302 Rotating Assembly in a 289 Block? - Ford Mustang Forum
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post #1 of 18 (permalink) Old 08-28-2019 Thread Starter
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302 Rotating Assembly in a 289 Block?

I understand that a 302 block's cylinder skirts are about .015" longer than those of a 289, supposedly to accommodate for the 302 crankshaft's .130" longer stroke.



Is it safe to use a 302 rotating assembly in a 289 block? Will there be enough cylinder skirt in the 289 block? Does the additional .015" make that much difference? Anyone run the 302 assembly in a 289 block?

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post #2 of 18 (permalink) Old 08-29-2019
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Bubba, it shouldn't be a problem. Lots of people have, even with stock pistons. If you're using some nice aftermarket slugs, they may even have shorter-than-stock skirts anyway. The main thing is that the stroke clears the counterweights, and that won't be a problem with a 302. Additionally, if you had the block bored, make sure the bottom edge of the cylinder holes isn't razor sharp, or it may scuff your piston skirts. This has nothing to do with the .015" extra clearance, just common sense and good build practice.

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post #3 of 18 (permalink) Old 08-29-2019
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+1 on Grimbrand's excellent advice. Make sure you use a '68-78 style ( two piece seal) 28oz balance crank . "I" like to use the '68-'70 "ribbed cap" rods which were brought back for the 5.0 Explorer engines. In '71 a change was made to what I call a "strap cap" rod cap and I feel they don't "stay round" which could cause a bearing failure. The piston actually pulls .130 further out the bottom of the cylinder over the 289 but there is no ill effect. Grimbrand is also correct that some aftermarket piston manufacturers ( especially performance forged ones) are shortened to reduce the amount of piston that comes out of the bottom of the cylinder. The long "tab" on the bottom of stock pistons is worthless.
Remember guys are adding 3.250 and 3.400 stroker cranks to these engines all the time. Yes the rod is .310 longer but the piston still is lower in the cylinder , so more is coming out. The "cylinder loading" some have concerns about isn't an issue on a two piece seal block . It's the 1 piece seal blocks that srein trouble there.
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post #4 of 18 (permalink) Old 09-02-2019 Thread Starter
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Thanks. I have a 1966 A code that needs a rebuild, and I would like to get the extra torque of the 302 but retain my original block. I have a 302 from a 1976 Mustang as a donor.

Failure is only the opportunity to begin again more intelligently. H. Ford

1966 A code 4sp Fastback
1976 302 4sp Coupe
1986 351 C4 Hatchback
1990 GT Convertible
2008 GT Convertible
2011 F100 XLT
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post #5 of 18 (permalink) Old 09-02-2019
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In terms of basic geometry torque is more related to bore diameter than anything else. A 289 and a 302 have the same bore. Any torque increase from a later 302 would come from details other than the increaed stroke.
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post #6 of 18 (permalink) Old 09-03-2019
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Actually, the increased leverage from the longer stroke creates a lot of extra torque. A 302 typically delivers about 15 lb-ft more torque than a 289. So long as you're not hitting excessive piston speed, increasing stroke is a great way to lower the RPM of your car's powerband, and deliver more torque. Horsepower is typically limited by the heads and cam, but of course, any part of the setup can be a bottleneck.

In practical terms, a 289 and 302 with the same heads, intake, cam, and exhaust will probably make exactly the same peak horsepower. You *might* notice the difference between the two if you drove them side by side, but probably not. The 302's average power (because of the torque improvement) would be slightly higher. The 289 would be able to stay in a given gear longer, and be a little more willing to rev.

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Last edited by Grimbrand; 09-04-2019 at 01:03 AM.
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post #7 of 18 (permalink) Old 09-03-2019
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+1. The change in stroke AND rod length produce more torque than the 289. Piston speed is faster overall because of the stroke initially and the shorter rod increases piston speed off of and back up to TDC. This results in lower "dwell time" which KEEPS the piston in motion longer. Remember a piston can only transfer energy when it is MOVING. Relating "burn time" to dwell time is a bad comparison as the spark started around 30 or more degrees before the piston got to TDC , so it had PLENTY of time to burn and 4-5 nanoseconds more don't mean anything. I will be glad to debate that with ANYBODY.
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post #8 of 18 (permalink) Old 09-03-2019 Thread Starter
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I want the engine to look original as possible on the outside, but would like a little more streetable grunt. I have a pair of 1970 351W heads that I planned to use also.
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Failure is only the opportunity to begin again more intelligently. H. Ford

1966 A code 4sp Fastback
1976 302 4sp Coupe
1986 351 C4 Hatchback
1990 GT Convertible
2008 GT Convertible
2011 F100 XLT
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post #9 of 18 (permalink) Old 09-04-2019
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Doing a bit of work on those heads, like matching the ports to your intake, and getting rid of thermactor bumps, etc. can give you huge benefits. Those D0VE heads are fantastic, if someone with a bit of porting knowledge really works them over. It sounds like you're more into making your car more fun on the street instead of making it a drag racer, so don't put in huge valves, which will usually kill velocity and hurt your bottom end. You'd probably even pick up some mileage.

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post #10 of 18 (permalink) Old 09-04-2019 Thread Starter
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You're correct Grimbrand, I'm not building a drag car. I plan to port match the heads to an original Shelby dual plane high rise manifold I have, and using tri-Y headers. I want more torque since my transmission is a wide ratio T10.
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Failure is only the opportunity to begin again more intelligently. H. Ford

1966 A code 4sp Fastback
1976 302 4sp Coupe
1986 351 C4 Hatchback
1990 GT Convertible
2008 GT Convertible
2011 F100 XLT
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'70 Windsor heads are good. Focus on the exhaust port and try not to "flair" or "funnel" shape it. The natural tendency is to "port match" it and it leaves a bottle neck at mid port that leaves the restriction you are trying to eliminate. Don't bother with the intake "port" , just smooth the "bowl" behind the valve of sharp edges. You don't need to remove the whole bump , just the sharp edges.
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Quote:
Originally Posted by Gt350HR View Post
'70 Windsor heads are good. Focus on the exhaust port and try not to "flair" or "funnel" shape it. The natural tendency is to "port match" it and it leaves a bottle neck at mid port that leaves the restriction you are trying to eliminate. Don't bother with the intake "port" , just smooth the "bowl" behind the valve of sharp edges. You don't need to remove the whole bump , just the sharp edges.
Randy

Along the same idea, can a guy use a 331 or 347 stroker kit in a 289 block? Scott
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Sure , it's done everyday. I have a 331ci assembly in an original 289 hi po block that's been in my racecar for 19 years.
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post #14 of 18 (permalink) Old 4 Weeks Ago
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If you lived closer, I'd give you my balanced 302 rotating assembly, complete with timing chain, and gear set. I ran this set in my 5 bolt 289, not a problem!

Ken
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333 cu.in, dual Webers, CI cam, TW heads,TRI-Ys, 3.55 rear, T5z, TCP susp., real leather seating
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post #15 of 18 (permalink) Old 4 Weeks Ago Thread Starter
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Dang, Kenash. I just got back from Ocean City, MD last weekend, after judging a show in Fredricksburg, Virginia.


Failure is only the opportunity to begin again more intelligently. H. Ford

1966 A code 4sp Fastback
1976 302 4sp Coupe
1986 351 C4 Hatchback
1990 GT Convertible
2008 GT Convertible
2011 F100 XLT
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