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| New slant build (how big can a slant be sorta-safely bored?) https://slantsix.org/forum/viewtopic.php?t=51598 |
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| Author: | 72polara [ Mon Apr 01, 2013 9:55 pm ] |
| Post subject: | New slant build (how big can a slant be sorta-safely bored?) |
So, I confessed to my previous failure. Now it's on to new things. New build: -'73 225 block/crank -'73 head (oversize valves and basic port already underway [1.70, 1.44 valves]) - Cam undecided (will pick when the build is closer to done; like what I've read about the Erson grinds) - Maybe a stock 225, but enamored with the long rod build - clifford 4bbl - Holley 465 vacuum secondaries - clifford dual header (sorry Doug - I love the duals, but no provision for cast manifold on the clifford intake!) I like the Holley carb because I have tons of jets, diaphragms, power valves, etc. (and exerience) compared to my pitiful selection of carter parts. I know I can get a holley damn close with what I have sitting on the shelf now. Would love to do a hyperpack build if I could come across one; would even more love to do megasquirt efi, but budget and time prevent it at this time (balancing a Real Job and grad school). I've been lucky enough that the classic cars have passed from my only transportation to being mostly toys, so I can now afford more down time. Although, For the past 15 years, I took great pride in never owning a vehicle newer than 1973. I had to pass emissions for the first time this year! I'm getting older, and have to act more like an adult... So my question is this: How big can I go on bore without spending huge amounts of money? I previously shaved around .100" on the head, much to my machine shops consternation. That wasn't the source of the previous failure. I really love the idea of these, and I think i can afford them this time around: http://www.campbellenterprises.com/slan ... istons.php K1 rods and wiseco pistons. Based on a little research, it's marginally pricier than 198 rods and 2.2 pistons. I've had an eye out for a 198 donor motor for years, and have not had luck getting one for a reasonable price. From research here, I've seen claims to a safe .080 to .120 overbore, with extreme cases in the .180 range. However, the build matrix mentioned in the engine FAQ didn't really stray above .060. I'm thinking that the .084 pistons mentioned above are a great choice with the 1.70/1.44valves. How much risk do I incur going that way? Do I need to get the block magnafluxed and all to go .084, or can I go that way blindly? Re-using the block isn't a concern; I've got a couple other 225's on the shelf for when a rebuild comes up again in a few years. I was unable to find much guidance using the search, if there's threads I missed, please link me! |
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| Author: | fastcorgigarage [ Mon Apr 01, 2013 10:09 pm ] |
| Post subject: | |
I'm also curios about this. I'm having head work done to mine as well with the same size of valves, but I can't figure out how big of a bore can be done. I have heard claims of a .60 bore with a 30pound turbo all the way to 1.60. Where did you find oversized pistons and are they stock style or performance style? |
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| Author: | slantzilla [ Mon Apr 01, 2013 11:14 pm ] |
| Post subject: | |
+.100" is pretty normal. We've had one guy build one at +.190" iirc. Yes, custom pistons are needed. |
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| Author: | Romeo Furio [ Tue Apr 02, 2013 7:56 am ] |
| Post subject: | |
Mike Jeffery Had told me that .100 is a good starting point. Most are safe at .125. Have the block sonic checked and really see how far you can go.There is a source for big bore head gaskets too. |
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| Author: | olafla [ Tue Apr 02, 2013 6:26 pm ] |
| Post subject: | |
Take a look in the articles, linked from the Home page, or here: http://www.slantsix.org/articles/dutra- ... blocks.htm Olaf. |
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| Author: | Rick Covalt [ Tue Apr 02, 2013 11:21 pm ] |
| Post subject: | |
Quote: Do I need to get the block magnafluxed and all to go .084, or can I go that way blindly?
I do not think so. I believe it was Lou who said that up to .100 is a not a problem and it is not necessary to have the block sonic checked. I know that I did for my .102 overbore, but only because I had access to a sonic tester.I do have the large bore head gaskets if you need some. Drop me a PM Rick |
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| Author: | Dart270 [ Wed Apr 03, 2013 6:04 am ] |
| Post subject: | |
I would not think twice about 0.084" over, unless the block is severely rusted/pitted or something. Lou |
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| Author: | Rug_Trucker [ Thu Apr 04, 2013 8:48 am ] |
| Post subject: | |
I wouldn't assume anything. I had a friend drop a bunch in a 318 stroker. It cracked #2 as the machinist didn't do a 4 way check. |
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| Author: | 72polara [ Fri Apr 05, 2013 10:55 pm ] |
| Post subject: | |
olaf, thanks to the link to the FAQ! I overlooked that one somehow. I finished tearing down my cast crank engine; #6 is not good; #1 is worse. #1 and #6 rod bearings don't look too hot, and neither do the #1 and #4 mains. I'm probably going to shelf this one, and start my new rebuild on the '73 engine. As a question of curiosity, has anyone noticed a difference in perceived quality between the earlier forged crank blocks and the later cast crank blocks? The '85 block I have has lots of sand inclusions, very clear parting lines, rough machining marks. The '73 block has very few inclusions, smaller parting lines, cleaner machining marks. A few years ago, I bought a few Russian Mosin-Nagant rifles that ranged from late 20's to late 40's. The 20's and early 30's examples were beautiful - very few machining marks, very precise fits. The closer the rifles got to the early 40's though, it became obvious that they made them as fast as could be done - really rough machining, sloppier fits. It was clear they were preparing for a war. Despite the obvious quality differences, they all performed the same (at least at the hobbiest/enthusiast level). Does the lower quality things I am seeing with my '85 block really reflect lower quality? I know that folks have built the cast crank engines to pretty amazing hp levels, and compared to the original configuration, the cast crank slants are significantly lighter. The things I usually perceive as quality are present on the '73 example and not on the '85 example, but they seem to perform the same. I think I'm really asking a philosophical question than an empirical one... |
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| Author: | DusterIdiot [ Fri Apr 05, 2013 11:14 pm ] |
| Post subject: | Yep... |
Quote: A few years ago, I bought a few Russian Mosin-Nagant rifles that ranged from late 20's to late 40's. The 20's and early 30's examples were beautiful - very few machining marks, very precise fits. The closer the rifles got to the early 40's though, it became obvious that they made them as fast as could be done - really rough machining, sloppier fits. It was clear they were preparing for a war.
