[pontiacmark]

I have a 69 and 72 400 block that are standard bore that were running good when pulled.. I asked a machine shop for quotes on cleaning, boring, decking, freeze plug and cam bearing install. The shop also quoted align hone of the mains and sonic checking. Aside from simply being thorough, how necessary is align honing and sonic checking of a known street engine that would be bored .030 over?

[HoneyHush]

I would skip the line bore on this engine. I would definitely skip the sonic testing too.
If it isn’t broken there’s no need to fix it. Ive seen a bunch of Pontiac’s get line honed and then start having bearing problems and especially timing chain issues.

[steve25]

How did your main bearings look when you took the motor apart ( not in terms of scratches) in terms of ware, and will you be the one assembling this motor?

[hurryinhoosier62]

Originally Posted by HoneyHush

I would skip the line bore on this engine. I would definitely skip the sonic testing too.
If it isn’t broken there’s no need to fix it. Ive seen a bunch of Pontiac’s get line honed and then start having bearing problems and especially timing chain issues.

Align BORE and align HONE are two different machine processes. If an engine machinist removes enough material from the main saddle through an align hone to reduce bearing crush and lower the main saddle to cam bore clearance he needs to give up being an engine machinist. I’ve align bored and align honed hundreds of blocks. An align hone, properly performed, straightens the main saddle alignment. I have seen few blocks that couldn’t use a good align hone. Iron distorts over forty years of heating and cooling cycles.

[hurryinhoosier62]

Originally Posted by pontiacmark

I have a 69 and 72 400 block that are standard bore that were running good when pulled.. I asked a machine shop for quotes on cleaning, boring, decking, freeze plug and cam bearing install. The shop also quoted align hone of the mains and sonic checking. Aside from simply being thorough, how necessary is align honing and sonic checking of a known street engine that would be bored .030 over?

Do you X-ray vision? All an ultrasonic inspection will do is confirm there is enough material in the primary thrust face to machine out. Blocks corrode internally; they also suffer from coolant erosion and cavitation. I know of two ‘66 389 blocks that had primary thrust face cylinder walls that were less than .090 thick. The MINIMUM primary thrust face cylinder wall SHOULD be .150-.180. Align honing simply insures that the main saddle alignment is correct. It’s a simple process that removes a modicum of material from the main caps and the main saddle. At most, .003-.005 out of the caps and .001-.003 out of the main saddle. Iron DOES distort over forty years of heating and cooling cycles. Have them check the cam bore alignment as well.

[mgarblik]

The crankshaft spinning in straight and true housing bores will produce almost no bearing wear and not put any weird stress on the crankshaft. As mentioned, if done correctly, only a few thousanths of material is removed. No need to line bore IMO. Line hone only. Sonic test is nice for piece of mind. If your on the fence, look carefully in the core plug holes for divots and rust pockets on the outside of the cylinder barrels. If you see anything more than a slightly rough "as cast" finish, I would recommend checking it. I am sure you want to do it once and do it right.

[tom s]

When Joe Reath was alive and was doing my engines,he would not take a engine in to build without a line hone.He was in the biz for a hell of a long time and had been burned a few times.As said,the hone takes a VERY small cut.Tom

[pontiacmark]

To be clear, I am not afraid of the align hone and I know the difference between it and align boring. It is another $300 that I wasn't budgeting for. Budget and reliability don't usually go together, lol.. steve25 makes a good point about checking the bearings. I haven't pulled the crank out of either short block yet. The 69 had great oil pressure, that I can state. Both blocks don't show any significant signs of corrosion. I suppose their could have been core shift when cast, but I don't think .030 over would be a concern on either block.

[tom s]

I have not done a sonic on a std bore block going just 30 over.Maybe just lucky.Tom

[grandam1979]

Usually I will have a block checked that I get as a bare block and don’t know anything about it or if it’s a complete engine that’s suspect. But if your freshening up a engine you know history on or can see run then no.

[1_Wild_Cat]

The last sonic check I paid for was $60...admittedly it was 4-5 years ago. In the grand scheme of an engine build it wasn't a big expense. I would align hone too actually.

[hurryinhoosier62]

Originally Posted by mgarblik

The crankshaft spinning in straight and true housing bores will produce almost no bearing wear and not put any weird stress on the crankshaft. As mentioned, if done correctly, only a few thousanths of material is removed. No need to line bore IMO. Line hone only. Sonic test is nice for piece of mind. If your on the fence, look carefully in the core plug holes for divots and rust pockets on the outside of the cylinder barrels. If you see anything more than a slightly rough "as cast" finish, I would recommend checking it. I am sure you want to do it once and do it right.

Mike, IMO the ONLY time an align bore is warranted is IF you have a spun main saddle and are installing a repair or if you are replacing the main caps. Rarely have I seen a main saddle so far "off" that it needed an align bore. Cam tunnels are a different story.

[Cliff R]

NOT a fan of messing with the mains in any fashion. These blocks are extremely rugged and it's rare to have to mess with the mains unless you are having aftermarket 4 bolt main caps installed.

I test mine by installing the crankshaft w/o a rear seal in place. If it turns easily with two fingers after everything is torqued to spec it's good to go. 99 percent of the engines I've done here have passed that test. IF I had a "tight spot" or the crank turned hard or showed witness marks on a bearing or bearings the build would go another direction.....FWIW.....

