RPM Air Gap on BBC - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 06-12-2011, 08:43 PM
31fordcoupe's Avatar
Registered User
 

Last journal entry: Gunked up 454 water jacket
Last photo:
Join Date: Dec 2008
Location: Las Cruces, New Mexico
Posts: 280
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
RPM Air Gap on BBC

Hey guys just bought a 1984 Chevy 1/2 truck with a 454 (I was told the 454 was transplanted out of a motor home). The trans is a Turbo 400 and I haven't pulled the 12 bolt cover yet but I am thinking the gears are around the 3.50 to 3.70 range. It currently has the factory cast iron intake on it with a Edelbrock 600 CFM carb and cast iron exhaust manifolds.

The truck is basically going to be used for towing and the occassional cruise night out. I am looking for good low end and mid-range performance.

I am thinking about putting a Peformer RPM Air Gap intake on it (because that is all I have as far as a performance intake) and a 750 Holley VS carb and some headers. Might go with a mid range cam later. You guys have any suggestions on the combination for my desired use? I know the RPM Air-Gap is probably not the first choice in intakes out there but that is what I have and I don't want to spend a bunch of money on the mods (rather use what I have). Better to stay with the cast iron intake? Let me know your thoughts. Thanks.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-12-2011, 09:38 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,794
Wiki Edits: 326

Thanks: 744
Thanked 956 Times in 806 Posts
One person can't possibly build and dyno all the possible combinations in cast iron, but he can do a bunch of them with software like I do with my DynoSim. All the tests that I have run in the past year show the RPM as the best carburetor manifold to use from idle to 6000 rpm's. If I were buying new, I wouldn't care about the Air Gap part of it, choosing instead the standard RPM. It's just a matter of personal choice with me.

Some fellows have argued that the RPM doesn't begin making power until 1500. OK, when's the last time you needed power at 1400 rpm's? Get real!!
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-12-2011, 09:40 PM
31fordcoupe's Avatar
Registered User
 

Last journal entry: Gunked up 454 water jacket
Last photo:
Join Date: Dec 2008
Location: Las Cruces, New Mexico
Posts: 280
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks tech. So just to clarify for me, and since I already have the RPM Air Gap, should I use that instead of the cast iron intake?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 06-12-2011, 09:41 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,794
Wiki Edits: 326

Thanks: 744
Thanked 956 Times in 806 Posts
Quote:
Originally Posted by 31fordcoupe
Thanks tech. So just to clarify for me, and since I already have the RPM Air Gap, should I use that instead of the cast iron intake?
In a word, yes.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 06-12-2011, 09:46 PM
31fordcoupe's Avatar
Registered User
 

Last journal entry: Gunked up 454 water jacket
Last photo:
Join Date: Dec 2008
Location: Las Cruces, New Mexico
Posts: 280
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for the response Tech.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 06-12-2011, 09:55 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
If you have peanut port heads, a cast iron intake and a Q-jet, you'd be better off w/it. But you do whatever you want.

You will get more of a performance gain by recurving the distributor than you will w/an intake/carb swap, anyway.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 06-12-2011, 11:13 PM
31fordcoupe's Avatar
Registered User
 

Last journal entry: Gunked up 454 water jacket
Last photo:
Join Date: Dec 2008
Location: Las Cruces, New Mexico
Posts: 280
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I haven't pulled the valve covers yet, but I will be amazed if they are not peanut ports.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 06-13-2011, 05:48 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by 31fordcoupe
I haven't pulled the valve covers yet, but I will be amazed if they are not peanut ports.
FWIW, as an 'experiment', in the late '90's I built a 468 BBC and used c/n 236 PP heads, ported to about 225cc, w/stock valve sizes. It ran very well, considering. I never had a chance to run it at the strip, but it would have easily outran my 455 Pontiac that ran mid 12's. Both engines were in my trusty '80 Camaro "mule", a car that had a dozen different engines in while I had it, from the 229 V6 it came with, to a 472 cid Caddy engine and everything in between. Oh, and the 468 was using a stock cast iron Q-jet intake and Q-jet carb.

A couple months ago, Car Craft did a test of a Demon Engines crate BBC 4-bolt 454 +0.030" (461 ci), Peanut Port heads (118cc chambers = 9.4:1 CR, stock valve sizes) w/a XE 268H Comp cam (.515"/.520" lift, 224/230 @0.050" duration on a 110 LSA), w/a Holley HP 750 carb and a (too-large) set of 2.25" headers.

It made 446 HP @ 4900 RPM/542 TQ @ 3600 RPM.
This was on the Westech Superflow dyno. I'm guessing this was "corrected" numbers. 490 ft/lbs @ 2500 RPM. There's no doubt the numbers would've been better w/a smaller primary header diameter, IMO.

