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Building a 318

Discussion in 'Performance' started by PCRMike, Apr 22, 2017.

  1. PCRMike

    PCRMike Well-Known Member

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    I happened to get a rebuilt 318 A of 1967 vintage for my sons truck. It has very low compression smog pistons in it and I am going to upgrade that. All the machine work is done on the block. It has the later cast crank. I don't like the little skinny rods in it which after checking are actually from a stock 273 or 318 two barrel. I got nosing around my shop and found a nodular iron cast crank from my magnum and a pair of forged 273 cranks. I am ordering some zero deck Pistons and going to use the magnum rods. I am curious what sort of power level the stock cast crank can handle. I am also wondering whether the magnum crank or the forged crank would be a better idea for this engine. I am mounting fully ported magnum heads and intake on this engine. My questions revolve around the bottom end. With a stud girdle that I will be installing, is the factory crank any good? Is the factory forged crank any better than the later magnum crank? I have built numerous small blocks, but they were always either with aftermarket cranks or with a 360. Advice here would be welcome.
     
  2. PCRMike

    PCRMike Well-Known Member

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    I am intending a range of up to 6500 rpm with valvetrain upgrades and such.
     
  3. dana44

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    You may want to get onto one of the compression calculators what with the flat topped zero deck clearance pistons and Magnum closed chamber heads, you will be pretty high up there on the compression, maybe a little higher than you would want and still be able to run 87 or even 91 octane, just as a thought, so get the cc of the combustion chambers and make sure to remove all sharp edges inside the combustion chambers (there are a lot of them, edge of the quench pad from the chamber, remove completely, it helps a ton, as in free 35hp at a minimum, and along the edges of the combustion chamber to the gasket edge, plug it into the computer and see what it will be, 10:1 can run on 87 octane with these mods all day long, not without them. As far as the cranks go, they should all be capable of handling upwards of 500hp without much problem, but cast and nodular cranks are not that happy at that rpm range, they tend to gall bearings above about 5500rpm after time, and additionally the steel crank from the 273 should be able to do what you want. Either crank you use you want to chamfor the oiling holes, as in removing the sharp edges and making a little dimple at each oil hole, helps with the higher rpm to prevent scraping the bearings, extra oil volume is always a plus, I run high volume oil pumps on everything I can. Heavier strength rods are always a plus, polish the sides with a carbide burr cutter, not a grinder, to remove stress cracking, and balance them and the pistons. I am kind of partial to adjustable rockers and anti-pump-up lifters, so if you have 273 rockers that are adjustable, zero lash and you are good for the 6500rpm you are looking for, otherwise, you might not get that part of the deal. I believe the AMC V8 lifters can be gotten in anti-pump-up that are Mopar small block size. You will have to go with some kind of Tarantula or Torker style intake, single plane (and if the heads and intake are ported it works just fine on the street, done it half a dozen times myself, dual plane intake peters out above 5000rpm most of the time). Looking back at your post, if the heads are early closed chamber heads (hopefully), double check that compression with zero deck clearance), and installing simple 360 1.88 intakes are a plus on the breathing for the smaller 318 intake valves even though 2.02s do fix, not really needed for the 318 and even 6500rpm. After the 1.88 valves are cut, just tulip the shape, don't hog it out, the flare really brings the small ports to life on the 318. Any more questions, keep them coming, I've done a couple of these and there are some good little tricks to make a 318 come alive.
     
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  4. PCRMike

    PCRMike Well-Known Member

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    I have built many sets of heads, and several 360 engines above 400 horses, but this is good info. I will be doing a full prep on the magnum heads (stock 68cc, but after mods, I will be equalizing and computing. I am figuring on having to run premium anyway. If the 273 crank would be able to take the rpm I will use it. I will stress relieve the rods (burnishing) and likely run the Comp XE268 cam with Rhodes lifters (fast bleed). May go one step bigger. With the magnum heads, I will be upgrading the rockers and studs too. 3/8 conversion studs are required for this.
     
  5. PCRMike

    PCRMike Well-Known Member

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    They come stock with 1.92 intake valves. I am midway thru the porting now. Lots of flow all the way around the valve. Bowl work is my specialty. I haven't removed the "hot spots" yet, but that is coming soon.
     
  6. dana44

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    OK, wasn't sure what heads you were using from the original post, so had to add both comments. My only concern with the 273 steel crank is flywheel bolt pattern, remember some of the early 273s had a different pattern than the standard 318, so verify that. And I'm sure, similar to the 3.9 heads, is the shark fin in the end of the intake ports (kind of stupid), so remove that, too. I always love the little ring lips around the intake and exhaust valves, so get rid of them, too. Additionally inside the combustion chamber, the lip to the quench area, remove it at the angle of the valve pocket angle, that lip is horrible, plenty of material not to worry about weakening anything. Run the sides of the combustion chamber outer edges of the pocket so they match the head gasket ring. This allows the flame to burn both faster and all the way out to the cylinder wall instead of having little dead spots until the piston drops. By rounding and removing these little quench areas improves bottom end torque and top end flow, keeps things cleaner inside because the flame moves outward the whole time (instead of reverting back into itself and then cokes up leftover fuel), and keeps the oil a whole lot cleaner, so a whole lot more efficient in the end. You will notice a difference over just a port job alone. The only thing I don't care for on the Rhodes lifters is the low rpm racket, otherwise, good on that.
     
