Re: Eliminate draft tube options
 

rtv comes in several colours including blue. I have seen orange, red, blue, black, clear and copper. RTV stands for room temperature vulcanizing which basically means it cures at room temp. there are different uses for the different colours of the automotive brands of rtv. the right stuff is also rtv silicone but it has been formulated to cure fast, so it is thicker and a little harder to work with because you gotta be quick with assembly. there are also other handiman brands, or types, of rtv which come in all sorts of colours but a lot of those are not oil resistant. some of the automotive rtv is also not oil resistant. it is always good to know the rtv you have so you dont use it improperly.
here is a little write up on the permatex brand and their colours and uses
https://4lowmagazine.com/rtv-colors-...20applications.
and here is one from the jbweld site with their colours
https://knowhow.napaonline.com/jb-we...ilicone-guide/

Re: Eliminate draft tube options
 

here is a permatex chart with the different uses and curing times etc
https://www.google.com/url?sa=t&sour...yBHLwYNgZRSBaI

Re: Eliminate draft tube options
 

I've been following this thread since the beginning.. I've been in this car repair business a mighty long time.. And during that time, I've seen some successful repairs made that many have said couldn't be repaired.. Freeze cracked heads and blocks, holes patched in the side of a block where a wayward rod went through.. I'd be willing to bet a highly skilled machinist (not an engine builder) could repair that flange area of the main cap.

Re: Eliminate draft tube options
 

just as a side note, RTV is basically any silicone that is made to air cure but a lot of the stuff you find will not be oil resistant and is made for sealing or bonding. the automotive stuff is made to resist oils and heat etc but even some of those are not made for engine use but rather are for sealing glass or holding trunk rubber in place etc. it's always best to know your product. there are a couple of "the right stuff" RTV's too. one is a 1 minute cure and one is a 90 minute cure. grab the correct one if you wanna add oil or coolant right away in the affected area.

rusty, you're probably correct on the machinist thing and I think thats what is going to happen, a skilled machinist is going to make a new cap or fix the old one and either way the crank bores from front to rear will likely need to be checked for alignment and size. welding or brazing on the original cap may warp it so it will need to be checked at least. thats why the engine is taken apart and sitting on a table ready for the machinist to see what can be done. it's gonna be interesting for sure. prolly not cheap, but interesting.

Re: Eliminate draft tube options
 

At this point, I don't have the head removed from the block. Waiting on my new buddy to check out the motor as it currently is.

Re: Eliminate draft tube options
 

Thanks guys for all the RTV references, I have bookmarked them all and will use them for my selection, once I begin the reassembly process.

As a side note, my engine builder new buddy is also an accomplished machinist. He used to have a 12,000 sq ft shop where he could do anything and everything with an engine. In semi-retirement, his shop is only 3,000 sq ft now, but still has much of the equipment, just not as many cars/engines in the building. I'm confident that between him and his 94 year old machinist friend in California that they will come up with a solution for me......cost to be determined...LOL

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well, worst case scenario, they could find a used cap from a scrap engine and machine the flat surface down a little to ensure it is flush and allow a slight bit more metyal to machine in the bore, then line bore that hole round again to size, just so the cutting bit is set so it doesn't also cut the block side of the hole. pretty intricate work and work that a lot of machinists will say is not correct to do. or the bore could be made oversize on the front bore only. or all the bores could be line bored and get oversize bearings, if available. the final option is what most engine shops would want to do I suppose. maybe custom sized bearings are available somewhere. the engine fellas should probably know that since they have been around for a bit.

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They have given me Plan A, B, and C options. I wish I understood them all. But these guys are pretty sharp and have thought through my situation. I do know that Plan A involves creating a new end cap from billet material. As for Plan B it sounds a lot like what you described, Plan C wasn't something that I understood.

They also plan on cutting another Woodruff key in the crank and the harmonic balancer due to the supercharger.

