Ford Boss block

[Chuck]

Getting ready to build our next SBF engine. The engine builder I am working with has highly recommended a new Ford Boss block. I understand it will be compatible with all the external accessories that would otherwise fit on a seasoned block, but will also handle a bit more power.

Obviously it will cost a few more bucks.

We are planning a 347 (which will actually be a 362 ci).

Anyone have any experience with the Boss block? Pros? Cons?

 

[EGLITOM]

My 331 is based on the new boss block. Cranking out 506 HP at 7200 RPM.
Heads are EDELBROCK VICTOR JR flowing 325 cfm on the intake and 241 cfm at the outlet @ 0.600 lift. , Intake is a SUPER VICTOR. Carb is HOLLEY 750 Pro Double pumper with mechanical secondaries and no choke tower. Cam is a custom grind solid lifter type. Lift is 0,592 inch and duration is 260° at 0,50 inch.

No issues to report so far after 3000 mls of mixed driving. Engine revs very fast and high . Pulls away nicely from 2000 RPM and realy gets the beat as of 4000. it revs into the limiter at 7200 like nothing. If i want i could use the engine up to 7800 RPM and developing more power, but that requires a more intensive valve train maintainance.
Currently i have the rev limiter set at 7200.

If i would do it over again i would go with one of KCR 408´s , if you are interessted i send you the spec. it is a 351 based engine using the Dart block and cranking out 580 HP and 550 lbs/ft of torque. THis all with hydraulic roller lifters. Max RPM is 6250. This engine is so powerfull but still mild on cam and virtualy maintainance free. Cost is around 13.000 USd including carb and ignition. KCR is fast in building those. Last engine i ordered took around 5 weeks from order to delivery, The previous one 7 weeks.

TOM

 

[Mark Clapp]

I was lucky enough to visit Mahlon Miller's garage (Miller Motorsports in Erie, CO) and he showed me a new Bosss 302 crate engine that he was putting in a client's GT40. It had all the accessories except intake and distributor and had cool "Boss 302" valve covers. They mostly come as 362s, 500 hp, all for $8600. Here is a link showing the crate engines (click on 302s): Crate Engines, Mustang Engines, Drag Racing Engines, Stock Car Engines, Funny Car Engins, Race Engines, Racing Engines - Ford Racing Performance Parts

 

[Chuck]

Thanks for the info.

Tom, curious why you selected a 331 displacement. My understanding is there is not much difference in cost between a 331 versus 347. Also understand that the 347 are a bit more prone to oil consumption, but that would not really be a big deal. Just curious. Regardless, you ended up with an impressive engine. Probably a bit more aggressive than our goal. We will probably end up in the 450 - 500 HP range.

 

[Mike Drew]

I just finished up having a 331 stroker built for my GT-350 clone, using a new Boss 302 block. That's a NICE piece. It's very strong, and very heavy (much heavier than a standard 302 block). They are pretty expensive, but I think they are good value for the money when compared with some of the other aftermarket offerings out there.

As for the 331 vs. 347 dilemma, painful experience (of others, thankfully) has shown that 347 motors are fine for street driving but often aren't up to the rigors of open-track use. The rod angles are just too great. A friend of mine has a fantastic blown-up 347 from his GT-350 (in fact it's pictured in a recent issue of Hot Rod magazine) where the whole block just split apart--this happened at 6000 rpm on the front straight at Thunderhill.

Oil consumption is also a concern because with most blocks, the 347 stroke has the bottom ring extending partially out of the the piston sleeve (the new Boss blocks reportedly have longer sleeves to control this better). The 331 has no such problems.

Unfortunately I don't have good dyno numbers for my engine. My distributor was breaking up at higher RPM and crossfiring. So the power curve suddenly flattened out and it peaked at only 395 hp. It has a new distributor fitted now and I'm confident the actual number will be in the 440-450 hp range. Plenty enough for me!

 

[Chuck]

Mike

Good info. Wonder if the Boss block would solve the problem with the 347 splitting the block. I assume that was a stock block.