  7. RalphP

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    My main question is - is it a "A" block 318, or a "LA" block 318? If an A block, are you sure you can use the 273 LA crank in it?

    Also, dana44's comments might not be applicable on the "A" block polyspherical heads; his are for the "LA" block wedge heads.

    (Or some of them may apply; the LA was derived from the A block after all.)

    RwP
     
  8. PCRMike

    PCRMike Well-Known Member

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    To be clear, this first engine I am building is a late A, or LA wedge head. I will be using KB167 pistons with it for a 10:1 ratio. Cranks are interchangeable from A to LA, but early poly has an 8 bolt flange. The later poly 1962 and up uses identical crank to the 273/318 wedge.

    I about have the engine combo sorted, cam and all, but I have a slight dilemma. I have the A-999 three speed with the truck, and a 42RH from a 1993 Dakota. I am wondering if a proper build with an upgraded rear drum and sprag set would handle a 400 plus horse 318. Must I upgrade to a bigger trans on a 3800 pound half ton?
     
  9. dana44

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    I would go for the hassle of the 42RH for the overdrive, which helps with the highway cruising rpm levels and doesn't have to be engaged if you don't want. There are kits for the kickdown and overdrive engagement requirement available.

    I would think the rear end would be strong enough, but verify it is a limited slip unit, that might want to be upgraded. Do you know which rear end it is, the 8,25 or the 9.25? A lot of times the 8.25 can be upgraded with an 8.75 with spring perch relocation if not mistaken.

    Oh, and one last thing, since you are into and know porting, do you use the carbide burr cutters to do your grinding? If so, do not polish after the burr cutting is done. I learned a whole long time ago, like 35 years ago (showing my age), that the little cup/chip texture prevents fuel from puddling and keeps the fuel suspended much, much better than polished surfaces, including preventing carbon buildup over time. I have a 361 B block set of heads I ported and then tore down because I thought 125,000 miles had used up the valve guides (which were OK, it was valve stem seals), chambers and ports looked like they had 3,000 miles of running on them, they run so much cleaner than polished. Any flow surface, combustion chamber, ports of heads and intake, leave the burr cutting surface for cleanliness and efficiency, the little chips in a simulator "force" the fuel and air away from the surfaces and can't stick.
     
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  10. PCRMike

    PCRMike Well-Known Member

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    I only polish the services in an engine that will be receiving forced induction. I agree with your perspective on the rough-cut walls. As to the rear end, it is currently an 8.25 however I am planning on a 9.25 swap. I am going to be using 3.92 gears and a limited slip. I am just hoping that the 42RH is up to the task of handling that level of power. I am sure that many of the same tricks for building a 904 would be applicable to it
     
  11. PCRMike

    PCRMike Well-Known Member

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    Depending on where the work is, I will often go back over the bowl with a stone to retain the rough finish but remove some of the more tangible imperfection.
     
  12. dana44

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    Yeah, I don't like the stone scratches in the surface of the ports or combustion chamber. Did a fair amount of testing back in the early 80s on surface texture, the carbide burr cutters leave a texture that works similar to the dimples on a golf ball, the surface tension prevents the fuel/air from separating. Stone cutters tend to cause a chatter of fuel and air and allow separation of fuel and puddling (smooth surfaces). Ever notice how you hit an rpm, like 2800-3000rpm and she takes off? Talking with a lot of hotrodders over the years and a lot of guys/gals don't like ported heads on the street because of the loss of bottom end power and loading up. Carbide burr cutting surface completely alleviates this issue, just like running a Torker or Street Master straight runner single plane manifold on the street is usually a no-no, this texture allows that.
    All the porting articles I have read over the years I have seen one guy, up in Idaho, that does it right. The articles do all the grinding and porting and throw them on the flow bench, then find out they make an extra 3-5cfm by polishing the ports. I don't care who you are, nobody can tell that difference on the street. Flow numbers aren't actual performance, it's just ability to get from point A (carb/TB-injector) to B (combustion chamber), and then produce power at C (flame travel). The best thought inside the combustion chamber is, the farther the flame travels without obstruction to the outside of the cylinder walls with the piston at its highest position (before it starts moving down the bore) the more power you will have, and sharp edges prevent that from happening. Rounded edges allow the flame to continue over the surface outwards, sharp edges revert (ever stand on the side of a building and move slightly to have a wind catch you? Or stand behind a tree to get out of the wind...doesn't work well). This is why the Hemi combustion chamber works so well, explosion at the highest possible compression makes the most power, the piston dropping to burn the residue because of quench pads and a sharp edge just gives you dirty quench pads. And then the carbide burr cutting surface makes the flame curl ever so slightly and outward from origin (spark plug) to burn more efficiently at all rpm levels.

