How to tell if my block is thick walled?

[mungus]

Just got bad news from my machinist. 45 over wear in one bore, 30-35 in the rest.

So I'm guessing I'm up for another block, unless I sleeve one hole and fit maybe 50 or 60 over Pistons. However I'm not comfortable about that much over on a thin walled 48 year old FE block.
So I have to ask, just how do you tell if you have one of these famous thick walled blocks?
All my Welsh plugs are out, so what do I look for?
I've read about looking for a 428 cast into the water jackets somewhere, but only for some of the thick walled blocks, not all. So is there something to look for, or is ultrasonic testing the only way?
It seems a waste of money to go straight to the ultrasonic, if there's another way to telling my block is even a candidate for boring.

This shop is an old and well respected family firm, and very good, in fact they were involved in building the Ford Australia small block racing engines many years ago, but they are not FE specialists...

[e philpott]

ultra sonic is by far the best way because it will measure core shift

[Joe-JDC]

Agree with sonic testing your block.  I have a 428 CJ block that I was afraid of at .030 over, and when I had it sonic checked, it will go +.080 if I needed it to.  I watched the whole process and he checked each cylinder bore in twelve places, top-middle-bottom.  I have had several blocks checked since, and now I trust that process as a means of taking worry away about whether I made the right choice or not.  I raced a 428CJ with .040 overbore so don't think all is lost with your block until you get it sonic checked.

PS.  Upon reading your question again, what block do you have?  The original '68 S code?  If so, then most 390 blocks are safe at +.045, or +.050, or with sonic check to +.080 in some blocks.  There is a drill bit test to try.  A 3/16, 1/4, 5/16.  If the 3/16 is tight, then you have thicker walls. The bits will require you to have all the sand core plugs removed to get access to the cylinders to check between them.   Joe-JDC

[Barry_R]

Ultrasonic is really the only solid answer - and fairly inexpensive in the context of things.  The drill bit can tell you if the casting is thick in some areas but wont tell you if its because the cores have drifted.  Even the sonic has its limits - corrosion in the water jackets can give you a false reading due to pitting.  I would not discard a block until I had a sonic map.

[mungus]

Thanks everyone. That's kinda what I was thinking. I read about the drill bit tests elsewhere today, but Barry makes a good point too. It's only $90 AUD for ultra sounding, so not big money. I may do it even if I am planning on buying another 390 block from a Mustang club friend. After all, useable FE blocks aren't easy to find in Austalia.

And yes Joe, mine is a 1968 390GT block. Thanks for the figures, very useful.

Next question. Are Melling sleeves a viable plan? 1/8" thick from memory.
They could well be a cost effective alternative to sourcing another block.
However I notice they don't appear to be stepped sleeves, just plain.
Presumably they are usually watertight, etc.
I'd hate to bust through the water jacket.

[mungus]

Well my sonic test has been done. Minimum wall thickness came in at 140. I haven't seen any paperwork for mapping etc, however they are known as a trustworthy and long standing outfit in the FORD performance world down here.
The shop says they would be happy going .060 over. That allows .015 for straightening and honing over on the worst worn cylinder.

It was running standard OEM pistons when I got it, worn to .045 on the worst cylinder, and around .030 to .035 on the others.
As we know getting .060 over pistons is no problem, but would the experienced FE builders here feel OK about that?
Maybe I'm reading this wrong, but if my worst cylinder was .045 over STD, and we go to .060 over STD, surely that leaves the thinnest bore at .125 thick by my reckoning... Is that enough for decent longevity on a street car?
On a 48 year old block from an engine known to have core shifting issues? Opinions definitely appreciated; Barry / Jay?

I have also found another FE 390 block through the Mustang club, that I'll take delivery of in a week. Not date correct (mine is an S code fastback Mustang so I like that sort of thing), but perhaps a better block for building. I want a spare anyway and the price was nice.

Anyway if we go back to the planned .060 job, (401 CID) what about a choice of pistons? Summit feature the Speedpro range.
I was thinking of their 4 pocket flat top forged alloy versions. Maybe adding a set of 4340 H beam STD length rods.
Any views one way or the other? Looking for around 9.00 to 10.25 CR. Pump gas only...  I haven't measured my chamber CC's (awaiting some CJ valves etc). But they are the factory C8AE-H smog heads. So I'm guessing may 68-69 cc.

