Can anyone tell me what external markings will distinguish a B20E from a B20F engine?

Thanks.

THICKNESS is the only way to tell. The pad on top only tells you that the head is from 1973 or newer.
B20E is 3.34"
B20F is 3.42" Thick from top to bottom machined faces.

--
Three 164's, Two 144's, One 142 & a partridge in a pear tree.

THICKNESS is the only way to tell. The pad on top only tells you that the head is from 1973 or newer.

Might be true in Australia, but in the US I'm pretty sure the photo I posted will work for ID of head types. There were clearly market-dependent differences between engines during the early 1970's. Your statement above is a good example. That simply wasn't true in the US, where there were no 1972 model year engines with "E" heads... thick, thin, or otherwise. :)
--

Gary L - 142E ITB race car, 73 1800ES
YouTube Racing Videos

You lost me a little, are you saying there was no B20E/F engines in the US before 1973?

The only difference between an E and the F for any particular year is the compression ratio and the settings of the MPS. The later model head is better to port if you don't want to weld or braze up the exhaust port. The earlier head flows a little better if porting is banned. The pre-injection B20 head I put aside. I have a K-Jet head, but haven't looked at it.

How's the Holden going? We won't be making any from 2017, all imports. I hope GM is going to make a RWD Commodore somewhere in the world.
--
Three 164's, Two 144's, One 142 & a partridge in a pear tree.

What I'm saying is there were no "E" heads in the US for '72, only "F" (as defined by the photos). It went like this in the US:

- In 1970 and 1971, all US spec cars with FI had "E" heads with 10.5:1 compression.
- In model year 1972 the "F" head was introduced with lower compression & different ports. There were no "E" heads sold in the US beginning with the 1972 model year.

Said another way, I'm pretty certain there were no early casting FI heads ("E" in the photo) ever sold in the US with anything but 10.5:1 compression. If I understand correctly, you're saying that was not the case in other markets, right?

The Holden is doing fine, we simply don't put a lot of miles on it (55k in 5 years), so it would probably easily last my lifetime if I so chose. I did commit to at least a couple of years further use by putting a new set of Michelins on it a few months back. Incidentally, all 4 OEM Goodyear RS-A's had shifted belts by that time, one of them bad enough it became impossible to balance. In any case, I'm thinking maybe a rear drive Cadillac is in my future. Here in the US, GM is getting near-Cadillac prices for the latest Holden (Chevrolet SS) anyway, while the Caddy's are more refined, just as fast :) and get better fuel mileage.
--

Gary L - 142E ITB race car, 73 1800ES
YouTube Racing Videos

In the U.S. market, we saw at least four different injection head castings:

1) The original '70 E, which has 11 fasteners holding the manifolds on, advertised at 10.5:1 CR using a .030" gasket (chambers around 48cc)

2) The second E (used for all '71 models and [possibly phased in earlier) using 9 manifold fasteners, same CR as the original

3) The first F used for '72 and '73 models with D-jet, 8.7:1 CR with a .050" gasket, chambers around 57cc. The '74 K-jet head is the same casting, just not drilled for AAV or coolant temp sensor

4) The final F head for K-jet in the '75 240. The bridge around the center head bolt extends around both #2 and #3 injector ports. I think it's functionally identical to the '74, but I've never worked with one. Maybe it's tapped for metric fasteners?

The head with the flat bridge both sides of the centre bolt might be a casting that can be used for an R-Sport head, maybe a bit less water jacket under the inlet ssr where it is needed when porting for high lift flow above .25D. I think JohnMc has one.


--
Three 164's, Two 144's, One 142 & a partridge in a pear tree.

I've always just assumed this was made from a late model F casting.

I guess the other reason to measure the head is that after 40 years a thicker F head may have been shaved down to E spec. Or further.
--
'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)

The easy way is to simply look at the head, particularly since that's the only real difference anyway. Here's a photo that should be self-explanatory:



BTW, this assumes we're talking normal production, US spec engines here.

--

Gary L - 142E ITB race car, 73 1800ES
YouTube Racing Videos

Thanks, Gary. Looks like I have an E.