318 Build? Help!

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superdart

superdart

Shade Tree Tinker Gnome.....
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This entire discussion is for a 318 that is in my '77 M880 Power Wagon. I'll skip the details of how we got where we are now...but it's original and losing core plugs, 3 in the block so far. The latest is under the starter. Not hard to replace....but only a matter of time before I blow one out on the road. So I need to pull the engine to get to everything, so I might as well go ahead and do the rebuild I had originally planned for a few years down the road. Engine is a 318, all stock internals the valves guides are wasted but we dropped in new valve seals so it doesn't smoke much at all. I added a 625 AFB carb and Wieand Stealth intake. Headers are Summit block Huggers, exhaust is 2.5 pipes to a single 3" Walker Super Duty muffler. I have a Pertronix vacuum distributor and MSD Streetfire box to install, but the factory ignition is working fine for now. Don't ask about my haphazard methodology. I was just trying to get it driving so I could figure what else it needed after sitting 30 years.

Drivetrain is a 727, 203 full time transfer case, Dana 60 rear/Dana 44 front with 4.10s and 33" All terrains.

Here is the dilemma..what to build? It's just a toy. I have a car trailer but doubt I would ever pull more than 8000 lbs, and only local in flat-ish north Texas. No mountains, no long distance highway stuff, and not very often. After driving it as-is, it gets down the road pretty well (you know, 4.10s), I just want to give it a bit more for pulling to make it a well rounded all purpose vehicle.

Here's where the questions come in:

My Dart has a set of decently built 596 heads, adjustable valvetrain, etc on its 360. But, I scored a set of RPM heads from the Summit discount shelf. When I swap those heads on, the 596s will be available for a 318 build. My thought process is a set of -6 cc KB399s, the 596 heads, and pick a good torque biased cam suitable for the truck application. Or I could also just get the KB167 pistons to tighten up the existing chamber volume, but then I'm still running small 318 valves, if that even makes a difference for my application.

Thoughts? I'm open for discussion.....but "360" and/or "stroker" are not part of it. Not planning a repower and stroker will be utterly wasted in this application, and then we're into stall converters and stuff I'm trying to not get involved in. I have other vehicles that need that funding.
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:popcorn: I want to be the first one to post this and I will stand back and watch the posts fill up the forum. It's a good engine but it is small cube. It can only do so much.
 
If the truck is set up right, the 318 will pull without a problem. In fact, a slant six can and will. Just don't ask them to pass 3 cars at once going up hill trying to hit 90 mph. Keep the expectations real, drive it as it would have been driven in '77 standards, not in 2025 standards.
 
I kind of like your plan with the 596 heads and the RV cam. The 318 heads might not hurt you much--hell, they'd help in the bottom-end grunt department--but the 596s are done. Any money thrown at the stock heads is money wasted in my mind, and you admit the guides are wasted.
 
NoCar340 said:
I kind of like your plan with the 596 heads and the RV cam. The 318 heads might not hurt you much--hell, they'd help in the bottom-end grunt department--but the 596s are done. Any money thrown at the stock heads is money wasted in my mind, and you admit the guides are wasted.
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Yeah, the valves actually rattle with the springs off, lol.

318willrun said:
If the truck is set up right, the 318 will pull without a problem. In fact, a slant six can and will. Just don't ask them to pass 3 cars at once going up hill trying to hit 90 mph. Keep the expectations real, drive it as it would have been driven in '77 standards, not in 2025 standards.
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No delusions there. The Army dash tag says "Do not exceed 60 mph" LOL. It'll be turning 2800 @ 65 on the highway. Can't say I'd want to drive it any faster.
 
If you are going to tow with it use a 4 inch crank.


Edit: yes I saw the no stroker in your post. I say don’t step on your dick. The cost to do a 4 inch cast crank isn’t bad.

If you are rpm limited then adding stroke is the best end around option.
 
Now that is a front bumper.

I did the same thing with a 78 power wagon, but I took out the 318 and put in a 5.9 mag, dressed as a LA.
Night and day difference. And the 318 was not wore out.

A good comparison, pulling my camper, the 318 would only pull a long up-hill reaching the top at 45 mph max, floor-boarded.
5.9 would top the same hill at 75 mph with 1/4 throttle, and got the same mileage.

If you are hell-bent on keeping the 318, seriously, add some stroke and compression, it will make a noticeable difference.
 
With the gears they put in them M880s and the low range in the transfer cases, them things would go up a tree with a Briggs and Stratton, much less a 318. Just don't expect any mileage out of it.
 
How do you know the guides are *wasted" if new seals made such a difference?
Guide seals are the actual blame on many cases where the guides themselves get the blame
 
volaredon said:
How do you know the guides are *wasted" if new seals made such a difference?
Guide seals are the actual blame on many cases where the guides themselves get the blame
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Last I knew, valves should not clatter within the guides. Literally, they wobble when the springs are removed.
 
