302 heads

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j.d.duggan

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looking for heads for my 340.I just read a mopar performance page that said on a mild to moderate build that the 302 casting heads would outperform the large valve j or x heads.I wounderd what you guys thoughts were on this.I,ve been consintrating on 2.02 vaulves j or x heads that are way more exspensive.i,m basicly building a stock 340,just a fun driver.trying to keep cr down to about the 9.00 to 9.50 range.will the 302 heads work ok?i haven't found cc's on the 302,s.whats your thoughts:poke:thanks.
 
No way. small valve/small ports will not outflow 2.02 larger port J or X heads.

I'd put smog 360 1.88 valves on that 340 before ever considering 302's. At least the port and valve size would be more fitting for the 340.
 
If I already had a complete ready to go low cr 340 short block sitting there, and the motor was going to be used in a pick up or van that might be pressed into some “truck like” duty........ and I also had some very nice 302’s on hand that I could just bolt on and go....... then....... maybe I’d use them on a 340.

For any type of “HP” street car application...... I’d use something else.
 
There are some 576 heads for sale on here (the 360 Hi-po version of the high swirl head sold by MP) for cheaper than you could get them built. If I were looking for heads, that's what I'd run.
 
looking for heads for my 340.I just read a mopar performance page that said on a mild to moderate build that the 302 casting heads would outperform the large valve j or x heads.I wounderd what you guys thoughts were on this.I,ve been consintrating on 2.02 vaulves j or x heads that are way more exspensive.i,m basicly building a stock 340,just a fun driver.trying to keep cr down to about the 9.00 to 9.50 range.will the 302 heads work ok?i haven't found cc's on the 302,s.whats your thoughts:poke:thanks.
Yep, no way on a 340. The 302's have the closed "swirl port" chamber but they have 273/318 sized valves and ports.
 
Mopar Performance states that on a low compression 340 that the 302 heads are a 25 hp bolt on. I’ll try find the article Kim
 
I’m pretty sure you’ll find that was a test between the ported big valve(2.02/1.60) 302’s they were selling at the time, vs an unported 360 head.
Edit: I looked through my book, the MP ported 302 head used 1.88/1.60 valves.

In 1993 I was commissioned to revamp a couple of existing 318 oval track motors.
The owner was using 302 heads, which were bought new, because of the MP info.
The head rules for the class were unported heads, 1.88/1.50 valves.
On the flow bench the 596 heads were clearly superior....... but he wasn’t convinced that MP could be wrong.
The CR rule was 10:1, so I built up some 596’s, put some ex seats in them to facilitate the smaller ex valve, and milled them down to match the chamber volume of the 302’s that had 1.88 intake valves installed.
The intake used was a 360 2bbl intake with an adapter for the required Holley 4412 carb.

Put the motor on the dyno, tested both sets of heads.
The 596 heads were almost 40hp better.
That was the end of the discussion about the 302’s.

It was also the end of them getting their asses handed to them week in and week out.
 
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Yes, MP was guilty of pushing the swirled port heads too hard, especially the 302s. the 596 heads have great low lift flow, which is going to make more power than any 318 port head. I believe the last time I checked that the 302 head specs at 58 cc’s, but some measure as high as 61 and as low as 55, depending on what day of the week they were cast and what life was like at home at the time! To give you an idea how good the high swirl 308 and other casting number heads are, I can buy a set of 915J heads from a friend for $100 right now that need refurbished (ona running 318 no less, one sticky exhaust valve), but I am going to scour through his mid eighties truck 360 stuff to see if I can find a set of early small pushrod tube boss or other high swirl 360 heads. I’ll use the J heads if I come up empty on the other search. Low lift flow and superior exhaust ports are what makes these heads.
 
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I’m not saying there couldn’t be some combination of parts where the 302’s wouldn’t make better numbers, but I don’t think that’s going to be the case 99% of the time...... especially if you’re talking about using stock, or lightly reworked 302’s on a 340/360.

On a really mild 318, reworked by someone who knows how get a nice gain without spending too much time on them........ I can see where they might be the better choice.

But if someone is looking for a low buck head for a HP street 340/360....... imo, 302’s aren’t the answer.
 
If I didn’t have to go whack around so bad right now, I’d buy a set of aluminum heads right now...
 
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I have a pair of 302's on my 360ci. 11.3:1cr
Measured 234 rearwheel HP, powered through a 518 transmission on propane fuel.

I have a pair of Streetmaster heads coming my way.
Will be very curious to see what they achieve on the same engine and see how 'corky' the 302s are. Also plan to mill the alum. heads to end up with the same CR.
 
I’m not saying there couldn’t be some combination of parts where the 302’s wouldn’t make better numbers, but I don’t think that’s going to be the case 99% of the time...... especially if you’re talking about using stock, or lightly reworked 302’s on a 340/360.

On a really mild 318, reworked by someone who knows how get a nice gain without spending too much time on them........ I can see where they might be the better choice.

But if someone is looking for a low buck head for a HP street 340/360....... imo, 302’s aren’t the answer.
Agreed. The increase in compression from the closed chambers won't out power the large valves and ports of a 340 head. Especially on a 340 (or 360)
 
"just a fun driver" is quoted from the topic starter's post.
Which would most likely mean the cam chosen won't be anything above .500" lift,
Most likely a hydraulic cam.
Which also might cause the engine hardly to see any action above 5K rpm.

I don't see the 302's as 'bad' rightaway here. But.... the 9-9.5cr requirement will put them out.
And.... don't all 340 pistons end up sitting above deck? That would kill off any closed chambered heads as well I would think.
 
