i was looking through summit and i saw that edelbrock makes all three of these kinds of intakes for sbc's. which one should i choose? this chevelle is 90% street 10% strip. and i need torque more than horsepower. i'd like to see a powerband of about 1500-6000 rpm or so. i heard that tuning is a nightmare with more than one carb? thanks for any input!
-jay

Weiand 8004, E-brock Performer, maybe Performer RPM - all good dual plane single 4bbl intakes.

IMHO.....

Summit's best buy is the great old Holley 300-36 in the satin finish!!

The old sucker will run with the best of them!!

pdq67

I have been a fan of the edelbrock intakes. I ran one on my SBC and i run one now on my BBC.

Daniel

For sure something like an RPM air gap is the safest strongest way to go. Throw on a 750 double pumper and have a blast. Don't be scared od DP's despite what folks tell you. They aren't hard to tune and will have better response. By the time you get a vacuum one to operate strong, you could have easily tuned a DP to outrun it.

I prefer Holleys, but the Edelbrocks work well out of the box. My only concern with them is.....

They just look BAD sitting there all alone! Nothing looks better than a DP Holley IMHO.

BUT....two of them ona lo-rise intake look great!

It may not be related, but I have a buddy with a 302 in a '67 Mustang. He has two 500cfm Edelbrocks on it and they work great. I've driven it many times and they never bog, load up or do anything stupid even in 100*+ heat around here. He drives it on long highway trips as daily driver and it runs 12.70's with a 4 speed and 3.73's.

I know the single carb/new style intake will maybe make a little more top end power, but if you like the looks, 2x4's are pretty cool!
Plus it's a little different. I bet some spacers under them would improve the top end considering how low the intakes are.

JIM

this chevelle is 90% street 10% strip. and i need torque more than horsepower. i'd like to see a powerband of about 1500-6000 rpm or soI think for a mostly street car, it doesn't really make alot of difference. Its more your preferrence...

More Torque than HP, so you mean you want more low-end... Best choice (IMO) would be a dual-plane single 4-barrel setup.
A high-rise single 4-barrel setup will generally increase the RPM where the torque peaks over the dual plane, but is still be drivable on the street...

Dual Quads will generally make slightly less HP than a single 4-barrel (for street/ low rise setups), but there is the Cool factor of having dual quads (See My signature below)...

Tri-power can give good drivability/economy and low end power while still having good upper end power...

Tri-powers and dual quads will be a little harder to tune and will cost much more, so budget has to be considered. You'll need the multiple carbs, linkage, air cleaners, the manifolds are usually more than the single 4-barrel manifolds, etc...


As for carbs, there are lots of choices, so its really your preferrence... Personally, I do not agree with the Holley DP for a basic street car. If you have the lower gears or a loose converter, and know how to tune the carb, then a DP will work okay, but its not really going to show much improvement for a basic street car. the Vacuum secondary versions will be more forgiving and driveable right out-of-the-box (usually). A 750 DP is probably way too big for your application (355), but depending on what you are doing with the 383 you mentioned, it might be a better long term choice, but again, unless racing alot (with the associated parts/setup), the DP isn't needed.

This is from the Holley carburetor website:

How To Calculate CFM:
Engine size (CID) x maximum RPM / 3456 = CFM
CFM @ 100% volumetric efficiency

(Example: 350 CID x 6000 RPM = 2,100,000 / 3456 = 608 CFM)

Approximately 608 CFM would be required for this engine. However, most Street engines are capable of achieving only about 80% VE; a modified street engine with ported heads, headers, intake and carburetor can achieve about 85% VE; a fully modified race engine can achieve 95% or greater VE. The CFM number arrived at with this formula must be factored by this percentage.

Next, you need to decide whether a vacuum secondary or a mechanical secondary carburetor will work best for you.

As a rule of thumb, vacuum secondary carburetors work best on:
Relatively heavy vehicles
Street gearing
Automatic transmission
Engines built more for low-end torque


Conversely, mechanical secondary carburetors seem to work best on:
Relatively light vehicles
Strip gearing (4.11 or numerically higher)
Manual transmission
Engines built more for top-end horsepower So based on that info, for heavy street vehicle (Chevelle), even with your new 383, expecting it to rev to 6500 RPM, you'd only need a 650 cfm (actually 612 cfm) vacuum secondary carb (assuming 85% VE of a modified street engine), especially for low-end power.

But that only the recomendation of the Holley engineers...


I personally like the Edelbrock Performers for daily driver/street car use... I have these on my dual quad, and it took minimal tuning to get it to runs great (ran good right out-of-the-box though). Price is reasonable too...

I used to like Holleys, but for street cars I began swithcing back when the old Holleys would tend to blow powervalves. I think they have now revised the carbs to eliminate the chance of blowing the powervalve.