Any recommendations?
Assuming my block is OK at +60, my crank has been checked OK, so CR calc's would be based upon that.
Alas I don't have all the required data for those web CR calculator pages. i.e.; deck height, gasket thickness & gasket bore unknown, valve opening etc not sure yet. But its basically going to be based upon a standard engine;
FORD cast 2U crank, STD length rods, block +.060, .

Standing by... 

[jayb]

I think you'll be fine at .060" over, although I wouldn't push the horsepower level too high; 500-550 would be about the limit, I think, with those cylinders.

[mungus]

Thanks Jay. I'm only aiming for about 380-400 HP and 480-500 ft/lbs, so that thickness should be fine. I'm picking the block up today so we will see what it's all like.

Any other views out there?

[Joe-JDC]

Typically the thinnest spot is on a not-thrust wall.  If after you get your sonic sheet, the thinnest spot is indeed on a non-thrust wall, then you should stop worrying about strength at +.060" over.  Even if that is a minor thrust wall, depending where it is located, it should be ok.  If the thinnest is at the bottom, then it is typical.  Joe-JDC

[mungus]

Thanks Joe.

My next problem is choosing some +60 Pistons...
As my 2U crank checked out OK I'm probably not going to pay for a stroker.
I figure 401 CID will be just fine with the other upgrades I'm doing. Probably end up with about 350-370 HP and maybe 460-470 ft/lbs. That will do for a street car...

Problem is some CR calc sites ask for some data I don't yet have (top ring to deck etc), and those that I can use produce differing CR's for the same data inputs! (Very weird, but I've redone and rechecked the data I'm using these several times now...) E.g Summits seems off compared to the page linked from Barry's at Survival.

Anyone have some +60 examples using a standard crank & rod length? Hoping for 9 to 10.5 CR.

[Heo]

With flat top speedpros and block milled for zero
deck height you end up around that. Slight variation
depending on headgasket, volume head volume

[mungus]

With flat top speedpros and block milled for zero
deck height you end up around that. Slight variation
depending on headgasket, volume head volume

Thanks Heo, Yes that's what I was aiming for. Using +60 flat forged Speedpros, their own specs and .015 deck you get around 10.14:1 according to Summits calc page, vs. 9.87 from Barry's using the same numbers. I think I'd be happy with either. Premium unleaded down here varies between about 95 to 98 Octane, so .5 either side of 10 is just fine. I think I may just skim the block say . 005 off for flatness and leave it at that. Its a very stock looking block, so that should end up at about .005 to .010 deck.

[Heo]

Aim for a 0.040 squish that way it more forgiving
on CR

[Heo]

Im building a similar engine now  060 over 390,
SP flat tops,Ported C4-G heads, zero deck, comp 282 S cam
Ported Edelbrock Streetmaster, 780 holley
Ordered a 294S With the calculated CR, but was sent
a 282S but i think with 98 it will be fine.
Estimate 350-400 hp

[mungus]

Sounds good. I actually just ordered a bunch of engine parts from Summit and Survival last night.
In my case I've gone for a slightly milder hydraulic roller cam in the COMP XR270HR. But I'm confident the hydraulic rollers will make up some, for less peak lift (.521/.521). I personally don't like big cams for regular street use or touring. Track use yes. But mines not doing that. I've had my time running lumpy street engines. I found them to eventually be a big PITA.

These days I'd rather get power other ways if I want it. It will still do what I want I feel; I've gone for +60 SP forged flat tops on Eagle's H beam rods, full balance, BT PI type intake, FPA headers, 2.5" Magnaflow exhaust, CJ 730 carb, OEM C8AE-H heads running CJ valves, mild port work & COMP double springs, upgraded rockers, Petronix ignition (OEM dizzy), etc. aiming for similar figures to yours.

I'm aiming for for a close to factory looking mustang 390 engine bay with no extra bling, Scott Drake repro factory 67' open type air cleaner (no snorkels etc), cast iron coloured ceramic coating on the headers, alloy Edel water pump with FORD blue paint on everything the factory painted blue, etc.

Would be nice to run it on a dyno when it's done...