[Gregdownunder]

Hi,

Ok, I started with a bog standard 1983 318 with only 100k miles on it.
Improvements:

-removal of all smog related stuff,
-256 XE cam,new springs,
-short block headers,
-3 inch single exhaust, no cats,
-vacuum advance dizzy/electronic ignition,
-600 holley with edelbrock performer intake.

Not sure what it sits at horsepower wise now (someone might like to give me an educated guess?)but it actually goes pretty well.
Now I'm Looking at the next step. I don't really want to get into a full rebuild ATM, possibly down the track.
Compression test and oil pressure is good so I'm pretty sure the internals are OK.
Compression ratio I'm picking is pretty low, so I'm toying with rebuilding/port polish the heads including shaving them down to increase compression.
I know it perhaps would be better to replace the pistons, but as I said I don't want to get that involved just yet.
BTW Replacement heads are pretty thin on the ground here, other than new ones  hence Im leaning to rebuilding the originals.
I'm not trying to make a HP monster, just a noticeable increase would be nice.
Am I on the right track?

 

[ToxicDoc]

What are your goals? That's the question you have to ask yourself. Honestly I would stop right where you are. You've done all the best-bang-for-the-buck changes. The next steps are all diminishing returns for the cost/effort.

In theory, if you really wanted to push this engine just to see what it could do, you would need more compression. But that would involve a piston change or shaving heads and thinner head gasket, including machining the intake side to line up the manifold. That in turn would require shorter length pushrods. All of which is expensive and involve a good bit of labor. For all that, a 360 with/without stroker would be smarter imho as a next step.

 

[dodge82273]

agreed , at this point YOU know its the pistons / rings etc next . With low compression pistons , 100k rings putting some good flowing heads on it really doesn't help . I'd drive it as is " it goes pretty well" and save up for a complete redo or change . 

 

[Elwenil]

If you have the typical stock 3.23 axle gearing, that would be the next logical step for overall performance in my mind.  Airplane gears might make the MPG numbers tolerable on the highway but they kill acceleration.

 

[neil4224]

Heads are going to be about the only thing that will be a return, but will change how the truck acts tremendously power band wise depending on heads you choose/valves etc.  Going aftermarket, since no available heads on the ground, is going to be your only choice, unless.... 

If you have some knowhow on sourcing a set from a pick and pull you might get lucky and come across some  "302" heart shaped heads.  These are late 80's smog heads found on 318's, have small runners and valves, but can be opened up quite generously with some time, effort, and money for larger valves/port job. 

Here are a picture of mine from back in 2012, I paid about $850 total back in 2012 for slight mill, 2.02 intake, 1.60 exhaust, springs, valve guides, port and polish, fully assembled.  Got the heads off of a different motor I had from another truck I picked up.  Gears will need to be a must with these though 3.73 may be most beneficial as the power band comes up by about 750 to 1000 rpms with these bigger valves. 


Other than that, you need more bore/stroke with higher compression for significant feel. 

 

[Canadian country boy]

Well, if you're not burning oil and you're confident that your compression rings are good then improving head flow won't hurt. The problem is that if you do the bottom end on a later date and increase the cylinder size and compression volume then you're going to have to re-do your cylinder heads again to match-flow the bottom end. Just so you know. If you put heads on it now that flow too much it will kill your performance and if you put heads on an engine that don't flow enough you will kill performance. You can spend a bit of money now to get better flowing heads that will definitely improve your power now, but when you bore it out and put bigger higher compression pistons in it later, then you will need to do your heads over again to match. Unless you do a mild bottom end rebuild and keep the numbers close to what you have now and then you wouldn't have to change your heads again.

 

[Reed]

Keep it as is now or find a set of the late 80s/early 90s 302 casting heads, have them rebuitl stock, and put them on the motor.  Save more exotic plans for later.

 

[ToxicDoc]

Keep it as is now or find a set of the late 80s/early 90s 302 casting heads, have them rebuitl stock, and put them on the motor. Save more exotic plans for later.

If he's going to as far as changing heads, he'd be better served using a set of Magnum heads.

 

[dodge82273]

head work will make it breather better , allowing higher rpm's , yessir , but the right piston top and compression ratio will be required or you will have a slow to rise to rpm engine . I still suggest saving up for a complete
"package " . 

 

[Canadian country boy]

If he's going to as far as changing heads, he'd be better served using a set of Magnum heads.

If you can find any without cracks though. Lol

 

[ToxicDoc]

If you can find any without cracks though. Lol

there are aftermarket, reasonably-priced, well-made iron replacements available

 

[Gregdownunder]

Thanks for the replies, you have given me something to think about and perhaps do a bit more research into.

Cheers,

GDU.

 

[Canadian country boy]

My 318 has 360 heads on it that have the 1.88 intake valves and a 480 something cam with a 4 barrel and stock exhaust manifolds and stockish torque converter and it runs strong and gets decent fuel millage. Magnum heads would be awesome that's for sure.

 

[Bikerdude]

https://www.hotrod.com/articles/mopp-0409-318-engine-build/ I liked this build. It used the magnum heads, as previously mentioned. Completely bolt on build for 400hp.

 

[Jeffy45]

Indy LAX.......

 

[ToxicDoc]

Indy LAX.......

linked:

https://www.aeroheadracing.com/chrysler.html

 

[Jeffy45]

IMMENGINES.COM
http://www.immengines.com/indyimmironheads.html

 

[Dick_Z]

Did somebody already mention the turbo option...? 
Can be done quite cheap if you have some fabricating skills....