Time for another odd combo, the web is full of 318 builds, fabo is packed full but ive found little on what id like to do.

My main question is which head to go with.

Here are the basics.

318 .040 over, KB399 6 cc domed pistons, Mopar 509 280 adv. duration, 106 solid lifter camshaft.

340 floating rods, arp bolts rods are 45 grams lighter then oem.

I can use a cast or steel crank, but with this cam the cast might be fine.

Stock 6bbl from my t/a car thats parked for a long while. (no worries about the jetting or adjustment, just mentioning what the intake combo is)

Now for heads ive a nice set of 2.02 J heads, SS valves without any port work OR ive a new set of 1.78 smog casting I can work over a bit with all new oem valves.

Both heads are like 65cc and im at 4k elevation.

1 5/8 to 1 3/4 step tti-s and probably full 3 inch ex, since ive got it.

904trans, 3200 vert, 4:56 gears, 28 inch tire

Thanks!

Either head is fine, I've done 318 builds in the past using both, IIRC the 1.78 your referencing is actual 1.88 ?...been awhile


Keep in mind once you go over the .470 lift into the 280 duration specs you'll need to valve relief the pistons and re balance them


I've done single 4, 6 pack and quad set ups on various 318 builds all were great performers...but if the opportunity arises to build 340-360 block, best to start with that foundation if possible, the extra cubes are worth it

Thanks Dayclona for the input, the 318 heads are 1.78 intakes.

The KB399 slugs have some decent valve reliefs so the .509 wont be an issue and there is the lash factor as well.

Im trying to do a stout little 318 on purpose in this particular car, thats why I say stout, ive a pretty mean 360 long block and a stroker sitting.

I could put the small valve 360 (1.88) in the 318 heads but that would almost defeat the purpose of my $100 each nos casting, but ive the time to do the bowl job and clean the ports up if needed.

With the 318 and oem valves the chamber is right at 65cc, the J head 2.02 thats been surfaced is also right at 65cc.

A good bandaid on using the small 2bbl center is its good to keep the air intake speed up vs the actual small port of the 318 head.

Just pulling a number out, say 325 hp the 318 heads would support that just like the J head clearly would but if the cam is going to nose over say at 6k for kicks would the J head really be better.

I dont know, ive not really tried much on a 318 but to get away from them.

As the pics show the KB399 is a nice little slug, the rods are really nice and balanced well and the reduced weight of the rod would dictate the re balance anyways and ive never understood why some mopar guys want to skimp on the balance job when I consider it mandatory.

The 318 casting are not as good as the 302 or the open chamber 302 but a bit better then the early 318 ones. It would just be alot less work to toss on the J heads but ive seen a couple real dyno sessions where the 318 made more max power and throughout the pull.

I considered performance valves for the 318 heads if i use them but they are hard to find and really are they needed for a .500 lift solid cam and maybe 6k rpm. As well if I use the oem 318 valves I can use the oem retainers with the proper single spring and still not hit coil bind.

And again thats why I say stout 318 vs like a class limited 318 that takes alot of time and money to go fast.

But some, including myself have dumped like a 340x head on a 318 and there improvement, but again it was like a 69? 318 that had the better compression to start.

The pic shows the 318 head wit the hardened ex seat already there and you can also see there is alot of cleanup to be done if I use them.

I know the port mismatch of the 340 intake vs the 318 inlet but its easy to (flare) the 318 head to match and on these castings some had the pushrod hole drilled big for the pre magnum 318, ive got the ones that didnt (std pushrod hole) so I can open the pinch a bit to like .900 I think thats what I got when I checked things.

Ok, I better stop here for now.

About 24 years ago I was building 318's for one of the local oval track classes.
10:1, 1.88/1.50 valves, no porting, stock 2bbl intake w/adapter for 4412 Holley 2bbl carb.

With a solid cam and headers those motors made over 350hp.

The rules changed to RPM intake manifolds, but I don't recall if that was before or after the rules allowed 360's to be used.

AFAIK, all 340's used the "heavy" rods.
The lightweight bushed rods were just the early rods like what would come in a 273 or poly 318.

Thats great info, the cam is actually a DC purple shaft for a 1/4 dirt track that ive found to be semi aggressive even for a DC cam.

I actually like these type cams for the street/strip cars.

