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swirl port vs J heads

  
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swirl port vs J heads

 
_streetvan76. _streetvan76.
New User | Posts: 3 | Joined: 01/13
Posted: 01/19/13
10:21 AM

heard alot of good and bad between 302 casting swirl port and the 915 casting j heads. My original plan for my 360 was to use the J heads,have the 1.88 intakes machined to 2.02s,install a stock grind 340 cam and headers. Should I stick to this plan or should I go with the swirl port 302s for the increased compession.If I went with the 302 castings could I still use the stock 340 cam.Are there any differences or mods to be done to valve train conponents.Main reason I'm wondering about this is that I read that these 302 swirl port heads will out perform the J and X heads.But their port volume is alot less than the 915 j castings.Any thoughts,experiences or suggestions would be great!Thanks  

marcohotrod340 marcohotrod340
Enthusiast | Posts: 461 | Joined: 09/08
Posted: 01/20/13
08:45 AM

good question, is the 360 in a van, what rear gear? increased compression will be better at all rpm's , especially with the very low stock ratio of a 1972-198? that measures around 7.9:1 . A 302 (small intake ports and small, around 60cc chamber, 318 head) will give around 8.9:1 , but the small intake ports and valves will hurt power over 4500 rpm. A 308 1989-91 is a swirl 360 head that will not change comp. ratio, but flows better than a J head on the exhaust. the 302 and 308 could use the stock 340 cam and need no diffs or mods needed with components. a 2.02 intake will help a little over around 5000 rpm.  Magnum heads?  

_streetvan76. _streetvan76.
New User | Posts: 3 | Joined: 01/13
Posted: 01/20/13
02:47 PM

thanks for the info.yes the 360 is in a short wheel base van.Gear ratio is 3.23 in a 9.25 suregrip.Forgot to ask about if there would be any valve/piston clearance issues with the swirl port heads on the 360 block.  

marcohotrod340 marcohotrod340
Enthusiast | Posts: 461 | Joined: 09/08
Posted: 01/27/13
08:18 AM

the valve to piston clearance is the same from a j head to a swirl port head, if the valve diameters are the same.  

pepsi1 pepsi1
User | Posts: 150 | Joined: 10/11
Posted: 01/29/13
07:35 PM

Just a little FYI:
In general piston to valve clearance is only one clearance to be concerned about.
The piston dome to the head clearance is another to be concrened about.
  Remember the piston is chasing the valves at a very high rate of speed. (The Piston Loves the Exhaust Valves).
  I like to play it safe. "I know it looses compression" (Noone was paying my bills). A steel rod engine should have .080/.100

  An aluminum rod engine should have .100/.120. With the minimum of clearance on the piston dome to the head.

  You can always squeeze the piston as tight as you want, but you should always have a min. all around that piston. Determine that on a mock up build. Then stick with it through out your build.

Bob  

slohanjames slohanjames
New User | Posts: 8 | Joined: 12/07
Posted: 01/29/13
09:07 PM

I built a 72 360 bottom end with 96 Magnum heads and came up with almost 9 to 1 comp and a good hydraulic cam with lift in the 480 to 490 range and 286 to 290 duration it ran stout enough to smoke enough Camaros and Mustangs and most other modern muscle cars and trucks in a 87 Dodge Dakota shortbed.You'll have plenty clearance and if you want even more valve Manley makes a valve with a 2.00 diameter and any stem length you spec. With new hard seats cut for the valves I'tll cook.
I built this motor back when guys from Mopar Performance and Dick Landy Ent. said it couldn't be done. Now Landy performance sell's the same setups. LA bottom end with Magnum top using AMC lifters, Crane Cams rocker conversion pushrods cut to correct length and Chevy 1.6 roller rockers. Mopar Mi single plane intake for Magnum head, 750 Edelbrock good MSD ignition and you have a economic muscle motor.  

pepsi1 pepsi1
User | Posts: 150 | Joined: 10/11
Posted: 01/30/13
03:26 AM

slohanjames (Like the name)

Please don't shoot me, I'm an old gear head and I love automobies almost as much as my wife. If she were here she would tell you the same thing...I've been racing them and working on them for 48 years. I wish my boys were into cars. Their love is Motorcycles. My Dad raced the old Indians. Sorry it brought up some good ole' times.

What is being done with cams and under the curve. Cylinder heads have almost put us old head porter's out of business. I'm that way also, when someone says it can't be done I try harder to prove them wrong...

I also wondered if they said that to push us in another direction. If you know what I mean...Back in the day...Brodix Heads were the worst flowing heads in the business, when compared to GM Factory, MoPar, and FoMoCo Heads, out of the box....
I didn't care who was driving what. I've seen cross/breeding of all makes and models.I didn't care. If they needed help and I could help them I would...Thats my 2 cents.

It's the combination of the components. Then the track, the weather, now there's computers to compensate for all that..
  I ran a '68 Camaro for for nearly 40 years using Grumpy's old Pro-Stock 331 Cubic Inch set-up. As I made more power, I upgraded it of course. It was for Nostalgia Racing and shows that was really it. I sold it 2 years ago and I miss it. The guy that bought it wants me to drive it, for Nostalia Days and Shows.

Bob  

.71RedneckStroker_ .71RedneckStroker_
Guru | Posts: 848 | Joined: 11/09
Posted: 02/08/13
06:59 AM

J heads ARE swirl port heads. Read what Larry Shepard says about them in the Mopar Engine Book. They were swirling before Mopar even designed them to.  
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