Dart Block or R Block Question??? How big can i bore it and other Questions!

[Xtreme Limits]

First what block size do i get, e.i. whats a 5.0 block hight, 8.2 or 8.7?
If i got a Dart block (4.00 inch bore), Could it be bored too 4.125/4.185???
Or do i have to get the 4.125 bore block to have a 4.125 bore?

Cus id like to do a 3 or 3.25inch crank , 5.4 H-beam rods, and have a 4.125 bore too give me more Torque down low, cus i want to build a spin 7000+rpm and the superchraged or turbochared it

 

[TIMMY2734]

If you want a 4.125 bore, youd be better off with the bigger bore block to begin with. At least i would imagine so. The extra torque would be gained by using a bigger stroker crank....

Then again, with the forced induction route, you probably wont have a problem with torque down low

 

[TT91]

http://www.dartheads.com/fsbiron.htm

Here arethe specs. You would need a 8.2 deck hieght.
Material: Superior iron alloy
Bore: 4.00” or 4.125” unfinished
Bore & stroke: 4.185” x 3.500” max recommended
Cam bearing bore ID: SVO 2.1995”- 2.2015”
Cam bearings: Special coated, grooved, w/3 oil holes
Cam Bearing O.S. + .010”, +.020”, +.030”
Cam bearing press: .002” - .003”
Cam journal OD: Standard Ford SB (can be bored for 50mm)
Cam Plug: 2.375” dia. cup plug
Cylinder Wall Thickness: .250” min @ 4.185” bore
Cubic inch: 385” max recommended
Deck Height: 8.200” & 8.700”
Deck Thickness: .675” min.
Freeze Plugs: Std Ford press in cup plugs 1.500” OD
Lifter Bores: Std Ford .8752” - .8767” Honed to size
Main journal size: 2.249” Std 302
Main bearing bore: 2.437” - 2.439” Honed to size
Main thrust width: .926” - .928”
Main Cap Bolts: #1 7/16” (2) 3/8” (2)
#2, #3, #4 7/16” (2) 7/16” splayed (2)
#5 7/16” (2) 3/8” (2)
Main cap press: .003” - .004”
Main caps: Steel - 4 bolt, all 5
Main cap register: Deep stepped register on each side (no need for dowels)
Oil system: Std Wet Sump or SVO dry sump
Priority Main oiling with external pump (wet or dry)
Oil Filter: Standard filter
Oil Pan: Aftermarket 302 with dip stick in pan
Rear Main Seal: Std 1 piece seal - FelPro# 2922 or 2941 4.250”x3.625”
Serial No. Right front & main caps
Starter: Standard
Stud & bolt holes, Head: 1/2" std SVO with Blind holes
Timing chain/gears: Standard components
Timing Cover: Uses stock 302 cover
Torque Specs: 1-5 7/16” bolts - 65 ft lbs
1 & 5 3/8” bolts - 35 ft lbs

Weight, approx: 160 lbs - 8.200” 175 lbs - 8.700”

 

[SmockDoiley]

Your crank and power adder are going to add your torque, not a monster bore. If you are going to bore it then get the big bore since its a total waste to completely bore out a brand new block because your ruining any chance of rebuilding a $2000 block for what? 10cubes? Just do a 30 or 40 overbore and have a nice 347-350. Your going to get a max of 20 cubes by fully boring it so why not just get a 351 based stroker or just do a .030 over 351 which would give you like a 357. Thats only like 5 less cubes than a maxed dart block. Every .030 overbore will give you 5-6 cubes so a .125 overbore is like 20 cubes. And a .125 overbore 327(3.25 crank) is essentially a 347. I say do a 351 since the stock blocks are strong enough to handle boost and are less than $500, and youll get just as many cubes and plenty of torque. And with aluminum heads your 351 will weigh about as much as a dart block 302.

 

[331 cobra]

I want to do something similar, a big bore with 3.25" stroke, but like SmockDoiley said, it's a big risk to bore the block to it's maximum because you have no chance to rebuild it without sleeves. So a $2,000 block can turn in to $10 scrap with one mistake.

Here is my radical solution, get one of the aluminum blocks. Dart makes one, and I have heard of a company called DEI that makes one, but for all I know, DEI could be dart. You can go up to a 4.155" bore I think, and if rebuild time ever comes around, you just get a new set of sleeves.

It will cost more in the beginning, and rebuilds will cost more, but you loose weight, if you have an aluminum radiator, intake, heads, timing chain cover and water pump, galvanic corrosion in the cooling system will be gone. It should last a long time and you will have major bragging rights.