It ironic you bring up oval track as ive also got a nos 69 4412 500 cfm carb I was considering milling the air cleaner mount to use as a center carb, ive also the DC 500 cfm center carb I could rebuild but oddly compared to the ford 4412 carb they are supposed to both be 500cfm but the throttle plates as well as the diameter in the carb body is way different.

Outwardly it looks like possibly the DC500 is the bigger carb with the 69 ford holley 4412 being bigger then the oem 350 center but smaller then the DC 500 center carb, but thats just by looks.

Im a bit skiddish of the smaller 318/273 rods, the ones I have are the 30 rods that just have polished beams, the nub trimmed off the top and maybe 1/3 the material removed off the bottom of the cap.

My heads are set for the 1.78, I could easily goto the 1.88 and tulip the bowls a bit but a couple of my dirt track guys have told me id do ok with the 1.78 but maybe go a hair bigger on the ex. valve.

I appreciate your input as in some ways my stout little 318-6 project isnt too far off from a oval track build when all is said and done.

I cant recall but I think my 500 2bbl carb is a 69 nos first year deal.

Im wondering if the 500 cfm center might do alot better then the 350 cfm and maybe use a pretty stiff spring for the end carbs.

I dont think in the whole mix of thing it would call for me to sleeve the end carbs.

I'd stay with the smaller center.
All total, the OE system is said to flow something like 780 cfm 4bbl. rated wise? That's a lot for a 318 even if it is .060 over.

IMO, I would use the larger valves 360 heads with th 6 pack.
2.02's would be better but I got the keeping it cheap thing.
The cast crank will be fine.

I don't know if you'll like the purple oval track cam for the street. I used there 288/.499/106 cam, 1/4 mile flat oval cam. While it made nice power, it was a lumpy choppy idle SOB.

Quote..While it made nice power, it was a lumpy choppy idle SOB.

I do have alot of other cams I could consider, but this is the most mild next to the 484/284 or the 508/292 hydros.

If the cam fits the application ive never understood why some, not the poster, worried about a choppy cam. To me the nasty chop/lope is an added bonus.

Im going for a stout 318 here if it runs well and sounds mean id be very happy.

Id like to hear more about running the 2.02 J heads. Ive always been somewhat a stickler on matched parts.

So if the block bore is 9.950, the chamber diameter of the 318 head is 3.80, the chamber of the J head is 3.99, say 4.00 and the diameter of the piston dome is 3.60 but would be alot less depending on the head gasket thickness.

The 318 heads would be a harder route to get them to where they need to be but from actual numbers across the rpm spread im leaning to go that way.

Alot of mis matched street cars want to go from a roll, although I prefer the dead stop hit, but the car for this has caltracks, mono springs, double adjust shocks and drag radials so it will hook but also needs to be able to roll with other situations and not be doggy.

Ive not squared the block yet, if the deck is on the high side ive another trick maybe, if an old mopar crank with a hair more stroke then oem.

This is from 1994...... 4412 on a 360 2bbl intake w/adapter........

1995...... new heads, different cam, new reworked 4412 carb, stepped headers........

(With a 650cfm, boosterless, annular discharge Venturi, 2bbl carb, it was solidly over 400hp, with the VE improving by over 10% and the motor using about 70 cfm more air at 6700)

This cam made some pretty good numbers on the dyno, but lost some grunt in the rpm range where they came off the corners, so it didn't really race quite as well(overall) as the previous set up.

What were the cam specs on that build? and compression?

It was a compression rule, 10:1.

Cam specs? Let's just say I wasn't doing anything really out of the ordinary for the application.

I was just about asleep and was thinking to myself, dang I wish I had a .040 over 318 block sitting vs the approx $300 for the 318 bore/hone/bake, ect...

Then I thought I do, so I got dressed and sure enough a pre mag 318 block at .040 and so i got out my tape measure and measured the bore and then my KB slug and just a hair over .002.

It might just work, ive used solids in pre mag block before, or ive even a nos set of big pushrod hole heads for the roller blocks.

Hmmm.

If I can use this block I should just use my solid cam as planned, ive already looked up the oem roller lifters and a decent cam and ive got a set of new dog bones and a spider in the shop, but thats going way off track and always seems to bite me in the end, but a nice hydro roller...

This is a new setup here, I could just run a ball hone over it for the type of rings ive got, might not even need to do that.

