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Topic Review (Newest First)
11-14-2012 01:56 PM
gmtony55 Thanks guys. I will definitely check back and report my progress. My son is wanting me too rebuild so he can learn as well so this will be a great project for us. Thanks again to all that posted on this thread as You have helped me a great deal.
11-14-2012 10:51 AM
oldbogie
Quote:
Originally Posted by gmtony55 View Post
ok guys I am learning a little,now I'm in trouble.lol..I have some decisions made but have a few still questions. As I said before I have the performer RPM intake,but As I read it seems as though it is for a high rpm engine which I dont have. a 400 I am told to build for lower rpm. Keeping with low budget should I buy a performer intake that would fit my quadra-jet carb and just sell my RPM intake? Or would the money be spent better on a new carb and use the RPM intake?
The Performer RPM is just fine. It is though of as being a higher RPM mainfold than the regular Performer, yet in back to back testing the RPM gives up very little on the bottom end while having very substantial gains on the top end. It makes me wonder why Edlebrock even bothers to inventory the standard Performer as I don't see where it has a market except maybe for smaller less than 350 cubic inch engines.

This brings me to the next concept which is as an engine grows in displacement the need to feed the bigger breathing cylinders has the effect of bringing the power peaks of what are high RPM parts when used in a smaller sized engine downward in the RPM band and smoothing such effects as seen with aggressive cams. This is to a large extent effects that are related to mixture velocity.

For example, if you take an intake manifold, cylinder heads, and camshaft that would be suitable for a high performance 350 that let's say has a 400 horsepower peak at 6000 RPM with a semi-rough idle. These same parts on a 400 inch engine will generate 400 horses at say 5600 RPM and will idle smoother. They very likely will not make much more peak power from the 400 inch engine because they simply can't supply any more mixture. A classic test of this was done by David Vizard many decades ago where he use the 300 horse 327 cam on a 350. The 350 peaked out at 305 horses. Now there is a compresison ratio difference in the engines he tested the 327 having a ratio of about 11 to 1 where the 350 being built for unleaded fuel has a ratio around 9 which if corrected might have made a 320- 330 some horse engine out of the 350, but it still is an excellent example of the limiting effects on cam timing and what would be the related components of the heads and intake system as they relate to feeding a larger engine.

For some top notch reading that summerizes a lot of these concepts I'd recommend two of Davd Vizard's many books, these rather bring the detail subjects of his other books into a summary form that makes a lot of the connections between the various components to help you understand the integrated whole how the parts and concepts work together. Go here as many of David's books are out of print so you need to hunt for them. <<< David Vizard: books by David Vizard @ BookFinder.com >>>

My starting recommendations are "How to Build Horsepower Volume 1" and How to Build Horsepower: Carburetors and Intake Manifolds, Volume 2". These books really tie the complex engine internal subjects together. When you're ready for nitty-gritty by subject you will see that is covered as well. Some of this stuff you have to read several times to get the concepts and at that some concepts such as how compression, camshaft timing and power output relate are much more subtle than reading most any book makes clear. There is always on any subject an assumption that the reader brings some knowledge with them that isn't well defined by the book. We can help with this so don't be afraid to ask questions.

Bogie
11-13-2012 06:38 PM
hcompton
Quote:
Originally Posted by gmtony55 View Post
ok guys I am learning a little,now I'm in trouble.lol..I have some decisions made but have a few still questions. As I said before I have the performer RPM intake,but As I read it seems as though it is for a high rpm engine which I dont have. a 400 I am told to build for lower rpm. Keeping with low budget should I buy a performer intake that would fit my quadra-jet carb and just sell my RPM intake? Or would the money be spent better on a new carb and use the RPM intake?
The performer rpm will work good for 400. It is a good flowing manifold but the 400 will make use of it. Why not just buy a edelbrock carb they are cheap and easy to work on. Qjet is good to but since you already have an edel manifold why not go with carb or holley. No one ever says i hate my holley 750 double pumper. The same cant be said for qjets.
11-13-2012 06:21 PM
gmtony55 good..That will save me money for sure..thanks i appreciate the advice.
11-13-2012 06:14 PM
cobalt327
Quote:
Originally Posted by gmtony55 View Post
ok guys I am learning a little,now I'm in trouble.lol..I have some decisions made but have a few still questions. As I said before I have the performer RPM intake,but As I read it seems as though it is for a high rpm engine which I dont have. a 400 I am told to build for lower rpm. Keeping with low budget should I buy a performer intake that would fit my quadra-jet carb and just sell my RPM intake? Or would the money be spent better on a new carb and use the RPM intake?
The RPM will work fine on your 400. Use an adapter and the Q-jet.
11-13-2012 06:11 PM
gmtony55 ok guys I am learning a little,now I'm in trouble.lol..I have some decisions made but have a few still questions. As I said before I have the performer RPM intake,but As I read it seems as though it is for a high rpm engine which I dont have. a 400 I am told to build for lower rpm. Keeping with low budget should I buy a performer intake that would fit my quadra-jet carb and just sell my RPM intake? Or would the money be spent better on a new carb and use the RPM intake?
11-09-2012 08:07 AM
F-BIRD'88
Quote:
Originally Posted by LJM97Z View Post
Have to disagree with its hard to over cam a 400, you can over cam ANY engine, I over cammed my 406 & it had iron eagle heads & 10.4.1 compression, It was a bear to tune, sure it would rev too the moon, but it ETs & MPHs exactly the same with the mild cam that i had originally put in it & i shift it at 5000, not 62-6300, So if you choose a cam, choose wisely, I'd just keep it on the cheap, you could re-ring it, clean up the heads, all new gaskets/chain/oil pump, mild cam, then just install headers/intake/carb, It'll run very strong, even with the stock heads. This was the cam that i installed that hurt my 406.

