cjsdad

Most people mention chasing the threads of the head bolt holes when prepping the block but I am in the process of cleaning everything on my disassembled 455 and it occurred to me that I have never heard anyone mention head or main bolt prep. I have cleaned the main bolts with a manually operated wire brush so they are clean but after they are dried off the surface is a bit rough. Is there a preferred method of bolt prep out there? Should a wire wheel be used to smooth the thread surface? Will this improve the tightening force compared to the torque value or is it better to have the rougher surface to make sure they won't loosen up? I wouldn't expect them to loosen with the amount of torque applied but would there be a benefit to smoothing the threads?

While I am asking noob questions, would it be worth it to add hardened washers to the head or main bolts? I see minor indentations in the heads and main caps from the bolts being torqued down so would the addition of hard washers give the bolt heads a smoother ride against the cast iron? It would be cheap to do, but should it be done? and would there be a benefit on a stock, or close to stock, rebuild?

rad

it dont hurt to chase the threads with a bottoming tap, but better yet if its in your budget replace the head and main bolts with new ARP bolts then your not dealing with 40 year old fasteners that have been heat cycled a bazillion times, if your doing a rebuild, definitely replace the rod bolts with arp and resize the rods.

MDchanic

Don't mess with the head and main bolts (screws, technically). Just clean 'em and use 'em.

- Eric

cjsdad

This is one of the reasons I am wondering about adding washers. The ARP fasteners utilize them. They also use rolled threads which are much smoother than typical cut threads. I guess this is the reason for my questions. Can anyone give me a reason NOT to add washers and smooth the threads on the factory fasteners?

I seriously doubt the bolts in my engine have been compromised by heat cycles or age and I am not building a boulevard bruiser but a cruiser. I just might get a set of new rod hardware though because they seems to be the most abused. And the rods themselves will be checked to see if they need to be re-sized.

cjsdad

That is what I have always done Eric. I have reassembled enough engines to say I am experienced but not enough to say I am good at it. I am not wondering if they factory hardware is up to the task. Just wondering it it is worth the extra effort to spend a little more time prepping them. Will the added washers give more consistent torque values across the bolts? Will smoothing the threads let the bolts tighten better before they reach proper torque? If it is good for ARP hardware, is it good for the factory hardware? I am not expecting ARP type improvements, I won't need that. Is it worth $5 dollars to try and improve what is already there?

oldcutlass

Do not use washers with the stock bolts. IMHO, if they were required they would have had washers from the factory. There is a difference in taps for thread chasing/cleaning and tapping. If you run a tap down the holes you remove metal weakening the threads. If the bolts are serviceable, just clean them off and follow the assembly procedures for torqueing.

oddball

Depends on your definition of "worth it".

For any stock or mild improvement build, just cleaning and reassembly per factory procedure is fine - light coat of oil on the threads (don't want to hydrolock in the hole!) and a good coat of oil under the head, smooth application of torque. As long as the fastener engages smoothly there won't be a problem with the torque readings. If it's actually rough due to burrs or a cracked thread, then something should be done.

Adding hardened washers isn't a bad idea, but need to make sure they don't cause any interference and there's still enough thread engagement (there should be!).

Felpro style head gaskets can also give a lot of room for error on mild builds.

Something I have to continually remind myself is that newer stuff, and nearly all aftermarket stuff, is always built to be "better". More precise, more repeatable, more accurate, etc. The kicker is those improvements may be entirely worthless for a particular situation. Like putting a 500lph fuel pump on a 300 hp engine. So while there are updated practices that are better, the "better" may just be wasted.

joe_padavano

Yes.

The aftermarket bolts have a more generous radius on the underside of the head. The washers have a chamfer on the ID that provides clearance for this radius so it doesn't bottom in the hole in the heads. The factory bolts don't have this and thus don't need the washers. Keep in mind that every washer not used on a car results in significant cost savings over the production life. The larger radius is incorporated to reduce stress concentrations, which is really only important if you are running cylinder pressures much higher than stock. For a stock or near-stock rebuild, the original bolts are fine. If spending money on ARP bolts helps you sleep better, go for it, but you'll still be using the stock bolts at the locations that need the studs for accessory mounting.

joe_padavano

You should remind yourself that aftermarket stuff is always ADVERTISED to be "better", othewise there would be no need for you to buy it. Whether or not it really is "better" in a specific application depends on the particulars of the application.

Octania

I was super impressed with the "steel" main studs that came with the CAT brand main girdle. Snapped right off before coming tight. Among this bullsnort is the actual photo


http://www.ebay.com/itm/Oldsmobile-M...zRpTKg&vxp=mtr


Quite an "upgrade" over the factory fasteners, which were OLD and DIRTY and had HEAT CYCLES on 'em. The CAT brand hardware will never know that sort of abuse!

MDchanic

Thank you, Chris. I think you nailed that down pretty darned well in just a few lines.

