1966 L79 Valve Sizes

[George D.]

On a 1966 L79 were the intake valves 2.02" or 1.94"?

[Timothy B.]

Re: 1966 L79 Valve Sizes

George, The intake valve is 2.02" and exhaust 1.60", I believe the head part # is 462.

[George D.]

Re: 1966 L79 Valve Sizes

Tim:

Thanks for the quick response. That's what I thought. I just wanted to confirm that the "461" heads were 1.94"/1.60" and the "462" heads used on the L79 engine were 2.02"/1.60".

[Jack H.]

Re: 1966 L79 Valve Sizes

The '461/462 designation refers to the CASTING number of the cylinder head and not the part number. It was the secondary operations during assy (final drilling of valve paths, selection and installation of valves, Etc.) that took the cast number to a finished part number. The part number appears NOWHERE on the cylinder head.

The same physical casting could be 'stuffed' in different ways to yield different final flow characteristics and that included the decision as to which intake/exhaust valves were to be used. Bottom line: do NOT go by the casting number to decide what valves to use!

Have a competent machinest measure and determine what valves that particular cylinder head was finally built up for. Remember, the difference in valve size is VERY modest and you can always machine a small valve head to become a large valve head assy...

[George D.]

Re: 1966 L79 Valve Sizes

Thanks. I was just trying to determine if there was an easy way to determine the valve size without pulling the heads to see if the correct heads were istalled. As you say, it's easy to read the casting numbers and date codes but without part numbers there's no way to tell the size of the intake valves without pulling the heads.

[James G.]

Re: 1966 L79 Valve Sizes

L79 engines 327/350hp were the same as 327/365hp and 375hp fuel injected engine of 65. Difference was the hydraulic camshaft and smaller oil pan so power steering could be used.

The L-79 was probably one of the best all around Performance engines Chevrolet ever made and were also used in 65-67 Chevelles and Novas. I had a 65 Chevelle SS L-79 new when I got out of college. Should have kept that car

65 and 66 used 3782461 heads, the same since 1962 on all 300hp, 340hp and 360hp engines. The valve size was 2.02 for 350, 365 and 375hp, and they all had 11:00 to 1 pop up pistons.

1964 was the first year for 2.02 intake valve when the new solid lifter 30-30 camshaft was released.

300 hp had the same heads, but 1.94 intake valve and flat top 10:50 to 1 pistons.

The 250hp of 62-65 used the small WCFB carb which flowed only 500cfm vs the 600cfm AFB used on 300, 340 engines, and used a 3795896 head in 1962 thru 64. That head had only a 1:72 intake valve.

All Corvette 65 and 66 engines with 350, 365 and 375hp used the 461 head with 2:02 intake valves. The 3890462 head was used from March 66 thru May 67. It was the same head as the 461

[Joe L.]

Re: 1966 L79 Valve Sizes

Thanks. I was just trying to determine if there was an easy way to determine the valve size without pulling the heads to see if the correct heads were istalled. As you say, it's easy to read the casting numbers and date codes but without part numbers there's no way to tell the size of the intake valves without pulling the heads.

George-----


It is rarely possible to determine valve size by reference to casting number. Most Chevrolet small block cylinder head castings were used for multiple valve sizes. The only way to know, for sure, the valve size is to measure them.

Also, it's very possible for the original valve size to have been changed. Heads originally fitted with smaller valves can have had the valve seats re-machined and the valve size increased.

[John H.]

Re: 1966 L79 Valve Sizes

Also, it's very possible for the original valve size to have been changed. Heads originally fitted with smaller valves can have had the valve seats re-machined and the valve size increased.

And the 461/462 and later 291/186 heads that were available in both valve sizes (within the same casting number) had an unshrouding cut made in the chamber wall adjacent to the intake valve on heads factory-machined for 2.02" valves, for improved flow; heads originally machined for 1.94" valves do NOT have that unshrouding cut, and if they're field-converted from 1.94" to 2.02" valves without having the cut made, they'll flow less air than they did with 1.94" valves.