Another 360 Build question thread...

[318duster73]

So, I have here, a stock bottom end '85 360. I have a set of '71 360 J heads, milled to a visible, but unknown extent, or the '85 smog heads that came with the 360. Also, I have an LD4B intake with Eddy 600, or the '85 360 intake with the original Qjet.

The rest of the engine will be consisting of a MP purple cam at .512/.512, Hooker headers, MP Chrome box, MoPar electronic distributor, MSD Blaster 2 coil, and MSD wires.

My plan was to use the J heads as is, as long as my lifters and rods aren't too long(Shouldn't be, as I was using the same heads and cam in the 318.), and the 360 intake and Qjet. I'm guessing I can hit 9:1 compression with the amount that's been taken off the heads already. Comparing between the '85 and '71 heads, at the shallow side of the chamber, the '71 heads appear to have maybe half the material between the face and the ceiling that the untouched '85's do.

So I guess my questions are :

1: Is this a realistic estimate on the c.r.? Higher? Lower?
2: Would the weight difference make using the smaller runner aluminum LD4B intake worthwhile, with that big of a cam? (I figured no, along with the size difference in the carve, but hey, why not ask some more experienced guys)

 

[rumblefish360]

Just check your Pushrod length as to how much the lifer is depressed downward.
You lack the mention of cAm duration. I myself would use the iron 4bbl and Q-jet. But that is just me.

 

[Oldmanmopar]

The heads you use would determine the intake choice. Some J's / 915 are smaller ports . Don't use the large port intake with the smaller port heads. I have both sets here for comparison pics if needed. . That cam choice will need more compression and high flow intake and heads. You may want to consider a single plain depending on duration. With a cam that large and compression ratio that low it won't have much low RPM torque. Get a high stall converter or it will be a pouch.

 

[rumblefish360]

J'a and 915's are 340/360 heads, there port size varies from year to year without much fan fare to bother with. Id like to see the pictires.
Suggesting a single plane maybe a bit premature. Basing a cam size on lift alone is t a good idea since a cam from Hugesengines tends to run higher lifts than normal vs. other cam manufacturers.

The mis-match between ports is of a low concern with smaller camshafts.

 

[318duster73]

Measured the difference in face height between the '85 heads and the 915's, and the 915's are shorter by .10 - by my calculizing, that's 8cc(give or take). Assuming (yeah, I know, im a total retard for assuming, but I don't have a cc tool just yet.) that the 85's are a typical 71~cc, that brings the 915's to 63cc or so. Which means they really could be anywhere between 57cc and 66cc~, depending on what the 85's are. OR, I could just be totally insane here.

The ports are the same size between the two sets of heads, so I'm guessing they're both the larger port size. I wouldn't mind seeing those pictures, though.

Looking at the list of small block Purple cams, I find it hard to believe the previous owner, as there are no MP cams that run a .512 lift(that I can find, anyways...). I'll be pulling out my calipers tonight to verify the actual lift, and find out advertised duration based on the lift data. It DOES have visibly fatter lobes than the stock cam I pulled out of the 360, but I'll measure when I get home. From what I can tell, all of the MP cams have more lift and duration than the stock 360 cam, with the stock 340 style being the smallest, so whatever it is, it's still an improvement. Still, with the way the 318 ran at low and high rpm, it must be at least the .508...

I've already gone through the Qjet with a rebuild kit, so it's good to hear that I was headed in the right direction there.

The 'teen that the cam and heads were in previously was a total dog at low rpm's, but it was a real kick in the pants at anything over about 3k, so I'm planning on a 3k~ converter. Worthy choice, or should I go higher?

I do eventually want to go with some domed pistons, but that could be awhile... And, of course, I can't stand the look I get from the engineless Duster every day when I head to work! It's getting angry at me!

 

[BrianT]

I would not run the LD4B on a 360. It's a good manifold for a 273/318 build and people are looking for it. If it is in decent shape, sell it and use the money to buy a different manifold. I sold this intake for $284 last week. That's almost enough to get you a NEW air gap intake.

 

[318duster73]

According to my calipers, the cam has a 1.250 center circle, and a max lobe height of 1.572, which works out to .483 at 1.5. Given that, I'm guessing that its the MP 284* hydraulic, p4120231, with .484/.484 lift, and .241/.241 duration at .050. So much for the p.o...