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the extra keyway is a great idea. sounds like they have you covered. you likely won't know what the plan is until they actually check the line bore so they know if the rest of the bores are where they should be first before they worry about the front one. no use spending time and effort to fix that and then find out the whole thing could use a line bore. knowing that first will likely change the plan A, B or C decision. kinda like knowing you have a bad spot in the road that needs to be fixed. no use spending a bunch of money on that bad spot and then checking the rest of the road to find it all needs paving anyway. might as well just pave the whole thing to begin with and not pave the same spot twice, if that makes sense?

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Maybe not too much? One of the big challenges faced by folks adding forced induction to late model engines is ring land breakage due to top ring expansion. Add boost, add heat, add ring gap.

Please also investigate anaerobic sealers. These sealers are opposite of RTV in that they only cure in the absence of oxygen. They are usually the best choice to use between two rigid surfaces, such as a rear main cap and the block. There are plenty of examples of situation in which RTV was not the correct choice and was not cured even years after it was applied. Classic examples include in manual transmissions and rear differentials.

Did it involve a blueprint that looked anything like this?

https://i.pinimg.com/1200x/1e/19/4a/...007997b8eb.jpg

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I believe Plan D is this:

Attachment 2332392

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Hopefully it never comes to that!

But don't be bound by the historical significance of the engine if it starts to impact the way you want to enjoy the truck. Put it on a stand under a spotlight in the corner, stick something else in the truck and enjoy it.

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When my friend, who sold me the truck after he purchased as a retirement project but never touched it for six years, said when he heard about the cracked end cap "sounds like a small block to me".

I'm hoping that it doesn't come to that given the history of the engine, but you are correct, I want to drive this thing and take it to local car shows.

Re: Eliminate draft tube options
 

This can be fixed. It's not impossible. It's made more challenging by not wanting to tear the engine down further, but it's definitely repairable.

But there is merit to building an engine that reinterprets the historical engine you have now. Modern electronics will do an amazingly better job of controlling fuel delivery and spark timing and will also be able to monitor for some failure conditions then try and take corrective action. And they will help the engine behave more consistently from idle all the way up to redline.

Maybe it's time to start planning your next truck? ;)

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To my wife's chagrin I've already begun talking about "what's next". I get as much enjoyment out of working (and learning) about the older cars/trucks as I do when I drive them.

Re: Eliminate draft tube options
 

Engine sealers come down to the concept of "this is what works best for me when I seal this area". Blue silicone has been around for ever and I use it along with the black and there are a ton of other great sealers out there.

The main thing with silicone is do not use too much. Years ago a buddy of mine who worked in a Honda Dealership said that the instructor at a school he went to told the guys to hold their finger out and squirted a dab on each guys finger and told them that dab was all the silicone they needed to seal the whole engine. I've pulled six inch long silicone worms out of oil passages of blown up engines before.

On the main cap thing, I would have the best idea is search out a good front main cap and line bore the block with it in place. Extra $$ but peace of mind knowing it was done right.

If you were closer to Waco I'd just say put the tools you need to pull a pan and pull the main cap in a 5 gallon bucket and head to M Lipsizt in East Waco and hunt through the scrap engine pile that after looking at the map I don't see where it was years ago. Scrap cars don't sit around in that place though, I can remember 50 years ago following a couple of charactors who would run an add in Penny press that they would haul scrap cars away for a fee of 25 each as long as they could be flat towed and they towed the cars across the scale at Lipsitz and over to the side where they would pull the tires off and throw them in the back of their tow rig that wasn't much better and go back across the scales and collect their money. Before I could get weighed, unloaded, weighed and out the door that car was often already in the Texas Shredder. Funny thing is that those two were often doing that three or four times a day when wages were about 3.50 and hour around Waco.

Re: Eliminate draft tube options
 

Well, I never said that I wasn't going to take the head off, but I waiting for my new best buddy (the engine builder) to look at the engine and take care of that himself.