Indeed we are actually looking at 362 CI with the boss block. Long term reliable performance is more important than a few extra HP. May need to reconsider.

 

[Mike Drew]

Mike

Good info. Wonder if the Boss block would solve the problem with the 347 splitting the block. I assume that was a stock block.

Indeed we are actually looking at 362 CI with the boss block. Long term reliable performance is more important than a few extra HP. May need to reconsider.

Excellent questions. I originally went for a 331 because I planned on using a Mexican block. When that turned out to be not so bueno (bored .033 over, thanks dude!), I was more or less forced to get the Boss block. That block is substantially stronger and heavier than the original Boss block, not to mention all the other Ford blocks. So perhaps it would be fine for a 347 in performance applications. I think there's enough meat to let you safely bore it more than .030 over, which is where those extra few inches above 347 would probably come from.

You would still be RPM-limited with such large displacement, which isn't necessarily a bad thing, if you are more interested in low-end torque than high-rpm power. I'd probably be reluctant to spin a 362 inch smallblock more than about 5500 rpm. But I freely admit that's based on superstition rather than genuine expertise in the matter....

 

[Chuck]

Thanks Mike

Been doing a bit more research. Several have noted that the Boss block cylinders are about an eighth inch short. A 347 or 363 will have a stroke of 3.400. A 331 will have a stroke of 3.000. The longer stroke can reportedly be a problem requiring the use of short skirt pistons. Even then there can be issues, including increased oil consumption. Sounds like another reason to go with a 331.

Wondering if anyone else has heard of this issue.

It has been suggested that a Dart block does not have this issue if one wants the larger displacement.

This is all new information to me. Interested in any ones experiences.

 

[David in Durango]

Ford calls this motor a 363.

The blocks that split are 302 production blocks prior to 1995 developing 400-425hp or more. *

???the new "Boss" block is a DART or Man o' War product with Ford branding.* ????

At some point I saw a photograph of a stroker motor that showed the wrist pin 1/2 our of the bottom of the cylinder - quite scary to me. Ford says one can use a 3.4 stroke with these blocks.

The added displacement comes from the 4.1125 bores vs. a 4.00 bore.*

Even though Ford claims the 3.4 stroke is ok, I'm reconsidering the shorter stroke and I think Mike is right on with this.

* these "facts" are from memory and I can't verify them at this time. Dan Jones could probably address these statements.

 

[Rick Muck- Mark IV]

???the new "Boss" block is a DART or Man o' War product with Ford branding.* ????

No, they are cast for Ford by Caterpillar's foundry using a proprietary iron alloy. There are several design differences between the "Boss" block and the Dart, M o' W, etc.

 

[David in Durango]

No, they are cast for Ford by Caterpillar's foundry using a proprietary iron alloy. There are several design differences between the "Boss" block and the Dart, M o' W, etc.

Anyone know what these difference might be?

thanks,

 

[Chuck]

The bit of research I have done suggests that the cylinder bottom on the Dart is about an eighth inch longer, this it would be better suited to a 3.400 stroke. But I claim no expertise in this area (which is why I did this thread). I would be interested in feedback on which block would be the better choice, pros and cons.

 

[EGLITOM]

Thanks for the info.

Tom, curious why you selected a 331 displacement. My understanding is there is not much difference in cost between a 331 versus 347. Also understand that the 347 are a bit more prone to oil consumption, but that would not really be a big deal. Just curious. Regardless, you ended up with an impressive engine. Probably a bit more aggressive than our goal. We will probably end up in the 450 - 500 HP range.

Don´t know what bore your are planning but even with 4,1125 your displacement will be max 320 CUI with the 3.00 inch stroke.

I wanted a engine which can rev up to 8000 rpm therefore we used 3,25 " Stroke forged steel internaly balanced crank instead of the 3,4" for the 347.

