Ford Boss block

[Ron McCall]

Chuck,

I have a friend who has a brand new 8.2" Boss block that he would like to sell.
He is asking $1200 for it.

 

[Chuck]

Decided to go with a stroke of 3.250 and a bore of 4.125. Essentially a 331 with a bigger bore that works out to 347 CI.

Saw some issues with a 3.4 stroke on the new Boss block. Some report that the cylinder walls are a bit short at the bottom end. The 3.125 stroke makes that a non issue.

Was reassured to see Ron had used that set up. Found a number of articles with the same configuration.

Had a nice discussion with Jim Inglese. Plan to go with an original style IDA Weber set up.
Call me crazy.

With a mild cam should end up in the 425 - 450 HP range which should be adequate motivation for a 2300 pound car.

 

[EGLITOM]

Chuck

would think again about it. On 427´s(bored 4.125 and stroked 4.00 351s) the cylinderwalls getting quite thin and lead to distortion of them ( even critical with Dart blocks). The angle of attack is bigger on those long stroke engines and therefore the sidewall pressures higher. Don´t know if this is an issue with the bore to stroke ratio and longer rods of the 3.25 but give your engine builder a talk about it again.

Thanks
TOM

 

[Mike Huddart]

Chuck

would think again about it. On 427´s(bored 4.125 and stroked 4.00 351s) the cylinderwalls getting quite thin and lead to distortion of them ( even critical with Dart blocks). The angle of attack is bigger on those long stroke engines and therefore the sidewall pressures higher. Don´t know if this is an issue with the bore to stroke ratio and longer rods of the 3.25 but give your engine builder a talk about it again.

Thanks
TOM

Not an issue, presuming Chuck is going to use 5.400 rods then the rod / stroke ratio will be 1.66, slightly better than a 350 and 427 Chev, both at 1.64 and only just less than a stock 302 at 1.7.
The 427W has a rod/ stroke ratio of 1.55, not ideal but still better than one of the best engines ever made, the 454 Chev at 1.53. Be careful of all that torque !
Mike

 

[Chuck]

Mike and Tom

Yes indeed, 5.400 rods

 

[Chuck]

I will freely acknowledge my areas of expertise. Building engines is not amoung them. So I cannot vouch for this information. But here are links to some threads discussing the issue of the Boss Block, short bottom cylinders and the reason it is not well suited to a 3.400 stroke.

http://forums.corral.net/forums/94-95-tech/1345187-boss-302-block-dart-shp-block.html

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http://forums.corral.net/forums/5-0-5-8-engine-tech/1309648-dart-vs-boss.html</o>
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<o>http://forums.corral.net/forums/5-0-5-8-engine-tech/1096651-boss-347-crate-engine.html<o></o>

Here are pictures from the first link. The first is a short Mahle, the second a Probe. The issue seems pretty clear to my non expert eyes:

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[David in Durango]

Chuck, thanks for that post! I learned something I NEEDED to know.

cheers,

 

[EGLITOM]

Chuck

also pay attention to get a "second generation" Boss block. The first generation had a issue with the webbing to the rear main bearing. They developed some cracks there.
Therefore Ford changed the design and added some stiffening ribs.

We had a post here about that topic with pictures. may be you can look it up

Thanks
TOM

 

[Chuck]

Tom:

Good tip. I will confirm that it is a new Gen II block.

 

[Julian]

My boss block ( Gen 1, no rear ribs) has lasted 2 seasons of competition in my 40. Rev limited set to 7000 rpm, power is 380 rwhp and climbing still at the limiter. It is a 347, 3.4 in stroke and 30 thou over bore. Revs very freely as you'd imagine from the power still rising at 7k. YouTube 200MPH GT40 to see what it puts up with.

 

[Chuck]

My boss block ( Gen 1, no rear ribs) has lasted 2 seasons of competition in my 40. Rev limited set to 7000 rpm, power is 380 rwhp and climbing still at the limiter. It is a 347, 3.4 in stroke and 30 thou over bore. Revs very freely as you'd imagine from the power still rising at 7k. YouTube 200MPH GT40 to see what it puts up with.

Good to hear. Sounds like the issue with the 3.4 stroke in the new Boss blocks is not across the board, as your engine proves.

 

[Jim Rosenthal]

Is this motor going in the GT40, or in the Mustang... or in something else from the Chuck and Ryan collection...jus curious...

 

[Chuck]

Jim

You just had to ask, didn't you. At the risk of being blackballed, it is going into a Shelby 289 Cobra. We are building a visual clone of CSX2129, raced by Ken Miles in 1963. It is based on an ERA slab side, but will require a fair bit of body work and detailing to duplicate the original.

Chuck

 

[Cliff Beer]

Keep in mind, if you already have cross-over headers for a 289/302 SBF, those same headers won't work on a 351 based engine because of the taller deck height....