In a fit of energy today (don't worry it won't last) I unbolted the head, kept the bolts in a numbered box that I punched holes in to held the bolts in the order they go back into the head/block. I also removed the head gasket and did a preliminary clean up job on the block, but haven't looked at the head yet.

Just an update.......

Attachment 2332666

Attachment 2332667

Any suggestion on how to clean the block and the head?

Re: Eliminate draft tube options
 

The bristle disc wheels mentioned previously are my first choice for this application.

Re: Eliminate draft tube options
 

when buffing the piston tops make sure to have the pistons at the top of their stroke so the cylinder walls don't take a beating.
eventually you will likely need/want to take the pistons out for machining work to be completed. the pistons could be cleaned up then. I usually put them in a tray of aluminum compatible solvent to soak and soften up all the carbon etc. for the gasket surfaces i use a long board with sandpaper. for the combustion chambers I use a stiff knotted wire wheel on a die grinder with the valves in place at first, then, after the valves are out, the same brush works well down inside the ports and bowls where the vales seat but be very careful not to go too deep or the steel body of the brush touches the valve seats and thats not a good thing. when the head is completely dissassembled you could use oven cleaner on it and then wash it all with hot water. then use compressed air to dry and when it is drying look for any traces of spots where the water doesn't dry uniformly as those spots may be holding water in a crack. the old heads had a habit of cracking in the combustion chambers. ensure to keep all the valves in order of where they came from if you take the head apart.

Re: Eliminate draft tube options
 

Are you going to tear it the rest of the way down? Pull a bearing cap or two to inspect? What to the bores look like? Valve seats, stems and guides?

The reason I ask, that block surface, piston tops look like more than break in hours to me. But maybe that is what you get from many years sitting.
And it may not be relevant if everything is in good shape.
The engine is clean enough inside to assume it has at least been apart in recent memory.

If I was preparing that block to put a new head gasket on without going any further:
plug oil passages with wound up rag
protect lifter alley from falling debris
stuff rags into each bore
clean block surface with scotchbrite pads by hand working around, away from holes holes
pull rags with a twisting wiping motion.
get everything as clean as possible & put it back together
degrease and paint once it is buttoned up

Re: Eliminate draft tube options
 

if taking the head apart for cleaning its a great time to replace the valve seals, check the valve springs and their retainers and the keeper grooves in the valve stems, valve stems for wear limits, stem to guide clearances, check the gaskets surfaces for warpage, etc. clean the head up well, check for any cracks, lube the valve stems with some assembly lube or molyslip grease (my personal choice for valves) and slip it all back together. then clean and check the rockers and the rest of the valve train, lube and assemble as much as you can, in modules, so when assembly time comes those parts are easy to unbag and you know they are good to go.

Re: Eliminate draft tube options
 

These are all tasks that I'm hoping to assist my engine builder buddy with. He's done this as a business for 60 years and now in semi-retirement (he's in his 80's) he's interested in passing "lessons" along and I'm a willing student.

I had already mentioned to him that when he was working on the end cap/line bore that I'd like to observe/assist/learn. He seemed to think that was a good idea.

Re: Eliminate draft tube options
 

Are the crankshaft bearing caps the same on the 235 Chevy as the 261?

I may have located an entire set of 235 end caps.

Re: Eliminate draft tube options
 

maybe. Sealed power 960M main bearings show as fitting both 235 and 261

Re: Eliminate draft tube options
 

Well, I may have wasted $40 if they aren't the same, however that isn't the most amount of money that I've wasted on this truck so far.....LOL

I found a used set on eBay and purchased them just in case they were a correct fit. I guess when they show up I'll have a better idea if the front end cap measures the same.

Attachment 2333414

Re: Eliminate draft tube options
 

If it fits.....
I'd be tempted to plastigauge it to check how uniform the bearing clearance is with the new cap and then consider if it could go back together without line boring.

