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What type engine do i have?


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Have done some looking on the forum, but could not find my answer, so forgive me if this has been asked before.   My 521 has a newer / bigger engine in it than the stock.  From the previous owners receipts it seems that it came from a 1979 620.   However, this weekend i was installing a new intake / exhaust gasket and the new one I bought was 99% the same as the old gasket, but the outer holes that go through the studs did not match up.  Also, the water jacket? holes that go through to the intake did not match up 100% either, so needless to say when i fired up the truck antifreeze just dumped straight to the exhaust!   Weird thing is that the gasket number on the old one is the same as the new one?! 


In my research and after taking off the exhaust manifold I realized the exhuast gasket holes are round, but my exhaust holes are square? 


long stoy short i guess...anywhere I can see on the block or head to find out what type i have?


Many thanks.



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A 79 620 would have had round exhaust holes. 1977 and earlier would have had square. '75-77 would not have had coolant jacket holes at all.


So, there's no way for us to guess what you have based on the info given, though there are lots of possible answers:


1) It's not a newer engine, just a plain stock L16 (with square exhaust ports and an intake coolant jacket).

2) Could be an L18.

3) Could be an L20B with a different or modified head.

4) Could be a hodgepodge or parts.


We need to know the head casting number, the engine ID number, the type of manifolds, and maybe some pictures of this to be sure.



Oh, and I agree with the above. The bolt pattern and water jackets are in the same place on all heads (well, water jackets on ones that have them). You put the gasket on backwards. It "almost" fits the wrong way.

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ugh..just took the old one off and swapped it ...yes..i am a dumbass..  Guess the beer to mechanic ratio was too much. ugh...any thoughts on flipping the new gasket and trying to use it or just buy a new one.  I only ran the engine for about a minute..thoughts..opinions?

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So, Engine is l20b with w58 head.   Exhaust ports on head are round, but the exhaust manifold inlets are square....think it is an aftermarket header as the exhaust is a custom pipe with magnaflow exhaust at tip....thanks for all the info....gonna try this again with the gasket on the right side....

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