347 Guys, Help Me Pick One!

brentwoodboy · Dec 27, 2005

Running into some cash, want a 347 kit. I've looked on ebay and there are prices ranging from 789.99-1,125.00...ANyone know who sells reliable kits and who does not? is this "piston pin intersecting the oil ring groove" just jibberish? I've seen "nodular iron" cranks, is this a reliable material? Basically, i want to do everything right the first time. Also, what is the best bore for a stock 302? Is there a kit I should stay away from?

Grn92LX · Dec 27, 2005

It does not make a damn bit of difference if the pin intersects or not. I run a scat cast steel crankshaft, probe ultra light I beam rods with 7/16" cap screws and probe pistons. I use the 5.315" rods with a piston that doesn't intersect ONLY because the 5.4" rods I wanted were on backorder.

If you go to www.adperformance.com you can get the scat 9000 kit for $999. It is what I use, except I use probe light weight rods (more expensive) and the kit uses scat 5.4" I beams with (iI think) 3/8" bolts. Comes with rings and bearings too. This kit will more than likely be fine for you. I went with lighter rods because I built a higher rpm n/a motor and I want it to rev and I wanted some "little tricks"

I would not suggest ebay specials, stick with a reliable source for your parts like the link I provided.

My assembly is balanced to 28oz and I use a aluminum flywheel and a light weight romac balancer.

GTS347 · Dec 27, 2005

The kit depends on the application. And be ready for the work you have to do to the block for clearance. As far as kit quality? I'm running a Scat kit with diamond pistons. I'd go with a forged crank for the peace of mind. Today's kits for the most part have fixed the oil ring problem. But mine has the oil ring going thru the wrist pin area and uses no oil that is noticeable.

Killercanary · Dec 27, 2005

If I was to do a 347, it'd definitely have the 5.315" rod. You are less likely to have an oiling problem, and your piston speed will be slightly higher which can increase low rpm cylinder filling slightly.

blksn955.o · Dec 27, 2005

with a healthy 347 I would also sug. getting a better than stock block...

Grn92LX · Dec 27, 2005

Killercanary said:
If I was to do a 347, it'd definitely have the 5.315" rod. You are less likely to have an oiling problem, and your piston speed will be slightly higher which can increase low rpm cylinder filling slightly.

Rod length (to my knowledge from what I have seen) won't change piston speed. www.camshaftinnovations.com has a calculator on the site for piston speed and rod length isn't a factor. It will, however, change the ideal camshaft valve timing. Rick 91GT among other builders, has said it doesn't make a bit of difference which rod you use as long as its built/machined properly. The problem is finding that builder. I got lucky, I found that builder

There are no oil problems with 3.40 stroke cars regardless of which rod is used. As long as its assembled/machined right, you're good to go! Only reason I use the 5.315" rod is because Rick could not get me the 5.4" rod I wanted right away so I had to take this rod. I MUCH prefer the 5.4" rod with the lighter 1.09" CH piston on top of it but i'll make do with what I have.

Fyi, there are some 3.25" stroke rotating assemblies that have the pin through the oil ring. Again, it don't make a lick of difference.

Killercanary · Dec 27, 2005

Mike, I checked the piston speed with different rods before I posted and it does in fact change. It wasn't much but it does change.

I used this calculator...

http://www.slowgt.com/Calc2.htm

Green 94 5.0 · Dec 28, 2005

Grn92LX said:
It does not make a damn bit of difference if the pin intersects or not. I run a scat cast steel crankshaft, probe ultra light I beam rods with 7/16" cap screws and probe pistons. I use the 5.315" rods with a piston that doesn't intersect ONLY because the 5.4" rods I wanted were on backorder.

If you go to www.adperformance.com you can get the scat 9000 kit for $999. It is what I use, except I use probe light weight rods (more expensive) and the kit uses scat 5.4" I beams with (iI think) 3/8" bolts. Comes with rings and bearings too. This kit will more than likely be fine for you. I went with lighter rods because I built a higher rpm n/a motor and I want it to rev and I wanted some "little tricks"

I would not suggest ebay specials, stick with a reliable source for your parts like the link I provided.

My assembly is balanced to 28oz and I use a aluminum flywheel and a light weight romac balancer.

holy crap.....i think i just found the place my shortblock is coming from. that price is awesome for a dart block 331.