Re: Eliminate draft tube options
 

as a guy who worked in an engine shop waaay back outta high school, i would say that there isn't a snowball's chance in......it's gonna be a direct fit. but, you could install it and torque it up with no crank in there, just the bare bore, and then use an inside micrometer on it to see if it is round or not and it it is round through the whole fore to aft length. otherwise the engine guy you know will surely be able to fix you up for cheaper because he will already have a good front bearing cap to work with.
too late now anyway since you already hit "pay the guy" on ebay, lol.
you can always make a cool lamp out of the stuff it it doesn't fit. lol.

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It could happen.......

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Lamp???? With all the stuff I've bought and not used I could make a huge lawn ornament and have the HOA throw me out of the neighborhood.

I have a call into my engine buddy to see what he thinks. He's the one who told me that this route might be my best shot time and money wise.

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Look what $40 on eBay got me.

Attachment 2334555

Attachment 2334556

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My engine builder buddy suggested I take the new bearing cap and the old bearing shell and smear a fingers worth of clean engine oil on the shell and the crank. Then mount the cap and in increments of 10 ft/lbs test how easy the crank turns by hand. I started by torquing the bolts to 30 ft/lbs and the crank turned just as easily as it had without the bearing cap. I continued in increments of 10 ft/lbs up to 90 ft/lbs and the crank was just s easily turned as it was without the bearing cap. I didn't want to press my luck at 100 ft/lbs, but will do that tomorrow. My engine buddy called me the luckiest guy in Dallas. More to come, but in the end the crank will still come out.

Re: Eliminate draft tube options
 

if you wanna see how tight the tolerances are all the way around the crank, clean the bearings and the crank with a clean lint free cloth so no oil to speak of is on the bearings or the crank journal, then put some plastigage the full length of the bearing cap 1/2 of the bearing, then put the cap back on and torque it up being careful not to turn the crank while doing this. then remove the bearing cap and see what you have for clearance on the plastigage. if you don't know what plastigage is, it is a plastic thread that comes in different colors for different clearances, you likely need the green stuff that will show up to a couple of thousands clearance. when you put that on the bearing and then torque it up it will get squeezed and flatten out some depending on the clearance there is left between the two parts. then when you take the thing apart and look you will see the thread has flattened out. the little paper package that the plastigage come in has markings on it to compare the width of the flattened out plastic thread. really flat means not nuch clearance. of course the opposite for a thread that didn't get flattened out much. when you put the thread around the whole half circle of the bearing cap bearing shell and torque it down when you look at the plastigage after you can see if there are parts that show a more flattened out thread that other parts are showing. this can help you see if the bearing cap you bought is a close match to being bored on the same center line as your old cap. it's one in a million but there is a chance it is close enough to run it that way without doing any machine work. if thats the case then you need to buy your engine buddy, LG, me and yourself a lottery ticket. haha.

Re: Eliminate draft tube options
 

could also plastigauge the clearance with old and new caps to see how they compare

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yeah, good point LG.
you think of everything. inside and outside the box.

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Ok, so today I inserted a piece of Green plastigauge on the newly acquired bearing cap (with the original bearing shell) and torqued the two bolts down to 100 ft/lbs and here is the result.

Attachment 2335714

Attachment 2335715

When I did the same thing on the old bearing cap (the cracked one) the result was even less thick than with the new bearing cap. It was clearly compressed by not by as much as the new bearing cap.

Did I hit the bearing cap lottery?

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that actually looks pretty good. maybe have your engine buddy look at it and see what he thinks, or send him the pics.
buy a ticket, lol.

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measure at it's fattest point and see what you get but it looks pretty good.

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I posted here first and then sent him the same photos.

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Where I have the paper plastigauge measuring guide (.002) was the widest part of the thread.

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hopefully thats not a nick on the journal there. gotta be careful moving things around etc. I usually put an oil moistened rag around my journals and use tape to keep them on there until ready to do something with the crank. you are already working with it but just a thought for when you store it until the engine guy has a chance for a peek or whatever your plan is.