460 Straight up Timing Chain upgrade

[viven44]

OK thanks! I'll need to use my old bad distributor (with a bad bearing) as a test vehicle to practice/learn about some of these things.

[Gary Lewis]

[viven44]

Thanks for making this video, I never doubted that you won't hold vacuum in steady state.. I THINK you need a constant source for this to work properly. My comments do read that way and I apologize, what I meant (or now mean) is that with a constant vacuum source/air pump such as an engine, with a restricted line, you won't be able to pull that much vacuum as you are pulling with the MityVac. I don't think the vacuum reading on the gauge is a good indicator of how much vacuum advance happens, it may be inversely proportional.

I don't know much about how vacuum advance works but

1) Would it be possible to see how much advance happens on the distributor with varying vacuum hose diameters on the MityVac ?
2) same above but with a constant 20" Hg vacuum ... Shop vac? or engine ?

[Gary Lewis]

I had a constant 22" of vacuum on the dizzy.  The Mityvac has a check valve, so if there's no leak then the vacuum is constant.  And I don't think the size of the hose will change that - unless you get to an extremely small hose, much smaller than we have on these vehicles.

And the amount of advance is proportional to the amount of vacuum.  However there are springs in the vacuum advance canister that the vacuum has to overcome, so that determines the start point for the advance.  That might be in the 10 - 12" of vacuum, but some canisters are adjustable for that - see the Crane Cams instructions for that.

[viven44]

OK I think i get what your are saying.

Going back to the electrical parallel, current flow would be proportional to resistance of the load and anything else in series, and if the load past the series resistor was an infinitely high resistance there would be no current flow, thus no voltage drop across the resistor.

In vacuum, since your distributor has infinite resistance, there is no air flow, so there should be no vacuum drop past the restrictor, but I am also intrigued by how the vacuum restrictor works.... One possibility is that the vacuum restrictor is a controlled vacuum leak device which would limit how much suction is placed on the distributor. If it is, should be called a "vacuum leaker" lol... Sounds like a case of marketing taking over.

I still have all the emissions parts I pulled from my donor truck. Hoping it has a restrictor. I'll play with the restrictor and see how it works. Some of the other things were broken with age so I decided to not reuse any of it, maybe there are bits and pieces that can be reused.

[Gary Lewis]

If the VREST does have a vacuum “leak” that would explain how it keeps the vacuum to the dizzy low. Otherwise I can’t see how it would work.

[viven44]

OK we are back to square one. Looks like it is just a smaller opening restricting vacuum.

Found this in the 84 Factory manuals -Emissions/Diagnostics book, which for some reason is a larger book than the engine book  It is an interesting read, I have never picked up that book until now.

[Gary Lewis]

Cool!  So now we now the orifice sizes, although I'm doubting there are any jets around that small.  I need to record this for posterity.  

[Gary Lewis]

It is now in my copy of the Master Parts Catalog, as shown below.  But it turns out that there are two different part numbers that are red, although I'm assuming they have the same size orifice.

[viven44]

Very cool. A cheap source of these orifices would be flux core welding contact tips and a rubber hose on either side.

I know there's 0.025, 0.030 for sure, Not sure about 0.020 and 0.015.

I don't believe a 0.025 tip would have a 0.025 opening though. There should be tolerance built in so its probably a larger opening.

https://www.harborfreight.com/0025-in-mig-welding-contact-tips-10-pack-63796.html

[ArdWrknTrk]

Most motorcycle jets are expressed in 1/100mm
So a 35 jet is close to 0.014"

>.35 x 0.040(ish)= 0.014...<

Bike jets are everywhere

Carburetor Main Nozzles,Carburetor Main Jets Set,25pcs Main Jet Carburetor Carb Main Jet Kit 55?115 M5 Replacement for Dellorto Carburetor PHBG https://a.co/d/4b8MvXb

[viven44]

While I’m waiting on the water pump I figured I would replace 2 of the long bolts with new grade 8 bolts. Those 2 bolts has signs of plastic deformation about 1 inch in from the head (its hard to see in the pic but there is thinning). The pitting doesn’t bother me as much as the deformation. The cleanest bolt will be the one to enter the water port. I try to always do the right thing for the next guy that has to work on it, hoping I will see the same in return … knock on wood I haven’t had to weld a nut to too many studs down here in TX.

[viven44]

I tried to look up charts, there is no standard Jet size anywhere  But agree these are the best sources.

[ArdWrknTrk]

I don't think it's plastic deformation , I think it's the ravages of corrosion.

Just last week I was discussing how much even a grade "butter" piece or 3/8 threaded rod was rated for.

There's just no way any of these things are seeing that tension at 40 #'

My ENTIRE engine is held together with the cheapest stainless fasteners I could find, and none of them are like that.

[ArdWrknTrk]

https://boltdepot.com/Fastener-Information/Materials-and-Grades/Bolt-Grade-Chart

https://www.nfgab.com/technology-quality/technical-pages/tensile-strength/unc-threads

[viven44]

That 5/16 bolt in the pic is clean else-where.. just that one thin spot. It could be corrosion but it could also be a case of "I have a leak I'm going to torque things until it doesn't leak". After what I saw in the water pump, paranoia has kicked in.

With it being thinner, and if it is corrosion, that is a weak point.

Agree. Grade 8 is overkill- price delta was probably $1 per bolt so why not :)  Torque spec is only 15-21 ft lbs.

[ArdWrknTrk]

I'm not sure what you mean "standard jet sizes"


I used to use Sudco for Mikuni & Kehin.     https://www.sudco.com/carburetors.html

Euro Moto for Bing & Dellorto.     https://www.euromotoelectrics.com/category-s/2249.htm 

Now you can get Chinese garbage at your door by 6am from the jungle/river market....

It's all the same. A simple hole in a piece of brass.

[ArdWrknTrk]

Look at the chart 5/16_18 = 33.8mm x 393Nm/mm =133000 Nm for gr5
/1.356 = 9,808 pounds EACH, tension minimum UTS.

You could literally hang your entire truck from a tree by one of those 5/16 grade 5 bolts.
And there are like seven of them in a water pump.

[viven44]

I'm not worried about the holding power, just the ability to withstand torsional shear stresses while removing after years of use. I'm going to use PST per your recommendation on a couple of those bolts so we should be good.

I know a lot of people who break these bolts while removing, they are clearly exceeding grade 5 shear stress limits. I have my method and knock on wood I always get them out intact, even exhaust bolts most of the time.

 

[ArdWrknTrk]

Edit: it's not shear. It's torsion....

Those bolts are corroded AND seized.
Corrosion provides beach head nucleation sites for cracks.

You're going to put Teflon on and in the threaded holes.
This will seal water in the pump where it belongs.

I used stainless because it doesn't corrode and seize in the threads,and the shanks CAN'T corrode when there's a less noble metal like aluminum or iron available.

They come out much smoother when the shanks are smooth as well....