All the goodies are there and if i would change the cam to a roller type with a more agressive lift curve i could bring the engine up to 600 HP. So for my stock 1,5" RCR Header with 2,5" collecters is probably already limiting my current setup. Would need to go to 1.75" headers with a 3" collecter and muffler to use the full potential of my engine.

But so far i´m still satisfied with the power it develops

Thanks
TOM

 

[David in Durango]

Thanks for the note, Chuck.

Its good we can collect information to share here.

 

[Chuck]

Been doin' a bit of math. Dangerous thing for someone with my background . . . .

A 347 CI engine would typically have a stroke of 3.4" and bore of 4.030.

A 331 would typically have a bore of 4.125" and stroke of 3.100. Or a bore of 4.030" and a stroke of 3.250. Do the math. Either way it works out to 331 CI.

A stroke of 3.250 should be fine with a Boss block.

So what if you have a bore of 4.125 and a stroke of 3.250? If my calculator is right that is 347 CI. Is that feasible? Surely someone has done that. It should avoid the issue with the short cylinders on the boss block that may be a problem with a 3.400 stroke.

My impression is that a 347 will have less RPM potential due to the rotating mass, etc. Would increasing the bore but keeping he stroke the same as a 331 (3.250") effectively get around those issues?

I am out of my element here, so any thoughts?

 

[Ron McCall]

Been doin' a bit of math. Dangerous thing for someone with my background . . . .

A 347 CI engine would typically have a stroke of 3.4" and bore of 4.030.

A 331 would typically have a bore of 4.125" and stroke of 3.100. Or a bore of 4.030" and a stroke of 3.250. Do the math. Either way it works out to 331 CI.

A stroke of 3.250 should be fine with a Boss block.

So what if you have a bore of 4.125 and a stroke of 3.250? If my calculator is right that is 347 CI. Is that feasible? Surely someone has done that. It should avoid the issue with the short cylinders on the boss block that may be a problem with a 3.400 stroke.

My impression is that a 347 will have less RPM potential due to the rotating mass, etc. Would increasing the bore but keeping he stroke the same as a 331 (3.250") effectively get around those issues?

I am out of my element here, so any thoughts?

Chuck,

That is EXACTLY what I had built for my NASA American Iron Race car!
I used a Dart block and went from the standard 4.030"bore/3.4" stroke ( original engine) to a 4.125" bore 3.25 stroke and actually picked up 30 RWHP with no other changes!
The compression on the new engine is lower and it runs on pump gas instead of 110 octane race gas. And it still made more power! I had to add ballast and a restrictor plate to meet the hp/weight limit of the class .

 

[flatchat(Chris)]

FWIW and its just my Opinion ---- a standard production 302ci Windsor is a stroked out to the max 260 / 289 ci W already-- to pump these out to 347ci is asking for trouble -- 4 more ci and you could start with a 351 W which is already built for what you want out of a "stroker" small block.
If you are insistant on say a 347, then you must start with a heavy duty after market block which almost uses all the 351 technology including the extra weight which needs the extra cubes to make the extra HP to move what a well built 302 would do in the first place....
.....Am I missing something ?

 

[Chuck]

Ron

Thanks. That is exactly what I wanted to hear!

 

[Chuck]

Flatchat

Totally agree. We would not use a seasoned block for a 347. We are planning to use a new Boss block. Current issue is what to do with it . . . . .

 

[David in Durango]

FWIW and its just my Opinion ---- a standard production 302ci Windsor is a stroked out to the max 260 / 289 ci W already-- to pump these out to 347ci is asking for trouble -- 4 more ci and you could start with a 351 W which is already built for what you want out of a "stroker" small block.
If you are insistant on say a 347, then you must start with a heavy duty after market block which almost uses all the 351 technology including the extra weight which needs the extra cubes to make the extra HP to move what a well built 302 would do in the first place....
.....Am I missing something ?

The deck heights are different - 8.2 vs. 9.5 (? I think?)

IF the tall deck motor will fit, I believe it IS the way to go. If not, then we are trying to figure out stroke and rod ratios for the 8.2 block.