thinking of using a set of 302 on a 408 small block build for the super coupe. i know they are a mild head for this engine,but i want a street engine,not a high hp twister,so..what are the chamber size in cc's???? thanks,mike
#302 head is a small valve/port head with a closed chamber 1.78/1.50
#308 is a 360 big port/valve head with open chamber,the exhast port on a #308 is better and the best head to use,1.88/1.60..they are known for cracking and they are hard to find also.
#302 heads would kill a 408 IMHO,unless they were max ported with bigger valves and would still hold it back.
#302 heads with 1.88/1.60 valves and a max port job will be good for around a 450 HP engine.
the bigger valves will increase flow and keep the port volocity up along with a comp ratio bump with the closed chambers.
I could be mistaken on the CC measurement but it is close IIRC
IMHO a 360 head/X heads with 1.88/1.60 or 2.02/1.60 valve size would be the better heads
Posted By: pishta
Re: need info on a 302/308 head - 03/05/12 04:38 AM
302 is a great head for a SB, its closed chambered head around 62CC's but has a intake shape that has a hard turn in it for the larger pushrod holes. I believe a stockish 318 head is about 65CC. 308 head is the 360 head, open chambered. I would use the 308 opened to 2.02 for the stroker though. Great exhaust post.
Posted By: MoparDan
Re: need info on a 302/308 head - 03/05/12 04:53 AM
several yrs ago, I was on a hunt for a set of 308 heads for my 416, the two set I found (salvage yard off the motor) were both cracked....then I took a set off a wrecked 92 truck (two three hours) took to machine shop only to find they were cracked
Finally I then took an old set of J heads I had laying around the shop put in ss 2.02 1.60 purchased a MP porting template kit and I'm prally pleased with the performance
If you really want new....I would recommend the Hughes LA-X iron heads: 'heart' shaped chamber, larger port size, 1.92 - 1.60 and for about $1100 you will have a great set of heads...
Posted By: HotRodDave
Re: need info on a 302/308 head - 03/05/12 05:02 AM
If you don't already have a head then you should look at magnums, they make more HP, TQ and MPG than ANY of the older ones either stock VS stock or ported VS ported. They have a better chamber, better ports, lighter valves, higher rocker ratio, better valve cover sealing... they do almost all have cracks but they don't ever seem to have any issues from the cracks.
If you are bound and determined to use the older heads you have to make compromises, X heads flow best by a tiny bit but no hard seats, 302 is closed chamber but flow sucks, 308 has good quality flow but very sucky chambers, really though all the big port 360, 340, 318 4bbl heads have horrible chambers. If I could pick any LA head for a street stroker it would probably be (reluctantly)a 308.
Posted By: dogdays
Re: need info on a 302/308 head - 03/05/12 05:10 PM
I am going through a set of 302s and there's no way I'd expect them to be up to a healthy 408. I think they'll work pretty well on my mileage 318.
One thing that no one touches on is that the intake valves are shrouded and when you put in larger valves it will only get worse.
The only thing that rescues these heads from the scrap heap of mediocrity is the chamber.
BUT, listen to your Uncle Dave. If you have no heads at the present, go for Magnums. They're much better flowing stock, really good chamber, etc.
R.
Posted By: Supercuda
Re: need info on a 302/308 head - 03/06/12 12:52 AM
I ran a set of stock 87 302 castings on a mild 79 360. Simply because I had them and the stock 79 heads tore out an exhaust stud that had already been repaired.
In an 87 Diplomat I lost about 15-20 mph top end (115 vs estimated 130'ish on the cop speedo)compared to the stock 79 heads and a set of J heads I tossed on it later. However, I gained lot's of low end torque and with an Edelbrock 1406 carb I would get low - mid 20's for mpg.
I would not use them for anything hotter than a mild 360 myself and only if I had a set lying about. If I had to buy a set of heads I would start with Magnums at the least.
Posted By: RUNCHARGER
Re: need info on a 302/308 head - 03/06/12 02:49 AM
We're building an interesting 360 for my kid's 360. It is a rock crawler so it needs to run at an angle and have lots of response.
I found some rare DC, forged 11.5-1 pistons on Moparts for it and we are going to try the 302 heads we have on it and run it on propane. I am expecting it to be very responsive on the low end and able to run properly at an extreme angle. We haven't chosen a camshaft yet but I'm sure it will be all done by about 4500 RPM.
Sheldon
Posted By: GO_Fish
Re: need info on a 302/308 head - 03/06/12 03:11 AM
I suppose to get 11.5, the DC pistons are domed above deck? What's your plan to work that with closed chamber heads?
Posted By: RUNCHARGER
Re: need info on a 302/308 head - 03/06/12 04:06 AM
We'll mock it up and probably machine just what needs it to zero deck.
Sheldon
Posted By: HotRodDave
Re: need info on a 302/308 head - 03/17/12 07:21 PM
The SP2P is just a throttle to slow down the engine, it has pretty bad fuel distribution and seperation issues, running it at weird angles will cause more issues. Ther is a real good reason they replaced it with the performer. This is one engine where the regular performer will shine.
Posted By: RUNCHARGER
Re: need info on a 302/308 head - 03/17/12 07:55 PM
He's got a stock 360 intake, LD340 and a Holley SD to try on it. My vote is the stock 360 intake, we'll see what works best.
Sheldon
Posted By: DARTH V8Я
Re: need info on a 302/308 head - 03/17/12 11:29 PM
Thats why I said, 'your results may vary'
Dyno sheets? ha! long gone! But I'm sure they fudged the numbers ALOT. Seat of the pants maybe 420ish..
Its always been an upper-mid 11 second car (4-speed/3.91's). life isn't always about flow#'s
I should add, never hit water with the porting, but did break through the pushrod wall. Sleeves w/brazing took care of that.
Posted By: 340duster340
Re: need info on a 302/308 head - 03/18/12 05:09 AM
What do you use to plug the smog pump holes on the heads under the exhaust ports.?
Posted By: dogdays
Re: need info on a 302/308 head - 03/18/12 05:58 AM
Drill the passages with a 13/64 bit and tap with 1/4-20 tap. Screw in anything you feel like, set screws work.
R.
