Hey guys,

I’ve got a ’70 442 and I’m in the middle of a build. I’ve got both the original E casting heads and a set of F heads sitting on the bench, and I’m trying to decide which pair to run for the best power output.

From everything I can measure and see, they look nearly identical—same valve sizes, combustion chamber volume appears to be the same, and ports look pretty much like twins. But if I’m going to button this thing up once, I want to know if there’s any hidden advantage (or disadvantage) between the two.

Here’s the twist: I’m totally open to porting, welding, and reworking the E heads since they’re not hard to replace. The F heads, though—I’d rather leave those untouched due to their value.

Anyone here ever dyno back-to-back, or know of any legit difference beyond the letter stamped on the casting? Or is this just one of those Olds mysteries where it’s six of one, half dozen of the other?

Appreciate any input—before I start chasing horsepower ghosts.

 

Only difference I've ever noted is the E head has 2 exhaust ports feeding the crossover, the F head only has 1 exhaust port supporting the crossover. I imagine with the aluminum intake less heat is needed. Otherwise they appear the same.

 

We have ran C, E and J heads on our dyno engine, all in "stock" form. Next time we get back to Detroit (late August) we are going to run a set of F heads in the same configuration. So in a month I'll have an answer. Until then here is all I can offer; We have flowed almost every big block Olds head (except H heads). The F heads have significantly more flow at low valve lifts than anything else out there. Now, flow doesn't translate into power. In a "stock" configuration (W30 manual cam, cast iron intake, W/Z manifolds, Quadrajet carb) the E heads made the most power (of the three stock heads we've tested so far) followed by J's followed by C's. But, once you start to modify the engine, away from it's stock form, the C heads perform better. We have a set of ported C's that flow about what the out of the box Gen 3 Edelbrocks flow, so there's that.

The first test we will run when we get back to MI is a set of stock C's with just the crossover filled and the center divided welded, to see what all that is worth (tested in a stock configuration). If you can wait a month to make a decision, I can give you some good answers. Have you read our dyno testing write ups?

jerry

 

Those 2 center ports fight one another on the E heads. Eliminating that constriction on the F head is significant, but to what extent, I would leave to the experts.

 

I will have a definitive number as to what it is worth in about a month. I don’t think it will be worth a lot, but a lot of stuff in the dyno testing has surprised me.

we are going to run stock C heads with a W30 manual cam, headers and a Torker intake. The heads we are going to run will have the center divider welded and the middle exhaust crossover filled with zinc and reshaped.

ill report back and then Dale can tell me how wrong I am.

jerry

 

Actually if the intake still has the ex crossover open, all four center cyls will be compromised.

 

there are two different E head castings even though they will have the same 403 686 casting numbers. If yours was an early production car it should have the better version of the E heads without valve rotators. mid year they went to rotators which changed the intake port design.

because of the deeper spring pocket requirement, approximately.180”, the intake port roof also needed to be lowered accordingly. There is a water jacket in the casting between the seat pocket and the intake roof.

the lowering of the port roof reduced the minimum port cross section in that most critical area. contrary to internet experts, the Olds BB head(s) minimum cross section is not near the pushrod pinch like most other manufacturers heads, it’s approximately .750” upstream of the valve guide.

if you can post a pic of your spring pocket, that will tell you which E head you have. here’s the early version and mid year revision.

all F casting heads ive seen and had here are deep seats. I have one set here now. If you are going to port the E’s, it’s better to start with non rotator heads

 

Thanks again to everyone who jumped in—this thread has been super informative and exactly what I was hoping for.

Jerry, I’ll definitely be waiting to see what your dyno numbers show next month when you run the F heads. You've clearly done the homework, and getting those back-to-back comparisons with C, E, and now F castings on the same motor is next-level helpful. Please keep us in the loop when that data drops.

CANADIANOLDS, big thanks for pointing out the E head revision mid-year—I wasn’t even aware there were two versions under the same casting number. My car is an early build (01/70), so I assumed I had the early-style E heads without the deeper spring pockets. But after inspecting and snapping a few closeups, it turns out mine have the deeper pocket design you described—visually identical to my F heads. So it looks like even some early ’70 builds ended up with the later-style heads. That was a great call to check.

I also attached pics of both the E and F center exhaust ports. Visually I can now see the one side of the F blocked, and understand the crossover and internal shape make a real difference.

On that note, I dug up some flow numbers comparing stock E and F heads. At 0.400 lift, the E heads flow noticeably more on both intake and exhaust (243/147 vs. 227/144), and that advantage mostly holds at 0.500 too. That said, the F heads still seem to perform well despite the slightly lower flow numbers—probably due to the blocked crossover and center port design. Curious if anyone here has tested or confirmed similar figures, or if these numbers sound accurate to you?

Hammerdrop, shiftbyear, and cutlassefi—you all brought up a great point about the two center ports on the E heads fighting each other. That crossover flow design really seems to change the game beyond just CFM numbers. That said, I will be using the w-30 aluminum intake if that makes any difference.

Again, I appreciate all the input. It’s been great diving deeper into the mystery behind these castings—and it’s looking more and more like this might not just be six of one, half dozen of the other. Looking forward to learning more as the test results come in.


E head

F head

E head

F head

 

I think that pic of the E head is the second version..which is deep seats on intake only. hard to tell because the pic is so close. Can you check to see if both seats are the same depth or a pic further out.

if your car was built Jan of 70, that’s not really an early car.

 

You do have what would be a "mid year" build car. Oldsmobile started building cars in August 1969, to fill up new car showrooms for 1970 new model introduction in September or October.

 

CANADIANOLDS, thanks again for helping break down the seat differences. I went back and measured the spring pockets—both seats on my E heads match the depth of the ones on my F heads. So that confirms they’re the later-style version with the deeper pockets.

And point taken on the build date. I’ve owned this car for over 40 years, and with so many of the parts dated from ’69, I always assumed it was an early build. Turns out 01/70 isn’t quite as early as I thought. Live and learn—I’m still picking up new things after all these years.

OLDSter Ralph, appreciate the historical context. Makes sense now with the production starting in August '69. That clears it up perfectly.

Jerry—still looking forward to your dyno data when you get a chance to run those F heads. Eager to see how it all stacks up.

Thanks again to all of you for the education. Great info all around.