[Glenn Jackson (Henner)]

I did a search for heads and did not see what I was looking for so here it goes what is the difference between the x, j, and u heads for the 340 which ones flow the best and do each need a different cam to make them proform best?

[Dave-R (Roppa440)]

I am not sure if there is any difference? If there is I would like to know too.
I always go by the casting number.

[Andy Neal (Tweety)]

I'll big up my how to mess up a smallblock Mopar book and se what I can find out.
I think that Dave's right though they are all much the same apart from the TA's
Basically they are pretty naff from a performance stand point, the intake valve is so shrouded it's amazing any air actually gets in there!
There will be some cam recommendations in the book as well, but these are the old Mopar Performance cams and most of them should have been retired a long time ago.
What are are you looking to do with this thing?
Ah I just thought of a fatal flaw in this plan all my car books have been put away while I'm building, try one of the builders websites, I know Dave is friends with Hughes Racing, try them first, good luck

[Glenn Jackson (Henner)]

ok here we go again the other day before you jumped down my throat andy I was asking not telling but asking if a good set of heads and a decent cam would get you close not there but close to where you would be with nos. without the worry of a melt down. I know it would not get you 150 hp extra but what do you think it would give you that is a question? you ask where do I get my info from I tried to get it from here but you did not read what I wrote you must have only read what you wanted to see and not what was written! THe other question I did ask was how much does gas cost you it cost me about 185 a gal here in Il. usa I could not find the mag with article about the 340 with 450 hp in it I mean the BOGUS article. I will keep looking but not to hard... PLease read carefully and try to help instead of insult. have a nice day!!!

[Roger Bettoni (Roger)]

I've just organised to buy a set of 340 x heads and the vendor said that these particular heads have "double value" springs - whatever that means. Someone else I spoke with, seems to think that the x heads were reserved for the T/A model as opposed to j heads which are standard heads fitted to standard 2 bbl motors.
I know not what I'm talking about because I'm still learning about all this stuff, but suffice to say that I paid a paltry A$150 for the heads and intend to fit them to my low-power, but reliable small block 318, along with a 600 cfm 4 bbl carb and new intake manifold. I'll reserve my plans for a big-block for the time being, as want a car that I can enjoy daily and economically. I can't afford to buy new tyres every month and do not wish to contribute too much to the big oil company profits. Just call me cynical, but these are my thoughts...

[Tony Miller (Owner4)]

It's time to open the good book of Galen Govier "by the numbers".
part# cast# yr engine int exh remarks
2531902 2531894 68-70 340 2.02 1.60 X head
3418432 3418915 70-71 360 1.88 1.60 Z or O
3418432 3418915 71 340 2.02 1.60 J or U
3462598 T/A 340 X
3577053 3418915 70 340 2.02 1.60 U or O
3671639 3418915 71-72 340/ 1.88 1.60 J
360
3671873 3671587 73 360 1.88 1.60
3698617 3671587 73 340 1.88 1.60
3698617 3671587 74 360 1.88 1.60
}

[Dave-R (Roppa440)]

Nice one Tony.

Glenn. A good set of heads and matching cam on a well built short block with good compression and light pistons can give you up to 150hp on a small block and 200hp on a big block before getting completely unstreetable. That is just a generalisation of course and just my opinion.

You will have to forgive Andy because he lives in the big money 9 second 'street' car world where bigger and more expensive always means better. I have had arguments with him in the past about heads. He equates big flowing ports you can get your fist into with power. Which is true if you live in a 7000rpm 9 second world. He forgets that real people drive these cars on the street 99% of the time where high velocity in the ports is key to making power and torque at 'street' rpms. It is easy to make a port flow big numbers by making it larger. Making it flow fast with a higher velocity and smaller port is the hard thing and that is what us guys that drive our cars need.

But don't get the wrong idea about Andy. He is a very big hearted soul that goes out of his way to help other Mopar owners. He lives in upstate NY and has single handedly helped many mopar owners over here in England get the parts and even cars they want. All without making a penny from it himself!
It is just that he is originally from Birmingham so he has a handycap compared to the rest of us!

Oh and petrol costs $5.00 a US gallon in England.

