331/347 vs 392/408...which one?

BIGJOE,
What do you see as being the power limit of a stock 289/302 or even 351W block? What is your procedure for breaking them in?

By the way guys, check out THE SHERMINATOR 347 at AFR Cylinder Heads Inc: Aluminum cylinder head manufacturing and flow dynamics and click on Articles at the top and then Small Block Ford Articles. Then click on the 527 HP 347 ci AFR 185cc.

I have made as much as 649 HP at 7500 RPM with a HI PO 289 block(347-12.75 to, big roller cam-AFR 205 heads)I have made 747 HP from a stock block 351 Windsor. I run the engine on the dyno for 10-15 minutes, then let it cool down, then I run it for 10-15 more, then let it cool down. I keep the RPM at 2200 or higher, with a light load ( 30 to 50 ft lbs of torque) while I am doing the breakinI NEVER let the engine come down to an idle durring this dyno breadin process. I set the timing with the light and monitor the temps with a radar gun and the dyno instaments. I watch the oil temp so it does not get too hot, and I keep the water at 160 degrees. On race engines, I cut this way shorter, maybe one 10 minute session, then go for it.

JOE SHERMAN RACING ENGINES

Well, I built a 306 based exactly on Joe's buildup in a magazine a while back. It is awesome. Same cam, notch on pistons towards the rear, etc.

I was going to do a 408W because I have a 78 351W shortblock sitting around.

After reading Joe's comments and accompanying insight, The fact that I have a '65 Mustang with the old style motor mounts that you can't get headers for with a 351W based motor (not cheap anyway). Spali32's 347 powered Cougar that I have helped him tune and felt the power of. (which he has consulted with Joe about a few times)

I'll just redo my current 306, and turn it into a 347 when I get the rest of the car all sorted out. My little (375-400 HP) 306 will have to do for now.

You are the man Joe. I am very thankful that you are a member here, and are very forthcoming with your knowledge.

The weak block issues are more of a concern with power-adder applications, and the general 500 HP limit is rear wheel HP.

Have built many a 331, 347, 393, and a couple 408's. If you have the room for a Windsor, there is no other choice. That is the only constraint-space. Some of us don't have a choice (early Mustang, Maverick, etc) because the engine bay makes it VERY difficult to drop in a 351w and still get any kind of decent header to fit. But if it fits, the 351w based engine is a better choice. Stronger, more torque, not much heavier, etc. There are so many things that are better about a 351 as opposed to a 302 that there really is not much of a comparison.

Once we did a 352 (.060 347)....same cam and heads as were on my 357w (.030" stock crank/rods), almost the same compression, etc. The windsor would run off and hide from the 347 in all aspects. It wasn't a measly .3-.4 faster, it was a FULL SECOND faster and in a heavier car with a crap converter.

I suppose if you were on a tight budget a 302 based job would be a better choice...or if you had no room for the bigger windsor, but those are the only 2 reasons I would ever consider going to a 302.

Originally Posted by mavman

Once we did a 352 (.060 347)....same cam and heads as were on my 357w (.030" stock crank/rods), almost the same compression, etc. The windsor would run off and hide from the 347 in all aspects. It wasn't a measly .3-.4 faster, it was a FULL SECOND faster and in a heavier car with a crap converter.

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Mavman any idea why?...I have heard the exact opposite of this...Normally the extra rotating wieght of the 351 makes the 347 quicker with the same parts?

I don't know. Rod ratio is slightly better with the windsor engine but that's never really been a big issue. I mean both of those engines were basically identical with the exception of the compression height and rod length. the stroke was within .030" of course. Then the windsor also had a much heavier crank and rods (obviously). I wish I knew an answer to the question, but as much as I try to think of one reason I just can't think of anything at the moment. Even the carbs were teh same home-built 830 carbs, I swapped them back & forth, even tried the 950 off of my 514 BBF that was in my truck (daily driver before gas was over $2.00/gal) and it made no difference whatsoever. That was the purpose of building the 347....to be quicker than the windsor but it just didn't happen for whatever reason. Sometimes you get into stuff like that where one engine is identical to the other but doesn't make quite as much power. I recently built a 414" which is identical to a previous build, and it is about a tenth slower...and everything is 100% identical. It just feels lazy compared to the old one.