273 special parts
- Thread starter Jeebis44
- Start date
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mygasser
Well-Known Member
aren't the early 273 heads/intake faces machined at a slightly different angle too?
neil.
Edinburgh Mopar
New Member
Cheers bud
Yes.
Who were you talking to or about? You need to hit the reply button so they know. Or, provide a link to the thread you are talking about.
Edinburgh Mopar
New Member
Hey bud, I was trying to reply on the thread with the 273 rockers on it, but message wouldn’t send.
I think I’ve sent you a pm about them
Edinburgh Mopar
New Member
Cheers, was the original post author
No, the 64-65 intake bolts are 5/16 and drilled and tapped on a different angle, but the intake face is the same as the 66 up heads.
BillGrissom
Well-Known Member
I assume my 1965 heads are the same 90 deg included angle where the intake mates as a 1966+ small-block. Indeed I currently have a 1966+ 4bbl intake installed. I had to bevel the holes and uae flathead bolts ro match fhe different bolt angle.
I since bought a correct 1965 4 bbl intake, so can go several ways.
I don't think I have ever seen it posted the exact angle of the bolt holes. I just know that the 64 and 65 intakes use 5/16" bolts and the 66 and newer LA intakes use 3/8" bolts at a different angle. Neither are 90° to the gasket surface.
I can't for the life of me find the photos of the 2 intakes side by side. Here is a photo of an early intake on late model heads. That shows you the angle difference.
Late intake on early heads. McMaster Carr makes wedge shaped washers.
BillGrissom
Well-Known Member
mygasser was asking about the angle of the intake manifold mating surface, not the angle of the tapped holes rel. to that face. It seems that angle is 90 deg (included angle between both heads) on both early and late heads. Another way to state it is that the intake surface is perpendicular to the deck surface. Since the decks of the two banks are perpendicular, that makes the intake angle exactly 90 deg. Thus a later head will mate flat to the two intake surfaces on the two heads, as shown in post 88.
The angle of the tapped holes for the bolts is another issue. The bolts are closer to vertical in early heads. Post 87 shows that later bolts are 5 deg off perpendicular to the intake surface (towards vertical) and early bolts are 15 deg off perpendicular, or 30 deg off vertical. That appears about right in the photo of Post 88. Interesting, since I always assumed that the holes in later heads were exactly perpendicular to the intake surface.
If I could have found those wedge washers, I wouldn't have hogged out the holes in my later manifold to conical. I had spent a long time looking for pivoting washers, i.e. 2 pieces that fit together with a hemisphere so can rotate to match.
The angle of the tapped holes for the bolts is another issue. The bolts are closer to vertical in early heads. Post 87 shows that later bolts are 5 deg off perpendicular to the intake surface (towards vertical) and early bolts are 15 deg off perpendicular, or 30 deg off vertical. That appears about right in the photo of Post 88. Interesting, since I always assumed that the holes in later heads were exactly perpendicular to the intake surface.
If I could have found those wedge washers, I wouldn't have hogged out the holes in my later manifold to conical. I had spent a long time looking for pivoting washers, i.e. 2 pieces that fit together with a hemisphere so can rotate to match.
Since this thread has been revived, I have often wondered if the 68 and 69 273 engines still used the smaller register on the crank for the torque converter snout? Can anybody confirm or debunk this?
I would use the word parallel to describe the intake and head surfaces for both intakes on either the early or late head. Those surfaces are all the same between all those parts. Perpendicular is a 90° angle and there really aren't any 90° angles involved in those surfaces.
Just to clarify to other members reading along, the intake bolt thread size and angle is different between the 64 amd 65 heads compared to the 66 and newer heads and intakes, The gasket surfaces are the same angles and the intakes will fit and seal but you won't be able to bolt it down without some modifications.
BillGrissom
Well-Known Member
I vaguely remember people stating that 1968 was the year that the torque converter snout became bigger, but search to ensure. Also, transition years can have carry-over parts from prior years. Often, the engine date is the year before the model year, likely because they stamp the actual production date, whereas model year is a marketing fudge (today, some start selling say 2027 model cars in Jan 2026). A member here in Silver Springs, FL used to sell an adapter ring to fit an earlier transmission snout to a later engine (or at least the crankshaft). True for both small-block and slant-six (same transition year?). Don't recall mention of BB or RB. Perhaps all cast-iron crankshafts had the larger snout hole.
Another kink is that crankshafts for stick-shift can differ from those for automatic, since need a deeper hole to fit the bearing. Perhaps can use a stick-shift crankshaft with an auto transmission. There is a trick to use an early transmission with a later engine, if you can't source the adapter ring. That is to install a later torque converter and the later input shaft. Getting a bit Frankenstein, but a few owners made it work. All comments for further research, so don't trust my memories, just what I read, never dealt with it.
cudamark
Well-Known Member
'68-up all have the big register. '68-9 273 cranks are the same as the cast 318 cranks.
Thank you Mark!
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