- Eric

quaddriver

Its been a few years(decades) since I screwed on an Olds head, but only a few weeks since I screwed on *a* head, so these comments are general rules of thumb:

1) unless you have reason to believe the bolt was damaged, re-use. A bolt, is essentially a spring and its elasticity allows the components to move around (and move they do) yet keep a good chomp on the seal. when not tempered or physically damaged, they are pretty resilient. Olds used a fairly arcane torque spec for decades, then near the end increased it dramatically. I question if that was because they went to tty bolts (below) which are not re-useable.

2) if the motor the bolts came from was destroyed by high heat, i.e. a coolant loss demo derby situation, discard all parts, salvage nothing.

3) never reuse 'torque to yield' (tty) bolts....replace. TTY specs, if they chose not to explicitly list the bolt as such are generally 'torque plus some final angle' (which means you put it together with different tools anyways)

4) never add a washer to a bolt that did not have one from the factory or in its package, if ARP comes with a washer, use, if factory did not - do not add.

5) not so much head bolts, more intake, but GM liked to indicate bolts that were tempered for even more heat with a raised circle around the grade markings. (not a 100% rule as I have found) but take an olds small block, the intake bolts near the exhaust crossover (and hence hotter) bear this marking.

6) if the bolt extends into a water jacket, use sealer on the threads and under the head (rare)

7) if the bolt is blind (just a tapped sealed hole) then use oil on the threads to resist heat galling and oil under the head to prevent false torque readings.

8) any washer used with a bolt MUST be of equal or higher hardness grade

9) to get a better seal, sneak up on the final torque in stages, a fairly decent rule of thumb is 50% final torque, then 75% final torque, then final torque and repeat 2-3 times in the pattern. IT takes a while, but you feel so ninja if someone is watching, like you really really know what you are doing ;-)

10) is it mandatory to chase/clean threads if loctite was used, a damn good idea if sealer was used, and somewhat optional if just oil was used. I have a brass wheel on the grinder and clean every bolt I ever use.

11) please do not use any form of anti seize on an engine bolt unless some oddball instruction from the factory tells you to.

joe_padavano

Oldsmobile NEVER used a torque-to-yield bolt in a cast iron V8. The increased head bolt torque corresponds to the change from 7/16" to 1/2" head bolts, which corresponds to the change from solid to windowed main web blocks. The lightened 1977-later blocks required the larger bolts and higher clamping force to ensure head gasket seal.

Oldsmobile also NEVER ran any head bolts into the cooling jacket on 1964-1990 motors. In fact, the only bolts on an Olds motor that are "wet" are the two that hold the t-stat housing and the four large ones on the water pump.

Steve70

Hi Joe,

I'm installing an Edelbrock Performer intake on my 68' 455 block with C heads. Sounds like you're saying none of the intake bolts go into water jackets, so therefore no need for bolt sealer. Is that correct? Also, should some bolts have sealer to prevent oil wicking up to the top? Thanks

joe_padavano

Every one of the intake-to-head bolts goes into a blind hole. There is no need for anything other than a light coat of motor oil to ensure correct torque readings. As noted above, the only bolts on an Olds motor that go to the cooling jacket are the two bolts that hold the t-stat housing to the intake.

Schurkey

The single biggest/most-common problem is corrosion damage to the fastener threads or shank. Sure, inspect the bolt. Needs to be not bent, not rusted, threads in good condition, etc. Beyond that, there's really nothing wrong with GM fasteners in almost all cases. The critical fasteners tended to be "Grade 8".

Steel is tempered at 700 degrees or more. How friggin' hot do you think an engine gets? Yeah, I've seen crank journals burned blue or even black; but that's so isolated that the main bolts should still be good; along with the connecting rods and fasteners that aren't blue.

Don't confuse Torque-Angle tightening specs as automatically referring to TTY fasteners. Plenty of re-usable bolts have torque-angle tightening spec.

Depends on the situation. If you add a washer and still have adequate thread engagement, I don't see the harm. If using lube on a fastener such as a head bolt, lube the threads and under the head of the bolt, DO NOT lube the under-side of the washer.

Assumes that the manufacturer provides torque specs for a lubricated bolt. Not always the case. Manufacturer's procedures should be followed unless you're willing to take responsibility for the end result.

Damn fine advice.

Yeah, as long as there's enough difference between the second-to-last torque pass and the last torque pass that the bolt actually turns. Static friction tends to be greater than dynamic friction; if the second-to-last pass is too close to final torque, static friction may cause the bolt to not turn on the last pass.

Brass wheel is good advice. Less abrasion/wear to the fastener threads compared to a steel-wire brush. More expensive, though.

You wouldn't like the way I do stuff. I anti-seize EVERYTHING that doesn't get thread-locker or sealant. But I also lower the torque spec by some amount, to compensate for the lubrication effect of the anti-seize.

The major manufacturers "should" be using much more anti-seize; they don't because they don't care how hard the machinery is to service once the warranty runs out, and the cost of materials and labor to apply anti-seize at the factory is more than the cost to not use it and accept a few fastener problems during the warranty period. (And some of those failures can be blamed on the technician, who "eats" the additional labor time.)