    Oh, and upgrading to the 9.25 is a good move. Haven't really heard of any problems of the 42RH being weak given the 5.7 was in front of it, too, and guys have been sticking it behind 440s for about 20 years and I haven't heard of any weakness issues, it's the overdrive that you want with 3.92s, so I would say a good rebuild can handle it without an issue.
     
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  13. PCRMike

    PCRMike Well-Known Member

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    Good info. I will leave it rough cut and have it tested. I flow balance all my heads.
     
  14. dana44

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    By all means if you have the ability to test them, great. Like I said, a 3-5cfm difference between burr and polished shows flow, the combustion chamber stuff can't be tested for efficiency through flow, except when it comes to deshrounding the intake and exhaust valve itself. A good example is the old 2.2/2.5 combustion chambers (782 head?), where a whole bunch of the quench area shrouds the intake and exhaust valve in a heart shaped pocket. The shrouded area is half an inch tall. No matter what you port, unless that quench pad is opened up so the taller the valve opens the wider the gap, you can port all you want. I once spent an hour and a half explaining this to a guy who then ported one of the head on a turbo engine. All the hotrodder porting companies indicated running a cam larger than .500 lift was a waste because of turbulence, as shown on many grafts I have seen. By opening the back side of the quench area on the combustion chamber to allow the flow, this guy was able to get the same quarter mile track time and speed with 20lbs of boost as he used to get with 30lbs of boost. That's efficiency at its best.
     
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  15. PCRMike

    PCRMike Well-Known Member

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    Exactly. I appreciate the info. I too have beat my head against the wall dealing with ignorance. Explaining why port velocity was as important to cylinder filling and thorough combustion was one of those times.
     
  16. dana44

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    Yep, and as a matter of fact, my mentor from way back still does some porting and indicates, which I too have done, leave the ports stock and just do the combustion chamber to get good results. The cool thing is, when the combustion chamber is done to improve the combustion alone there is a noticeable difference. The 283 in my 39 Nash, when we learned all this combustion stuff, it was described by his mother calling from 150 feet away at night to quit revving his big block open headered at 11pm, it was rattling the dishes in the china cabinet. In other words, small blocks can change the tone to a big block, because it is burning that much more efficiently. Oh, and if removing material and dropping the compression is thought to be an issue, no, 1 or 2cc out of the combustion chamber is more than made up for in efficiency of the flame travel itself.
     
  17. PCRMike

    PCRMike Well-Known Member

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    I have always believed in deshrouding the valves and removing any heat risers. My mentor in head porting was was none other than the late Bill Maverick Golden, of little red wagon fame. He said for street use it was important to round and contour any square edges or sharp spot. He said that bowl work is important and contouring for smooth and non turbulent flow was vital. For race engines I always went beyond the rough-cut, but I am always eager to learn something new. It requires almost the eye of an artist. We are a dying breed my friend.
     
  18. PCRMike

    PCRMike Well-Known Member

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    And acquaintance of mine in Arkansas for whom I built several engine, got his first eye-opening experience from me with his 350 Chevy. He has the heads ported by a so-called professional. I convinced him to take the heads off and give them to me for a couple days Free of charge. After doing the D shrouding work, he dropped 2/10 of a second off his quarter-mile time in his little S 10 pick up. OK, I did a little more than that the shrouding but no work to speak of. If I remember correctly, I went no further than the bowl. It has been about 12 years ago, so my memory is a little bit fuzzy.
     
  19. dana44

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    Yeah, the combustion chamber work was an accident with my mentor and me, too. When he was a teenager, he was in the machine shop at Pomona International Raceway, so dry sumps, shaving heads and blocks so tight that head gaskets weren't required, things like that. He had ported the heads on my 283 (he had talked me into hotrodding the Nash instead of going stock, I had found a 40 Hash so had a stock motor and transmission to use), and needless to say, the engine did not get completely run and about a year later we installed it and the rings had gone lax and wouldn't seat. So, in pulling the heads found out the studs had pulled out of the heads so we had to stud the rockers, and in his knowledge, noticed the black build-up in the quench area and figured out what had caused only 65 percent of the cylinder to be burning, thus the edging of the combustion chambers. Until I put a 33 gallon fuel cell where the back seat would be (it's a business coupe), I could pull the front end off the ground enough that it scared the living daylights out of me the first time I did it. Not bad for a 283 with 1.78 intake valves and .465 lift cam, 4bbl.
     
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  20. PCRMike

    PCRMike Well-Known Member

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    As long as the 42RH trans will hold, I will be oh-tay.
     

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