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Discussion Starter #1
Hey guys, I have a 347 that I am having trouble getting the oil pan sealed up on. I purchased the long block around 2005 from Coast Performance and thought it was a later model block used for the build, but the last 2 gaskets I have purchased don't fit very well on the rear main seal area of the block and I am getting a leak. To be certain I get the right gasket this time, I pulled the date code of the block (the number that sits just above the starter) which reads "4C23" which I believe translates to 1964 block. Would appreciate if someone could fact check me. The engine definitely has a 1 piece rear main seal and runs hydraulic roller lifters and uses the spider hold down in the lifter valley. This plus I thought I recalled reading that Coast Performance used later model (86-93) blocks for their stroker engines. I have tried the Fel-Pro 1 piece gasket, the Ford 1 piece gasket and they both leaked. I recently ordered a Fel-Pro 1809 gasket and the front rubber end seal fits good, but the back rubber end seal seam a little big. I don't want to put it back together until I know for sure I have the right gasket this time. Appreciate the assist!
 

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Not a 64 as roller motors are much later--85 and up are rollers
 

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Discussion Starter #3
That’s why I want to verify the date code from the block casting number I posted. i seem to recall machine shops can convert older blocks to a 1 piece rear main seal and to use roller lifters. Hoping someone here can help set me straight.
 

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1967 Mustang Convertible
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What was the other casting numbers around the 4C23? Was it Cxxx, Dxxxx, Exxx or Fxxx? That will show if thats 64, 74, 84 or 94. If 302 I figure its 74 or later.
 

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Discussion Starter #5
This is a pic of the casting number. This was all I saw above the starter. Note I rotated the photo so it could be read.
 

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1967 Mustang Convertible
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Any other numbers lower then that? Here is the 302 I took out of my now long gone 89 GT:
1821164740_e6cd6a67ab_w.jpg


As you can see it has the 7J10 but has the E7TE in it for 87. Or September 10, 1987 5.0

And your sure its the oil pan gasket and not the Rear main seal? I know folks have had to use a Teflon rear main seal to get them to stop leaking.
 

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Discussion Starter #7
This is the original pic before I rotated it. Tough to make out the other number, I might have to wire brush it tomorrow and see if I can get a cleaner pic. Any guesses?
 

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1994 block. If you have a "smooth rail" oil pan, use the Ford Performance M-6710-A50 gasket.
 

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I want to say that F1SE at least thats what it looks like to me, so you have a March 23, 1994 302 block.
 

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Discussion Starter #10
Thanks Woodchuck. I’m using a Milodon 8 qt pan and I think it has smooth rails. Do you know if the Fel-Pro 1809 gasket will work with this block? I believe it is supposed to.
 

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Discussion Starter #11
I want to say that F1SE at least thats what it looks like to me, so you have a March 23, 1994 302 block.
I think that’s what it says and that jives with Woodchuck. I will double check tomorrow for sure. Thanks man.
 

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Thanks Woodchuck. I’m using a Milodon 8 qt pan and I think it has smooth rails. Do you know if the Fel-Pro 1809 gasket will work with this block? I believe it is supposed to.
Sorry, I really can't say as I've never used that particular gasket... at least that I can remember. I've always used the Victor-Reinz OS30531 cork & rubber set.
 

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Engine block year has nothing to do with the gasket selection, oil pan dictates the gasket.

If you have the early style pan with the "dimples" in the rail, then if you decide to run a one piece gasket, it needs to be for that style pan. The later "smooth rail" pan gasket will leak like a sieve. The reason is not the dimples, but the radius where the pan rail transitions into the crank seal area. Early pans have a very small radius, while the later smooth rail pans have a much larger, more gradual radius. If you use an early pan with a later gasket, it'll split the gasket at that transition. Saw this a lot at Canton when the 5.0 guys would buy a pan built on the early core and use a stock 5.0 one piece gasket.

Felpro OS13260T - early dimpled pan
Felpro OS34508R - later smooth rail pan

FelPro 1809 is for the early dimpled pan
 
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Discussion Starter #14
@Hemikiller thanks for the detailed information, this makes a lot of sense. the Milodon pan I have does have the dimpled rails, verified today. The one piece gasket I removed this weekend because it was leaking at the rear crank area was ribbed. Totally aligns to what you are saying. I installed the Fel-pro 1809 gasket set that I had purchased and it fit perfectly. I added some black RTV in the corners and buttoned her back up. I’m doing a few other things while I have her on the lift, so will be a. Few more days before I fire it up and look for leaks, but I am feeling pretty good about it. Appreciate the help guys!
 
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