408

87ttopgt · July 8th, 2007, 11:21 PM

hey guys im looking to build a 408 for my mustang, ive done a couple 302s before but im not real fimiliar with the 351s. Whats a good year block to get to start this project with. Ive been told that the 351s can hold upwards of 650-700 just wondering how accurate that is. I have a twin turbo kit that i dont want to even try putting a 5.0 with the stock bottom end even though the engine is farily built. Any suggestions are much appreciated. Thanks alot. Matt

ryans88gt · July 9th, 2007, 12:27 AM

With the correct prep and rotating assembly a 351 block "can" hold between 600-800 hp. For how long??? Depends on your driving style, how well it is tuned, compression, type of power adder ect...

Also, a turbo kit that would work for a 302 is nowhere near workable on a 408. You'll need to learn to study compressor adiabatic efficiency maps to determine what compressor housing you'd need and for the exhaust side I would think you'd need at least a decent size T4 housing for a twin turbo kit. Another thing to think about is the compression, you'll need some serious dished pistons to keep comp low with a 408 (or opened up combustion chambers). Another thing to remember is that a 351 block is wider, so a 302 turbo hot parts are not interchangeable with 351 turbo hot parts.

What years to look for in blocks?

Early blocks 69-71/72 had a 9.480 deck height
Later blocks had a 9.508 deck height

When buying a 408 kit, you need to make sure you know which deck height the kit is made for. If made for the later model deck height, you wouldn't have enough material to clean up the block deck and you'd end up with pistons "out of the hole".

F4 casting blocks (94 and later) have larger lifter bores allowing the use of standard Ford roller lifters, unfortunately these blocks are also a little lighter and were cast from lower nickel metal and are not as strong as the earlier blocks.

In general I think the earlier the casting, the stronger, heavier, and higher nickel it is, but I do not remember the cut offs for the years they changed the castings off the top of my head.

86er · July 9th, 2007, 01:17 AM

69-74 or 75 are the stronger factory 351 blocks

a 1st gen lightning block is also a sturdy base to work from as its different from the regular truck motors of that same year

ryans88gt · July 9th, 2007, 10:20 AM

I think the 1st gen lighting motors are the same F4 castings...I am unaware of any differences there.

86er · July 9th, 2007, 10:37 AM

Originally Posted by ryans88gt

I think the 1st gen lighting motors are the same F4 castings...I am unaware of any differences there.

they are different

neverfastenough1 · July 9th, 2007, 12:10 PM

I'm with Ryan on the Lightning block. Everything I can find on it says they went with the existing 351w block. Which makes sense with only 240 hp. If you can find something that states otherwise, I would like to see it because I am thinking of the stroked 351 route and would like to know for sure if it has a better block. Has nothing to do with the Lightning block but its a good read on block choices.

http://www.alternativeauto.com/water..._strokers.html

July 8th, 2007, 11:21 PM	#1
87ttopgt Newbie Join Date: Jul 2007 Posts: 3	408 hey guys im looking to build a 408 for my mustang, ive done a couple 302s before but im not real fimiliar with the 351s. Whats a good year block to get to start this project with. Ive been told that the 351s can hold upwards of 650-700 just wondering how accurate that is. I have a twin turbo kit that i dont want to even try putting a 5.0 with the stock bottom end even though the engine is farily built. Any suggestions are much appreciated. Thanks alot. Matt

July 9th, 2007, 01:17 AM	#3
86er Hardcore Enthusiast Join Date: Nov 2006 Location: Orlando, Fl Posts: 1,742	69-74 or 75 are the stronger factory 351 blocks a 1st gen lightning block is also a sturdy base to work from as its different from the regular truck motors of that same year __________________ 1989coupe 419w/c4/2 stages of the smack faster than you faster than your first sexual experience

July 9th, 2007, 10:20 AM	#4
ryans88gt MM Fanatic Join Date: May 2007 Location: Bloomington, IL Posts: 4,333	I think the 1st gen lighting motors are the same F4 castings...I am unaware of any differences there. __________________ 88 GT CHI headed 351w 10.8 @ 125 - still figuring it out. 03 Cobra 2.3 whipple 10.7 @ 129 - sold it 04 Mach 1 12.7 @ 109 mostly stock - sold it 89 LX procharged 302 515 hp 497 ftlbs 10.7 @130 mph - sold it

July 9th, 2007, 12:10 PM	#6
neverfastenough1 Hardcore Enthusiast 2002 Mustang GT Join Date: May 2007 Location: Savannah, Ga Posts: 2,244	I'm with Ryan on the Lightning block. Everything I can find on it says they went with the existing 351w block. Which makes sense with only 240 hp. If you can find something that states otherwise, I would like to see it because I am thinking of the stroked 351 route and would like to know for sure if it has a better block. Has nothing to do with the Lightning block but its a good read on block choices. http://www.alternativeauto.com/water..._strokers.html __________________

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July 9th, 2007, 12:27 AM	#2
ryans88gt MM Fanatic Join Date: May 2007 Location: Bloomington, IL Posts: 4,333	With the correct prep and rotating assembly a 351 block "can" hold between 600-800 hp. For how long??? Depends on your driving style, how well it is tuned, compression, type of power adder ect... Also, a turbo kit that would work for a 302 is nowhere near workable on a 408. You'll need to learn to study compressor adiabatic efficiency maps to determine what compressor housing you'd need and for the exhaust side I would think you'd need at least a decent size T4 housing for a twin turbo kit. Another thing to think about is the compression, you'll need some serious dished pistons to keep comp low with a 408 (or opened up combustion chambers). Another thing to remember is that a 351 block is wider, so a 302 turbo hot parts are not interchangeable with 351 turbo hot parts. What years to look for in blocks? Early blocks 69-71/72 had a 9.480 deck height Later blocks had a 9.508 deck height When buying a 408 kit, you need to make sure you know which deck height the kit is made for. If made for the later model deck height, you wouldn't have enough material to clean up the block deck and you'd end up with pistons "out of the hole". F4 casting blocks (94 and later) have larger lifter bores allowing the use of standard Ford roller lifters, unfortunately these blocks are also a little lighter and were cast from lower nickel metal and are not as strong as the earlier blocks. In general I think the earlier the casting, the stronger, heavier, and higher nickel it is, but I do not remember the cut offs for the years they changed the castings off the top of my head.

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