Grn92LX · Dec 28, 2005

Killercanary said:
Mike, I checked the piston speed with different rods before I posted and it does in fact change. It wasn't much but it does change.

I used this calculator...

http://www.slowgt.com/Calc2.htm

I must have done something wrong in the calculator, I got a negative # lol. But you were correct, the 5.315" has 9.1 more ft/min than the 5.4". Looks like I stand corrected, my bad for saying you were wrong. I guess the reason I never heard this was because the difference is so insignificant.

Green 94, why buy a dart block to only go to 331? Go 363" man!! 3.40" stroke and big bore.

Rick 91GT · Dec 28, 2005

Depends on the application but I am with Mike if you want to go with a aftermarket block go 4.125" bore, 5.4" rod, 3.4" stroke 363ci.. I just finished one last month for a customer, very nice trick piece. Depends on budget and application..........

Properly assembled the 5.4" vs 5.315" rod is a joke, they WILL NOT BURN OIL.

nmcgrawj · Dec 28, 2005

GTS347 said:
I'd go with a forged crank for the peace of mind.

Wont a stock 302 block blow before a cast steel crank?

Rick 91GT · Dec 28, 2005

nmcgrawj said:
Wont a stock 302 block blow before a cast steel crank?

In most cases yes, I've used cast cranks up to 600hp depending on the application. Most stock blocks bow out before that

Killercanary · Dec 28, 2005

That engine is just pure sex Rick!!! I just got down telling a buddy of mine that is looking to go low tens NA to build a dart based stroker with a 4.125" bore and a 3.4" stroke crank to end up with a 363 cube small block. I want one so bad after talking with him, damn I need to hit the lottery!

Killercanary · Dec 28, 2005

Grn92LX said:
I must have done something wrong in the calculator, I got a negative # lol. But you were correct, the 5.315" has 9.1 more ft/min than the 5.4". Looks like I stand corrected, my bad for saying you were wrong. I guess the reason I never heard this was because the difference is so insignificant.

No problem Mike, the difference is pretty small and like you said you will more than likely have a heavier slug that you have to accelerate and decelerate with the shorter rod which might offset any possible gain with having a slightly faster piston speed. I like to ponder these things though!

Edit... my mind is churning now...
If you wanted to build a HIGH RPM 347/363 (>7500rpms) then I guess the 5.4 rod would be better as its slower piston speed will help in the higher rpms for a number of reasons that we have mentioned above. Hmmm.....

Joes95GT · Dec 28, 2005

From what I gather, the primary differences between piston speeds of the 5.400 and 5.315" rods come at TDC and BDC. With the 5.315" deal, the piston isn't being "hung" at TDC and BDC as long as the 5.400" rod....

Joe

brentwoodboy · Dec 29, 2005

Thanks for all your input. You guys added stuff I never even thought about...I'm going to do a little moe research before I jump into this. Also, thanks for the website. BTW I have an extra 302 block from an old 90s cobra. COuld this block be made stronger or is an afermarket the only way?

Grn92LX · Dec 29, 2005

You can't really make it stronger but good quality machine work will go a long way.

GTS347 · Dec 29, 2005

nmcgrawj said:
Wont a stock 302 block blow before a cast steel crank?

I've heard several people the majic number for a stock block is close to 550-600 hp max... I don't know from experience how much the block will hold as I have never cracked one. However, I personally am not going to put a 200 shot of juice on a stock crank. I'd rather my block crack and possibly save the rotating assembly...or most of it. But that is just my opnion. Besides, if you buying a rotating assembly, why not put alittle extra with it and get someting you can build more power with later...

94GTLaserRC · Dec 29, 2005

Rick 91GT said:
Depends on the application but I am with Mike if you want to go with a aftermarket block go 4.125" bore, 5.4" rod, 3.4" stroke 363ci.. I just finished one last month for a customer, very nice trick piece. Depends on budget and application..........

Properly assembled the 5.4" vs 5.315" rod is a joke, they WILL NOT BURN OIL.
]

Very Nice Stuff Rick....I still need to wait myself until April 07, but I may be contacting you again (I had emailed you a few months back)
Thanks
RC

Rick 91GT · Dec 29, 2005

Thanks RC, when ever your ready buddy... we aren't going anywhere www.rnhperformance.net

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