Which 273?

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demondaddy

demondaddy

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I have a 66 Barracuda Formula S that was delivered 10-12-1965 according to the certicard. My question is do I have the 65 and earlier engine with the unique intake/ head angle bolts or the later. I would like to use a newer dual plane intake. Driver side casting # 2465330-4. Passenger side 3-17-65. See pics, please let me know what you think.
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Why pigeon hole yourself with a 65 when you can use a 66 without any headaches?

Jake
 
I think the 65 has 5/16" bolts so 1/2" heads on intake, 66 has 3/8" bolts on intake 9/16" heads.
Very easy to figure out.
 
brian6pac said:
I think the 65 has 5/16" bolts so 1/2" heads on intake, 66 has 3/8" bolts on intake 9/16" heads.
Very easy to figure out.
Click to expand...
Exactly, the block could have been cast 6 months or more before the car was built. If it has the 9/16" headed bolts that bolt in at 90 degrees to the intake surface you have the 66 and newer engine.
 
look at the bolt angle. There is a casting line on the intake end that follows the bolt angle, as the 66 is almost perpendicular to the head surface, the 65 is at an upward angle. If it is not evident, look at the bolt holes. The early ones are smaller (hard to tell if you dont have a comparison next to it) and have a angled pad they seat onto. The 66 and later is a flat plane.
 
If you habe an engine block casted in March of 1965 is just fine. They just mounted the new head and intake for 1966 on the block.
 
Judging by the 9/16 bolt heads and the angle I would say these are the later heads. Agreed? I should be able to use the 318/340/360 intake.
 
The 318 and the 340/360 have much different intake ports. 318 are smaller
 
Mike69cuda said:
The 318 and the 340/360 have much different intake ports. 318 are smaller
Click to expand...
Sure, but aftermarket intakes don't make that distinction. I'm not talking about port matching, I'm talking about physically bolting up.
 
1966 and up to Magnum engines will bolt up. The 64 and 65 and of course the later Magnums are different.
 
If you are installing an intake manifold to increase the airflow into the engine, you should consider headers. The 273's restrictive exhaust manifolds were (are) its Achilles heel. So to address increasing air and fuel intake without addressing exhaust may not give you the increased performance you're trying to achieve.
 
Those look 66 and up. Notice the exaggerated bolt angles on these 64 heads. See that bolt angle line I was referring to on head casting?
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I think we concur that the initial post giving casting numbers for the block is irrelevant since the tapped holes for the intake manifold are in the heads. Any small block heads can bolt to any block. You could even bolt Magnum heads to your 1965 block, but then would have to use a Magnum intake, which may be desired - cheap way to realize multi-port fuel injection. I understand the stock valves will clear the 273 cylinder walls. Downside is that Magnum heads are known for cracking at the valve seats (no inserts, induction hardened). No comment on posts 18, 21, & 23.
 
I just can't see a dual plane big-port intake offering any kind of improvement on a low-compression 273... especially if you still have the stock rear hi-way gears, and an automatic with a stock convertor.
And here's why;
The factory 2bbl is good to at least 3200 rpm@100% VE (Volumetric Efficiency), more like 4000@70%; which with 2.76 gears is over 40 mph, in first gear. If your engine can only process 250 cfm then it doesn't care how many barrels are on it, it will still only process 250 cfm. If you need more than 250cfm, then you need to dig deeper into the engine.
Where did I pluck 250 cfm from?
a 273 engine means if you add up the swept area of all 8 cylinders, then you will get 273 cubic inches. But it only fires 4 cylinders every revolution which is 273/2= 136.5 cubic inches at one rpm. At 3200rpm it would be 3200x136.5=436,800, which divided by 12x12x12 to convert to cubic feet is 253 cfm....... if it could fill every cylinder 100% at 3200 rpm. But with the stock cam,pistons and exhaust system, that will never happen. 70% IMO is a generous number, so that would be 191 cfm. And I think your 2bbl is about 230 to 250cfm, which would be good to 4000 because the engine is rapidly losing efficiency.
The point is I hate to see you spend a couple of paychecks and come out little to no better.
But if you just gotta try it; I highly recommend to stay with a small-port design. And not just at the head but all the way to the plenum.
And I see you are in Colorado. If you are at altitude, the situation is even worse.
 
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