[Dragncar]

Originally Posted by pontiacmark

To be clear, I am not afraid of the align hone and I know the difference between it and align boring. It is another $300 that I wasn't budgeting for. Budget and reliability don't usually go together, lol.. steve25 makes a good point about checking the bearings. I haven't pulled the crank out of either short block yet. The 69 had great oil pressure, that I can state. Both blocks don't show any significant signs of corrosion. I suppose their could have been core shift when cast, but I don't think .030 over would be a concern on either block.

Sonic check it. Complete lunacy to not check the block.
Putting good money into bad blocks, it happens all the time to people who do not thoroughly check their blocks out.
The difference between "thinking" and "knowing" is only a few bucks. Good 400 and 455 blocks are not as plentiful as some think.

[Elarson]

I'm not a machinist...but I know a really good one.

If the old bearings are undisturbed, I'd start by inspecting them. As alluded to in a few previous posts, looking for unusual wear is a great first start. If any bearings show uneven wear (one side worn more than the opposite side), that's a strong clue that you would benefit from a GOOD line hone.

I'd rank your options for a great engine in this order:

1) line hone by an excellent machinist. Ask Mike (mgarblik) to describe the extra steps required to get them really straight with no taper.
2) do nothing
3) line hone by a sub-standard machinist. It's easy for an idiot to make things worse.

Eric

[Formulajones]

Originally Posted by hurryinhoosier62

Align BORE and align HONE are two different machine processes. If an engine machinist removes enough material from the main saddle through an align hone to reduce bearing crush and lower the main saddle to cam bore clearance he needs to give up being an engine machinist. I’ve align bored and align honed hundreds of blocks. An align hone, properly performed, straightens the main saddle alignment. I have seen few blocks that couldn’t use a good align hone. Iron distorts over forty years of heating and cooling cycles.

Ditto....

I don't understand why someone wouldn't want to at least check the alignment of the mains, all of your block work is based off that. Why worry about decking the block and attempting to square things up if you aren't going to bother with align honing the mains along with that.....

I've never had a 50 year old block that "didn't" need an align hone and haven't met a machinist yet that didn't recommend getting it done.

But you really need a good machinist.

[72projectbird]

If the bearings look good, I would skip it.

[hurryinhoosier62]

Originally Posted by Cliff R

NOT a fan of messing with the mains in any fashion. These blocks are extremely rugged and it's rare to have to mess with the mains unless you are having aftermarket 4 bolt main caps installed.

I test mine by installing the crankshaft w/o a rear seal in place. If it turns easily with two fingers after everything is torqued to spec it's good to go. 99 percent of the engines I've done here have passed that test. IF I had a "tight spot" or the crank turned hard or showed witness marks on a bearing or bearings the build would go another direction.....FWIW.....

Cliff, with all due respect I do not agree. I have machined 6,000 blocks. Out of that 6,000 blocks roughly 20% didn’t need an align hone. The 6,000 includes blocks with far stronger bottom ends than Pontiacs. 6.9:/7.3 IDI blocks and 7.3 PowerStroke blocks have massive steel main caps and incredibly thick main saddles but most of the blocks I saw needed an align hone due to distortion of the iron. The cam tunnels were absolute nightmares on many of these blocks. I do like your idea on checking main saddle alignment. It’s similar to the “go/no go” gauge bars we used.

[hurryinhoosier62]

Originally Posted by pontiacmark

To be clear, I am not afraid of the align hone and I know the difference between it and align boring. It is another $300 that I wasn't budgeting for. Budget and reliability don't usually go together, lol.. steve25 makes a good point about checking the bearings. I haven't pulled the crank out of either short block yet. The 69 had great oil pressure, that I can state. Both blocks don't show any significant signs of corrosion. I suppose their could have been core shift when cast, but I don't think .030 over would be a concern on either block.

Mark, all the machine shop is attempting to do is alleviate their liability. They are attempting to cover all their bases. 6.9/7.3 IDI cylinder barrels are incredibly thick ( nearly 3/8 of an inch) but I have seen these cylinder barrels “eaten” through due to coolant cavitation and corrosion to the point where the block wasn’t salvageable. Yes, it’s $300 you didn’t plan to spend but it will give you a block that you CAN have confidence in.

[mgarblik]

The $300.00 charge to line hone would be roughly $100.00 an hour. With the old, manual Sunnen LH-100 line hone it takes me 3 hours to get a Pontiac block dead nuts on. That would be +-.0001 through the 5 mains, 70% of the diameter, taper .0001". Factory tolerance is +-.0005. Even a marginal shop can hit that range. Used Pontiac blocks will generally fall into the factory tolerance range if the bearings are not damaged. It all amounts to your goals, your budget and your luck to some extent. I have lousy luck, a small budget, and high expectations. But I machine my own engines. Line hone is a fairly complex process. The exact hardware and torque specs. you are going to run must be considered. The caps must be cut parallel and square and even. The edges de-burred. When honing, shoe height must be adjusted exactly to avoid cutting too much out of the block. To get round and straight results, I generally have to flip the block end to end 4-5 times. This is all time consuming, oily, heavy work. Sonic testing, on the other hand is quick, fast and clean. If I was getting $300.00 to line hone a block, I would probably throw-in a sonic check free. Especially if I was doing other machining on the block. You can get 32 quick measurements, 8 cyl X4 in less than 1/2 hour on a clean block with a hand held Dakota sonic tester.