piston skirt clearance recommendation?

[tsteiner61]

How much should I increase my piston skirt clearance by if I'm going to short fill my block?

[Jims451]

Call Muscle Motors, I think they do this quite often and Chuck Senator is a really nice guy, he probbly spent over 1/2 hour answereing some of my questions when I got my 451 stroker short block from them.

[tsteiner61]

Yeah. Muscle motors is really good, they spent about as much time with me. I was going to buy their 360->408 stroker kit, but I've been to the pick n pull twice, pulled two early 360 blocks that looked good, only to have both come up cracked. I have a cherry 72 318 block in my garage that tested A+, so I'm going to get custom pistons and build a 390 stroker with it....I may just call them anyway, but I feel bad since I know I ain't gonna buy nothin'. Know what I mean?? Thanks for the advice, though..

[sbuc72]

Uhm. you stroked a 318 to 390?~ How did you manage that?. Please let me know, cuz that would make a 318 actually useful

.sbuc

[tsteiner61]

Yeah. And I'm not the only one. Check out www.cratemotors.net, they offer it as one of their standard stroker packages. The only reason I didn't just buy it from them is because they couldn't promise me the block they would use would be a pre-1975 casting. They're stronger than the newer castings and have more overbore potential and are less prone to core shift.

How I, and anyone else who wants to is by starting with the new MPP 4 inch cast stroker crank (they also have a forged version, very expensive though. Then use stock length rods. The only catch is the pistons. I know JE makes them because that's the brand cratemotors.net is using, but when I tried to buy the kit off the guy without the block, he wouldn't sell it to me separately. So I said no deal. I'm in the middle of putting together a spec sheet to have Ross Pistons make me a custom set, they're only about $250 more than off the shelf pistons. 4.0 stroke + .030 overbore on 318 = 390ci. If I like the way it performs, I'm going to put a kit together and offer it for sale on the internet. If I get that far, I'll post and let the Moparites know.

By the way, if you ask me why not just build a 360, I will have to shoot you . I have been asked that question so many damn times. The bottom line is originally I was going to build a stock 318, so I went and got a really good block that checked for no cracks and minimal core shift. Then I saw that Muscle Motors 360/408 stroker kit and thought, hmm, maybe a 360 is the way to go after all. Pulled three blocks and all came up cracked. I finally got tired of spending all my free time at the Pick n Pull. So I thought, if I stroke a 318, I am still getting big cubes (only 18 less than the 408 kit), so why not go for it. Besides, the 360 has been done to death, and it feels right to do something different.

[sbuc72]

uhm that url doesn't show anything, unless theres some hidden link somewhere in there that shows is something other then insurance junk.

thanks
.sbuc

[sbuc72]

AH! its www.crateengine.net not cratemotor.net

heh, yeah they got a bunch of stroker kits, thanks.

.sbuc

[tsteiner61]

Oops. Yeah, pretty cool, huh. Like I said, the only real bummer is that they only have the newer block castings at least for the 318 anyway. I was really hoping to get a motor rather than have to build it, but I really don't trust the newer castings for high performance applications. I still don't understand why he wouldn't sell me just the kit for a 318/390, but he said he would sell me a 318/349 kit. And when I asked him why, he just fell silent. Asked him twice and he just didn't say a word, so I hung up on him. I wonder what the deal with that was. Oh, well, I'm gonna build this damn thing if it kills me!

[sbuc72]

Heh, too bad you dont live in Ontario . i have 2 318 blocks here, both manufactured '71. (One from my Charger that i wrecked, and one for my Challenger, which is gonna have my transplanted 440 soon). and i'm looking to get rid of one of them.

.Sbuc

[rumblefish360]

I'm totaly with you on doing a 318. What the hell. It's somthing that is different. Everybody knocks the 318 for being to small. That stroker kit will really give it a new attitude. he he he
In stock form, there really not bad. Stroked should be fun. A real stump puller.

[sbuc72]

Yeah, but i wonder what the performance would be like at a streetable CR, since i think that kit's CR is like 10.79-12.16:1

(quote)
JE Custom Forged Flat Top Pistons
Can be used with Turbo, Nitrous, and Supercharged Engines.
Compression Ratio for Flat Tops:
60cc Heads - 12.16:1
70cc Heads - 10.79:1
(end quote)

way too high for pump gas (on those heads). hrmm what about open chamber heads, arn't they 88cc? or am i thinking about a big block?

.sbuc

[tsteiner61]

FYI...You can actually have that kit customized to any CR you want. It's in the fine print somewhere. I'm gonna spec mine out to be 9.5. Still working out the combo. Just for fun I ran a few possible combinations on the desktop dyno just to see. Here are the numbers I got (all figures are at the flywheel and not the rear wheels).

Combo 1: 1.90/1.60 ported stock heads (65 cc), 600 cfm, Crane hyd-roller cam .488/.509 -

492 ft/lbs. @ 2000rpm & 351hp @ 4500rpm

Combo 2: 1.90/1.60 ported stock heads (65 cc), 600 cfm, Crane hyd-roller cam .509/.528 -

483 ft/lbs. @ 3000rpm & 386hp @ 5000rpm

Combo 3: Edelbrock (2.02/1.60) heads (66 cc), 780 cfm, same cam

490 ft/lbs. @ 3500rpm & 406hp @ 5000rpm

So really not too shabby considering this is going to be my daily driver (1973 Dodge B100 Van). The real decision is going to be what cam to pick. I heard how easy it is to overcam a 318, but the number show a marked difference from one cam to the next, at least theoretically. Any suggestions?

The heads are a no brainer once I get the money. The 1.90/1.60 are the heads I have now, and I will have no choice but to run them until I scrape together an extra $1300 for a pair of Edelbrock heads. For the street they should do fine for now, my top end will just be a little soft. I guess that will give me time to break it in before I start abusing it...

Just for fun, I ran a stock 360 (w/ 9.5 CR) and a 360->408 stroker with the same combo as the best combo (#3) above.

360 stock:

460 ft./lbs @ 3500rpm & 394hp @ 5000 rpm


360->408 stroker:

510 ft/lbs. @ 3000rpm & 391hp @ 4500 rpm

Of course, there are probably more optimal combinations, but the numbers are actually in the same ballpark.