Also, if something goes really wrong, you can weld up the block. They do it all the time for the aluminum block top fuel dragsters. You can't do that at all with an iron block.

 

[ScatStroker]

What are you guys basing any of this on?!

Lets get the FACTS straight:

First, a 4" bore DART block has the SAME cylinders as the 4.125" bore block, one has simply been bored father.

Second, the DART blocks are SAFE to 4.185" bore, we've sonic'd them to 4.200 pretty regularly.

A 4.125" still allows for a MINIMUM of .060 bore in the block, leaving more potential than 99% of users will EVER need. If you'd like to use it for longer than those 20 years of racing then sleeve it.

Aluminum is roughly $1500 more expensive, and provides what most Mustang enthusiasts would consider a very small bang for the buck return. If it wasn't about money then most of us wouldn't be driving Fox body Mustangs, lets face it. Spend your money on induction components, you'll be far ahead of the guy who bought the aluminum block and didn't spend the $1500 on induction.

As for the corrosion people are still driving their 60's Mustangs around 40 years later... are you REALLY talking about a $1500 benefit?

As for the 'too much torque' it's 10 cubes, and as was previously pointed out, the boost will make the power, not the displacement change. The real point to consider is, if it costs the same, and is just as safe, why NOT do it?

8.200 is the '302' deck height you need.

Brian

 

[331 cobra]

I hope you didn't take any offense.

I was taking about going straight to 4.185 on a new block.

Like I said, aluminum is a radical solution.

I have seen what 40 years will do to a mustang's cooling system. I have seen it on two cars, both of which had at least one rebuild with a timing chain cover replacement and who knows how many water pumps. The covers corrode to the point that there isn't enough left for the gasket to seal to. I was working at a machine shop at that time, and while I was welding up the dammaged section, the owner of a local mustang shop came by and asked if we would do that for them because they had a whole stack in the back of their shop.

The timing chain cover isn't the only thing that corrodes. I also flushed out lots of iron rust from both blocks.

Also, by the way, what is the price for the new sportsman block from dart? I'm looking for 8.2" deck, 4.125" bore.

A quote for an aluminum block would be nice also, and is DEI related to dart?

 

[SmockDoiley]

I still say instead of messing with monster boring expensive blocks just do a 30-40 overbore 351. You'll get the same cubes. Get a 72-74 block and itll withstand any boost you throw at it since I know guys that get 700 to the wheels out of those blocks. I just saw a 72 block go for $100 on ebay, not $2000. Spend your money elsewhere.

 

[ScatStroker]

Smock,

We're obviously on a different level. If you've broken numerous 5.0's, and it's design brother (albiet a little more stout) then you'd be looking into a real race block as well. The 2 bolt main blocks simply don't handle the power. He also wants a 3.25" and a 302 so it's a different debate all together.

331,

No offense, it's just so much BS is spewn across the boards I sometimes wonder where so much can come from.

As for the corrosion it's a matter of maintenance and the fact that 99.9% of these combo's won't see 40 years. It will either be changed, sold, torn down or wrecked before it really becomes an issue IMO. For the cost of the aluminum I'd call it a perk at best. While I'm not argueing that after 40 years things do corrode I certainly don't think it's worth the cost.

Sportsman's are $1699 shipped. Aluminum is ~$3200-$3400, I can't recall off the top of my head but that's the general range.

I'm not familiar with DEI. I've been at PRI and SEMA for the last few years and do not recall any company with SBF blocks and that name. I do a small volume of aluminum so it's not to say they couldn't be but they certainly aren't a very large company if they are.

Brian

 

[331 cobra]

$1699 is awesome. That's only about $800 more than a ford sportsman that is only rated for 4.030, which means 1 rebuild only.

With a 4.125" bore, that makes a real 347 that won't burn oil. And you still have two or more good rebuilds left in it.

I'm going to be calling AD pretty soon.

 

[TT91]

$1699 is awesome. That's only about $800 more than a ford sportsman that is only rated for 4.030, which means 1 rebuild only.

.

........Everytime u do a rebuild, its not mandatory to do a .030 overbore. That would be just a waste of money. If the cylinders are in good condition, simply hone the walls and make aure they are within specs. If there is a ridge or somthing else that needs to be taken care of, take car eof it. You CAN bore the block just. 010 over and get custom pistons. I bought at used 306 motor, had it rebuilt 3 timestotal. 2 times professionally, and I did the last one, and everytime the bores never exceeded specs, so i left it at 4.030 and had it cleaned up....power is in my sig.

Edit: and if I was to use the sportsman block, i would keep the 4.00 bore as long as possible before going any bigger. Stronger sidewall..

