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is there anyway to tell if a block was previously align bored, my 400 sbc engine has a fairly good leak from the rear of the engine and it has been like that since assembly, i have not pulled the tranny yet to verify that it is the rear main seal and not a galley or cam plug but plan to this winter, i bought the block from a machine shop but they do not know if the block had been align bored previously, i know they make a special rear main seal for the 400 but i could only use it if it was bored, i goofed when i assembled it since i did not use sealant on the cap to block mating surface, it seams to leak a little to much for it to be coming from there or can it, thanks
Scotty
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Discussion Starter · #5 ·
my crank was turned .010 on mains and rod journals, so going by the article you provided am i safe to say i have undersized bearings? i automatically assumed they were oversized because the pins were turned smaller, thanks Bogie for the lesson
 

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are you sure the seal is installed correctly?
is the crankcase vented?
the lack of sealer on the rear cap can be a good size leak, depending on the exact surface condition of the block and cap.
 

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are you sure the seal is installed correctly?
is the crankcase vented?
the lack of sealer on the rear cap can be a good size leak, depending on the exact surface condition of the block and cap.
Before you pull the trans or engine put ultraviolet dye in the oil and run it. When you pull it apart you can check the leak source with a dye light. If you don't have one perhaps you can borrow one. Or buy an in expensive one if need be. Good luck. Ernie.
 

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Discussion Starter · #8 ·
i did install the seal properly and have a good working pcv system on it, my lack of sealing the cap block surface may indeed be the source of the leak, i am going to look into the ultraviolet dye and light as suggested, thanks for the replies
 

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I asked because the 2900 and 2909 look slightly different on the transmission side, it's a slight difference with the molding. I don't remember off hand and I don't have one here right now to compare.
 

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Discussion Starter · #14 ·
i bought a oil leak dye kit, the bottle has 30ml in it but does not say how much to use, do i use the whole bottle or just a little and should i change the oil before using it or is the oil in it okay? fairly new oil in it already, after driving the car for a while and shutting it down how long will the dye stay visible to the light? the car may have to sit for a short while before i can pull the tranny, if it is the rear main seal and i pull the engine should i get a different brand of seal and if so what would you suggest?
thanks
 

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i bought a oil leak dye kit, the bottle has 30ml in it but does not say how much to use, do i use the whole bottle or just a little and should i change the oil before using it or is the oil in it okay? fairly new oil in it already, after driving the car for a while and shutting it down how long will the dye stay visible to the light? the car may have to sit for a short while before i can pull the tranny, if it is the rear main seal and i pull the engine should i get a different brand of seal and if so what would you suggest?
thanks
Use about half the bottle. Oil that's in there now ok. Put it in drive it get it hot. The dye won't wash away. Drive it now plenty before to take it apart say an hour or so. U need uv glasses with the light to dee the color. I'll set someone else advise on the seal part #. Ernie.
 
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