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First post here, hope not a beaten horse...max hp out of an '85 block?

 
scooper77515
New User
Posts: 3
Joined: 02/14
Posted: 02/02/14 03:08 PM

Internet banter suggests that stock blocks split around 500 hp. I have a Ford Maverick with a moderately built 5.0 bored over .040, and currently putting out around 350 hp. I have a nitrous plate installed, capable of putting out 100-125-150 shots. If I add the 150 shot, I hit that 500 hp "limit".

I figured you guys at 5.0 Mustang and Fast Fords would know the truth.

This is an '85 5.0 block, I drilled and tapped, converterted to full roller cam and lifters, with 1.72 rockers, approx 9.5:1 compression, GT40 heads with a bit of port and polish. Two bolt mains.

Will this block handle the 500 hp? Confused  

Post Reply
wayne712222
New User
Posts: 13
Joined: 10/13
Posted: 02/02/14 11:04 PM

this is a great question...

i looked around and 302/5.0's with 2 bolt main blocks with cast cranks should.. if the owners want them to live.. should set the rev limiters to 5800. beyond that with even main cap studs and girdles its going to fail  there is too much downward and angled force on the webbing above the main caps..  they just rip right out..

4 bolt main with steel cranks don't have this issue..

did you see the 302 failure article over at hot rod magazine??

http://www.hotrod.com/techarticles/engine/hrdp_0604_ford_302_engine_parts_failure/viewall.html



look at this image from the web..

the main cap is still bolted in..  the block webbing failed. where it was thinned to lighten the block during the design phase...

Sbfwebbingfailure Zpsa3a466ad

4 bolt main blocks have thicker webbing designed in..  or are supposed to have thicker webbing to handle the additional RPMS and Detonation..

this is probably because of harmonic resonance..  where the harmonics of the rotating assembly reach their resonance frequency and the whole thing exceeds the structural strength of the block..

i have seen a picture of an aftermarket block.. where the RPM range was exceeded.. and the bottom end blew out in a similar fashion..

i personally wonder.. if a cryogenic treatment of the block might increase its structural strength.. this is where the bare block will be subjected to significant liquid nitrogen temps in a slow to cool.. slow to warm up fashion..  

Post Reply
scooper77515
New User
Posts: 3
Joined: 02/14
Posted: 02/03/14 05:46 AM

Man, that is too bad, because I built this engine so that it REALLY enjoys being shifted at 6500. All my torque is from 3500-6500 (fairly flat torque along this range).

I guess if it blows, I can always stick in a chevy engine! Shocked  

Post Reply
wayne712222
New User
Posts: 13
Joined: 10/13
Posted: 02/03/14 11:34 PM

i agree..

i think about the aftermarket block i saw an image of.. same type of failure.. don't know the speed.. i don't know what the actual failure speed is..

there are 4 bolt main 302 blocks available ..

i hate being a naysayer..i used to shift my 327 chevy small journal engine at almost 7000 rpms.. and it lived and lived and lived..

if it shifts great at 6500... shift it there.. i could be totally wrong.

i cannot think why a stock block would not hold up..  but i can see its weaknesses in the images above..  lighter weight.. more power.. where is the tipping point..  

Post Reply
scooper77515
New User
Posts: 3
Joined: 02/14
Posted: 02/04/14 06:30 AM

I only have about $400 in this engine, (plus a $600 carb) so if it craters, it can be replaced on the cheap.

I have put this on the dyno for several pulls, and routinely shift at 6500 when I am at the drag strip or showing it off for riders.

I have since cut out the shock towers and put in a Rod and Custom kit, power rack and pinion, etc. So I have plenty of room for anything I care to drop in there.

I guess I will take my chances, keep beating the snot out of it, and start saving for a new engine in case this one ever gives up the ghost.

If I had know that the 5.0/302 was a relatively weak block, I would have never replaced the stock 302 with this one, and gone on to something bigger (351W?)  

Post Reply
wayne712222
New User
Posts: 13
Joined: 10/13
Posted: 02/04/14 10:53 AM

same issues..  4 bolt blocks are stronger..

its not that its a weak block.. they are all just light weight blocks..

ford tested these at WIDE OPEN throttle for hours and hours and hours..

perhaps there were some RPM excursions that were not talked about..

i have only seen images of a few blocks that had this issue..

if you don't have a lot invested.. pull the pin.. its just entertainment..

and a great story ..  if it holds together it does..  

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