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Posted March 18, 2005 at 12:47 am
Posted March 18, 2005 at 01:32 am
Casting number 4323302 is the "302" head. They were used in '88 through '91 on the 318. They have a smaller chamber and ever so slightly different angle on the pushrods if I remember correctly. I have never tried to interchange them onto a different year motor, I've read that the holes for the pushrods are drilled out bigger because the later years used roller cams instead of the previous hydraulic design, but I've also seen references to people having to do some work to put them on older motors. The small block hotrodding book that I'm reading specifically states that the motors that used the 302 heads can't accomodate older heads without work too.
I hear a lot of mention of "302" heads. How about a description, benefits, identifying, etc... Whats the scoop on these?
The 302 also had some swirling effects that aided operation, but I don't know if they're on the valve or in the port.
There's also some references here to the 360 heads referred to as "308/576", with the full casting number being 4323308 and 4027576, but the book says that these heads weren't used exclusively in their years (576 '77 through '79 police package only, 308 '90 up trucks), so they're harder to find. My '78 Magnum XE has an E58 motor in it, so one of these days I'll check the casting number to see if it's equipped with these, and if so, if I can find more of them for my other small blocks.
The book that I'm getting this info out of is How to Hot Rod Small-Block Mopar Engines by Larry Shepard.
Edited by TWX, March 18, 2005 at 02:20 am.
Posted March 18, 2005 at 02:49 am
The 302's came on 318s with the arrival of the roller cam engines in 1985. If your not sure of the donor car, look for an '86 or newer. If loose, they are easily identifiable due to the “heart” shaped chambers and smog injection holes. Older 318 heads had round chambers. (there were a few 273/318 heads from the 60’s with heart shaped chambers, but these don’t have smog injection holes)
302s have 57cc combustion chambers, compared to the older 318 heads that had 62-64cc, thats what raises the compression. The "swirl" is in the port, not so much the chamber, but one half appears lower so that probably keeps the mixture spining in the cylinder too. They are supposed to burn more efficiently, providing better fuel economy & lower emissions. The only drawback, is that the ports are narrower, then the already narrow older 318 heads. That was probably to facilitate the larger pushrod clearance. Great for street engines, but not so much for high RPM competition environments.
A popular upgrade is to swap-in the larger 360-sized intake valves (1.88), smooth-out some of the sharp turns in the intake ports, and enlarge the exhaust ports a bit. This is supposed to be good for a 50+hp increase.
Some guys also install the 360 exhaust valves (1.60), but most machininsts say it isnt nessesary. Other guys have also put in 340-sized intake valves (2.02), but that requires alot of material removal & is supposed to hurt the swirl effect. Which brings us to the 308 heads.
The 308 for the 360s are the ones that appeared in 88 in trucks. I dont think they were available any earlier. They did not come on E48 & E58 engines. 308s already have the 1.88/1.60 valves, and they are also advertised as "swirl port" heads, but they have larger port passages, so the swirl effect is much less. And the chamber size is much larger, somthing like 65-70cc, so if you use them on a 318, you'll loose alot of compression.
But they do flow better at higher RPMs due to the larger ports. If you were building a 360 for occasional high RPM competition, then the 308s with 2.02 intakes, and milled down for better compression, might work better than the old 340/360 "J" head which had been the most desireable head for many years.
Edited by Webslinger60, March 18, 2005 at 03:00 am.
Posted March 18, 2005 at 12:16 pm
I asked a number of questions over the past year about the 302 heads. Most of what I received back is what you have read above (higher compression from smaller heart shaped chambers - about .5, narrower intake ports due to larger push rod holes, swirl port etc.)
Even though these are considered smog heads, on a street engine my feeling is that they offer advantages. The primary one being port velocity over port volume. If your looking to build a high rpm screamer, other heads would probably be better. However, in typical driving or use in the 5,000 - 5,500 rpm range they seem like a very effective head. It is recommended that the 1.88 intake valve be used and port work to clean things up (especially the bowl under the valve). Some also install the 1.60 exhaust valve, but this can cut into the hardened seat and the info I got stated the intake change was more important than the exhaust.
One of the magazines did a test with a somewhat mildly prepared 318. The test with 360 heads produced 290 hp and the test with ported 318 "302" head produced 330 hp. As I recall max. rpm was about 5,200.
I'm putting mine on a 1973, 318 with an equivilent cam to the Edelbrock Performer (about 260 duration, .420 lift). The heads will have the ports and bowls cleaned up (home port job). I got my 302's at a Pick A Part half price sale for $25 each. So, in the end I would think it's application that makes the 302 heads viable if appropriately used.
Edited by wittsend, March 18, 2005 at 12:18 pm.
Posted March 18, 2005 at 01:25 pm
Posted March 19, 2005 at 07:29 pm
Posted March 19, 2005 at 08:56 pm
Posted March 20, 2005 at 12:30 pm
Edited by Gibons, March 20, 2005 at 12:30 pm.
Posted March 20, 2005 at 03:07 pm
If you dont go rhough the extra work to unshroud the 2.02's, I'm sure they would get their butt kicked by the 1.88's.
Looking at the dyno charts from the HotRod test, it looks like they flow great all the way up there in the RPM range. You wouldnt get a peak of 400 HP at 6000 RPM if the heads weren't flowing good
I read an article on compcams.com where they tested a reman 318 longblock with stock 302 heads. It had the XE 262 cam, and only peaked at 5000 rpm. The heads were choking it down big time. 6 degrees of duration doesnt get a 1000 rpm jump all by itself.
Posted March 20, 2005 at 10:44 pm
What did you do to them before installing them? I'm evaluating my options for a 360, and it looks like there's a place local to me that sells 360 short blocks for less than $600. If those heads are able to be ported to 360 sizing without too much work (ie, too much expense) then I might go for a set of them on that 360 instead of looking for better and harder to find heads.
I have a set of 302's on my fresh 360...get em and use em, yhey are GREEAT