now for myself or friends can usually find them for 50 or 60 bucks used they stopped making them and i havent found a new style like it but the only intake i found with that kind of range and it is good for anything ive used them on 305's up to 383's and they can take it all...
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it is tall but it will fit under a camaro stock hood fine its a squeeze under a stock bird hood though...

 

The RPM and RPM Airgap both have the carb flange .7" higher than the standard Performer. They also have larger runners and other little tricks and tweaks that let them breathe better than the standard Performer in the uppper RPMs without sacrificing much down low.

 

I don't have direct experience with these intakes on SBC's, but based on what I saw with my BBC, you'd have to rev higher than 5000 RPMs to see any difference. The XE268 should be more than capable of 5800 RPMs in a 327, and if the 305 heads have been ported, the RPM intake should run circles around the Performer when you do run it above 5k RPMs.

 

It's all about a good power curve. To give you an example of how much power the performer rpm makes over the performer. Sallee chevy has a intake swap for a zz4 option that they do. I called them and they said they dyno every mod. they do this to the stock zz4 one at a time to give the customer an idea of what should be expected within a rough range. They made 10hp and 5ftlbs more torque over the zz4 intake,which is an edelbrock performer built for gm by edelbrock.It changed peak hp from 5250rpm to 5450 and peak torque from 3800 to 4100rpm.This is just an example of what it does to the zz4. Your 327 might see better or worse results but either way the RPM intake moves the power band up a little. On the dyno my zz4 pulls a flat hp reading from 5200-5700 and then starts to fall,but my cam really is not big enough to have the full benifts of a RPM intake. If you plan of reving it over 5500 a lot get the rpm but if not I would say the performer.

 

well, who the heck builds a 327 as a torque motor though? that motor was made to work in the upper rpm range...

 

Very true. I think every 327 I have seen had at least a Performer RPM, Stealth,or single plane.

 

You will notice a nice difference with an RPM over a performer especially in the rated power band. The RPM really helped my 383 where the ZZ4 (performer) was lacking in upper RPMs but also made quite a bit of difference just lugging around at the bottem of the gears even in a full size truck.

 

I am with you, I ran a performer RPM with a TBI-Carb intake adapter on my 305 in my fullsize van. I noticed gains from off-idle all the way to redline with the performer RPM. My comparison is against the stock aluminum intake, very similar if not the same piece as the LG4 one.

 

Common misconception. The first 327-equipped vehicle I drove was a 20,000 lb gross vehicle weight farm truck. Pulled a whole lot better than the 262 straight-six powered truck I was used to. . .

 

Yeah, I bet the 5.5-6:1 gears in the high range of the two speed rear-end helped alot though.

 

Sorry, they both had the 2-speed rearend. The 327 just had more grunt, plain and simple.

 

I wasn't arguing that it didn't, just that the low gearing was responsible for moving all those 20,000 lbs!

BTW, they put 305s in 70 passenger school buses too.

UPS delivery trucks have 4.3s

 

the heads have not been ported(that i know of, the machine shop might have blended them a little when they put the 1.94 valves in) they are coming off this fall to get the treatment though. do you still think it would peak higher than 5k being unported or very mildly ported? the machine shop recommended the cam for those heads.
thanks for all the info on it though.