360 heads on a 318?

[vinnys63valiant]

can this be done if so, is it just a swap, is it worth doing?

[valiant64]

Yes it can. But for what application? 360 heads-larger port, less velocity. Also larger chambers-less compression on otherwise stock 318. Unless you're building a 318 for top end power, stay with the small port heads on the 318. Many posts on this topic, just as many opinions. Do a search on it. Factory late 70's & early 80's "HP" 318 4bbl engines were equipped w/ 360 heads & intakes-total slug.

[vinnys63valiant]

something to think about. i know where a 85 ply fury ex cop car is complete running318 4bbl for 300.00 my buddy has it.trying to figure the all time question , i drive my cars but with gas like it is im trying to figure how to get decent power/gas milage.

[3404spdvaliant]

You can build a pretty powerful cam'd high compression 318 .
If I was building a 318 and had to use 360 heads i'd bring the compression
up to about 10.8-11.1 and would run a good dual plane intake and go roller
then keep the cam duration around 238*-242* @ .050 for the street w/1 5/8
headers.
Milage is how heavy your foot is.

[dodger1]

That 85 cop car "should" have a 318 H.D. engine, which would include 360 heads (1.88" intake, 1.60" exhaust) as well as a spreadbore iron 4-bbl. manifold. (Not sure if the carb would be a TQ or Rochester QJ) I bought an 84 Ply. copcar for parts, and discovered that sometime during it's lifetime, it got a set of std. 318 small-valve heads.(Took the rest of the running gear for my Mirada and called the junkyard to take away the carcass.) You might want to double-check the head casting # before you buy. If it's only the heads you're after, I'd pass unless you can unload the rest for $$, and find a set of '302's for your car.

[valiant64]

If you're concerned about mileage, I'd say stick with a mild 318. Large cams, hi-stall converters, low rear end gears, etc, are not what you want to obtain fuel mileage. Use the 318 head w/ the 360 valves (1.88/1.60) with some minor port/bowl work. A 600 cfm 4bbl carb, headers, a 340 cam or similar, keep duration @ .050 below .230 and lift in the .450-.470 range. 3.23-3.55 gears and maybe, depending on cam/rear gear/rear wheel dia./vehicle weight, a converter w/ a little more stall. Compression should be around 9.0:1 so you can run on pump gas w/ no detonation issues.

[rumblefish360]

The 318 4bbl. should have 360 heads stock and you'll NOT want to port them in any way. The heads will flow approx. 200 cfm stock and support approx. 400 HP for the 318. No problem.

IF you want to do any work to the head, back cut the valves for better low lift. Mill the head for better compresion.

[valiant64]

If using the 360 heads, milling them to get around a full point of compression isn't the way to do it. A piston change is what should be done, then mill the heads if necessary to fine tune the comp. ratio & ensure a good sealing surface. The 318 port size is still better for a mild 318 than the 340/360 port when not running high rpm.

[dartboy71]

So to continue that topic...

If I have a choice between some stock 318 heads and stock 360 heads(both mid-70s smog heads), and I plan on filling up the chamber with more piston what kind of RPM do I need to be running to make the 360 heads worth it (if the only mod is to back-cut the valves...would like to keep the stock rockers and shaft).

More port: more fuel/air, less velocity for the same chamber at a given RPM, so how much faster do I need to run before I get into the power? With stock rockers and shafts I'm sure I'm limited to about 6000 RPM, yes? Certainly I must get *some* benefit out of 360 heads on my 318 with all else equal.

[3404spdvaliant]

Originally Posted by 3404spdvaliant

You can build a pretty powerful cam'd high compression 318 .
If I was building a 318 and had to use 360 heads i'd bring the compression
up to about 10.8-11.1 and would run a good dual plane intake and go roller
then keep the cam duration around 238*-242* @ .050 for the street w/1 5/8
headers.
Milage is how heavy your foot is.

To answer you I put my own quote & elaborate further.
The point of the 10.8-11.1 comp is to get piston closer to the valve to speed up the signal/initiate air moving sooner.
The difference is like turning on then off a vacume cleaner hose with your hand a foot away, only after a second you can feel a little rush of air go by your hand from the pull of the vacume. Then hold your hand 3 inches away and turn on an off the vacume, now you can feel the air instantly.
So if ports are too big resulting in lazy air speed, getting the piston closer will help speed up the initiation of in coming air somewhat making up for lack of velocity/air speed.
This however will not completely fix the lack of port velocity, but will help greatly when using these heads on street 318.
Hope you can understand.

[dartboy71]

Perfect sense. But can I still use my stock valvetrain and realize benefit without detonation? Bigger seat pressure is called for at some point to get the valve opened quicker and compliment the CR, and how do I prevent the detonation since this is still a street 318 that needs to live with 92 or 93 fuel.

[3404spdvaliant]

Seat pressure is gonna be what ever the cam manufacturer recommends when you choose your cam.
I know your talking about fast ramp speeds, And in this situation I would be looking into a solid grind, they generally have a lot faster ramp speed than hyd cams.
To get away with with that much compression you will need a combo of things 1 being just the right amount of cam overlap & 2 being the right timing advance curve & 3 lowering total timing.
[example]14*-18* initial & 25*-28* total.
BTW do al the bowl work you can but don't get carried away enlarging the whole port as some one else said for you will only lead to less velocity at a certain point.

[3404spdvaliant]

Seat pressure is gonna be what ever the cam manufacturer recommends when you choose your cam.
I know your talking about fast ramp speeds, And in this situation I would be looking into a solid grind, they generally have a lot faster ramp speed than hyd cams.
To get away with with that much compression you will need a combo of things 1 being just the right amount of cam overlap & 2 being the right timing advance curve & 3 lowering total timing.
[example]14*-18* initial & 25*-28* total.
BTW do all the bowl work you can but don't get carried away enlarging the whole port as some one else said for at a certain point you will only lead to less velocity.

[it's all dodge]

Not all the 4 barrel 318s had big valve heads, like my 318 4 barrel 83 W 150 longbed 4 speed

[260Mopar]

A mildly domed piston is a pretty good solution.

Check out Kieth Black Part Number: KB845 CHRYSLER 318, V-8

I talked to their tech about this parts ability to quench and according to him the quench remains in place. Using a 360 head with a 75cc chamber and this piston will give you about 9.5:1 compression.

[260Mopar]

Originally Posted by 3404spdvaliant

To answer you I put my own quote & elaborate further.
The point of the 10.8-11.1 comp is to get piston closer to the valve to speed up the signal/initiate air moving sooner.
The difference is like turning on then off a vacume cleaner hose with your hand a foot away, only after a second you can feel a little rush of air go by your hand from the pull of the vacume. Then hold your hand 3 inches away and turn on an off the vacume, now you can feel the air instantly.
So if ports are too big resulting in lazy air speed, getting the piston closer will help speed up the initiation of in coming air somewhat making up for lack of velocity/air speed.
This however will not completely fix the lack of port velocity, but will help greatly when using these heads on street 318.
Hope you can understand.

Thanks for your description of the air velocity issue. I'm just trying to wrap my head around this. Do I understand you correctly that velocity would play as important a part as volume? In other words huge volume would need an appropriate velocity balance?
TIA

[rumblefish360]

Yes, you seem to have it. However, a huge port will not have high velocity on a small displacemnt engine.
For an example, most mildly built to hot street 360's will do fine with the stock window size and just a bowl porting. Gasket matching is small potatos.

Edelbrock heads work well up to approx. 372 cubes with there window and flow rates.

These heads on a 318 will make power, but in the upper RPM range. It'll be abit doggy down low.