510/510, 245/245 @50, 108 LSA, installed at 104*, even tried 102*

I have 4.11 gears & a 4200 stall.
You probabily found it "Hard to tune" because of incorect timing curve for the cam. This cam likes a locked out timing curve 36deg at idle.
Thats right , it needs full timing at idle to idle nice and clean.
And a 4.5" power valve. Without these two set up mods it will
idle like crap and have crappy throttle response. and tend to load up the plugs.
Once these set up mods are done it will be a whole different beast
especially with a 4200 stall and 4.11's.

Its a matter of set up. This is a very good street machine/ bracket cam for a 400sbc.
good power from 3500 to 6000+

The cam I run in my 406 is very very similar to this (it has the same exhaust cam lobe)
runs 11's, run fine on the street. idles rock steady at 900rpm, 750 in gear. can't be that bad.
set up makes or breaks the deal.

the 180cc Iron eagle heads suck. Is that what you had?
Very modest port flow out of the box for a 180cc head.
The 200cc and larger heads are the platinum series and a much better cylinder head.
The 180 is not a Platinum series head.

qjet to performer rpm carb adapter:

if you modify the proform 4 hole adapter like in the picture so its a split plenum design
it will allow the Q jet to work pretty good on a square bore manifold like the RPM.
Modify and blend the Qjet flange shape into the Square bore flange shape But keep the
plenum split intact.
11-08-2012 11:01 PM
cdminter59
sbc 400 heads

If you are running short on money I would get rid of the big cam and replace it with something like this. Summit Racing Street & Strip® Cam Kits SUM-K00042 - SummitRacing.com. If you choose to mildly port the heads follow cobalt327 advice. Just swap your intake and carburetor to the 400 motor. Then install it in your El Camino and have some fun driving it.
11-08-2012 09:17 PM
gmtony55 Ok thank you very much!!!
11-08-2012 08:48 PM
cobalt327
Quote:
Originally Posted by gmtony55 View Post
thanks cobalt..extremely good info. I will need an adapter because it had a holley on it before.

I been reading up on porting heads, It doesnt look hard to do at all just time consuming work. but I recarpet boats on the side so I am used to that..Do you think I should bother with that? porting that is.
Smoothing and blending the lip that's just below the seat helps (see arrows below). I wouldn't go much beyond that and cleaning up any casting flash or irregularities, though. Once you get in too far you can easily do more harm than good unless you're experienced.

Click on image for an article w/some porting info:

11-08-2012 08:41 PM
gmtony55 thanks cobalt..extremely good info. I will need an adapter because it had a holley on it before.

I been reading up on porting heads, It doesnt look hard to do at all just time consuming work. but I recarpet boats on the side so I am used to that..Do you think I should bother with that? porting that is.
11-08-2012 08:28 PM
cobalt327
Quote:
Originally Posted by gmtony55 View Post
I do have another part to this question. Is the stock carb on my 83 elco something I can transfer over or not?

It is a 4 barrel Q-jet
Yes, the Q-jet will work fine. You might want to tune it to match the engine its going on, but that would be the case regardless of what carb you were going to use. But if you want to use the Performer RPM- which is a very good intake- the Q-jet won't bolt up w/o using an adapter unless it's the Q-jet model RPM. In most cases an adapter will not be something I'd recommend. But unless you wanted to use another intake or a different carb, that's the route you'd have to take. And there is at least one test that shows only a very small loss using an open adapter to mount a Q-jet on the squarebore RPM intake.

If you DO use an adapter, use something like Edelbrock p/n 2693. Summit sells a similar one for a lot less although it might not move the carb back 5/16" like the Edelbrock adapter does. What you want to avoid is the 4-hole jobs (like Proform p/n 66253).

The Q-jet carb will almost surely be the 750 cfm casting, not the 800 cfm casting, although in practice there's very little real-world difference in the performance between the two. The 800 cfm casting does have a slightly larger primary bore and venturi, but compared to most any other similar size carb the primaries are still smaller- which equates to good throttle response and potentially better mileage.

BTW, it's a little known fact that the V6 4.3L GM trucks in the later years (up until '86) used a non computer controlled Q-jet w/the 800 cfm casting. I have one right here from a '86 4.3L V6 Sierra! Good place to source a Q-jet.

Good luck.
11-08-2012 08:27 PM
gmtony55
Quote:
Originally Posted by LJM97Z View Post
So if you choose a cam, choose wisely, I'd just keep it on the cheap, you could re-ring it, clean up the heads, all new gaskets/chain/oil pump, mild cam, then just install headers/intake/carb, It'll run very strong, even with the stock heads.
this is hitting it on the head.This is what I am going to do.

my head casting number is 3973493
11-08-2012 08:20 PM
gmtony55 Techinspector..this is very helpful and I apprieciate your time. the cam figures I must admit is over my head but I do get the keep it close to stock. I will definitely get the book you recommended. thanks again
11-08-2012 08:18 PM
gmtony55 this is very helpful and I apprieciate your time. the cam figures I must admit is over my head but I do get the keep it close to stock. I will definitely get the book you recommended. thanks again
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