block Id

Mark Lewis · 01-07-2017, 01:47 PM

I have a sbc with the casting number 3914638. It has a TII30DF stamped on the pad at front of block. Book says the number is a 327, 4 in bore but it measures 3.875 like a 307. Numbers on front indicate a 1968 307. It is a big journal crank. Could this have been intended to be a 327 and instead is a thick 307? Has not been cleaned or sonic tested so I don't what that looks like. Let me know what you think.
Mark

Alan Nyhus · 01-07-2017, 02:22 PM

Mark, several sources list the 3914638 as a 307 block. Hope this helps. -Al

http://www.probuildamerican.com/tech...5327350383400/

Timetraveler · 01-07-2017, 05:22 PM

GM did use some blocks for 3.875 and 4.00 such as the 3789817 is a 62-67 327 block but I have one that is 3.875 and was used with a 3.00 crank for 283 in 1966. This makes for a very thick cylinder wall but leaves a lot of room to bore.

NORMAN BARNARD · 01-07-2017, 05:42 PM

I would still have it sonic check'd before puting $$$$ into it.

MAURICE BLENDHEIM · 01-07-2017, 07:09 PM

Mark…A 3914635 or 3914636 is a 1968 307 and are 3.875 bore, possibly the last number is filled in with casting making it into an "8". There are 1968 blocks with a casting number 3932386 that are 4.00 bore. Are your intensions to bore it to 4.00? Wondering what numbers are cast into block behind the timing cover? Hope this helps…Maurice.

Greg Reimer 7376 · 01-15-2017, 10:39 PM

Could you imagine sonic testing and filling that block and building the ultimate 283 out of it?283 blocks are getting pretty rare. 307 castings seem to still be out there.There is definitely a use for that block.Another block number is 3870020 and 3870024. Set of space saver main bearings might be difficult to locate,however.

tim worner · 01-16-2017, 06:31 PM

3914638-----1968 2 bolt main truck block 327
3914636------1968 2 bolt main 307

01-07-2017, 01:47 PM	#1
Mark Lewis Member Join Date: Apr 2006 Posts: 330 Likes: 55 Liked 184 Times in 37 Posts	block Id I have a sbc with the casting number 3914638. It has a TII30DF stamped on the pad at front of block. Book says the number is a 327, 4 in bore but it measures 3.875 like a 307. Numbers on front indicate a 1968 307. It is a big journal crank. Could this have been intended to be a 327 and instead is a thick 307? Has not been cleaned or sonic tested so I don't what that looks like. Let me know what you think. Mark

01-07-2017, 02:22 PM	#2
Alan Nyhus VIP Member Join Date: Dec 2002 Location: Lower Dakota territory Posts: 1,166 Likes: 1,016 Liked 762 Times in 226 Posts	Re: block Id Mark, several sources list the 3914638 as a 307 block. Hope this helps. -Al http://www.probuildamerican.com/tech...5327350383400/ __________________ "That'll never work....."

01-07-2017, 05:22 PM	#3
Timetraveler Member Join Date: Aug 2002 Location: Florida Posts: 103 Likes: 79 Liked 12 Times in 6 Posts	Re: block Id GM did use some blocks for 3.875 and 4.00 such as the 3789817 is a 62-67 327 block but I have one that is 3.875 and was used with a 3.00 crank for 283 in 1966. This makes for a very thick cylinder wall but leaves a lot of room to bore.

01-07-2017, 05:42 PM	#4
NORMAN BARNARD Member Join Date: Mar 2006 Location: EL PASO, TEXAS Posts: 156 Likes: 0 Liked 2 Times in 2 Posts	Re: block Id I would still have it sonic check'd before puting $$$$ into it.

01-07-2017, 07:09 PM	#5
MAURICE BLENDHEIM Senior Member Join Date: Jun 2011 Location: Langley (no igloos), British Columbia, Canada Posts: 551 Likes: 269 Liked 228 Times in 78 Posts	Re: block Id Mark…A 3914635 or 3914636 is a 1968 307 and are 3.875 bore, possibly the last number is filled in with casting making it into an "8". There are 1968 blocks with a casting number 3932386 that are 4.00 bore. Are your intensions to bore it to 4.00? Wondering what numbers are cast into block behind the timing cover? Hope this helps…Maurice.

01-15-2017, 10:39 PM	#6
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,111 Likes: 164 Liked 649 Times in 208 Posts	Re: block Id Could you imagine sonic testing and filling that block and building the ultimate 283 out of it?283 blocks are getting pretty rare. 307 castings seem to still be out there.There is definitely a use for that block.Another block number is 3870020 and 3870024. Set of space saver main bearings might be difficult to locate,however. Last edited by Greg Reimer 7376; 01-15-2017 at 10:54 PM.

01-16-2017, 06:31 PM	#7
tim worner Senior Member Join Date: Jan 2002 Location: duncannon Posts: 838 Likes: 14 Liked 126 Times in 20 Posts	Re: block Id 3914638-----1968 2 bolt main truck block 327 3914636------1968 2 bolt main 307 __________________ Tim Worner SS 1747