Roger. Some engine builders use double valve springs (one inside the other) as a way to increase the valve seat pressure to keep the lifter on the cam with wilder cam profiles. Some valve springs look like a double spring but the inner one is just a 'damper' that works with the outer spring.
There is no need for double springs these days on a street car.

[Andy Neal (Tweety)]

Thanks for the kind words Dave, I did actually drive the cuda around with the W2 (340) smallblock for about 5000 miles in England in under 4 months, fortunatley I wasn't paying the petrol bill!
I would just like say one thing here you can actually have big power at low RPM but you either need a big motor, (lots of cubes or a blower.
Having been down the 340 with big heads and a cam route it is simple not one I would recommend to anyone, especially now that you can build a 400+ cubic inch smallblock for comparitively little cost.
A 4" cast crank is only 300 bucks new and now that you can get rods cheaply it is a definite possibility for anyone thinking of a power smallblock.
The problem comes with heads the old 340 and 360 stuff just won't cut it here and you are into after market heads which pushes the price up again.
BTW my hemi makes all it's power at 6000RPM and that's a street motor!

[Andy Neal (Tweety)]

Here's a question for you does anyone know what a 340 motor really produced, I know the 318's were in reality about 185HP, I can't see a 340 being much more than 250, I'm talking real numbers here with the alternator on, water pump connected etc.
I'm curious....

[Andy Neal (Tweety)]

You know Dave this whole thing about huge heads only being for race use is not entirely accurate you know?
If you have a head design that has lots of flow with the valve just off the seat and you have a cam that matches these characterics then you can still make lots of power at low RPM. You just need a big motor to doy it, mine made close to 800HP and still made 740+ ftlbs, so it can be done, it just requires some thinking about.
I've been putting Gav's 416ci stroker SB motor in a crate ready to ship out and that's a nice combo. plenty of power, lots of low end torque and about 200lbs less weight than a 440.
The world has changed a lot since the Mopar Performance books were written, ho hum time for a cuppa then back to building packing crates

[Roger Bettoni (Roger)]

Good to see you're back on line Tony. Dave, I believe these heads I've ordered have double VALUE springs not double springs (I assume this to mean much stronger springs), however they have not yet arrived (due this week sometime). I intend to get them reconditioned and have stellite valves installed to cope with unleaded fuel.
As you know, I'm on a budget and can't afford aluminium racing heads and the like. At the end of the day, it seems pretty obvious from most of the comments made by MB members, that there's not much point in spending big bucks on the 'ol 318, so until I can afford to go down the BB road (later I promise) I'll make do with what I have. When I receive the heads I'll compare the casting numbers with Tony's post to see what in fact I have bought. If I can make around 230-250 hp from my set-up, I'll be extremely happy!

[Andy Neal (Tweety)]

Hey Roger don't count the 318 out so quick, I fitted some 360 heads to mine with a crane hydraulic cam and a decent intake, I put a 600 Vac Sec Holley on there with the secondary metering plate.
And I have to tell you that little motor worked great for really very little cash outlay
I've probably got the part numbers somewhere in the collection. From memory the only aggro' was with the rocker shafts. As for a budget you can do it all out of cheap bits, nothing fancy, stay in touch and I'll see what I can find out for you, best of luck
Cheers Andy

[Dave-R (Roppa440)]

Andy.
Big flow = big runner volume.

Big runner volume + small cubic inch + low rpm = very low air/fuel mixture speed.

And that adds up to poor performance at lower rpms + very bad milage + poor throttle response + lots of fuel dropping out of suspension.

When a guy is building a smallblock street engine all he needs is enough flow and as high an intake velocity as possible.

The bigger your engine the more velocity in the runners given the same runner size. So a big cube engine can work with big runners.

Another interesting fact.
Fitting a bigger stroke crank and doing nothing else will give you LESS power.
If you fit a stroker crank you need to up the cam and heads too.

[Andy Neal (Tweety)]

very good Dave, you'd better tell Barton what he did wrong then, my motor is what? Because it's less than 120 ci bigger than yours and makes at least 250 more horse power (about 50%) it's only 11.1 on ally heads and has a weenie little mechanical cam, ho hum....
Oh dear the 'other' Dave will show up in a minute I can feel it, but still it's a Sunday morning and it's raining here so I can't work on the house and I could do with a good laugh and some intellectual banter today, so bring it on....

