79 360 cam selection

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goldduster318 said:
This is exactly what I have. Stock late '70's pistons (flat top), 0.060" down the hole, etc. There won't be ideal quench, but if you've ever taken the heads off a stock magnum 360 (I have), you'll find the pistons are still down the hole about .040 and are dished. They also run a 0.054" head gasket and I run LA head gaskets which are 0.041". What he would end up with would be within the factory tolerances for a stock 93+ 360 magnum. If the LA heads were better they would have kept them.
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.060?
I've taken 3 sets off due to cracking into the exhaust ports from & just off the seats
You're forgetting the magnum motor was not pushing any compression/octane boundrys or anywhere near the limits of pump octane, so just because they had the closed chamber does not mean it did anything when it came to octane vs actual comp ratio, the cylinder pressure was weak , as in 'stock' like 135-140 maybe dynamic/cranking.
I really like the idea of a dish and closed chamber, but in that example it's yielding squat for new found hp cause the quench & compression is not there.

They made the switch in heads to save money and more easily meet emission standards, the mags are a thinner casting closed chamber head, the rockers require less material/money to produce, the also used the 1.6 with a roller on top of that so they could lift the valve very lil yet a lot faster to make up for the lift loss/lil dur, they also run them 200 or so to keep them hot for emissions, too bad they didn't consider this when deciding on using a thin casting head.
Performance was not really in the design of magnum heads 1st and foremost.


I've also been running 16 degrees of timing up front and 36 total (in at 2200rpm) with a 4-speed on 89 with no pinging.
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I run 87 octane with a ported x head 340 w/ kb243 flat tops, that come out of the hole .019 w/4spd 26* intitial/34*total.
I have a 410 stroker that has 10.1 comp, ported open chamber J heads w/11/32 stem 2.02/1.60 with quench dome hypers set at .038 q dist cranking 175psi w/89 octane, haven't tried 87 yet.

if you keep the cranking psi to around 175, you can use open chamber heads all day long...now if you do some prep work 'like correcting the chambers to the bore size being used, polish the chamber a lil, you can go higher.

If you're buying an intake anyway, the mag intake is hardly different in price. Junkyard the heads and rockers, and head bolts, buy some 7.650" pushrods and you're ready to go. "LA" valve covers bolt right on.
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That must be based on a rebuilt set of magnum, cause wrecking yard magnums at this point, unless redone, will be worn out and junk, and the springs are beehive and WAY to weak for anything beyond a stock magnum cam.
The average set of LA heads are in need of a valve job, and have all the same spring limitations as the magnum heads. Most people also aren't going to spend the money to get serious head milling done (would make up the price difference for the magnum parts), and then you still end up with an open chamber turd anyway. Magnum heads start at 10cc smaller than LA heads to begin with.
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What do you mean by spring limitations, cause they use 2 diff styles of springs to start, and the LA head will work with 'no magic' in the 1.65-1.75 inst height range all day, mine are set a 1.80 for instance.
all heads are gonna require the spring seats to be machined for inners if a double is gonna be used, and guide to retainer/cut to .500-.530 for positive seals

Case in point...I've been trying to sell a decent set of 2.02 intake "J" heads with good springs and bronze valve guides that came with the 340 I bought....and there's been little to no interest. I don't think that's a coincidence.
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You can still find those heads everywhere, why would someone buy yours when when they could have their own done and not pay shipping and not wonder what was actually done or NOT done to them?

Not only that, but you can buy NEW RHS heads that flow like mildly bowl blended j/x heads, have all the closed chamber crap that people think is gona make or break their combo AND have shaft mounted rocker setup on them.
 
The MP 360/300 was a production magnum engine with the super tiny cam and made 300hp with no modifications whatsoever. Not to mention the 380hp one was known to make well over 380hp with the stock heads and had some compression and cam. Power to be reckoned with by any stretch of the imagination.

I doubt they saved any money. The 302/308 heads were likely the cheapest to produce out of any that could have met the requirements...they are LA heads and are known for cracking too. The R&D time alone on the revised valvetrain, not to mention all new tooling would have been very expensive. I doubt they would have done it just to save money. The 318 alone picked up 55 hp between premagnum and magnum versions. They did it for better performance+cleaner emissions+better fuel economy. Also, as you say, the RHS heads are even made on this design (castings are slightly different, but they are a magnum design)

Your 340, unless the heads are cut probably has 9.3:1 or less compression. And you also must have an ignition kill switch to be able to start that thing with that much initial timing. I tried to run more initial timing and the denso mini starter can't turn my low compression engine over at more than 18 degrees when hot.

Fuel injected heads/blocks are always in better shape than ones from carb vehicles as long as they weren't run too lean. Mine were not cracked, had 135,000 miles...they were run with CNG, really not any valve guide wear. Passed the kerosine test too with no problems. I have the mopar springs and retainers, but for under 0.500 lift, the 3100 springs are very cheap. Hughes has springs and retainers for a bit more installed height. The stock installed height is roughly the same on stock LA and magnums, so you are buying springs anyway.

I did sell another set of magnum heads that were very low mileage the other day and were also not cracked. The 318 with 175,000 miles that I swapped out for a 360 in a dakota because the block was cracked didn't have cracked heads either, and that 360 I put in also didn't have cracked heads. Its all overblown.

Since I live in metro detroit, there are a lot of mopar people here...still no interest in the J heads...craigslist or not.

I will be using the RHS heads in my build.

