Click here to search for Mopar cars and parts for sale.


Moparchat - Home of MOPAR enthusiasts worldwide!  

Go Back   Moparchat - Home of MOPAR enthusiasts worldwide! > Technical Forums > Circle Track Chat
Register FAQ Members List Calendar Mark Forums Read


Welcome to the Moparchat - Home of MOPAR enthusiasts worldwide! forums.

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.
Reply
 
Thread Tools Display Modes
  #1  
Old 12-15-2004, 03:50 PM
DonCarr's Avatar
DonCarr DonCarr is offline
Registered User
 
Join Date: Oct 2003
Location: Prescott, Canada
Age: 50
Posts: 242
Default Seeking head porting advice - 318 with 302's

This is a question of "how far to go". Have collected the tools to do the work myself. Stubborn, meticulous and willing to make mistakes (common Mopar traits ?)

Have 318, hydraulic cam (235/0.507), Holley 4412 (2 barrel), cast iron exhaust manifolds, cast iron single plane 318 intake adapted for 4412.

Please resist the temptation to tell me to build a 360 (coming later).

I believe the port size of the old 318 intake may limit the practical size of valves used. Is this so?

Can I cram 2.08 valves in there? Is there enough meat on the short side for porting? Will better low lift numbers mean anything ?

Or is this way over the top for these ports? Should I stick with stock valve sizes or 1.88? Idea is if I have to buy new valves, why not go huge?
Reply With Quote
  #2  
Old 12-15-2004, 08:35 PM
dwc43's Avatar
dwc43 dwc43 is offline
Banned
 
Join Date: Sep 2002
Location: Shelbyville,Tn.
Age: 45
Posts: 23,988
Talking

Get a set of X,J, or U heads and install 2.02 valves and use a dual pattern cam to get more out of the exhuastside and have your manifolds extrude honed to a larger size. The truck R/T '92 and '93 years work the best.
Reply With Quote
  #3  
Old 12-16-2004, 01:30 AM
DonCarr's Avatar
DonCarr DonCarr is offline
Registered User
 
Join Date: Oct 2003
Location: Prescott, Canada
Age: 50
Posts: 242
Default Cheap, cheap, cheap.

Would 360 heads not gut the compression. Guess they could be massively milled. Then it would likely make more sense to use a 360 2-barrel intake. Must admit this would be a better idea. Then again might as well build a 360.

Guess I have to add one more point. I want to beat the Chevy 350's in two neighbors street stocks - with a lowly 318. It just wouldn't be the same to beat them with a 360 or a too highly tuned 318. Their 350's kinda suck anyhow. This is a grudge match. I have heard just too much lip flapping for Chevies and against Mopars.

I'd love just to port the heads with the stock valves to see if that would beat them. Just wondering how far these heads will go with valve size - and that old 318 intake. (it just looks cool).

I should be able to report on the duel in the spring. If the 318 won't destroy them I have a 360 in mind.
Reply With Quote
  #4  
Old 12-16-2004, 08:32 AM
dwc43's Avatar
dwc43 dwc43 is offline
Banned
 
Join Date: Sep 2002
Location: Shelbyville,Tn.
Age: 45
Posts: 23,988
Talking

It's just not worth the money to port the 318 heads when bolt on 360 heads will out do them. You will still need the valve change plus all the cost to port them. It would be cheaper to get the 360 heads and 2.02 valves and mill them some and go from there. The 360 intake will flow better too. And you will already have the top end ready for transfere when you get the 360 short block finished. Besides, they wont know the diff from 360 and 318 heads.
Reply With Quote
  #5  
Old 12-18-2004, 03:01 PM
DonCarr's Avatar
DonCarr DonCarr is offline
Registered User
 
Join Date: Oct 2003
Location: Prescott, Canada
Age: 50
Posts: 242
Default Conflicting information

I tend to agree that with all out power, the more head flow - the better. To me, this would include even relatively stock engines. My gut tells me that the ram or tuning effect of an engine would be very small. Yet we see other makes of engines with lousy torque curves, ie a boss 302 or stock 350 Chevy. Why do dyno charts of relatively stock Mopar engines tend to pound comparable Chevies and Fords. It can't be just the head flow or slightly longer connecting rods. I tend to think the higher deck height of Mopars results in a wider intake manifold leading to longer intake runners.