By 1939 they were at war, by 1941 it was pretty ugly for them and they were relocating their machinery to the other side of the country in anticipation that the wehrmacht was going to continue taking territory...The late cast crank blocks are not as pretty as the 1976-1978 blocks, the 2 1979 block I have the non-used oil pump port on the block is missing metal and not cast right in both cases...The blocks are still strong and the late cranks are much more lighter than the forged crank counter parts (on the street this doesn't mean much, but the engine will recover from shifts faster and revs up faster than the heavier forged crank). I would trust a 70's forged crank block to pass a .100 over sonic check vs. a 1985 cast crank block more often than not. -D.Idiot |
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| Author: | Dart270 [ Sun Apr 07, 2013 4:19 am ] |
| Post subject: | |
The mid-late 80s blocks are much lighter (~25lbs) than the forged blocks and earlier cast blocks. This is great for car wt, but I doubt you can bore them as far. My new 85 motor is only bored 0.045" for this reason. I did not do any sonic checking. Lou |
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| Author: | Romeo Furio [ Sun Apr 07, 2013 6:43 am ] |
| Post subject: | |
Like Lou, My 1980 block is only .020 over. Just enough to clean up and straighten the bores. |
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| Author: | Supercharged SL6 [ Sun Apr 07, 2013 4:29 pm ] |
| Post subject: | |
Definitely sonic check later cast blocks, an 85 block bored .030 that I had was at .090 wall thickness on a couple cylinders |
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| Author: | Rug_Trucker [ Sun Apr 07, 2013 6:21 pm ] |
| Post subject: | |
Quote: Definitely sonic check later cast blocks, an 85 block bored .030 that I had was at .090 wall thickness on a couple cylinders
What thickness do we get nervous?
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| Author: | DadTruck [ Sun Apr 07, 2013 7:06 pm ] |
| Post subject: | |
Chrysler had a block and head foundry in Indianapolis IN until the mid 2000's. Chrysler Tibbs Avenue-Harding Street Foundry. From the late 70's to the late 80's through the local AFS ( American Foundrymens Society) I had a couple opportunities to tour that Chrysler foundry. In the 70's and 80's this was a very large shop, One of the biggest block and head foundrys in the US. During that time period Chrysler was making huge capitol investments to improve the productivity of that casting plant. Some of the improvements involved cutting edge new casting and mold making technology. One of the new technology methods that the Chrysler Indy foundry employed was Impact Molding. In a green sand foundry clay bonded sand is pressed against a hard mold (pattern). An old foundry process is to use a Slinger, where the sand is physically thrown agains the pattern. A newer process is to use a hydraulic ram to compress the sand to the pattern,, in the 80's what the Chrysler Indy foundry had was Impact Molding, this was state of the art technology, with Impact Molding the molding sand was dropped on to the pattern then a tight fitting chamber was located above the sand, natural gas was injected and ignited, the explosive force then compressed the sand to the pattern. Sounds good,, eliminates a lot of machinery,the pumps, the hydraulic cylinders, and the hydraulic leaks that go along with the high pressure squeze mold process. Hydraulic oil contamination in the molding sand causes gas and fissure defects in castings... In real life, Impact Molding did not work well in casting cylinder blocks, Impact Molding produced a mold that had near uniorm sand compression in all areas,, where what was actually needed was more compression where the mold was deeper and less where the mold is shallow. With hydraulic rams, foundrys had the opportunity to set multiple hydraulic cylinders above a single pattern and tune the compressive pressure by area. Impact Molding could not do that. As a result,,blocks and heads from the Chrysler Indy foundry had big problems with exterior burnt in sand and mold scabbing issues. This is an example where Chrysler attempted to leap ahead,, for good reasons, but the technology just did not work in that application. I believe that by the 90's the Chrysler Indy foundry has moved away from Impact to conventional hydraulic molding. Initially under Damler there were many capitol investments made at the Chrysler Indy Foundry,, then it was closed. Today that foundry is completely leveled. http://en.wikipedia.org/wiki/Indianapolis_Foundry |
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