It don't take too much power to tow, just with smaller engines you might have to drop it a gear or two to get in the powerband, unlike a diesel that makes it's power at rpms that happen at general road speeds so no or little down shifting required.

Your probably gonna be in the 2500-4000 rpm range most the time, hp is 50% of torque at 2626 rpm and 75% @ 3939 rpm. With a decent 318 should be able to make 330 lbs-ft @ 2626 rpm so 180 hp and around 360-380 lbs-ft @ 3939 rpm so 270-285 hp.

Sounds like your plan is on the right track just don't go crazy with cam and everything should be fine.
 
Built many trucks and all had 410's. My choice in the same truck was a completely stock 69 340 with the AVS it came with. It pulled like a freight train.

I had a 73 360 HP in one and I did not like it. The only other choice would be a P pump 5.9 or 2004-2007 5.9 Common rail. I did that too the problem was the cost. I also did a Dyers blower on a 340, The common rail out performed it. You ask for an economic advice Look for a 10.5 340 use iron heads and dual plain intake.

" Or keep your 318 and install early 340 large valve top end and cam". This would be the best bang for the buck. Now this is my opinion on what worked for me using what I had, I am sure there are late magnums out there that would work just fine with fuel injection for today's fuel.
 
the key to this whole endeavor is two fold: making power down town (ie under 5K) and maximizing the the parts to work together in the best possible way.

i like the idea of the bumping up what is surely dismal compression with either of those pistons and pairing them up with those 596's, with the stealth up top and a reasonably sized carb that should provide excellent throttle response, and a modicum of fuel economy (i mean, what there is to be had from pushing that brick thru the air).

the trick here is going to be the cam and resisting the urge to go big. i would 100% pick something with a split pattern that is around 450 lift with sub 270 duration. the old purple shaft P4452759 was an absolute gem for a build like this with 430"/.450" lift, 260/268 duration 110LSA. heck, even a stock 360 2bbl cam would do well.

with something like this, the devil can be in the details. your tune needs to be spot on, and that starts with the distributor. get it curved properly for the upgrades you've done and the type of driving you'll do- this part is far more important that what kind of box is sending the sparkle pixies to the end of the line. you can free up some HP with an electric fan, duct in cool fresh air, utilize lightweight components where you can. i don't know how married you are to the block huggers, but some tri-y's would probably be a much better fit producing more low and midrange power. ounces add up to pounds and in the same way a few hp here, a few there from some simple tricks and you could be realizing 20+ hp right in the meat of your operating range.
 
More compression and higher velocity through the carb = success in my view
In my book that means
small carb, well matched small runners, small ports, small valves, big capacity
= superlative operation at smaller rpm

never built a 318 never owned more than 6 cylinders in one motor.
but i achieved similar in my old VWs days by building big capacity motor with higher CR and the heads off the small capacity motor, a cam designed for towing and a carb that everyone said was too small, because everyone was fixated with drag race motor specifications. original dizzy with vacuum advance most definitely connected.
lets call it a "touring" rather than "racing" motor....

Nice induction roar, and i could tow a plough up a cliff..well that's what it felt like....bags of torque from 1000 rpm onward is a nice thing. top end power not needed when you are driving a cute looking fridge overloaded with spares, junk and solid wood camper conversion furniture.
could overpower the tyres on a very steep hill if not careful, and that's one silly-looking bouncy, burnout, reduction gears on the ends of 60s VW van back axle leads to odd behaviour , nobody is impressed other than the builder of the motor :) .

Your wishes sound similar, you just have more capacity and more options.....
the key was 10:1 the right carb heads and cam, that small carb that acted as a rev limiter somewhere a little bit short of the redline of the original car specifications for the motor

this was all done with, more luck rather than judgement, having to use what i had rather than any great insight, i chose the cam but i only really understood why it worked quite well later on

Dave
 
I am doing something similar with my 318; it is a stockish combo with -5cc kb pistons, cast crank and stock rods, and the only machine work being done is a light ball hone and zero decking it. I have speedmaster 170cc heads; and a torker for the top end. Going through different camshaft options on desktop dyno with my boss at work, we found the best off the shelf cam for low to midrange torque is the Hughes SEH1620AL https://www.hughesengines.com/Index...Y2sgIkxBIg==&level1=Q2Ftc2hhZnQ=&partid=30239

My engine is going to have 9.72:1 SCR and be a nice little street 318 for right now ~2000$


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shittyslant6 said:
I am doing something similar with my 318; it is a stockish combo with -5cc kb pistons, cast crank and stock rods, and the only machine work being done is a light ball hone and zero decking it. I have speedmaster 170cc heads; and a torker for the top end. Going through different camshaft options on desktop dyno with my boss at work, we found the best off the shelf cam for low to midrange torque is the Hughes SEH1620AL https://www.hughesengines.com/Index...Y2sgIkxBIg==&level1=Q2Ftc2hhZnQ=&partid=30239

My engine is going to have 9.72:1 SCR and be a nice little street 318 for right now ~2000$


View attachment 1716326954View attachment 1716326955
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Sorry, but there is no way in hell a 9.7:1 318 with 170cc heads and a 216/220 cam will make anywhere near that power and torque. What program is that?
 