Does a Mopar 440 not have crappy heads, yet results in an earthpounding combination that stacks up very well against big port 454's and 460's ?

And so the lowly 318 with the small intake runners. My first impression is to toss the heads and intake - go with 360 heads and a single plane intake. But the RPM intake will trash single planes at moderate power levels. What's up ?

I have the MP dyno chart of great controversy in front of me. It shows a .450 lift 318 with good rings and 9:1 compression and stock 360 heads at 270 HP (no stock 318 head data). A swap to ported 360 heads comes in at 300 HP. To everyone's surprise the 1.88 valved and ported 302 head came in at close to 350 HP. The name of the game here seems to be that "tuning" of the ports has more effect than airflow.

I suspect that the test did not adjust for compression ratio losses in the 360 heads. This would bring the numbers closer. Yes the information presented from MP is very vague to the point of being bad.

To support the MP theory of port velocity tuning (ram effect) I found an interesting article on compcams website. http://www.compcams.com/Community/Ar...?ID=1826270359
A 318 (non-302) with pocket ported stock valve heads, cam and 9.8 compression made 324 HP and 370 TQ. A well ported 360 head made 346 HP and 381 TQ. Again, who knows what happened to the compression ?

To me, I speculate that large valve, well ported 302 heads will easily tie the large valve well ported 360's (at the same compression ratio), maybe beat them (At the 350 HP level). The 360 heads will blow the 302's away at some higher HP level. Ported 302's should make better TQ below 2000 RPM - if that even matters.

So lets say we have a tie between 318-swirl and 360 heads. I'm curious what would happen when the Holley 2 barrel and cast iron exhaust manifolds are introduced?

I tend to think the port velocity will be more critical than head flow at the reduced HP level. (I could be wrong - this is a guess. So, I'm still fascinated with the old cast iron single plane and ported 302 heads.

And yes, the whole story should change when speaking of a 360.

Guess I'm still conflicted. Port velocity seems a difficult subject.
Reply With Quote
  #6  
Old 12-21-2004, 02:50 PM
cageman's Avatar
cageman cageman is offline
Registered User
 
Join Date: Dec 1999
Location: Bismarck ND
Age: 36
Posts: 5,517
Default

I think the reason you dont see them putting big valves in the 318 is that it hurts more than it helps, it puts the valve closer to the cylinder and actually closes off the airflow around that part, so before with the small valves you were gettiong 360 degrees of flow around the valve and now you are getting like 180 degrees with the bigger valve.

I have a 318 in a 70 3/4 ton. It has 273 closed chambers, 488 lift, alum intake, 500 holley and hedders.
I think the trick to this motor is the compression and the cam. It kind of sucks at idle, but it pulls that truck hard. I just wish I had a better tranny in it, the shifter is a mile long and the gear spacing is really bad, You have to start in second then turn it real hard, then it lugs in to third, If I could get a tranny to keep the rpms up there it really would perform.
The downfall to the compression it has is I have to bring the timing way down to run pump gas, and it runs like a sick dog then,
So if all you want to do is beat a 350, there really isnt a challenge.
Put a set of milled 318 heads on and a better cam like 455 and it will run.
__________________
If my old Dodge pickups were woman, I'd be a pimp.
Reply With Quote
  #7  
Old 12-21-2004, 04:58 PM
dirttrackracer dirttrackracer is offline
Registered User
 
Join Date: Jan 2001
Location: Boyd, TX USA
Age: 55
Posts: 789
Default

The 1.88--1.6 valves will help that head a lot. 2.02 are to big. get the compression up as high as u can say 14-1 (requires race gas) and you will be able to run with the brand X's. The compession is really the best thing you can do for a 2bl motor helps torque off the corner and brakeing going in.
Reply With Quote
Reply


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

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

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


Want to contribute to Moparchat?  Click below!




120x60_green

rollback0306_120X90.gif




New 2006



468 x 60 with phones
2GB Totally Free Online Backup!  Compliments of Mozy!


All times are GMT -4. The time now is 12:11 AM.


Powered by vBulletin® Version 3.6.3
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.

www.pchelp.com

Forums Directory