Boredom 391FT thoughts

[pbf777]

     Note that SeaMaster offered the Ford 534 engine in a twin turbo configuration providing in excess of 400 H.P. and 600 ft. lbs. torque for boat installations.       

     Scott.

[Dr Mabuse]

Many good ideas and interesting comments ... if I ever modify my F-350 I would likely go with a 390/445 stroker and wish for a Gear Vendors overdrive, or some kind of automatic OD.

[frnkeore]

I have a TRW reference, that says that 1971 and earlier blocks, both 361 & 391's, have thicker cylinder walls.

[My427stang]

I have a TRW reference, that says that 1971 and earlier blocks, both 361 & 391's, have thicker cylinder walls.

Sonic check everything, or at least a drill bit test if not very rusty inside.  I wouldn't believe anything like that TRW reference from what I have seen.  Not that I haven't seen thick blocks, but I haven't seen any pattern other than C scratch 428s, which seem to be more consistent

One point with sonic checking is that even if the block a decent drill bit test, fairly often a whole bank can be offset making a consistently thin side or sides, so it's always good to sonic check before the build

[frnkeore]

I have a TRW reference, that says that 1971 and earlier blocks, both 361 & 391's, have thicker cylinder walls.

Sonic check everything, or at least a drill bit test if not very rusty inside.  I wouldn't believe anything like that TRW reference from what I have seen.  Not that I haven't seen thick blocks, but I haven't seen any pattern other than C scratch 428s, which seem to be more consistent

Ross, how many pre-'72 361 - 391 blocks have you looked at?

My post was informational only, on what you might want to look for but, TRW, in their day, made pistons for some OEM Ford's and the reference was regarding how much you could bore a post '72 block.

[blykins]

I have a TRW reference, that says that 1971 and earlier blocks, both 361 & 391's, have thicker cylinder walls.

Sonic check everything, or at least a drill bit test if not very rusty inside.  I wouldn't believe anything like that TRW reference from what I have seen.  Not that I haven't seen thick blocks, but I haven't seen any pattern other than C scratch 428s, which seem to be more consistent

Ross, how many pre-'72 361 - 391 blocks have you looked at?

My post was informational only, on what you might want to look for but, TRW, in their day, made pistons for some OEM Ford's and the reference was regarding how much you could bore a post '72 block.

There are no "safe" years.  All of them need to be sonic tested. 

[My427stang]

I have a TRW reference, that says that 1971 and earlier blocks, both 361 & 391's, have thicker cylinder walls.

Sonic check everything, or at least a drill bit test if not very rusty inside.  I wouldn't believe anything like that TRW reference from what I have seen.  Not that I haven't seen thick blocks, but I haven't seen any pattern other than C scratch 428s, which seem to be more consistent

Ross, how many pre-'72 361 - 391 blocks have you looked at?

My post was informational only, on what you might want to look for but, TRW, in their day, made pistons for some OEM Ford's and the reference was regarding how much you could bore a post '72 block.

Between industrial of that era, dedicated large distributor bushing blocks, and 70s 360/390 (although not the topic of discussion) likely only 30-ish ?   You can sneak in with the drill bit test, but shift is an issue, they need to be checked, like it or not

Additionally, your deduction with TRW does not lead to a viable solution,  TRW made .040 and  .060 over 427 pistons, just because something is sold or bought, doesn't infer the block can take it.

What I advise when building a stroker or healthy original engine is: Use whatever you want, but sonic check first, then if the block will work, align hone/square deck and torque plate hone.

In fact, although I haven't had a bad C scratch block, I wouldn't even use that as a filter, anything could happen back then and it seemed to get worse in the 70s

[frnkeore]

So then Brent, I ask the same question to you. How many pre '72 and post '72 361 - 391 blocks have you had your hands and examined?

I'm not discounting the use of sonic testing but, if the core is thicker, to begin with, then core sift has less effect on the amount a block can be bored.

While I'm at it, I will ask everyone on the forum.......... Has anyone either, allen wrench or sonic tested any pre '72 361 or 391, truck blocks?

It would be a interesting question to answer, right? And don't forget, you get a forged crank, with it, too.

[My427stang]

So then Brent, I ask the same question to you. How many pre '72 and post '72 361 - 391 blocks have you had your hands and examined?

I'm not discounting the use of sonic testing but, if the core is thicker, to begin with, then core sift has less effect on the amount a block can be bored.

While I'm at it, I will ask everyone on the forum.......... Has anyone either, allen wrench or sonic tested any pre '72 361 or 391, truck blocks?

