Would this set up be desireable in my 66 Cuda?

One reason I never like doing the 360 heads on the 318 is because the chambers are so large that you have to shave the heads .060 to get the compression up, have to use the 360 intake so there are not any vacuum leaks, and there is usually a flat spot on the bottom end because the intake runners are too large for the size of the engine. A good port job works good for the 318 heads, headers work well, and a dual plane intake with a 600 cfm Holley, or Carter, work well. Really want to make it a little better, get the closed chamber 318 heads, get a set of 360 intake valves 1.88 vice 1.78 (one tenth of an inch is a lot for a small engine, but they work really well), and port the intake runner in a tulip fashion from the floor to the valve edge. The small runners keep good throttle response, the tulip design packs the charge really good and adds a good amount of torque on the mid to upper rpm range. Cam selection is really good in the .444 range. Not too big to kill the bottom end, not so small that it won't rev to 7000rpm, either, and you won't need a stall converter with an automatic. There is a cam that was for the 340 in about this size, very nice. Remember, this is a small bore/short stroke engine, so they rev well, but too much lift and too large a runner (as in the 360 heads) does not work unless you are running above the 4000 rpm range, which is not feasible on the street, only the strip.

Factory 360 heads are indeed larger inside than 273-318's. However, they are not nearly like Ford's (351) cleveland. Around 1978, MOPAR first sold the 'LA' version of the 318-4Bbl. They simply bolted on a 360 intake/thermo-quad. Shortly after, a (so-called) H.P. version was 'unleashed' on the motoring public. This version used the (current) 360 heads with the 1.88/1.60 valves. In fact, this H.P. 318 was available through 1984. Hey, some of you must have owned one.

By 1977, 318 heads were only 1.0 c.c. smaller than the 360's. From 1968 through at least 1984, all 'LA' heads, either 318, 340 or 360 were of the 'open' chamber design. The 318 chambers were in the 61-62 c.c. range to 1975 then they slightly increased to about 63 and then to 65 a couple of years later. The 360 heads at that time were mostly 65's.

If you mill either the 318 or 360 heads by about .005'', the chamber volume will be reduced by 1.0 c.c. Therefore, a cut of .050'' will reduce the 'c.v.' by 10 c.c.'s. This will in turn raise the C.R. by 3/4's of a point, on average; depending on the piston diameter.

Finally, as taken right out of the MOPAR (factory) Engines manual, edited by Larry Shepard; "In general, the 318 lends itself to the 340 type conversion better than the 273, because of the larger bore, more cubic inches and basic low level of performance in standard 2-Bbl. trim. - - - the first conversion to be made will be assumed as the installation of the 340 heads (or 360). To install the 340 cylinder head (360 or '72-'73 340 is recommended on the 318) - - - The 318 bore does not have to be notched. - - - With the 340 heads installed, the next most likely change is the cam. - - - A good compromise choice for an automatic is the 'standard' 340 cam (1968-1971), - - - Now that the heads and cam installation have been discussed, the next step is the intake system. - - - etc., etc."

Next find a set of late model 318 heads I believe the are 302 castings, circa 86-91 pre-magnum, they flow better than the early 360 heads and have swirl port heart shaped combustion chambers. Have the valve unshrouded, the ports mildly cleaned up and clean out the bowl area under the valves, for an intake use Edelbrocks dual plane intake set up very good for building power out of small cubes like the 318, buy there complete kit, intake carb, cam and lifters package which can be purchased thru Jegs or Summit for a small amount of money.

Volunteer, one small correction to your open/closed chamber dates. I had a 74 Barracuda 318 with closed chamber heads in that car and floating piston pins, vice pressed pistons. I had to replace the motor after freezing and cracking a head (thanks mom and dad), and I found a 74 Road Runner engine of the same configuration. Might have been a fluke, but after about 1973, closed chamber heads have the hardened seats and closed chambers on occasion. Those really help to keep the compression with the rest of the smog pistons in around 8.5 - 9.0, depending. There is additionally, when you can find them, a tarantula 2 bbl intake manifold that is good for about 8-10 hp over the stock 2 bbl H pattern. I have seen them on cars, but usually on pickups and vans.

