Author Topic: Ford's Big Bore Boss 302 block  (Read 2542 times)

shelbydoug

  • SAAC Member
  • Hero Member
  • *
  • Posts: 4298
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #30 on: October 08, 2021, 07:44:10 AM »
I seem to remember "Ford" explaining the change in the firing order as a fix for the "recently" discovered tendency of even just the little 289 to break cranks.

I don't recall the B2 with it's steel crank having that reputation?


I've got a Scat 347 stroker in my 68 302 block. Looking at the crank, I had concerns. Especially after I got it back from the balancer who turned it into swiss cheese.

I put in a girdle, as if that would help. People run 331's for a reason. I'm thinking all 347's are on borrowed time anyway? Wasn't it Capt.America that said, "we're all living on borrowed time"?
« Last Edit: October 08, 2021, 08:07:18 AM by shelbydoug »
68 GT350 Lives Matter!

gt350hr

  • Hero Member
  • *****
  • Posts: 2279
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #31 on: October 08, 2021, 11:06:08 AM »
   In 52 years of racing them , I have never "broken" a 289 crank nor have I cracked one. Spun bearings? SURE. The Boss 302 cranks ( especially DOZE) have a reputation for cracking in road race use. You have nothing to worry about with a 347 crank. The .150 difference in overall stroke is NOTHING to be concerned about. People act like these cranks create all kinds of stress and strain. I put 50,000 miles on a 347 as a daily driver before I pulled it to inspect and resell. I did go to .040 over because I sold it to a friend. "I" would have simply ball honed and re rung it if I kept it. There are all kinds of "internet isms" out there that are repeated by clueless people. My favorite is "the pin in the oil ring groove will cause excessive oil consumption". Next is "the increase in side loading will wear the pistons out more quickly".  Neither is true.
   Randy
Celebrating 46 years of drag racing 6S477 and no end in sight.

shelbydoug

  • SAAC Member
  • Hero Member
  • *
  • Posts: 4298
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #32 on: October 08, 2021, 01:09:35 PM »
   In 52 years of racing them , I have never "broken" a 289 crank nor have I cracked one. Spun bearings? SURE. The Boss 302 cranks ( especially DOZE) have a reputation for cracking in road race use. You have nothing to worry about with a 347 crank. The .150 difference in overall stroke is NOTHING to be concerned about. People act like these cranks create all kinds of stress and strain. I put 50,000 miles on a 347 as a daily driver before I pulled it to inspect and resell. I did go to .040 over because I sold it to a friend. "I" would have simply ball honed and re rung it if I kept it. There are all kinds of "internet isms" out there that are repeated by clueless people. My favorite is "the pin in the oil ring groove will cause excessive oil consumption". Next is "the increase in side loading will wear the pistons out more quickly".  Neither is true.
   Randy

What was causing the issue with the Boss 302 cranks?
68 GT350 Lives Matter!

CSX2259

  • Full Member
  • ***
  • Posts: 219
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #33 on: October 09, 2021, 03:21:02 AM »
Another trick my engine builder likes to do is use a 351W firing order instead of the 289 firing order. The 289 firing order creates more stress on the engine block.

shelbydoug

  • SAAC Member
  • Hero Member
  • *
  • Posts: 4298
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #34 on: October 09, 2021, 04:25:54 PM »
Another trick my engine builder likes to do is use a 351W firing order instead of the 289 firing order. The 289 firing order creates more stress on the engine block.

I never heard that about the block, just late production ('67ish) broken crankshafts. It wasn't about race engines. It was about warranty replacements on production cars.

I never saw that. Neither did I see main bearing failures on 351c's but Ford said yes.

I can see where running the engine out of oil caused the bearing issue but broken crankshafts? How do you do that?

Ford thought they might have an oiling issue with the C's and put 20-50 oil in the B351's.

The 289 crank has to be a casting issue? I never even heard of a racer breaking one. Spun bearings, yes.

The firing order on the 5.0's was changed to the 351w firing order somewhere around 1981. So what took so long if there was an issue? The small block was in production since 1961. It doesn't make sense unless they felt the weaker roller block needed it?

