removing and installing a 318 in '70 Fury...and fuel economy
- Thread starter PM27G0D
- Start date
Mother didn't start with the hardened seatz 'til 73. But any Machine shop should be able to install hardened seats in the exhaust side including a 3 angle valve job without breaking the bank(common sense as part of any rebuild)
Landyacht
Active Member
Increasing your compression ratio might help your fuel economy but you will have to pay more for premium fuel. 318 s already have decent fuel economy compared to a big block so I would just keep the original 2 barrel carb on it perform a basic overhaul and don't do any other mods if you want to maintain good fuel economy.
MrMoparCHP
Old Man with a Hat
If economy is the goal then the only mod I'd do is electronic ignition, then fine tune the carb and timing.
Alan
Alan
1970FuryConv
Old Man with a Hat
I agree with electronic ignition for a more consistent spark. I used the DUI system on a 360 with a marked increase in performance.
mpgmike
Member
An easy low-budget economy swap would be the Edlebrock SP2P intake with a relatively small (like 500 cfm) carb, Comp Cams 255 DEH camshaft, and a dual roller timing chain set-up with multi-keyway crank gear set 4 degrees advanced (unless you want to degree it in to be sure). Ideally this would all bolt around the later (88-92) 302 casting heads. They already have the hardened seats, and since you're not shooting for the 450 HP range, no serious porting needed. Plus, the manifold matches the heads.
Mike
Mike
mpgmike
Member
Just remembered another project I tackled 27 years ago. I took a 360 block, had it machined with a 0.030" over bore. Used '71 flat top pistons, and a Comp Cams 260H. The ENTIRE top end was 318 stuff. I used open chamber heads (which yielded a 10+:1 compression as I recall), 2 bbl carb & intake, and factory 318 exhaust manifolds. This went into a '74 W100 that could pull a house trailer and get 24 mpg on the hwy. Torque & fuel economy were awesome. Power died off around 4200 RPM. The icing on the cake is it would run just fine on low octane unleaded.
Wollfen
Old Man with a Hat
Now I wonder why doing that setup on a 360 gets you that mpg but if you did it to a 318 you would get less?
mpgmike
Member
Longer stroke allows for a more thorough conversion of the pressure to kinetic energy. Small ports keep intake velocities high for better homogenization and vaporization of the fuel with the air. The higher compression adds to the chemical-to-kinetic energy conversion. With a choked volumetric efficiency, actual cylinder pressures never reach detonation point; which is why it runs just fine on 87 octane fuel.
fury fan
Senior Member
Agreed with all of that except about the OD, the A500 and A518 both use the same OD section, so the A500 fits better simply because the trans in front of it is smaller, so the OD moves closer to the engine where the tunnel is larger. A benefit of the A500 is it would have a 2.74/1.54 gearing for 1st-2nd (like the A999), whereas the A518 has 2.45/1.45 (same as a 727). But if you keep the 2.76 gears, the OD is not much benefit (engine would lug too much). And this is outside your project scope anyway.
For your engine, though, a little change of direction increase in scope is probably worthwhile IMHO, so:
Agreed, the 5.2 Magnum is a winner for your goals. Will add 50+ hp easily (5.2 are usually 220-230 net vs 230 gross of a 1970 which is probably not far off from the 150hp net that started in 72) + better MPG vs a standard 318. A magnum will give hp and efficiency due to roller cam, significantly better heads, and a few other minor improvements. There are some things to consider to installing one of them though, relating to front cover-WP housing, fuel pump, intake manifold/AC compressor and belt drive. If you dig around on Dippy.org I did a few good write-ups some years ago (IIRC I am Fury Fan there also). Lots of good MAggie info on that site.
I agree with the references to the -302 heads of the late 80s, but those aren't easy to find anymore. MAggies are everywhere in JY. You might even be able to find nice low-mileage one that needs only an inspection and new gaskets. EFI engines last so much longer as there is less fuel washing into the oil. If you find a candidate, give it an oil pressure test, CR test, and pull the VCs to look for sludge. If it looks good, I'd 'clean 'er up' and run it.
I've heard numerous references that the 5.9s (and 360s also) are kinda gas hogs, so don't be tempted there. Plus the 5.9 and 360 are both externally-balanced (and they are different!), so there are some extra parts needed there, whereas the 5.2 is more of a bolt-in.
I major thing to watch - if using a Maggie and the factory EFI, you need to make a nice rounded slot in your trans housing near the pass-side cyl head, there is a sensor that mounts to the block to read the tone wheel on the flexplate (so you need that flexplate too).
I kinda think in your case a 5.2 with a 500 cfm Eddy (get an elec choke so it has the 'economy calibration') or maybe a new 650 cfm Street Demon (a reincarnation of a Thermoquad) would be an easier choice.
fury fan
Senior Member
I heard a similar story about one of those, except the guy put the late-80s closed-chamber -302 heads (the precursor to the MAgnum head) and he said the same thing - awesome torque! Always wanted to try to duplicate that, but, well, I just can't accomplish everything my brain concocts.
@PM27G0D – it’s be great if you would share more pics of your 1970 Fury iii ´vert. Your fender tag would be a great addition to the thread that acts as an informal « last convertibles » registry.
@1970FuryConv is in Virginia too.
I'll take some tag pics later today and post on that thread. As I remember, mine is not a late build though.
Don't worry. The thread was started by @c-barge thinking about the last built 'verts, but that has since an informal but pretty effective repository of information about all the 1970 C-body 'verts.
Look forward to your contribution! If you can share some of the history of the car as you know it, along with the tag, all the better
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