318 stroker

[TrxR]

What do you think of a 68 318 with a hughes steel crank 390 stroker kit with ported J heads or possibly Indy heads?? The reason for the 318 is because i can get a good one for free and if I ever find a 340 I can use it all on it except for the pistons and rings??

[lenweiler]

Don't do it. It's no deal when you find out it was not what you were expecting.

[Ausydad]

There are a lot of things that can be done with a 318 with less dough that will still make it a lot of fun while you're searching for you "final" motor. It won't be the fastest out there, but it can turn some heads!! check out my website to see what I've done with my old 318's and get some less expensive and more dependable ideas for 'round town fun. Leave the "Stroker" for the "final" driveline.

[Doug Wilson]

I wouldn't be inclined to do a stroker 318. If you are going to pay for a stroker kit, and the other goodies you mentioned, spend the few extra bucks and do a 360, or spend the QUITE a few extra bucks and do a 340.

As mentioned, you can make a nice 318 without stroking it... ask cuda66273!!

[FASTDARTCHESTER]

Just out of curiosity, why is everyone dogging the stroker? I talked to Diamond (about 8 months ago, before the kits were available) and they said a few people have done it with real good results. Do you guys know any reasons not to do it? First hand experience? Just curious.

TD

[Doug Wilson]

It's just that, if you're going to spend the money for a stroker to begin with, you might as well start with the block that will give you the most cubic inches for the money, and has decent heads. You would really be best off starting with a 340, but a 360 is a better financial plan.

[FASTDARTCHESTER]

Yeah, but the extra 18 inches gets you 18 hp (if you acheive the 1-1 hp to ci factor) aren't worth it (to me) if you do proper research and spend the time designing your engine. It seems to me that 360's are getting more and more expensive these days too! 318's are kinda like the chevy smallblock, they're everywhere you look, which translates to CHEAP.
Just thoughts because I was thinking of building the 390 stroker this year.
I haven't gotten an answer to my question though: Does anyone know firsthand how one runs????

[TrxR]

whats wrong with the Idea?? Head are a joke I can get 360 heads and wont they bolt right up ?? Wont the stroker kit bolt right into the 340 with new pistons and rings with the right bore??
from what Ive found the 318 has the same stroke and jurnal size as the 340 the only difference is the bore??? I was thinking of using the 318 for this reason and may never get a 340 block theres only 18 ci difference between the 318 stroker and the 360 stroker. Is there somthing Im missing???

P.S I am finding it imposiible to find a good older 360 (70-74) and people want over $1000 Canadian for their 340's

This motor will be going into a 87 2x4 Dakota that I want to run in the mid 12's or better

[FASTDARTCHESTER]

TrxR

yeah, I'm with you. i tried to build a 360 last year but the cost of a used core was fricken outrageous. I think the 390 will be a tractor in the torque dept which is what you need for the truck (assuming it's close to production wght when done). You should be able to hit the 12's pretty easy. Just choose the combination right. I don't think you can research your combo enough because there is always something new to be learned.

My concern is the bore/stroke ratio and the pistion o.d. to valve comination (port volume/design is of equal importance). Gotta study more about it to be sure of my combination decision.


Keep in touch.

[lenweiler]

The cost of a 360 core was outrageous! Where are you guys getting your cores?
I picked the 360 cores over the 340, anyway and I have 5 340 core on hand. I did this for what me and a few other benchers thought made sense.
The early 360 block has the same casting mold as the 340 thereby attaing a thicker cylinder wall at final bore.
The 360 has larger and therefore stronger (I assume) main caps than the 340.
The 360 has a larger main than the 340 and therefore has more overlap, on the main and rod throws. Definitely stronger that the 340 stroker, and a real plus if you're using the cast stroker crank from MP.
That's my reasons. I could be spittin' in the wind, but I've always gone the durability route, and never been dissappointed.

[6 packin]

If your building a stroker engine the whole point is to add cubic inches and power? Ether way you go the same stroker kit you will be giving up 22 cubes to a 340 and 42 cubes to a 360.... stock! So a 1/4 inch stroker crank on a 318 bored .030 over would result 347 cubes, on a 340 it would be 370 cubes, on a 360 it would be 398 cubes!