Quadrajets are pretty good if tuned right, but they are old and most will need a rebuild or an expensive new one, so I would go with the Edelbrock performer

Jim- thanks for the stang example. i have a holley 600 with vacuum sec. right now on my 355 and i leaks all over the place even thought it has been rebuilt 3 times. is this a problem with DP's?

1966 L78- thanks for the formula. i have a bad problem with buying into the "bigger is better" statement, so its good to have something to look at.

thanks to everyone else who replyed graemlins/waving.gif
-Jay

I'm gonna say it again!!

Summits latest cat. lists the satin finished Holley 300-36 at $125.95 and an RPM at $129.88, but check the rpm range of both!!

Holley = 1,500 to 7,200 and RPM = 1,500 to 6,500rpm...

Plus the fact that the Holley is a true high-rise intake definately gets my VOTE!! I personally think it is a GREAT buy!!

AND that Holley WILL do the rpm!!

pdq67

Ya the 300-36 is a very slightly modified version of Chevys 302 Z28 / LT-1 intake...I still have the 302 intake that I had on my 1st 327...and yes that manifold will take ya to 7200 if the rest of the engine will... Wouldnt be the best intake for say a 4500 rpm engine but for something from say 230 to 254
deg @ .050 cam it works great... Pretty tall tho and in some cars can cause hood clearence problems.

pdq67-sorry i must of overlooked your post when i was going through them. my friend did have that holley intake manifold on his 69 camaro with a 327 and he wouldn't of traded it for anything, he would wind that thing to 8 grand and he said he never had any loss of power. but what about bottom end and midrange power? is it down on those? becuase i can't afford a bottom end that can handle 7000 rpm even thought it would be nice. seems the high rise would kill some low end torque, and thats where i need my power most. thanks for any more info on this intake!

Imho, it's a dual plane and it's rated from 1500 to 7200 rpm so should have very good lowend for the types of cams needed to go to 7200 rpm..

pdq67

Every time I think I know what I'm going to use, something like this happens.

Shortly after I began coming to this site I searched and found a thread where Mr. Bigley said that all of his friends who ran 355's at the drag strip used the E-brock Performer RPM. These guys took the time and effort to try all kinds of different intakes and used track times to determine their choices.

Just checked Summit's site:
The 300-36 is for 87 and newer engines with aluminum heads.
The 300-36S is for 57-86 sbc's and costs about $190.
Could be a misprint on their website since the paper catalog states the 300-36S is a polished 300-36.

I think it wouldnt hurt to put this into historical perspective....

Now this is just my opinion but of the dual plane intakes that were generally available in 1967.... the OE 340/360 HP 327 , the Edelbrock C4B/C3B , The Weiand dual plane and the OE 302 Z28 intake...without question the 302 intake was the best for mid to top end power...it is not a small intake internally.It couldnt be small and still work at 7000 RPM.

The newer Edelbrock Perf RPM is a much newer updated design and how air leaves the plenum and enters the runners is totally different than the older intakes including the 302... Mixture distribution is better and it has a broad RPM range.Personally I would really rate the RPM for working best in the 2200 - 6500 RPM and the 302 Z28 / 300-36 intake as something that works best from 3000 - 7000 RPM range... There is nothing small about that 302 intake.... I think that for an under 5000 RPM engine the 302 isnt really the best choice.But for the mid to upper range it's quite good...but then again so is the Perf RPM and may be superior to the 302 in mid range torque.

Isn't this fun??

I've run the old GM aluminum intake and it was a great piece in it's day. Still good today..but the RPM air gaps are light years ahead in terms of airflow. If you can swing it and it will fit, I'd use it in a heatbeat on a typical 355-383 deal. Probably a 406 too depending on combo.

On carb sizing, all I can say is I've never seen a small block anything over 300" that couldn't use a 750 carb. I personally don't fall into the "formulas rule" category for everything. They are great to use to "think" through combos, but a lot of it involves "Theory Vs Reality". If you want to have fun, go to Edelbrocks site and check out THEIR carb sizing rules. They recommend MUCH larger carbs than most and add even more to anything running a dual plane since the motor "see's less carb area. I think Barry Grant and others go away from lots of this stuff too.

Check out the size of what Chevy put on their performance engines...even Q-jets were 750's. They had to know something.

I can tell you that over the years making lots of track runs, experience shows you can get a DP to out perform a vacuum almost everytime. Plus it may be personal preference, but for me in a "limited traction" situation, I much prefer using my foot to control secondary application vs the "rubber band" feel of vaccums. Having the ability to induce a slight little bog can be great to help get a street car moving and not spinning.

If your Holley is leaking...something is wrong with it. Most likely someone has overtightened the bowl screws and warped the main body or bowls. Check them with a straightedge. You can straighten them possibly with a flat file. Seriously, I've never had an issue with leaks. The carb on my motor right now has been around 10 years or so and has been opened up numerous times playing with it and I reuse the same gaskets all the time with no leaks. And they aren't even the cool new blue ones! Just the old brown ones.


JIM