Now, I'm not going to recommend everyone run out and bolt up a set of PP heads- but the point is, the PP heads can be effective- it depends on where you want the power, how much you want to spend and what you have to work with, etc.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 06-13-2011, 07:25 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by cobalt327
A couple months ago, Car Craft did a test of a Demon Engines crate BBC 4-bolt 454 +0.030" (461 ci), Peanut Port heads (118cc chambers = 9.4:1 CR, stock valve sizes) w/a XE 268H Comp cam (.515"/.520" lift, 224/230 @0.050" duration on a 110 LSA), w/a Holley HP 750 carb...
The intake used was a dual-plane intake from Procomp, in case it sounded like it was a stock piece being used.

PP heads cannot be opened up to match an oval port intake, but a lot of PP heads are running around w/mismatched intakes- the only intake that I knew of that was actually made for the PP heads was the Weiand p/n 8017 Action Plus but it has been discontinued for soime time now. Might score a used one from eBay, etc.

Article in it's entirety HERE.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 06-13-2011, 07:02 PM
31fordcoupe's Avatar
Registered User
 

Last journal entry: Gunked up 454 water jacket
Last photo:
Join Date: Dec 2008
Location: Las Cruces, New Mexico
Posts: 280
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks Cobalt. I always appreciate your input.

I too have ready articles about mods to PP heads and getting pretty substantional torque and HP gains.

I am just looking for something that is going to help me maximize bottom end torque and some mid range performance.

I have the 600 CFM Edelbrock carb on their now and was just thinking about putting my 750 Holley on there just because I understand how Holley's work more so than Edelbrock carbs (never had real good luck with Edelbrocks).

Figured that a 600CFM carb might be a little small for 454 that will potentially operate up to the 5000 RPM range.

I just got some 1.75" primary headers for it and those will get installed soon. I might add a low to mid range cam later so I am just trying to weigh the pros and cons of the cast iron intake vs. a mismatched (ports) RPM Air Gap.

Thanks again.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 06-13-2011, 09:10 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by 31fordcoupe
Thanks Cobalt. I always appreciate your input.

I too have ready articles about mods to PP heads and getting pretty substantional torque and HP gains.

I am just looking for something that is going to help me maximize bottom end torque and some mid range performance.

I have the 600 CFM Edelbrock carb on their now and was just thinking about putting my 750 Holley on there just because I understand how Holley's work more so than Edelbrock carbs (never had real good luck with Edelbrocks).

Figured that a 600CFM carb might be a little small for 454 that will potentially operate up to the 5000 RPM range.

I just got some 1.75" primary headers for it and those will get installed soon. I might add a low to mid range cam later so I am just trying to weigh the pros and cons of the cast iron intake vs. a mismatched (ports) RPM Air Gap.

Thanks again.
If you are using an adapter on the Q-jet iron intake, w/a 600 cfm carb, go ahead and put the RPM on there w/the 750. The squarebore 600 carb/Q-jet adapter combo is a losing proposition, and there's no way the mismatched intake manifold ports will be as bad as that combo. If you use an aftermarket cam, the adapter/600 carb would be even more of a handicap.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 06-14-2011, 06:39 AM
Member
 
Last photo:
Join Date: Apr 2004
Location: Georgia
Posts: 3,578
Wiki Edits: 0

Thanks: 10
Thanked 61 Times in 39 Posts
Quote:
Originally Posted by cobalt327
If you are using an adapter on the Q-jet iron intake, w/a 600 cfm carb, go ahead and put the RPM on there w/the 750. The squarebore 600 carb/Q-jet adapter combo is a losing proposition, and there's no way the mismatched intake manifold ports will be as bad as that combo. If you use an aftermarket cam, the adapter/600 carb would be even more of a handicap.
Please clarify for me, I know the 600 carb is to small but if that QJET was say 800cfm are you saying the adapter is killing me??
Or are you saying the QJET is killing me?

Thanks
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 06-14-2011, 07:28 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by BarryK
Please clarify for me, I know the 600 carb is to small but if that QJET was say 800cfm are you saying the adapter is killing me??
Or are you saying the QJET is killing me?

Thanks
It would be the adapter that would disrupt airflow, and yeah, the 600 cfm carb is on the small side for max output. A Q-jet on a spreadbore intake would work great (or a Q-jet on an intake that accepts both a square- and a spreadbore carb like many aftermarket intakes).

Some adapters are better than others, but none of them has as good of flow as using a matching carb and intake flange. In the case of the stock Q-jet intake where there are 4 separate holes instead of like an aftermarket dual plane that has 2 open sides divided down the middle, the flow disruption can be even worse w/an adapter. Also the shorter the adapter the worse, and a short adapter w/4 holes is the worst of the worst, IMHO.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 06-14-2011, 10:42 AM
Member
 
Last photo:
Join Date: Apr 2004
Location: Georgia
Posts: 3,578
Wiki Edits: 0

Thanks: 10
Thanked 61 Times in 39 Posts
Thank you sir!

I had a funny feeling when I kicked in the secondaries, like I needed to be setting on the engine pouring a gallon of gas in the carb.

I have spent days rechecking everything on this engine and then this weekend I took my neighbors holly 850 and it was like a different engine, today drove it to work with the quad back on and I think I best summed it up to an employee, its like driving 400 hp with a one barrow.

Thanks again.
Reply With Quote Quick reply to this message

Recent Hotrodding Basics posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 09:02 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.