Posted By: gsambray
318 stroker - 06/13/12 03:10 AM
First of all i already know its easier to get a 360 throw a cam at it and be done but I am going to be building a poor mans 318 stroker. using a 318 magnum block with a cut down 360 crank, a decent cam for some low end grunt. still undecided on what heads to go with either stock 318 heads or maybe 360 heads. The only question is I am not too sure about the computer. will the stock 318 comp. still do the trick or will I have to get it reprogramed? anyone ever do one of these builds or know what i will have to do with the computer.
Posted By: viperblue72
Re: 318 stroker - 06/13/12 04:40 AM
I would check to see what your piston options are before you try this. I doubt there are too many people out there doing this.
Once you get your pistons figured out, a 360 head would be better. Not sure about the stock computer.
I hate to say it but your idea sounds like alot of work for not gaining anything.
Posted By: patrick
Re: 318 stroker - 06/13/12 02:07 PM
is this going in a magnum powered truck? if so, mag 318 and 360 heads are the same.
pistons may be tricky. some looow compression pistons may be down enough in the hole with the stock 3.31" stroke to fit...otherwise you're into custom piston territory.
in the end you'll have a .090 under 360....guess I fail to see the point.
if you're going to stroke a 318, just put a 4" crank and get Icon pistons and be done....
Posted By: JAKE68
Re: 318 stroker - 06/13/12 03:21 PM
Cutting a 360 crank mains down to 318 size make it prone to breaking or cracking near the filett area.This is not recomended. Put the 4in. strocker crank in it.
Posted By: dogdays
Re: 318 stroker - 06/13/12 08:14 PM
Seems to me this would be better in the regular Q&A section, but here goes:
If you can get the machine work done for cheap enough the 360 crank will be a happy street engine. Your machinist will need to leave a nice fillet radius on the mains, in other words no sharp corners, but after that it shouldn't be any weaker than say a 350 chevy cast crank, and those are in dirt trackers every Saturday night across the US. It has been done before and probably if you are going to drag race the engine a better crank is indicated.
There are three 318 pistons with the correct compression height, Sealed Power LC371, Silvolite 1278 and Clevite 224-1930. Comp distance on these is around 1.658, same as a 360 piston. They weigh around 20 grams more than a 360 piston so for a street engine it should be bolt together and go using the 360 external balance stuff.
The pin bosses will run into the crank counterweights so some material has to be ground off the undersides of the piston pin bosses. This has also been done before.
The real problem is the machine work could cost you nearly as much as a brand new 4" stroker cast crank and if that's the case, why bother with the 360 crank?
R.
For this engine you'd use a 360 head.
Posted By: dogdays
Re: 318 stroker - 06/15/12 12:30 AM
Yer right, but.....we're not building a race motor here, this is ON THE CHEAP.
Milling the bottom of the piston can be done with a flat file. Or a right angle sander with the right paper. I'd build a jig from Baltic Birch plywood and use some sort of homemade depth gauge.
Putting the valve notches in the tops of the pistons can be done at home, takes a little more time but if you get paid nothing at home, you can afford it.
Again, this phantom build is on the cheap! The only big cost is the crank machining. That depends on how hungry the local machine shops are. I think that's the real obstacle.
R.
Posted By: DusterDave
Re: 318 stroker - 06/15/12 12:50 AM
None of that plan gives me a warm fuzzy. If money is that tight, then leave it at 318 cubes. My
Posted By: dogdays
Re: 318 stroker - 06/15/12 04:07 PM
Like I said, this really belongs in the Q&A section because it's a low-end build.
The engine is just a lump of insensate cast iron. I learned this decades ago from a racer named Vern. He'd sold his dirt track engine so he put together another out of spare parts to finish out the season. He said he had at least three different brands and compression ratio pistons in the motor, also I believe two different heads on it but it ran strong.
So if a person is already going to put new pistons in a block and can gain nearly 30 cubic inches for a hundred dollar bill it may be worth it. OF COURSE there are more sanitary ways to do it but we're talking cheap and it is, after all, an experiment.
R.
.....But why..... 