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Technical How to determine engine size for an sbc?

Discussion in 'The Hokey Ass Message Board' started by evintho, Nov 4, 2020.

  1. evintho
    Joined: May 28, 2007
    Posts: 1,680

    evintho
    Member

    A friend just purchased a '63 Chevy 1/2 ton longbed and is trying to determine engine size. He pulled the # off the back of the block, 3914678 and matched it on this website.....
    http://outintheshop.com/faq/casting/castings2.html

    It comes back as a '68-'79 302/327/350 two bolt main. Not very helpful except we know it's a later model and not the stock engine. What's the easiest way to determine whether it's a 302, 327 or 350?
     
  2. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,671

    56sedandelivery
    ALLIANCE MEMBER

    Look at the head casting numbers to help narrow it down. 2 or 4 barrel? Single or dual exhaust? A 302 in 68 or 69 would not be a 2 bolt main, so you're left with a 327 or 350. If you can get a look at the rearmost of the crankshaft, the crankshaft flange area, there will be a "balance pad" on the crankshaft flange; the 327 will have a smaller balance pad than a 350 (you may have to Google that info to get an idea about the sizes of the balance pads). I went ahead and Googled your posted casting number, and it comes back as a 1968 Camaro, 327, specifically, a 300 HP 327, so it should be a 4 barrel engine if it's all stock. It could also just be a 300 HP short block with almost any heads on it, any carburation, etc.
    I am Butch/56sedandelivery.
     
  3. 302, 327, 350 biggest difference is the stroke. but anyone including Chevy could swap any crank and piston into a 4” bore block.

    3”, 3.25, 3.48” stroke respectively.
    Sometimes a zip tie in the spark plug hole used for a marking gauge with piston at top and again at bottom them measured can get pretty close to determining the stroke.
     
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  4. anthony myrick
    Joined: Sep 4, 2009
    Posts: 7,118

    anthony myrick
    Member

    It’s a vette engine.
    They all are
     

  5. bobscogin
    Joined: Feb 8, 2007
    Posts: 1,761

    bobscogin
    Member

    Isn't the engine build data stamped on the passenger side deck surface? Should be the foundry, build date and letters designating the original application.
    Bob
     
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  6. squirrel
    Joined: Sep 23, 2004
    Posts: 47,919

    squirrel
    Member

    yup, look for the stamped number on the block. And you can also look at the damper, and especially the crank flange, to see what crank it might have.

    But if the casting was actually used from 68-79, then the odds are very high that it's really a 350, because they just didn't make hardly any of the other sizes in those years.
     
  7. that is the best thing, unless the block has been decked at some point, those numbers dont usually survive as they are not very deep.

    on the back of the block is a casting date as well to help narrow the window. I will say you best bet is its a 350. 68 302's are 2 bolt main blocks(front pad code MO), 69's had 4 bolt(the famous DZ code). 327's died off late 68/early 69 as the 307 replaced it. If the the heads are original to the block a 68 motor was the last year of no accessory holes at the ends of the heads, but has the temp sending unit location on the side of the head.
     
    loudbang likes this.
  8. The casting numbers will tell you what engine(s) the parts were to, 302, 327, 350. If you have an all original unmolested engine, then it shouldn't be too hard to figure out. If, however you don't know what you have because being 40+ years old there may have been parts swapped. Since the head i off, just turn the engine over an measure the stroke, verify the bore and do the math.
     
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  9. squirrel
    Joined: Sep 23, 2004
    Posts: 47,919

    squirrel
    Member

    I don't see where he said the head is off, but if so, then this is definitely the easy way to tell!

    4.000" bore will give you a 302 with 3" stroke, 327 with 3.25" stroke, 350 with 3.48" stroke. Add about 4 cubes for .030 over, etc.
     
  10. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 1,848

    ekimneirbo
    Member
    from Brooks Ky

    Pull a spark plug. Put a straw or some type of small round rod like a welding rod etc in the spark plug hole. Rotate the engine by hand till the rod is at its deepest point and mark the rod. Then rotate the engine to its highest point and mark the rod again. Then measure the distance between the marks and you know the crankshaft stroke. No guessing on whether parts have been swapped some time in the past.
    Friend of mine bought a street rod years ago with a supposed 350 Chevy engine. Went out of state and trailered it home. Wanted to tune it up so he gave me some info off the engine. When I looked it up, it was a 283..... You never know what has been done to these engines in the past. Best to measure and then you know for sure.
     
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  11. Aren't oil pan gaskets cheaper than head gaskets. Really, does a tape measure care?
     
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  12. squirrel
    Joined: Sep 23, 2004
    Posts: 47,919

    squirrel
    Member

    Looking at the crank flange might be the easiest way to tell for sure, if there are no stamps on the deck surface.

    The drinking straw trick is iffy when the plug hole is at a 45 degree angle, like on a Chevy
     
  13. Black Panther
    Joined: Jan 6, 2010
    Posts: 1,702

    Black Panther
    Member
    from SoCal

    3914678 blocks were used in 1968 only. Internet lists that show this block being used till 1979 shouldn't be trusted. In 1969 there was 4 different blocks used for small blocks settling on the 3970010 that WAS used until the later 70s in 350 applications.
     