It would be a interesting question to answer, right? And don't forget, you get a forged crank, with it, too.

Frank, the shift can be significant, it's not just a little.  I had an industrial 428 (which in 390 form would have passed the drill bit test) it was thin enough I sent it home with a note to bring me a better one and I am all about minor overbore to use a block. 

I understand what you are asking, but in the end, there is no constant for the blocks, and even if the crank is added to the mix as beneficial, expect to: 1. pay more to modify it and buy FE connecting rods or 2. pay even more to modify it and use cheaper BBC rods.  So unless you have a serious reason, it is really more cost effective to just grab whatever std bore block you can find, sonic test it for cheap money, and build a stroker with new parts

Granted desire for period correct accuracy, love for 391s, etc, all could lump in to the "serious reason" category, not my job to determine that for the guy who walks in, but no free chicken in a 391 IMO

[frnkeore]

Granted desire for period correct accuracy, love for 391s, etc, all could lump in to the "serious reason" category, not my job to determine that for the guy who walks in, but no free chicken in a 391 IMO

Only hands on testing of pre '72, 361 - 391 will prove it, or not but, it's something that could be beneficial for FE builders. Core shift is random and may or may not be present in any block.

[blykins]

So then Brent, I ask the same question to you. How many pre '72 and post '72 361 - 391 blocks have you had your hands and examined?

I'm not discounting the use of sonic testing but, if the core is thicker, to begin with, then core sift has less effect on the amount a block can be bored.

While I'm at it, I will ask everyone on the forum.......... Has anyone either, allen wrench or sonic tested any pre '72 361 or 391, truck blocks?

It would be a interesting question to answer, right? And don't forget, you get a forged crank, with it, too.

Frank, I build FE's.  I build a lot of them.  I'm a small, one-man shop but I have 9 builds going right now and 6 of them are FE's (the others are all SBF's; I'm a Ford shop).  I don't know about other builders, but I don't keep a log book with every FE block I've touched. 

I will tell you emphatically that the year doesn't matter as to how thick a block is or isn't.  I have sonic tested (and drill bit tested when I was younger) all different years of blocks.   They all vary.  Back around 14-15 years ago, there was a time where I was trying to take 390 blocks out to a 428 bore and ruined quite a few to tell you the truth.   We sonic tested many blocks, including some C4 blocks all the way up to the D4TE stuff.   There is not a consistent standard to any of them.  As Ross pointed out, core shift will ruin your day. 

I'm sorry that TRW led you down the wrong road, but you're on the right forum to learn some new stuff.   All of the FE gurus are *right here*. 

[plovett]

For a heavy towing application, I like the idea of getting as many cubes as possible.  That is, a 4.375" crank.  With a 4.08" bore you're looking at 457 inches.  Keep the cam very small, say 212 or less duration.  Performer intake with a 600 Holley.  1-3/4" headers or maybe even 1-5/8" if you were to have them made.  Compression at around 8.5:1 to 9:1 with forged pistons.  Good ignition curve for the application.  Almost any garden variety passenger car FE heads with pocket porting and a good valve job. ……...and as much gearing as you need, or can tolerate.

JMO,

paulie

[My427stang]

Granted desire for period correct accuracy, love for 391s, etc, all could lump in to the "serious reason" category, not my job to determine that for the guy who walks in, but no free chicken in a 391 IMO

 Only hands on testing of pre '72, 361 - 391 will prove it, or not but, it's something that could be beneficial for FE builders. Core shift is random and may or may not be present in any block.

I posted a reference about the blocks and since you have no direct knowledge, what your saying has no bearing on the subject.

Frank, I am a polite poster but you have no idea of the extent of my experience or what I do. 

Go for it, YOU do it, YOU see, YOU take the chance and report back. TRW catalogs are not an accurate source of block thickness. Sonic testers are cheap and so are 391 blocks. I would love to hear back your findings

[blykins]

And don't forget, you get a forged crank, with it, too. 

Do you know what's entailed in using an FT crank in a normal application?

[plovett]

I would say that Ross and Brent are correct even if some 360/361 or 390/391 blocks are thicker than others.  You never know for sure unless you check.  And even then it is generally better to bore a block as little as possible.  Thicker walls are better than the small gain in displacement and/or any gain in breathing from a slight bore increase.

I have two mirror 105 blocks and I did the drill bit test on them.  According to that they might go .060" over, but I don't know for sure.  I wouldn't actually do that without a sonic check. 

JMO,

paulie