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#1
12-01-2020, 12:52 PM
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Machining questions
1) Did 389 blocks have three freeze plugs per side?
2) The dowel pins for the main caps measure 0.3093". Is that the correct width? 3) The main caps have 0.003" slop from side to side when located by just the pins. How is this fixed? 4) Can you install splayed caps on a 389? 5) Does anyone offer two bolt steel main caps? 6) Who would you recommend for pontiac expertise in a machine shop in the socal/az area? Must be top notch!
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Inside of every small problem there is a big one struggling to get out..... |
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#2
12-01-2020, 01:07 PM
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All 326, 389 and 421 blocks only have 2 freeze plugs per side.
4) yes. 5) no.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#3
12-03-2020, 04:31 AM
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Quote:
The only way I can think to fix it would be with oversized dowels. Quite a bit of work involved in that.
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---------------------------- '72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car! '73 Firebird 350/4-speed Black on Black, mix & match. |
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#4
12-03-2020, 04:52 AM
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I don't really see that much of a problem with .003" play. That's .0015" off centerline of the pins, and not really a critical area. Probably just as much or more of a chance that any block/head combination of dowel pin holes wouldn't be that precise anyway. In other words, the pins could fit tight but the holes could be a few thousandths off center from the bores.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 Catalina Safari Wagon. |
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#5
12-03-2020, 07:18 AM
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The question needs to be asked here as to how much hp are you looking to make and is the stock 3.750" stroke being retained?
If your looking to make upwards of 550 hp with the stock 2 bolt mains then I would atleast want to install longer dowel pins that extend up thru the cap, and installing larger diameter dowel pins is not that massive of a job. With either of these two mods you want to check that the line Bore is still within spec. Also if your keeping the stock 2 bolt caps you want to spend the time needed to deburr them and polish over any and all sharp edges ( especially the dowel pin hole !) but for the Bearing parting line. If you are going to stroke the motor passed 4.00" while keeping the 2 bolt mains I would change over to studs and then once again check the line Bore.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#6
12-03-2020, 10:42 AM
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Everyone is giving you good advice here. I would just add if you wish to keep your original 2-bolt caps and just restore the fit, the longer pins available will probably take care of this for you. Unless the pins are loose in the block, the looseness is in the top of the short pin/cap interface. The new pins will go into the caps much further and correct the fit for a stock to light performance build up to 475-500 HP with the stock 2-bolt caps and a switch to main studs IMO. If you go this route, you will need to line hone because the extra clamp load from the studs will close the housing bores to an out of spec. condition.
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#7
12-03-2020, 10:49 AM
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PM sent.Tom
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#8
12-03-2020, 04:36 PM
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Not sure what you mean by slope but I had a main cap issue a few weeks ago I have never had happen before. Checking all caps on block after getting it back come machine shop so I could hard block and install lifter bore brace setup. Checking caps the rear main would not sit flat on block started checking for a burr something not flat so and so on. Well I found small shot peen beads imbedded around the dowel pins in block not a lot 4-6 on each side but enough to stop the cap from sitting flat.
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#9
12-03-2020, 06:14 PM
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I would just say that Tom S seems to know any and everybody involved in the art of speed in So Cal. Whatever recommendations he makes I would follow them. He pointed me in a few choice directions when I had my engine built.
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1967 Firebird 462 580hp/590ftlbs 1962 Pontiac Catalina Safari Swapped in Turd of an Olds 455 Owner/Creator Catfish Motorsports https://www.youtube.com/@CatfishMotorsports |
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