How do I build a Mopar 318 for 350 to 400HP?

[geoffreyj318]

Hello. I have a 1968 Mopar 318 engine. I want to build it up, to produce 350 to 400 HP. The only decision I have made is to fuel-inject it with an Accel or Holley EFI system. What is a good intake manifold, cam, cylinder head combination?

Also, I plan on changing the 727 transmission to an overdrive unit.
Which would be better, a Mopar 518 or a GM 700R4 w/ adapter? I know that both will require shortening the driveshaft.

[go-fish]

I can't remember if 68 was what they called the Poly 318 or the LA 318. If it is an LA it's probably the first year for it, the LA was used from 68-9? till Magnum. It was produced in Los Angeles. If it is a Poly, ditch it. It would be better as a boat anchor. If it's an early LA it comes from better ore and better structure, but also a potential for past abuse. Go with a later 318 or better yet 360 if you happen to have a new anchor. The #'s are on the drivers side of the block. http://www.allpar.com/mopar/318.html This will help with identification.
Once you know you have an LA you can start searching for you stoker crank, popular 4" strokes and .030" bore in the cylinders will get you 416 cubes from a 318 or 340 and 408 cu in from a 360. These new cranks are the best things to happen to small mopars since the W-2 heads. You can get a kit on the cheap through internet shopping, try ebay.

I know you weren't lookin for bottom end recommendations but the 4" stroker crank is alot of bang for the buck. A good stroked 360 with a good valvetrain and induction will just about desimate any SBC(disclaimer: not LS).

With the heads, you will have to do extensive work for the factory style heads to produce, they were all open chambered. W series heads are way too expensive for a modest budget. Edelbrocks are good value, aluminum, closed chambers, 2.02 & 1.88 valves, and lighter to boot.
For intakes, Edelbrock makes a good F.I. setup, comes with all hardware and software. But, again, for the modest budget a new Edelbrock Super Victor single plane and a 750 will get you there.
As for the cam, I wouldn't really be asking around here unless there is a cam grinder. There are plenty of guys on here that could give you great recomendations and they are bright people but a cam choice is best made when you call up a grinder and tell them, this is what I have and this is what I want to achieve. Have all of your specs ready, including valve sizes, carb size, displacement, comp ratio. You wanna have all that nailed down when you start talking cams. It is not so much as asking, "Hey you make alot of power, what are your cam specs?", then getting thier grind and expecting the same results. For some really good advice from a small block Mopar wizard call Hughes Engines, they can hook you up with a good cast crank stroker kit, heads, intake, and they grind cams too. Dave Hughes is well respected in the Mopar world. www.hughesengines.com or 309-745-9558. He will take the time to BS with you and won't try to just sell, sell, sell.

[Rolling_Thunder]

http://www.hotrod.com/howto/113_0304...ild/index.html

[lantzn]

The poly 318's last year was 1966. I had a number of 1967 Mopars that came with the newly designed LA318. The predisesor to it was was the 273. From that 1967 318 came the 340, 360 and I believe even the Viper V10 was designed from the LA by adding a couple more cyclinders. That engine design was around for a very long time.

[mmosley]

Edit: OK - sorry if this seemed random, somehow read this post and did not realize it was from 2006...

Hello. I have a 1968 Mopar 318 engine. I want to build it up, to produce 350 to 400 HP. The only decision I have made is to fuel-inject it with an Accel or Holley EFI system. What is a good intake manifold, cam, cylinder head combination?

Also, I plan on changing the 727 transmission to an overdrive unit.
Which would be better, a Mopar 518 or a GM 700R4 w/ adapter? I know that both will require shortening the driveshaft.

400hp would be a mild build. The 518 is a horsepower thief. I would do a 727 or 904 with a Gear Vendors OD or the GM transmission. Call this guy: http://www.cpttransmission.com/ and ask him about running a GM 200-4R in a Mopar and see what he says. I would not use a 727 in a mild build on a small block unless it was a towing application, I would use a 904/999. The 727 is heavier, and the 518 is basically a 727 with an OD. The 500 is the lighter "904 version" of the Mopar OD transmission.

318 zero deck, about 10.5:1 with 63cc Aluminum Edelbrock heads and a dish piston would be strong. A 318 block with a 4" crank, zero deck, the Edelbrock 63cc heads, and a very mild cam will make 400hp with no effort at all. You may have to run a larger dish to reduce compression if you run too small a cam to keep the dynamic compression at a reasonable level. Either way I would dial in the compression with piston choice, retain the good squish and small chamber. Basically choose the cam, then calculate the dish volume needed to keep the compression low enough for pump gas. If you run a wide LSA 112-114 EFI will be very easy to tune.

318 is 3.31 stroke, 3.91 bore. 0.030" overbore yields 323cid. 0.030" overbore and a 4" crank yields 390cid. The disadvantage of the 318 vs. the 340 or 360 is that the smaller bore does affect head flow, but a 390cid engine can make plenty of torque.

Here is a build article Car Craft did with cheaper RHS iron heads and made 470+hp: http://www.carcraft.com/techarticles...t/viewall.html
For a more streetable build I would reduce the cam a few sizes down to about 230 @ 0.050 with a 112-114 LSA and run EFI, it would not make much less power. Same combo at 323cid would make about 380hp.

[72BBSwinger]

Magnum 360 heads with good valve job, 10.1 CR and a 484/284 purple shaft. DONE.