 

[331 cobra]

Yes, I know you don't always have to go .030, but some times you do have to, usually after you break something, or your rings go bad.

I know a guy that is building up a sportsman block, and his machinist wasn't impressed with the factory bores, so he had to bore it 4.010 to get what he wanted. That only leaves him .020 for a future rebuild. I'm sure he could exceed that if he had to, but my point is that the Dart has lots more iron to work with, a bigger bore, it's stronger and it has four bolt mains.

Also, you could have lots more iron if you go with the 4.000" bore dart, but what's the point of a siamese bore block if it isn't a big bore?

 

[TIMMY2734]

Also, you could have lots more iron if you go with the 4.000" bore dart, but what's the point of a siamese bore block if it isn't a big bore?

Umm, strength
If you have money to burn, go ahead and bore it out to whatever you desire.
But if your like the rest of us, just go .030 . Spend the 1400-1500 on the 4340 scat assembly w/ the dished pistons and call it a day. Bring it to a quality guy that knows what hes doing and the last thing on your mind will be how many more times you can bore/rebuild your motor.

 

[Rick 91GT]

Brian set a lot of the facts straight but I have a few questions...

The gain on that large of a bore is minimal to say the least and now you are also stuck buying custom pistons, not worth it in a street car IMO. Most guys run the large bore to help unshroud the 2.10 valves that the larger race heads have, you won't have that issue with a 1.94 or even a 2.02 on a 4.03 bore.

Also, you could have lots more iron if you go with the 4.000" bore dart, but what's the point of a siamese bore block if it isn't a big bore? Huh? The siamese bore is for strength, to help keep the cylinders round, just because you have the room doesn't mean you need to use it....it also takes a good bit of cooling away

Alum blocks are a PIA and the investment is not worth it for most guys....who cares about bragging rights, or what type of block you have?

Sportsman Dart vs. Iron Eagle Block.... if you were considering the investment in the alum block, why consider the Sportsman, for another $300 or so you can have the Iron Eagle...

 

[TT91]

AMEN!!

 

[331 cobra]

Unless you are running huge boost with a supercharger, the four bolt front cap is pretty much pointless, and I can't figure out any way that a rear 4 bolt would be an advantage. The middle is where you need the strength, and the Dart sportsman has 4 bolt mains there.

Think about it, $300 for two caps that are a marginal improvement in strength.

That block has .250" thick cylinder walls when you bore it to 4.185. At 4" bore, that would be a .340" thick wall. At 4.125 you get a .280" wall. As long as your machinist uses a torque plate for the bore and hone, those cylinders will stay round.

The cooling issue is there no matter how big your bore, so when you step up to siamese, it makes sense to take the displacement advantage because the block is thick enough to run a big bore without becoming oval.

Also, you don't always need custom pistons. I'm sure there are some off the shelf chevy 400 pistons that can be used to make a big bore ford stroker. Just go look at the list of compression heights that JE has available.

 

[TIMMY2734]

331 cobra, no offense or anything, but i dont see why you want the guy to save $300 on a block when better can be had. But then you turn around and are pushing for the more expensive route with the custom pistons.

For $300 more, i would imagine that most people would go for 4 bolt mains on all 5 of the mains.

Like Rick said, just because you have the room doesnt mean that you need to use it.
If i were in your shoes, i would just buy some .030 over pistons and be done with it. If you want more power,then get bigger heads, a better designed cam or throw some more boost at it. Theres no need to waste money on custom pistons when your money can be better spent elsewhere.

 

[SmockDoiley]

The guy is talking 347 so I still say 351 to save money since hes worried about money. A 2 bolt main supported 5.0 can handle 600, and a 351 block can handle roughly 150 more. Thats not garbage, thats the truth. Unless you plan on running like 900+ horsepower, I dont see why more people who are concerned about their budgets dont use 351s. The stock block will handle loads of power. If your stuck on a 306/331/347 and your making more than 600 then yeah, get the dart block, but if you just want more cubes than a 302 then keep the 5.0 block if your under 600 and a 351 if your over 600. A 2 bolt 351 will handle more power than I'm sure he's planning.

 

[muddslide]

Just my 2 cents
Everyone is diffent in their thinking but here is mine. when I looked at spending money on a block and having ther machine work done to it I only wanted to do it once. so I choose the dart block with a 347 stroker kit. But I also have a blower with 10 pounds of boost. my thought was save the money and build a block that will last for years, i'm not a gambling man when it comes to motors

 

[TIMMY2734]

The guy is talking 347 so I still say 351 to save money since hes worried about money. .

He never really said that he wants a 347. He plans on using a 3.25" crank, not 3.4, so its all coming down as to what he wants the bore to be.