help with 351w swap

[torquelover]

I work in aerospace, specifically with gas turbines/ jet engines. Where, as you know, things are much more controlled, and design is extremely rigorous.

Even still, whenever I fly, I make it a point to not sit directly in line with the turbine/turboprop. They don't fail very often, but when they do, the results are gruesome.

[sick88tbird]

I can't currently provide any proof on the size of the head bolt holes...but I had to have the head bolt holes drilled out on my F3ZE heads for use on my 351W...my only explanation for the larger bolt holes in any 5.0 GT40 head on '96-'97.25 Explorers would be "build out". Which could also explain why I haven't come across any. I wonder how many of those heads they had left after the end of the Lightning run.

[P72Ford]

Even still, whenever I fly, I make it a point to not sit directly in line with the turbine/turboprop. They don't fail very often, but when they do, the results are gruesome.

Well, we do our best to prevent fan blades from exiting the fan case.

I'm not sure if you're familiar with a 'blade out' condition or not, but those are the primary causes of engine parts exiting the case. But even still, disk ruptures have happened in the past.

In a blade out, one of the fan blades (those that you see on the front of the engine) detaches and is ingested into the engine. The fan cases are designed to contain the blade (which weighs 20 or more pounds, and is spinning at 4000+ rpm). The cases are aluminum, about 3" thick. The extrior is milled in a triangulated fashion, to provide almost a honeycomb structure. Then they are blanketed in kevlar, often an inch or more thick.

Under blade out testing, that case can deflect as much as 12+ inches radially. Plenty of energy... :smirk:

As the blade is ingested in the LPC, HPC, diffuser, intermediate case, HPT, LPT, and TEC, there is incredible damage done. Often times the rapid deceleration of the engine (from cruise speed to 200 rpm or so) causes it to backfire, with an explosion out the front, and sometimes rear of the engine. Usually, though, in a blade out condition, if pieces are going to exit the case, they exit from the fan case.

All engines have to pass a blade out test to enter production, just so you know. There is extensive testing done, trust me. In blade out testing, they actually use a planted explosive charge to detach the fan blade.

With the advent of hollow fan blades, there is much less stored energy in a spinning fan blade, so containment is 'easier' if you will.

[torquelover]

All engines have to pass a blade out test to enter production, just so you know. There is extensive testing done, trust me. In blade out testing, they actually use a planted explosive charge to detach the fan blade.

With the advent of hollow fan blades, there is much less stored energy in a spinning fan blade, so containment is 'easier' if you will.

Good to know. If you haven't seen this yet, I'm thinking you will find it interesting:

http://www.ntsb.gov/Publictn/1998/AAR9801.pdf

Not thinking the OP is considering jet propulsion instead of a 351W, but if you are, don't let talk of fractured fan hubs sway you away from installing one of these bad boys in your Panther

/regain post topic

[gadget73]

A 7/16" bolt used in a properly sized hole has a larger contact area with the cylinder head than a 7/16" bolt in a 1/2" hole. sigma= p/a.

quite true, but given the amount of precision a lot of things in the auto world are built around, its probably good enough. Its not sufficient for really extreme applications, but stock 9:1ish engines that don't see over 5000 rpm can get away with a lot of stuff that just won't work in a boosted or sprayed environment. Same reason why a lot of people run around with 302s that have almost zero oil pressure and a death knock. It works fine for grocery-getter duty but spin that thing up to 6000 rpm while trying to do a 1/4 mile blast and it will quite likely eject parts in a hurry.

[Mercracer]

I can't currently provide any proof on the size of the head bolt holes...but I had to have the head bolt holes drilled out on my F3ZE heads for use on my 351W...my only explanation for the larger bolt holes in any 5.0 GT40 head on '96-'97.25 Explorers would be "build out". Which could also explain why I haven't come across any. I wonder how many of those heads they had left after the end of the Lightning run.

Any GT40 head purchased through SVO/Ford Racing/FRPP would have come with 1/2" holes. Anecdotal reports are that some Cobras came with 7/16 and some with 1/2" holes. Obviously the Lightning heads were 1/2" holes. From all of the comments on the internet across several forums it appears that very few heads had 7/16" bolt holes and that most all GT40 heads had 1/2" bolt holes no matter what the application.

[P72Ford]

Good to know. If you haven't seen this yet, I'm thinking you will find it interesting:

http://www.ntsb.gov/Publictn/1998/AAR9801.pdf

Not thinking the OP is considering jet propulsion instead of a 351W, but if you are, don't let talk of fractured fan hubs sway you away from installing one of these bad boys in your Panther

/regain post topic

I am vaguely familiar with this incident, just because the JT8D is/was produced by the company that I work for.

I believe blade containment regulation started in the early 80s, but engines already in service did not have to comply. The JT8D has been around in one form or another since the mid 60s. I'm not sure if that meant it was exempt, or whether the later revisions of the engine were indeed held to it.

[86VickyLX]

Were any of the P heads factory made ever have anything other than a 7/16" bolt hole? Like the regular GT40s?

[Mercracer]

Were any of the P heads factory made ever have anything other than a 7/16" bolt hole? Like the regular GT40s?

Nope. The GT40P heads were only used on 302 Explorer engines.

[marquisman]

GT40P heads FTW!

[sick88tbird]

Any GT40 head purchased through SVO/Ford Racing/FRPP would have come with 1/2" holes. Anecdotal reports are that some Cobras came with 7/16 and some with 1/2" holes. Obviously the Lightning heads were 1/2" holes. From all of the comments on the internet across several forums it appears that very few heads had 7/16" bolt holes and that most all GT40 heads had 1/2" bolt holes no matter what the application.

Yeah, I know about all the FRPP heads having 1/2" bolt holes...I guess the very few heads with 7/16" bolt holes all came my way...lol. By me making a blanket statement and not augmenting it with the phrase, "from what I've seen", kinda made me look like an arguementative know-it-all jackass...lol.

Good times,
Don