[Ausydad]

Mine is planned to be a stroker 318, but that is what I choose to be my final motor. Many people say I can't pull 600 h.p. out of a 318, so I have to try!!!! The concern that most people have is the webbing around the cam bearings and such. My original point was that you had already decided that this wouldn't be your "final" motor and I would hate to see you throw money out for the machining necessary for a stroker 318 when that's not what ou really want. Good Luck!

[ajmopar]

I think with the small bore, and that much stroke, it would be very hard to get that thing to breathe. Not saying it can't be done, but notching the bores to unshroud the valves would be a necessity. There is a point of diminishing returns for this kind of thing. The 318 is kind of a stroker to begin with, so adding more stroke kind of mystifies me.

[Doug Wilson]

I think the same length stroke on a 318, 340 or 360, all punched 0.030 over, will give you the most displacement on the 340.

[FASTDARTCHESTER]

AJ

I suppose in some respects (bore/stroke ratio) you are correct when you compare a stock 318's ratio with, say, the 505 horse crate engine's ratio from MP (which is a "stroker").

But what really qualifies an engine as a stroker? The 435hp Magnum has a 4" bore and stroke. Seems it breathes well, and a 318 punched 30 over is pretty darn close in ratio and cubic inches.

With a smaller bore it seems that (with an identical head, design not important at this time) it would breathe easier, but there would be less velocity. I guess you need to know the rpm range of your engine to determine the route you take.

Just thoughts, but I think stroking the 318 is a good thing.

[Doug Wilson]

The 435 horse Magnum is a stroker. A stroker is defined as an engine whose bore and stroke include a stroke which did not appear as a factory option, with that engine's bore, installed in a standard production car, where that stroke is longer (on the same bore) than on such a car.

An example that's well known is the 383 chebbie.

Also, a stroked 318 would breathe "easier" with equivalent heads, than a larger bored engine. The mixture velocity on that 318 would also be higher, because of two things: more vacuum, and more dwell time on the intake stroke.

[FASTDARTCHESTER]

Thanks Doug,

I agree with you 100%.

TD

[ajmopar]

How do you think a smaller bore could breathe better? The very nature of a smaller diameter bore means that there is much more shrouding of the valves. If a huge stroke and small bore were ideal for performance, the slant 6 would rev 8 grand and make tons of horsepower. But the slant 6 was ment to build torque, and lots of it for it's displacement. I understand where the stroker 318 would make a good mild street engine because of the torque generation, but to suggest that it would be a deep breathing high rpm wonder is in my opinion, misguided. But hey, build it and prove me wrong! I have been wrong many times before.

[Brian Mills]

318's are a blast. Never be afraid to build one. Correct me if I'm wrong, but I thought there was a cheapo stroke deal for a 318 using a cut down 360 crank. Might be a less expensive way to go till the 340 drops anchore.

[FASTDARTCHESTER]

I Guess shrouding depends on the head you use (and valve combination) with relation to the bore diameter. It all seems relative.

Isn't the "shrouding" of the valves mainly restricted to the head design? When I built my 318 a couple months ago my porting manual said to deshroud the areas around the valves on the head. On the '302 heads this is the meat immediately next to the o.d. of the valve head. I thought the reason is to decrease restriction in this area.

Any thoughts?

[sanborn]

Seems like everyone has an opinion on this one. Let the "old geezer" add his.

Life is about "what you want to do"! There's nothing wrong with a stroker 318. It probably would not be what I would choose if I was doing it-but if it "feels good", go for it!

Now to the practical aspects of it. I understand the scarcity of 340-360 in Canada. And the price, and the exchange rate for the Canadian $, talk to your politicians about that.

So you may be stuck with a 318, no big deal, it will work and could be a very good engine for you. If I was doing it, I would try to find an early 318(back in the 60s), they could accept a much larger bore safely. The later blocks had much thinner cylinder walls and a .030-.040" overbore is the practical maximum. The early blocks would go to 4.000" without a problem. The early blocks also had slightly thicker webbing around the mains.

