I have the oppertunity to snag a '71 Plymouth Sebring with a 318ci and 904 trans, and the seller also has a 440 pulled out of a truck of a smilar year that he'll sell to me too. I'm not a Mopar guy, but I think that this is an oppertunity I simply can't pass up. Problem is, I really don't know what I can do with them budget-wise. Can you cheaply upgrade the 318 with a port/polish and cams for a good street motor? What can you do with a hunk of iron like the Big Block Mopar? And can you do it on a small budget, like a couple grand?
Hit up the Roadkill guys on FB or Instagram.
Aaron_King said:
Hit up the Roadkill guys on FB or Instagram.
Good suggestion. They love their mopars!
We have plenty of mopar guys here.
Hi!
Having dine plenty of small block stuff, i can speak credibly to that, and a little vague on big block.
318 biggest hurdle is shrouded valves due to small bore. That being said, a set of late 90s 5.2 magnum heads, a goid dual plane air gap manifold, headers, mild cam, distributor recurve, and a 4bbl will make them plenty peppy. Dont expect built small block chevy, but a decent 305 or 327 would be a good comparison. Plenty. Heck, a full magnum engine swapped to carb would get you a ton of torque, and a lot of street fun. For 400-600 bucks depending on the price of engines in your area.
The big block will be limp from that era. Hoelwever, mi us the heads the same plan as the 318 i outlined above really wakes them up. For reference, i had a milder version of that 318 in my duster and blew it up. Proceeded to swap in (temporarily. Hated it.) A 1978 motorhome 440. Other than the extra weight, it had a bit more torque. Thats about it. Wasnt really any faster than the bolt on 318 it replaced. Then went bolt on 77 360, which was faster. But thats a long stiry....
My reccomendations: bolt on/mild 318, carb-ed magnum 5.2 and be done. All the brackets, mounts, linkages, flexplates., driveshafts already there.
https://www.hotrod.com/articles/mopp-0409-318-engine-build/
That's a 400hp build for the street. Factory heads that are available all over the place. No turbos, no nitrous, nothing exotic at all, and it was built to run on common pump gas.
NickD
PowerDork
7/1/19 3:07 p.m.
https://www.hotrod.com/articles/318-small-block-build/
Waaaay back in the day, Hot Rod did a Junkyard Jewel build on a 318. With ported and milled factory heads with bigger valves, a cast-iron 4-barrel intake with a Thermo-Quad, off-the-shelf cam and headers, they made 379hp. An Edelbrock 4-barrel intake, a 1" spacer and a Holley 650 carb bumped it up over 400. And the heads they used weren't even some 1968-only optional exotica, they were #302 heads, a 318 2-barrel swirl-port head from ’85-’91 Chrysler Fifth Avenues, Diplomats, Grand Furys, pickups, and vans.
Edit: Dammit, pre589 was just a little faster on the draw.
Cheap-ish ticket to decent power from a Mopar is a junkyard 360 Magnum, better heads (almost every set of factory Magnum heads out there is cracked and they only flow decent-ish, plus there are good cheap-ish heads out there). That plus a cam, decent intake manifold and headers will get you into the 400 - 450+ hp ballpark without touching the bottom end of the motor (depending on the heads you run and how much cam).
This article has a good example: https://www.hotrod.com/articles/hrdp-0804-small-block-mopar-engine/
You need to make some oiling modifications for competition.
A 71 vintage 318 would be a fairly snappy performer. It would still have some compression.
Streetwiseguy said:
You need to make some oiling modifications for competition.
A 71 vintage 318 would be a fairly snappy performer. It would still have some compression.
Yep. Learned that the hard way. The oil pump drive shaft on these is a weak point. I had a built-up 360 in a '74 Sebring and lost oil pressure one night. I was just tooling along about 50 mph, when "down in the dips she started a knockin'" Gauge was flatlined. I had the presence of mind to instantly kill the engine, roll to a stop, and sleep in the car until morning. The new high (insert one: volume, pressure, can't recall) pump was too much stress on the stock drive. After getting the car home I popped in a special hi po hardened steel oil pump drive shaft and she was happy again.
Man. I had Edelbrock heads, a thumpy cam, headers, etc on that 360. And 3.23 gears with a 727 trans. It was a real ground pounder. Now you've got me jonesing for another Mopar....
volvoclearinghouse said:
Now you've got me jonesing for another Mopar....
Same. Sometimes I think about my '64 Savoy, only this time around, a 5.2 Magnum and some kind of five speed behind it, probably a W58, with a host of other things done to make it a good daily driver.
And then I start thinking about Ford Capri's and forget about the Savoy.