[Andy Neal (Tweety)]

Oi and before you start getting steam coming out of your ears, I was offering Roger in Oz' some advice with his small block in my last message and when I get a few min's I will try and find the details of what I did, with Blue's help of course.

[Dave-R (Roppa440)]

Because it is 120 cubic inches bigger it can use bigger flowing heads on the street. A lot of the power of your Hemi is in the very light mass of the moving parts and possibly he best machining in the world. That cam is also very, very much bigger than my mild hydraulic.

My engine also cost a tiny fraction of what yours cost Mr Neal Sir!

[Andy Neal (Tweety)]

no it's not the cam is a .570" lift mild little mechanical thing, and it was built by someone from Stoke on Trent , what the hell could they possibly know about engines there, they make plates


But it does just go to prove that it's all about the heads

[Jeff Maxwell (Redchalleng]

Dave, thanks again for 'splaining things. My car is running super rich and the milage stinks. But I've been in the "Who cares" mode. Tony said he sweared at the carb and wanted to yank it out. I had assumed that it needed to be set with a high engine speed at idle to get it to run while cold. I also didn't have the balls to take off the shaker and attempt to mess with it. I remember how I screwed up my bike when I was a kid attempting to "fix" something I knew nothing about, so I'm not anxious to get inside. At least it runs now, and I want to keep it that way despite the fuel consumption and smell of rich exhaust!

[Andy Neal (Tweety)]

Oi Dave and as for having lightweight bits in there, not so mate,It's got steel Superstock rods, an ex-fuel crank that's been re-balanced with Mallory metal, heavy nitrous pistons and the big pins.
You are right about the machining though, I'm glad the deal with the police worked out, now back to smallblocks

[Roger Bettoni (Roger)]

Andy - I would appreciate your thoughts as to the best way to go with my small block. As previously stated, I'm on a budget, cannot afford to replace the motor as yet, so plan to make the best of what I have. It's a standard bore factory 318 with approx. 60K miles on it, currently set-up with the standard intake and exhaust manifolds and 2 bbl Holley economaster carb (350 or 380 cfm I believe). I've just installed electronic ignition (magnetic pulse type) as the previous owner had a twin point mallory distributor on, without any vacuum advance. Right now it runs worse than a pig, with no get-up, a bad flat spot, won't idle properly and gets poor mileage. The '72 model that I owned as a teenager (some years ago) ran like a charm and seemed to have far more power with exactly the same set-up. Maybe it's just my enhanced memories of being a mislead teenager, but I do recall it being far more streetable than my current car. In actual fact, I won a race for "pink slips" when competing against a friend in his Che*y Chevelle with a 327, but that's another story...

All I'm hoping for is a car that runs sweet, is fairly economical, and has some degree of go factor. Currently, I would not attempt to compete with a Corolla for fear of embarrasement.

[Andy Neal (Tweety)]

Roger i don't know how you are set up for maching and stuff where you are?? but IF you can find a pair of 360 heads I reckon between us we can work out how to transplant them on to your 318 mate. Now providing the 318 is in fairly good order there's now reason at all why you can pick-up some power and still keep it nice and driveable.
I was amazed when we did mine the difference the heads, the intake and the cam made.
Why don't you email me mate and I'll dig up what I can, it was a few years ago and on a different continent, but I keep fairly good records, well of course when I can find them.
Where do you live in Oz' I have some friends over there.
Stay in touch
Cheers Andy

[Tony Miller (Owner4)]

I pulled out my 70 challenger literature and here's the advertised horsies with 8.8:1 pistons, 275 HP @ 5000 rpm and 340 ft- lbs of torque @ 3200 rpm running on premium fuel.

[Andy Neal (Tweety)]

yeah but that'll be on a mopar dyno with no alternator etc, I'd figure 250 tops in the real world. So we shall have to get a pair of 360 heads on Roger's 318 and experiment won't we.
I might even get tempted to throw oone together here, the parts wouldn't cost much, it'll have to wait a month or two though