Whatever though...you want to run ancient "technology" or use dome pistons to get the same effect as a closed chamber head, go ahead. Nobody runs open chamber heads in new engines anymore, and they make more power than ever. He can run those 72 cc heads with very far down the hole pistons and get lit up at the track by a V6 mustang....or a Honda. Heaven forbid we go away from what we used in 1985.

My "doesn't help" combo is substantially more powerful than it would be with the identical cam/intake with the LA heads and the 7.8:1 compression I would have had with the original 974 heads. And it all bolted together and nothing went to the machine shop. I spent something like $900 on the whole thing, but w/e. It just sounded like exactly the same thing our topic starter wanted to do. I also have a milder cam than even the MM article. That Chevy guy that lost terribly to me in his camming out, aftermarked head equipped 350, lots of other aftermarket parts Nova was sure surprised. My tires didn't even hook in first.

In this case, he will get an extra half point or so of compression with no machining. The best setup would be to buy some cheap zero deck pistons and do a re-ring. Not everyone wants to do that so why I brought up the benefits of using magnum heads.
 
skyhawk61 said:
The May 2001 issue of Mopar Muscle had an article doing pretty much what you are trying to do. They started with a junkyard .040 over 360-4 bbl out of a Dodge truck and built it on the cheap, step by step. The initial dyno baseline (stock) showed 266.2 hp at 4300 rpm and 371.3 ft/lbs at 3300 rpm. They tried different component combos and finally got 335.6 hp at 5100 and 400.6 ft/lbs at 3700 without spending too much and with stock heads. Note that this engine was to be used on the street and had to pass a smog inspection. I'm getting ready to do a similar project on the 360 that's in my 79 Chrysler 300.
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this helps the op more than just about any other post so far.

more info on the cam,intake,carb,exhaust for the op would be great.
 
I love the fact that everyone here is giving me some ideas and input on all of this stuff, cant thank you guys enough!
As for fish's question with the exhaust, i was gonna do standard 1 5/8 headers with the three inch collectors, dumped. it was ok on the three forty i had like five years ago, but if i need some more pressure i have three inch flowmaster dual chambers that flange right to the header. Trans has a reverse pattern shift kit in it. does anyone know what the part number is for the b&m plate is?
 
I had it, have the part laying around here, just can't think of the numbers. Try calling Summit racing and let'em know what your doing. I believe they can help ya.

On your exhaust, FWIW, ya might wanna look at a summit or jegs exhaust. I did a 2-1/2 to the rear bumper for a tick over $200. The exhaust is designed to hook to basic street headers and included mufflers. Mandrel bent and fit well.
 
1wild&crazyguy said:
You can still find those heads everywhere, why would someone buy yours when when they could have their own done and not pay shipping and not wonder what was actually done or NOT done to them?

Not only that, but you can buy NEW RHS heads that flow like mildly bowl blended j/x heads, have all the closed chamber crap that people think is gona make or break their combo AND have shaft mounted rocker setup on them.
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I was always curious how with a single plane intake a 501/292 cam and slightly more compression how the 360/380 engines made almost 400 horsepower. I have read several places other than here that the 360/380 engines dynoed at almost 400 horsepower. It is inconceivable to me that basically with a cam and intake change boosted horsepower almost 25 percent. I could easily see that with a 2 barrel swap to four barrel. But I read a PHR article that they had a stock magnum with an M1 intake with 1 5/8 headers and a 750 demon that dynoed at 300 hp and with a cam, head and intake change jumped to almost 450 hp!!
 
rumblefish360 said:
I had it, have the part laying around here, just can't think of the numbers. Try calling Summit racing and let'em know what your doing. I believe they can help ya.

On your exhaust, FWIW, ya might wanna look at a summit or jegs exhaust. I did a 2-1/2 to the rear bumper for a tick over $200. The exhaust is designed to hook to basic street headers and included mufflers. Mandrel bent and fit well.
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I'm glad to hear that the Summit/Jegs prepackaged 2 1/2 set up worked well for you. I am considering that or either the 73 inch Doug Thorley look Patriot sidepipes.
 
Well, the engine was a 9-1 engine, the heads were stock OE as were the valve sizes.
Proof of the heads worth even in stock form.
(LOL, and theres those who said the late model Magnum heads suck! )

An engine will make power if you let it breath, hence the best intake (breath in) and exhaust (breath out) combined with a cam designed to operate in the performance parts perameters work wonders.

I'v seen a dyno high of 415 with those parts, higher with bigger carb and bigger tube headers. IIRC it was 435 hp.
 
All 360 heads new and old flow in the 200 range which is good for 400 hp.

Great for the guy who needs around 400 horse power

After that, buy other better heads.
 
TurdFerguson said:
All 360 heads new and old flow in the 200 range which is good for 400 hp.

Great for the guy who needs around 400 horse power

After that, buy other better heads.
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Correct the first sentence, I wouldn't spend the money on new heads when for a cheaper price, you can upgrade and/or port the iron for a head that can support 500 HP without getting crazy on the port work and price of doing so.

Everybody under ets. the OE iron head and it's abilty and posssssabilty.
 
rumblefish360 said:
Correct the first sentence, I wouldn't spend the money on new heads when for a cheaper price, you can upgrade and/or port the iron for a head that can support 500 HP without getting crazy on the port work and price of doing so.

Everybody under ets. the OE iron head and it's abilty and posssssabilty.
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In that case the old heads win with the ability 'in ported form' to flow well into the 280+ cfm range which about 30-35 cfm more than anyone has been able to get from porting a factory cast magnum head.:burnout:

What gets in the way of helping others in making the right choice is the championing of preference.:newb:
 
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