TT5.9mag said:
Sorry, but there is no way in hell a 9.7:1 318 with 170cc heads and a 216/220 cam will make anywhere near that power and torque. What program is that?
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Well, it's just desktop dyno 5, I believe and I know it's within 8-12% accuracy.
I think it will make that much because it's going to spin to 7000+, and surprisingly the speedmasters flow exceptionally well for what they are.

But pertaining to this thread; even if it does not make the calculated power the program says; this combo at LEAST make more than enough torque and horsepower for OP's similar build to have fun with.
 
Love a good 318! Can't wait to see how it comes out. And luckily everyone here prefers a 318 to any other small block :)
 
shittyslant6 said:
Well, it's just desktop dyno 5, I believe and I know it's within 8-12% accuracy.
I think it will make that much because it's going to spin to 7000+, and surprisingly the speedmasters flow exceptionally well for what they are.

But pertaining to this thread; even if it does not make the calculated power the program says; this combo at LEAST make more than enough torque and horsepower for OP's similar build to have fun with.
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410 lbs-ft ain't impossible it's 1.29 lbs-ft per cid which is kind of on the high side for that level of a build 370-390 lbs-ft is a more likely number (1.16-1.23 tq:cid).

Main problem I see with that desktop dyno prediction is what's happing after 4500 rpms highly doubt gonna carry the torque up that high both peaks seem around 1000 rpms too high.

Say the 318 makes peak power 1000 rpms lower 6000 rpms which is probably on the high side with the cam you got and 1.2 lbs -ft per cid = 382 tq.

382 x .9 x 6000 / 5252 = 393 hp
 
punched my numbers for my 318 into dyno 2000, 315hp! Sounds bout right :) no need for more than that.
 
Oldmanmopar said:
Built many trucks and all had 410's. My choice in the same truck was a completely stock 69 340 with the AVS it came with. It pulled like a freight train.

I had a 73 360 HP in one and I did not like it. The only other choice would be a P pump 5.9 or 2004-2007 5.9 Common rail. I did that too the problem was the cost. I also did a Dyers blower on a 340, The common rail out performed it. You ask for an economic advice Look for a 10.5 340 use iron heads and dual plain intake.

" Or keep your 318 and install early 340 large valve top end and cam". This would be the best bang for the buck. Now this is my opinion on what worked for me using what I had, I am sure there are late magnums out there that would work just fine with fuel injection for today's fuel.
Click to expand...

What didn't you like about the '73 360? My '72 D200 (3.54 gears and 33" tires) has a mostly-stock 360 and it has plenty of torque although the RPM range is limited, runs out of breath around 4000 RPM. I don't dislike it but then I haven't driven a truck with a 340 or Cummins.

To the OP, I like milder engines in trucks. Compression no more than 9-9.5:1 to be able to run regular gas (since mileage will be terrible no matter what), milder cam to not require a higher-stall converter which will slip and build heat when pulling loads. Better heads won't hurt but will improve performance mostly just at higher revs. With a theoretical top speed of say 75 mph (you said you don't intend to go much over 60), there isn't much need for more than about 300 HP, if that. 300 is a very doable number for a 318 with over 9:1 compression, good heads/intake (Performer RPM...?) and a realistic mild performance cam. I think those 596 heads would work fine.
 
i've built a few 400hp 318's and they all had more cam than that. also they were just at 400 and straight up done at 6000ish

the graph shows most all of the power at 4K and more, with that big goofy torque dip and flat right in the meat of where you'd be cruising.

you could make the same torque with a smaller cam all day and be right in the wheelhouse of where the general operation for this type of vehicle would be.

also, i wouldn't buy a cam from those jokers based on the experiences of others.
 
junkyardhero said:
i've built a few 400hp 318's and they all had more cam than that. also they were just at 400 and straight up done at 6000ish

the graph shows most all of the power at 4K and more, with that big goofy torque dip and flat right in the meat of where you'd be cruising.

you could make the same torque with a smaller cam all day and be right in the wheelhouse of where the general operation for this type of vehicle would be.

also, i wouldn't buy a cam from those jokers based on the experiences of others.
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3/4-ton pickup truck (heavy), full-time 4x4 and 727 trans, D44/D60 axles, aerodynamics of a refrigerator... lots of parasitics to work against by the time the power gets to the road. Agree 1000% the performance will be far better if the focus is on bottom-end and mid-range torque instead of a peak HP number.
 
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