Opinions: R302, Dart, World or Boss

DK832

DK832

New Member
Apr 11, 2006
291
0
0
Copenhagen, DK
#1
So, about to have a new motor built. Personal experience only includes stock and FRPP 315W Sportsman. For a 8.2" deck based 331-363 there are several choices at about the same price:

FRPP R302
FRPP Boss
Dart Sportsman
World Products Man O'War (fine product, but the name sucks!)

This is a ~650hp turbo build by the way. 50/50 street and road course use. The selected builder will probably have final choice anyway, just want to hear your opinions and especially experiences.
:SNSign:
 
#2
DK832,

I don't have any tech to back this up, but I have heard that the new Boss 302 FRPP will not reliably handle a stroker kit. I'll try to find some solid info on this.

The World and Dart products are comparable blocks, and should "easily" handle 650 HP. (If built and tuned properly).
 
#4
R302 and Dart blocks are actually about the same price. I have the R302 in my car, and my dad has the Dart. Personally I'd go the Dart route though. But really, unless your making some serious HP I doubt either would ever be an issue. The thing I like about the Dart though is being able to easily go 4.125 or larger for a big bore stroker. I can't recall on the R302 but you have to check wall thickness when you get up there around 4.100 I believe it was. (been 10 yrs, cant remember)

With your 650hp est, I would probably just go the Dart route, and if its a fresh build why not spend a couple more bucks and go the big bore.
 
#5
01ragtop said:
DK832,

I don't have any tech to back this up, but I have heard that the new Boss 302 FRPP will not reliably handle a stroker kit. I'll try to find some solid info on this.
QUOTE]

? Ford sells 347 crate engines based on the new Boss block. They don't even offer a non-stroked version. Pretty sure it was designed to be stroked.
Click to expand...
 
#6
Ford recommends max 3.4" stroke on the Boss, bore to 4.125.

R302 will go to 4.185 bore so a 363 with 4.125 is in the plans :rock: The R302 can be had as low as $1650 so comes out as the cheapest by a little.
This will be around 650hp in street trim, but with single or possibly twin turbo, depending on some issues with sway bar and rack and pinion, it can be pushed quite a bit higher. :rolleyes:
 
#8
The cylinders are not the same length on a new Boss 302 block. They are about 3/8ths of an inch shorter compared to the Stock, Dart, or Man o War. Ford does indeed sell this block with a 347 stroker, but the piston comes farther out of the cylinder with this block than it will the others. This is why I said "reliably". I don't think it is such a big deal with the shorter stroke, but with a 3.4 stroke it could cause some longevity issues.

There is a whole post on this over at SBF tech. Pretty good info.
 
#9
Yeah, I don't mess with those little engines too much.

Engine001.webp
 
#10
The following is taken from this link: http://www.mustang50magazine.com/images/m5lp_0803_boss_340_engine_build/block_honing.html

Read into this what you will, but I think it leaves some room for concern at the very least especially considering the cost of a stroker engine.

In a side-by-side comparison, we learned that a stock 5.0 block has longer cylinder walls (5 1/8 inches) versus shorter holes (4 3/4 inches) in the Boss. "I think this may have been done (shorter cylinder) to allow for more crankshaft stroke," he says. "However, longer-stroke cranks (3.400) may experience problems that can include pistons coming completely out of the cylinder, piston slap, or abnormal oil consumption due to poor ring seal. We recommend 3.250 as a good maximum stroke for this block."​
 
#12
Hmmm, probably why no builder I've talked to wants to use the Boss block. Anyway, so far it's going to be a R302.

Snakepilot: nice paperweight! ;) This is for a track car so it has to take turns well. Big blocks definitely not an option.
 
#13
01ragtop said:
The following is taken from this link: http://www.mustang50magazine.com/images/m5lp_0803_boss_340_engine_build/block_honing.html

Read into this what you will, but I think it leaves some room for concern at the very least especially considering the cost of a stroker engine.

In a side-by-side comparison, we learned that a stock 5.0 block has longer cylinder walls (5 1/8 inches) versus shorter holes (4 3/4 inches) in the Boss. "I think this may have been done (shorter cylinder) to allow for more crankshaft stroke," he says. "However, longer-stroke cranks (3.400) may experience problems that can include pistons coming completely out of the cylinder, piston slap, or abnormal oil consumption due to poor ring seal. We recommend 3.250 as a good maximum stroke for this block."​
Click to expand...

Hmm, now if I was bitter about the last thread, I could link this to one of the other posts I linked when everyone, who doesn't know, said there was NO WAY they would have done that. I mean, that's pretty much what I stated when I saw it, and someone said it wasn't possbile, Dynacorns "showcar" had one with a 3.4 stroke. Heck, one guy even had a magic motor that was completely differnt, and "wasn't as bad as" I said it was.haha, I'm not bitter.:nonono: Don't get me started on AFR's or Heidts.
O1rgtop, where are you....might know ya.
 
#17
D.Hearne said:
The magazine articles touting the new Boss 347 clearly state it's got a 4.125 bore and 3.25" stroke. Could be they're doing both versions, the other with the more conventional 4.03 bore and 3.40" stroke. The link you posted doesn't specify what the bore size is.
Click to expand...


Given that the stroke is a 3.4" and the cubic inches = 347 the bore would be 4.030.

I haven't seen the article in question, but if the article is correct, it makes me wonder if Ford is having problems with the 3.4" stroke.:shrug:

Why the change?
 
#18
If the bores are 4.75" deep the wrist pin would be visible from the bottom at BDC by about .2135" when using a 3.40" stroke. The center of the wrist pin at TDC is 1.10" down from the deck. It then moves down 3.40" and is now 4.50". With a .927" pin the bottom of it is .4635" lower than the center. That puts the bottom of the pin 4.9635" below the deck in a 4.75" long bore. That can't be right.
Some of the Engine Masters engines sleeve all 8 cylinders with longer sleeves to reduce the amount of piston coming out of the bottom of the bore. The better the piston is supported at BDC the better the ring seal. Think suck by as opposed to blow by.
 
#20
10secgoal said:
Hmm, now if I was bitter about the last thread, I could link this to one of the other posts I linked when everyone, who doesn't know, said there was NO WAY they would have done that. I mean, that's pretty much what I stated when I saw it, and someone said it wasn't possbile, Dynacorns "showcar" had one with a 3.4 stroke. Heck, one guy even had a magic motor that was completely differnt, and "wasn't as bad as" I said it was.haha, I'm not bitter.:nonono: Don't get me started on AFR's or Heidts.
O1rgtop, where are you....might know ya.
Click to expand...

I still have trouble believing that Ford would set up the Boss block so that a conventional 347 stroker could not be done (or wouldn't be advisable). However, maybe I'm wrong.

I have seen several people posting on the Corral with their Boss block 347 builds - and they say their motors work great. So I'm not sure who to believe. :shrug:
 
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