This is what I’m seeing from the first post:
I just read a mopar performance page that said on a mild to moderate build that the 302 casting heads would outperform the large valve j or x heads.

I read that as....”I don’t have any heads for my 340, and from what I just read..... 302 heads are actually a better choice for my moderate build than 2.02 valve X or J heads”.

And to that I say........ I don’t think they are.

If I have to buy heads to put on a hot street 340/360....... I’m not going to hunt down some crack prone 302’s instead of a set of 360 heads.

If original looks aren’t a concern, and you’re trying to make some power........ installing some EQ heads are going to be the best bang for the buck.
Just go the whole Magnum heads/valvetrain route.

If you’re only looking to make 325-375hp, some very mildly reworked 1.88 valve 360 heads will easily get you there.

Maybe the 302’s work fine on a milder combo, but after I did that dyno test with them in ‘93, they weren’t even on my radar.
 
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576 heads being a performance over the counter head do not have an exhaust heat crossover, so they may not be as street friendly as what is being looked for. Depends on if running an air gap.
 
I don't see the 302's as 'bad' rightaway here. But.... the 9-9.5cr requirement will put them out.
And.... don't all 340 pistons end up sitting above deck? That would kill off any closed chambered heads as well I would think.
Not completely; it depends in which pistons the OP has in his 340. For example, the Silvolite 1267's sit maybe .002 above nominal deck, and have 10 cc's of valve reliefs, so they would come in at 9.6 SCR with standard Felpro 8553PPT head gaskets and 60 cc chambered heads.

SO, OP, we need to have more info to answer your questions. Can you post a pix of the pistons in your engine block, so we can get a better idea of what you have to start, and then work from there? I can think of 4-5 different pistons that you may have and that needs to be nailed down to figure this out.

And OBTW, OP, the stock advertised 10.5 CR for the 68-71 340's was not reality.....it was more like 9.75.
 
I have had a few 340s and the pistons were .045 above deck. In fact I’m building a 1971 340 and the .040 over pistons measure right at .043 above deck. Kim
 
:drama:pistons are .013 out of holes,I'll try to put some pics on and let you see if you can id the piston brand and relief size.this short block was probably built 10-15 years back and ben sitting in a warehouse every since,as far as I know it,s a stock cam.felpro 8553 head gaskets are in kit I have and that's what I plan on using.325 -350 H.P. would tickle me for what I use my cars for.I have a 71 nova with a GM create in it that puts out about 320 H.P. and it's a blast to drive and very trouble free.It's been driven 44000 miles in the last 7 years and will get anouther 5-8k put on her this year,I drive my cars, and burning the tires is a monthly thing not a daily one.anything over 350 H.P. is a waste for what I do with my cars.MP had that write-up about the 302 or 308 small valve heads stock off the shelf adding 25 H.P.to the stock 340 and I thought would work just fine for me, because I can go down to the local parts store and buy a set for around $500.00 bolt them on and go.I figgerd to good to be true, but I do like to see the different opps I get on here.the pistons are L2316 I think.

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This is what I’m seeing from the first post:


I read that as....”I don’t have any heads for my 340, and from what I just read..... 302 heads are actually a better choice for my moderate build than 2.02 valve X or J heads”.

And to that I say........ I don’t think they are. Correct in my humble opinion

If I have to buy heads to put on a hot street 340/360....... I’m not going to hunt down some crack prone 302’s instead of a set of 360 heads. Agreed- total waste of time

If original looks aren’t a concern, and you’re trying to make some power........ installing some EQ heads are going to be the best bang for the buck. Bingo!!
Just go the whole Magnum heads/valvetrain route.

If you’re only looking to make 325-375hp, some very mildly reworked 1.88 valve 360 heads will easily get you there.

Maybe the 302’s work fine on a milder combo, but after I did that dyno test with them in ‘93, they weren’t even on my radar.Agreed again but you were way before me[/QUOTE]

In essence like I've said in the past--'302's are doorstops and they aren't really good at that either! J.Rob
 
Those indeed look like TRW L2316F/SpeedPro forged units.

With 60 cc heads, PT8553's and those pistons, you are going to be around 10.3 SCR. With the stock cam, the DCR will be in the low 8's which is tunable with care and caution and use of premium fuel. But I can understand wanting to be lower.

I personally would go with something with better breathing; it opens up the high RPM operation and help mid range too; just makes a better, more flexible street engine. My son and I just went straight to Edelbrocks on his 340 to get decent flow out of the box, got the efficiency and detonation resistance of the closed chambers, and the detonation resistance of aluminum, and never worried over running an 8:1 DCR.

Maybe go 308's, mill them some get the static CR up where you wanted, and forget the X and J.

The pistons .013" out of the hole and the PT8553 heads gasket would make an ideal quench gap with closed chamber head, to help stave off detonation.
 
For the OP’s desired 325-350hp....... any 1.88 valve 360 heads will get you there.
Just get some mid-70’s-80’s smogger heads in nice shape and have them gone through, and have a little bowl porting done.
915, 587, 974, 051, 596, 308...... any of those will work just fine.

If you’re having guides installed, convert them to 11/32 and use +.100” 1.94/1.60 sbc valves.
 
.030 over 340 with cast replacement pistons I originally built in the late 80’s.
I freshened it a few years ago..... rings, bearings, valve job, etc.

Pocket ported 587’s, 2.02/1.60, std Performer intake, Holley 650dp, headers, Comp 268h cam.

This motor was being used in a lil Red Express truck.

A very mild build that makes 325+hp for over a 1200rpm span, and willingly pulled 6k in the vehicle.
C95CD88E-891A-4D39-9E5D-88C40ED2F81A.jpeg
 
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