I assumed that all '68 - '74 318 heads (with the '675' casting) were of the 'open chamber' design because that's what all the manuals say.



I guess nothing is 'etched in stone'. My '74 Challenger should have a 'blacked-out' rear-end panel according to Paul Herd's resto guide but it definitely has a 'charcoal-gray bum' and I proved it. Thanks.

P.S. I remember seeing the infamous 'single-plane' 2 Bbl. intake on a '71 Challenger and it had a Rochester carb., p.n. 7041180. Seriously.

Hey Brad, I think the 318 heads would wheeze on a 360. I was debating myself on using my chiged' out 302' 318 heads cause I opened them up ALOT. But I'm thinking of staying with 360 heads instead. The intake runners are a lot bigger. Another reason why, is that I was told that going 2.02 intakes on the 302's was a bad idea, mainly because they would be too big for the 318. But looking at them more, (they are closed chamber) I think that putting in 2.02 valves would "shroud" and lose the effect anyway.

318 heads have 1.78/1.50 valves,<--that might be 1.74 intake///

most 360 heads have 1.88/1.60 valves, if you go with that, you can have the intakes enlarged to 2.02 and have the same thing as a 340 X head. Then just have it gasket matched and polished in the exhaust runners.

Dana was mentioning 73? 74? 360 heads that were closed chamber as well, but I don't think he ever mentioned a casting #? If he did I've forgotten already.

The closed chamber heads I was talking about were 318 heads. Boosting the compression by using 318 heads is one way to do it, and the smaller runners would work by opening them through porting. Thought on the subject is that the ports for a 360 can only be opened as wide as the pinch between the pushrods anyway, so gasket match and open up the runners wherever you can.



I do not know the casting number to the 318 closed chamber head. They were rather common early in the 318 history, but the 73-74 castings had hardened seats in them for unleaded gas, already.

. As far as I know, that's the same description on the 302's I've read, they still bolt up the same and all, the only real differences other then the chamber are the air holes, and the over sized 11/16 pushrod holes. Which is a bummer because i've had to be extra careful cutting in that area.

I heard that they were also a template for some sb aftermarket heads, MP?

After more thought, if any 318 heads were chopped and tricked they might be real monsters on a 360. you'd have close to similar sized runner to stock, but with all the obstructions gone, like a happy medium.

I think Brad's thinking about regular open chambered 318 heads, it still would knock the compression up though, they just need to be chig'd out, which btw, i have an extra set just sitting around.

That's about right. The 302 head with the small heart shaped chamber is fine to make the swirl, but after taking .050 off the top, it kind of destroys the purpose, thus, after the cut, the valves are shrouded, especially with the added valve size (which doesn't shroud the valve with the smaller valve). To make these heads work more efficiently, the edges of the machining process needs to be rounded, which will also allow more advance to be run, especially when they noted that they were getting the best results with less advance. SB always do best with about 38 degrees advance, brought in by 2400rpm, vacuum advance all in around 3500. They were talking about the best advance curve of a lot less, which confirms they had too much sharp edge, fuel not distributed properly. I would bet the piston top would show that there are quench areas at the spark plug top and the whole bottom of the piston. Poor flame travel because of the sharp edges.

Just to set the records straight, there was only one 273/318 casting, #2843675, from 1968 through 1974. It was of the open chamber design, 61-63 cc's, and the valves were 1.78" and 1.50". In 1975 and '76, the #3769973 casting was used but there were no other significant changes.

The next version was from '77-'84? but they were still of the open chamber config. After that came the 'infamous' and soon to be legendary - 302's.



I rather liked the heads, simply punched to 1.88 intakes and ported because they would give the dropped deck flat top pistons a nice mellow 8.8:1 or so compression.


I did section this article and recommend you read the whole thing..
CAMCamshaft is the next best upgrade you can do for the 318.

They really like the 340 hipo cam, which is still very mild, but is just enough to wake a 318 up. It has a lift in the .440 range, so any aftermarket camshaft between .430 and .455 work really well and mileage will not suffer, won't have to be high compression and doesn't require any high torque converter. Any more than that and you will kill the bottom end and the 318 will run like junk. This is an excellent cam for the 318.