Small bore/long stroke engines have been around for a long time. They give good torque, produce less emissions and are generally a smoother engine to drive on the street. They also work well with "limited breathing" cylinder heads like the "X" or "J". For a high performance application they don't work quite as well but with your limited heads they may work fine. The longer stroke produces more friction loss but the smaller bore give better ring seating due to less cylinder wall distortion. Small bore engines generally run cooler -Not because of thicker cylinder walls but because the heat is dispated over a larger area due to the longer stroke. Small bore/long stroke engine respond well to camshafts with a little more duration than a short stroke engine. You don't need more lift, just more duration. With you heads, I wouldn't go much more than .520-.540" lift, don't think your heads would breathe much past that anyway. I would stay with a reasonable stroke length-in the 3.75" range-you don't want to get too undersquare with a 4.00" crank. With your heads, that additional .250" may never get filled due to your heads. And all you would end up with is more friction and no more torque.

Several people have talked about shrouding of valves- and it can and does happen- but most shrouding occurs due to the cylinder head, not the bore. If you use 2.02/1.60 valves you won't have to worry with the bore. Now, you may want to put the head on the bare block, flip the engine over and mark the bore on the cylinder head mating surface and relieve the combustion chamber out to the bore line to reduce shrouding but that's probably as far as you need to go. With your camshaft lift, I doubt if the outer diameter of the valve would ever get to the bore.

Humm, I wonder-since the "R" block are cast in Canada, I wonder if they would be cheaper there than here? Humm-forget that thought!

My $.02 worth.

[Doug Wilson]

ajmopar - I never suggested that an increase in stroke would provide an increase in redline. There are lots of factors, other than bore and stroke, that determine how tight you can twist an engine.

What I was specifically referring to is the ratio of valve and port breathing ability to the swept volume of the cylinder. A 45 cubic inch cylinder will not breathe as well as a 40 cubic inch cylinder, using the same head. Shrouding at the intended operating RPM of his 318 is not an issue.

[TrxR]

What kind of HP numbers do you think this engine could pull with ported J heads or 302 cast heads , a m1 intake and 9.5-1 compression and headers?? Do you think it would pull my 87 2x4 Dakota down the quarter in the mid to high 12's??

Im going to use a 727 tranny with a manual valve body and a 8&3/4 rear with 3.55's on the street and 3.91 or 4.10 on the track.

[Doug Wilson]

No.

[FASTDARTCHESTER]

TrxR

mid to high 12's are very realistic numbers. I think there should be no problem if you do your homework.

I just did a 318 with '302 heads opened to 1.88/1.60 valves and ported the heck out of them. The engine is an absolute screamer. I can't get over how good it runs. I think it should propel my dart to mid 12's (i have a 4.56:1 rear w/sure grip and lotsa unmentioned goodies). Gonna get it there in 2 weeks so I'll let you know times.

Go for the stroker, I'm going to start mine this winter. Let's keep in touch if you decide to do it. I plan to put the stroker in my 69 charger and maybe an ATI Procharger (6-8 psi of boost). Should be around 550 horse at a fraction of the 575 hp MP Wedge crate engine cost (even with the supercharger).

Keep in touch.


BTW: I want to section a '302 head to see just how rad you can get witht he porting. I have a spare set and will let you know.

Gimme your email and I will send some pics of the most recent set of 302's I did.

TD

[TrxR]

FASTDARTCHESTER My email is mcall@nbnet.nb.ca
I would realy appreciate the pics thanks

[Billydelrio]

When stroking a 318 from 3.31" to 4" and boring to 3.97", using a couple inches of block filler to assist the iron cylinders in keeping their shape seems like a good idea.

A little more blabbing about Bore/Stroke ratio. I did a few popular small block B/S calculations:
289 1.384 Ford
302 1.333 Ford
327 1.231 Chevy
340 1.221 Mopar
318 1.181 Mopar
350 1.149 Chevy
351 1.142 Ford
360 1.117 Mopar
400 1.100 Chevy
273 1.095 Mopar
400 1.000 Ford
396 0.993 Stroker 318 3.97" bore with 4" stroke
331 0.859 Ford 5.4 liter in F-250

Billy