Before Black BS'ing thread.

And here I thought a block with a couple deck cracks would be a last resort. I know the stuff is getting scarce though and have no intention of scrapping any of it. I tried to score a 291 from the u pull it on 25% off day and even had a core engine ready to go up there. But the engine was bright orange so I pulled a head off it. Bore measured 4" on the nose but the pistons said .030, no wonder it wasn't locked up despite being full of water. With rust and wear I think it would need to go minimum of .045-.050 to clean up and I don't know if the water freezing in it did any other damage so I left it. Would have cost me $175 plus core.

So here's a question: do stock heads have tight enough build tolerance to use the center to center head bolt hole measurements as a pattern for a drill jig? The final hole diameters could be any size, we would just use the head in the machine to measure the center to center and then build a steel plate based off those dimensions. Or does anyone have the exact dimensions?

Cool thing is, once that was drawn up, you just have to basically click "print" and they will nest as many plates as I want in between other parts. And I could order another run of them 5 years later with one text message. We did a run of 200-4r pan spacers using this exact process and they cost me like $8 each and I have a full scale blueprint and everything. That was 12 gauge sheet though and I don't know what 3/4 or 1" plate would cost me. He has access to some damn nice machinery AND he knows how to write the programs for it.
And to ponder this even deeper, I would assume the bolts are all square enough to make one hole in the jig large enough for the drill bushings and tap and the other three just large enough for a shouldered bolt and then rotate the jig to the desired hole. Less margin for error. Also would probably make them out of 3/4 or so plate and just stack them on top each other 2 or 3 deep for drilling. Thoughts?
The center bolt holes in the block are evenly spaced so you could drill the .750 hole for the drill bushing and tap guide, then measure the rest and they should be square. The other 3 holes don't have to be exact as long as the .750 hole lines up with the threads you are drilling. The other 3 bolts just hold the plate to the block so it does not move and keeps the .750 hole steady and on center. That's why I put a 7/16X14 bolt into the drill bushing, to center it in the threaded hole, then tighten down the plate. You can then drill the hole through the drill bushing, then countersink the hole just enough to let the insert stay above the deck. Then you insert the tap guide and tap the threads oversize. The countersink tool is designed for a Chevy block with no cracks to worry about. The insert is designed to sit below the deck, but with cracks to the water passage, it needs to be flush so I did not go deep. My block with the cracks had cracks in 4 holes on each side. The plate will only work on the two center bolt holes. I had to Mickey Mouse the plate on the end of the block holes. Something I found on my 4.1's that cracked, If I used Cometic .027 head gaskets, I had no cracks. When I switched to Fel Pro composite, the decks cracked. It happened on 2 engines. The one I am running now has Cometics and did not have any cracks when I tore it down. I spoke with Mike at TA about it and he said it could be because it's metal to metal with no way for the bolt holes to pull up. I think if inserts are used and machined flat to the deck, composite gaskets would have to be used to prevent water getting to the bolt or stud, but now the insert has put way more strength in the area of the threads.
I get it, I was just wondering if I had the ability to make a plate measured and bored down to the gnats ass, if the block to block variance would allow it to be accurate with no wiggle on three shouldered bolts. You're telling me I'm overthinking it lol. But it really wouldn't be that difficult for me to have the plates made that way IF they'd work. Even a different plate for the outside holes. I'm a ways out from needing this setup but I'm also picking up a 291 block soon from the same yard that had yours and my 484 blocks and starting to think these should be done on uncracked blocks too. Did you countersink the stock threads on any of these blocks beforehand and they still cracked?

How deep are the BBC time serts?
I countersunk the bolt holes on all those blocks. The funny thing is I had two 484 blocks with the bolt holes countersunk from the factory only on one side. Everyone wants the 291 blocks, but the 484 has the large oil pickup passage and the front of the block has more material. I don't see any difference on the blocks i have in the water passages at the bolt holes. They all look the same but I have seen photos of a 291 that show different water passages. Maybe it was a production change. I have a 044 block that has been fit with a girdle that I am saving for future use. Those were the last 4.1 blocks to be made and are rare. I think if the threads look really good in a block with no cracks, I would not put the inserts in. The inserts in the big block Chevy kit are .600 long. Specify steel inserts, not the stainless inserts that come in the kit so you can machine them flat. Stainless is too hard. Thread Doctor will switch them out or you can get the steel inserts separately. I think he also has a generic 7/16x14 thread repair kit that will work but you would have to buy the tap guide. The guy is easy to deal with and helpful.
When I put the aluminum headed engine back in my truck I used new GM Grand National motor mounts because I was pretty sure they are softer than aftermarket mounts. The truck has a lot of vibrations unlike a car. It made a noticeable difference. Half the shake at idle and much smoother throughout the RPM range. Both of my engines were balanced by two different shops and both had a vibration at 4600 RPM. That is now gone with the new mounts. The downside is the front yoke of the driveshaft hits the driveshaft loop and makes one heck of a noise on hard acceleration. I had to take it off and will try to re-engineer it. The trans mount is new and pretty stiff. It's hard to believe the drive train shifts that far to the right. There is a Gear Vendors overdrive on the back of the TH350, so the yoke is way back. The whole project turned out great except for two NAPA Gold 1258 biggie oil filters that both drain back overnight. Both have drain back valves. I cut the first one apart to check for metal, which was totally clean, and the rubber valve looked fine. The filters are now painted black instead of white and maybe there has been a change in the valve material. It takes 3 seconds to get pressure cold now and it never did before. Hot, it's instant. 23 psi at hot idle and 70 psi at 6000 RPM.
I was over on the GM side of the complex picking up a special tool today and look what was staring me in the face...


I'm unsure of how much of this kit, if anything, I can use. I just thought it was funny. I will make my own plate instead of modifying theirs. So I may not be able to use any of it. They have two other kits but they cover all metric bolts and no standard.

Need to bust out the calipers when I'm off the clock to see if anything is of use
That may do the job if it is 7/16-14. It has an alignment arbor that puts the 3/4" hole in the middle of the bolt hole. It has a tap guide and a drill bushing. All you need is the Time Sert big block chevy installation kit. If you are lucky, the bolt pattern may line up. That is an expensive kit.
Well like most Kent Moore or OTC special tools they are brutally expensive when they "inject" the dealers with them, but since they inject every single one of their dealers with them, they eventually trickle out to the used market where they usually sell for pennies on the dollar of what gm and Kent Moore decided to f@$& us into paying for them. (Sore subject).

The j-42385 number has a whole sh!tload of suffix numbers/kits! Type it into eBay and browse. Unfortunately they all look to be metric. That will likely deserve an evening in the chair with the laptop and a drink in hand to explore the possibility of a 7/16 kit being out there on the cheap "or make offer". Might settle for a bargain on a multi-size metric kit just to have around for general purpose but then again we apparently have that kit at work too, I'd just have to replenish the inserts.

Maybe I'll convert all 16 holes to metric lol. THAT won't piss someone off in the future...
I was reading the August issue of Car Craft and got to the WTF section at the back, and there is my truck. They asked for daily driver photos 16 months ago so I sent some in of my 338,000 mile truck. I figured they lost them or had plenty of others to print. They got a few things confused like a 3.8 odd fire made into a 4.5. I started with the odd fire in 1977 and went through many different even fire setups until the latest 4.1 stroker.


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