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  14. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,508

    Mr48chev
    ALLIANCE MEMBER

    I didn't have a suffix number photo so I snagged this one even though it is big block off the net. Full Creds to Popp's speed shop
    Location is the same on small block, on the machined pad in front of the right head. There are lots of suffix code decoders on the net or post it here and someone will do it with about fifteen seconds of effort.

    Most likely the engine is a 327 or 350 as 302's only came in Z28's that year or any year for that matter. The chance of a 68 Z28 302 being stuck in a 63 truck are pretty slim.


    suffix number.jpg
     
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  15. squirrel
    Joined: Sep 23, 2004
    Posts: 47,919

    squirrel
    Member

    That's what I suspected....the 014 was used for 2 bolt 350s into the early 70s, then we mostly only saw the 010 blocks, as almost all 350s were in trucks, and most of them were 4 bolts.
     
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  16. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 26,101

    Jalopy Joker
    Member

    what site has the most complete listing of numbers/codes for the front suffix code? my motor has apparently been decked and I can very faintly see some numbers
     
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  17. Budget36
    Joined: Nov 29, 2014
    Posts: 5,802

    Budget36
    Member

    I don’t know about suffix codes, but mortec.com has a lot of casting numbers. Years ago I emailed them with suffix codes and they got back to me shortly with info. Keep in mind it was 10+ years ago
     
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  18. squirrel
    Joined: Sep 23, 2004
    Posts: 47,919

    squirrel
    Member

    I have a pretty good collection of books that show codes well into the 70s, including big trucks to 1969. The truck codes can be hard to find.

    Sent from my Trimline
     
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  19. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 26,101

    Jalopy Joker
    Member

    - good site with lots of info - also, www.1968ss.com/sbcsuffix.asp is good - I do not have a clear set of letters/numbers to ID my motor this way
     
    Last edited: Nov 4, 2020
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  20. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 3,950

    Lloyd's paint & glass
    ALLIANCE MEMBER

    Check the date code on the back of the block. If it was cast in 1976 you pretty much know it's a 350.
     
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  21. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 3,950

    Lloyd's paint & glass
    ALLIANCE MEMBER

    Never mind, missed the 68 only thing. I'm with Myrick, it's a vette motor
     
  22. Black Panther
    Joined: Jan 6, 2010
    Posts: 1,702

    Black Panther
    Member
    from SoCal

    Lloyd...thats pretty much true after 1970. 1969 used the same block for 327s, 350s and 302s. 4 different block numbers were used in 1969. After 1970, a 307, 305 or a 400 which were the other small block displacements had unique blocks for them. So after 1970, any stock engine with a 3970010 block is by definition a 350.
     
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  23. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,677

    mgtstumpy
    Member

    I believe that 350s also didn't have the provision of road draft tubes at the back of the block
    SBC crank flanges.png
     
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  24. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 1,848

    ekimneirbo
    Member
    from Brooks Ky

    Lot of these solutions require a lot of work to get to the point where you can look at something .......try the sparkplug and straw thing. Only takes 5 minutes. If it doesn't work for you, only thing you lost is 5 minutes and a straw.:p
    I've bought some 500 Cadillac engines and the only way to tell for sure its a 500 (4.304) instead of a 472 (4.060) stroke is to remove a spark plug and check it. Again, if it doesn't work on your Chevy, all you lost is a straw......smaller straws are better.;)
     
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  25. 55blacktie
    Joined: Aug 21, 2020
    Posts: 258

    55blacktie

    The 302 was used in the 1967-1969 Z28 Camaros exclusively. The 1967 Camaro Z28 used a 283 crankshaft/w smaller main-bearing journal. 327s also were small journal. The 350 main journal is larger. 68-69 Z28 is large journal 350 but same 3" stroke of the 283.
     
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  26. anthony myrick
    Joined: Sep 4, 2009
    Posts: 7,118

    anthony myrick
    Member

    That’s the number 2 SBC engine.
    If it’s not from a vette, it’s a z28 engine.
     
  27. MARKDTN
    Joined: Feb 16, 2016
    Posts: 87

    MARKDTN

    68 and 69 327s were large journal.
     
  28. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,671

    56sedandelivery
    ALLIANCE MEMBER

    Ding, ding, ding; we have a winna' here; this is what I was trying to say way back in the second posting about looking at the crank flange balance pad. Although it says, "pre-74 SBC, it's probably because that article was wrote in 1975 or so. Keep in mind, those are ALL 2 piece main seal blocks/cranks, and not late model one piece main seal blocks/cranks (that open up a whole nuther' set of issues). Thanks for posting that stumpy! I am Butch/56sedandelivery.
     
  29. If you have a circle track in your area, find the track guy that does the cubic inch testing. They have this hand pump that tells the cylinder size pronto.
     
  30. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,508

    Mr48chev
    ALLIANCE MEMBER

    Anthony is right, the 302 never came in anything except a Z28. Small Journal in 67 and Big Journal in 68/69.

    You could buy a small journal fitted 302 block straight from Chevrolet for a little over 300 bucks in the early 70's. Use a steel crank and rods out of a 283 and you had a hard running 302.

    You used to see a good number of 68 327 big journal engines in the late 60's and early 70's Simple reason = the 307 crank is the same stroke as a 327 crank. Just by using the 4 inch block and pistons with the 327 pin height they had a 327.

    Still everything in the big journal 327 is the same as the 68 350 except the crank stroke and pin height in the piston.
     

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