Maybe I should rip it down and measure it all? These early roller block always seem to have way too much casting flash to grind off.

So I will rip this apart today and see how a KB399 fits in this block and see where the deck height is at.

Ive committed to a couple of parts/items.

I will use the nos head castings and the new oem valves, Ive under $300 in the heads and so I can put the time in on the porting and cleanup work.

These castings have the tiny intake ports like the 302 heads do, however as you can see in the pics they do not have the large push rod holes like some for the roller cam lifter height that throws things off so I can easily open the pinch area to the same as the early 318 heads and I measured and .900 seems like an easy target.

I cant see not using oem valves, I will toss a good 3 way vj on the heads and a little back cut on the intakes. With a hughes like 1110 spring I think I can get things to work with the oem retainers but might need to cut the spring seats .050, no biggie.

As well im going to use the mopar cam I planned, the .509 280 adv. 238@50 106, 68 deg overlap solid lifter cam.

Looks like im going to have a good bit of time in the heads, but thats fine.

Im happy to be using NEW head castings and valves and they are mopar heads, not from china or rebuilt 30-40 year old castings.

I'm guessing a dyno session isn't in the budget.........so whether or not it makes 325hp probably won't really be known.

Those heads will likely need a fair amount of work to get you there.

I'm guessing a dyno session isn't in the budget.

Thats actually why im looking for input on this particular build because im so in the dark on the little 318-s ect and I will dyno it and flow he heads as I go because I can find easily 50 head projects/318 builds that go so far and the info just ends.

So on some of it I read I question its usefulness since there is no completed projects.

Less then 500 feet from where im sitting. Im just not dumping alot in parts for this project.

I will flow these before I start.

On of the hard hitting ls guys in our street race group has a nice dyno cell and a chassis dyno as well, so that part wont be a problem.

When I did those oval track 318's, I just built them the way that made sense to me.
I really didn't seek any outside input.

I looked through the rules, saw what those guys had been doing previously, felt like there were a few things to be exploited that they weren't taking advantage of, and ran with it.

The new motor combo was pretty successful.

I'll be curious to see what you come up with and what kind of power it makes.

When the rules allowed 360's we just went that way........and they just did everything better(obviously).

The car im doing this build for was one of those 150hp 2bbl deals but the car has alot of meaning to me and the rest of the drive line could support a healthy stroker.

I cant find any more specs on the cam Id like to use so I guess I need to just toss it in a block and do my own work.

Ive a comp grind in mind if this cams not enough but I hope it is.

Im actually pretty excited doing this since its out of the norm for me.

I know the roller cam block and a hydro roller would improve things greatly and ive not ruled it out but Im thinking of just letting the shop go ahead and bore the block I had planned to use just because of the freakin lil partial vin stamped in it that really dont mean dick to anyone but myself.

I did find a set of oem 1.88s on ebay and if I can get them cheap I think I will make that step up.

I just cant justify spending alot of money on a 318, the 6bbl intake ive alot in with the pro max plates, metering blocks, ect but one day it will go back on my T/A car.

Well off I go, im gonna see what this cam I got specs out at.

Its still early on this build, if the kb399s are below deck just a hint Ive a better crank with a hair more stroke I might be able to throw into the mix and im factoring in im at 4k above sea level.

I tore my 86 truck (roller) block down, was a new rebuild with oem pistons) and it looks like thats the block im going to use, I got to just touch the cylinders for the finish I need for the cheap rings that came with the KB399-s.

It looks like im going to use my steel cheater crank which puts me .050 above deck and with the crank my lil 318 will be a 338 incher.

Ive always used the wallace calcs as a constant on builds and doing all the math it looks like 12.2 static, 8.3 dynamic and right at 165 cranking.

The 3.31 crank left me .020 below deck, zero deck would not put me where I wanted to be either.

So this looks like the plan for now, the cranks going to need over two pounds off it and ive alot of flashing to remove from the block.

I'm assuming custom Cometic head gaskets & I would suggest some plasma moly file fit rings & dingle berry hone it with a BRM 320 grit flexhone in your drill (takes minutes/very well worth it).

Be careful torquing heads. Those blocks have tendency to crack from heas bolt hole to coolant passage. I wanna say 65-70 ft-lbs is all those can take.