68 GT350 Lives Matter!

68countrysedan

  • Full Member
  • ***
  • Posts: 144
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #35 on: October 09, 2021, 08:18:08 PM »
It has been suggested that Ford switched from the 1-5 to the 1-3 cylinder firing order because the two consecutive power strokes contributed additional wear on the number 1 main cap bearings.

csxsfm

  • Full Member
  • ***
  • Posts: 110
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #36 on: October 10, 2021, 10:52:46 AM »
I lost a few 289 cranks in my road racing days but they were always preceded by rods exiting the block.  LOL

mlplunkett

  • SAAC Member
  • Full Member
  • *
  • Posts: 157
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #37 on: October 12, 2021, 09:36:25 PM »
Let me change the direction of this post a little bit. Sounds like there is agreement that I don't need a racing block to build a 331 stroker that will give me about 450 HP so thanks for that guidance. My new question relates entirely to the appearance of the 302 vs the 289. Since I'm building a GT350R tribute I want the finished engine to look as much like the proper 289 as practical. What problems am I going to have if I start with a 302 block instead of a 289?
67 GT500 tribute under construction
65 R-model tribute under construction

mlplunkett

  • SAAC Member
  • Full Member
  • *
  • Posts: 157
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #38 on: October 13, 2021, 09:22:03 AM »
   Use "retro fit" tie bar lifters and it's a breeze.

Randy, Where can I find more info on the lifter package you mention? I'm leaning toward the 289 block to maintain original appearance. Do these lifters require a custom roller cam or are they compatible with standard roller cams? Mickey
67 GT500 tribute under construction
65 R-model tribute under construction

gt350hr

  • Hero Member
  • *****
  • Posts: 2279
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #39 on: October 13, 2021, 10:43:22 AM »
   Mickey several manufacturers have "tie bar" hydraulic roller lifters, or "retro fit" hydraulic roller lifters. Howard's cams , Morel , Lunati, Crane, etc.
Celebrating 46 years of drag racing 6S477 and no end in sight.

mlplunkett

  • SAAC Member
  • Full Member
  • *
  • Posts: 157
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #40 on: October 13, 2021, 11:55:30 AM »
Thanks Randy. By the way, this is the motor that I'll used that oil cooler on so whenever you get time to ship it, I'm getting closer to needing it.
67 GT500 tribute under construction
65 R-model tribute under construction

deathsled

  • SAAC Member
  • Hero Member
  • *
  • Posts: 2472
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #41 on: October 13, 2021, 02:16:35 PM »
  Maximum safe bore on those blocks is 4.155 not 4.200. They do not accept a "standard" camshaft because of the "common size" cam bearing machining. 1/2" head bolts ( 351W) head bolts are required as well. The block is significantly heavier than an early 289 block. "I" would ( and have) use a '65-69 block and add Cobra Automotive "HiPo" caps. My 520hp 331 has done this for 20 years without issue. However it is your money.
   Randy
That's what you are rocking in your Hertz drag car, Randy?  That's a hell of a lot of HP for such a light car.  Amazing!
Richard E.
"Low she sits on five spoke wheels
Small block eight so live she feels
There she's parked beside the curb
Engine revving to disturb
She's the princess from his past
Red paint gold stripes damned she's fast"

gt350hr

  • Hero Member
  • *****
  • Posts: 2279
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #42 on: October 13, 2021, 03:33:42 PM »
    Richard,
        Yes the current engine in the Shelby is a 331 that makes about 525 by the 122 mph at the finish line. I previously had a 351ci Boss 302 that made closer to 600. It rand 10.70's at 127MPH. The engine "on the stand" is a 374CI all aluminum Boss 302 that I "hope" will run in 9.99 "once" . LOL That takes close to 700. Then I might put it "out to pasture".
Celebrating 46 years of drag racing 6S477 and no end in sight.

deathsled

  • SAAC Member
  • Hero Member
  • *
  • Posts: 2472
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #43 on: October 13, 2021, 10:23:58 PM »
That is pretty damn fast.  Gives modern day cars a serious challenge...
"Low she sits on five spoke wheels
Small block eight so live she feels
There she's parked beside the curb
Engine revving to disturb
She's the princess from his past
Red paint gold stripes damned she's fast"

TA Coupe

  • Full Member
  • ***
  • Posts: 207
    • View Profile
Re: Ford's Big Bore Boss 302 block
« Reply #44 on: October 14, 2021, 02:59:10 AM »
Link to lifters. You might need a small base circle cam? Randy can tell you.

       Roy