As far as the '74 and '75 eight bolt B20F's ...is there a early and late F head? I believe i read somewhere there was a difference and the later one could be polished more for more flow....if so ..how do you tell the difference?

Thanks
Abram

ok new question.....would the 74 and 75 B20F's have the later head on them (being the last years the engine was produced?

The 74 and 75 should be the same, they're both considered "late" heads.
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Kyle - 142, 145, and 244! - Oregon Volvo Tuners?

No differenc ein flow in stock configuration, but those who know say there is some more metal in the exhaust ports that allows more work to be done to the late heads before the wall gets too thin. Of course, some heads had core shift - a slight misalignment of the internal passageways created during the initial casting, that makes them unsuitable for modification. I think you need a trained eye to look one over and see that.

But anyhow, on to how to tell an E from an early F to a late F head. It's fairly straight forward. these are all injection heads, and have injector 'pads' on the top of the head, on top of each intake port. And between the exposed row of 5 cylinder head bolts on that side (the other 5 are under the valve cover). What you need to do is look at that center exposed cylinder head bolt. It sits on a raised section of machined metal, with lower rough cast metal around it.

If it sits on a separate 'island' of machined metal, completely surrounded by rough, lower casting, it is an 'E' head.

If it sits on an island connected to ONE of the adjacent raised, machined injector pads with a thin 'ithsmus' of raised, machined metal, then it is an early 'F' head.

If it is connected to BOTH adjacent injector pads via thin, raised, machined ithmuses (ithsmusii?) then it is a late 'F' head.


Here's a pic of my R-sport head that was created from a late F casting:

You can see the connections to both adjacent injector pads. Although the injector pads weren't drilled on this head.
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'63 PV544 rat rod, '93 Classic 245 + turbo

I never knew there to be a head that was raised on both sides. Here's my two heads, which supposedly are both late F heads, with only one connected portion. I know that at least one of those heads came off of a 74 block, and I'm pretty sure it's a 74 head as well.

Anywho, here's my take on what's a late and what's an early head: Headshots
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Kyle - 142, 145, and 244! - Oregon Volvo Tuners?

It's interesting to compare the side shots of these heads.

Yours: http://www.ovtuners.org/gallery/headshots/IMG_0844

Mine: http://webpages.charter.net/muddybiker/R_Sport_2.JPG

Put them up in two windows and flip back and forth.

1) You can see how much metal has been shaved of the bottom of mine. I actually had to use some shorter pushrods, the 'normal' length SBC lifter tubular pushrods I had were too long, even with the adjusters backed all the way off. Of course, part of that is also the decking of the block and the lowered rocker shaft and different geometry of the roller rockers, but it appears that something close to 1/4 inch was taken of my head.

2) Intake ports have a lot of metal taken out of the top of the curve. The stock head hits the rough casting area and start to plunge downwards rather abruptly. The R-sport head continues farther back in a more gradual curve that leaves a lot of the valve guide hanging out in the open (the ends of the guide are ground down to smooth tapers).

3) You can see more of the exhaust valve through the R-sport ports. I wish I had take some pictures of the valve seat areas on my head when I had the valves out, that was the most dramatic change on the whole head compared to my stock F head. The F head kept on constricting past the valve seat, leaving a pretty small hole. The R-sport head was significantly roomier, and the roof of the port above the valve seat had a different shape.
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'63 PV544 rat rod, '93 Classic 245 + turbo

I wish you had taken more pictures as well!!!

Those R-sport ports look a lot like what I'd imagine them to look like for optimum performance, based on what I've read by Smokey Yunick. Awesome to see it in action on a b20 head. Now, if only I had the skill to do a port job like this. HA.

I think when I get around to building a motor, I'll just toss on a mildly opened up head on top of my beautiful built bottom end until I can gather the funds for a niiiiiice head from sweden. Something along the lines of the MPPE style head, and I'll have to work with whoever I get the head from in order to figure out what I'll be using for an intake and exhaust. Megasquirted it'll be... =D
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Kyle - 142, 145, and 244! - Oregon Volvo Tuners?

John!
The correct term is "isthmi". (Since I lived on "the Isthmus" for 22 years
I know that stuff.)

Thanks for the shot of your head. Raises a couple questions:
1. The bolt or plug just above the front exhaust port - what is it?
2. The plate bolted on the side of the head in front of the front exhaust
port (Auxiliary Air Valve location on D-jets) looks VERY much like the little
steel plates on some B18 heads. Is it the same? (smaller than the AAV flange)
Thanks,
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George Downs Bartlesville, Heart of the USA!

1) Don't know what the bolt thing is. I took it off once, it's into solid metal. just a threaded hole.

2) I'm not sure if it is exactly the same as the B18 sized hole, but it is certainly smaller than the aux air valve on the injected heads. Did oil coolers hook up to that fitting? Might explain why it was on the R-sport head.

That was quite an eBay score, really. I think I paid $157 shipped. That head would probably cost $1000 or more to duplicate from John Parker or one of the Swedish shops. BIG valves (as big as you can possibly get without offset drilled guides), hardened exhaust seats, very well worked ports, much larger in the exhaust than my stock B20F head, double valve springs.
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'63 PV544 rat rod, '93 Classic 245 + turbo

You certainly got a deal on that head but........
There is really very little use for R sport heads these days, unless you really get a deal. Most of them have been milled for too high CR for the street.
These heads were designed well over 30 years ago and a lot of knowledge on head design and porting as been gained since then. I doubt that the R sport heads were even designed and tested with a flow bench. Put one on a flow bench and you will know why I say this.
Basically the ports are large but not well shaped. Some will flow a good deal of air because of their size, but that size tends to slow down the flow. This may work for high rpm HP but does not for faster acceleration through a wide rpm range. The deal of large port vs small ports gets complicated, because you can have small ports that actually flow more on a flow bench, will support faster acceleration in the real world in mid rpm ranges, but will give you less high rpm power because of there smaller volume. In an actual race situation which way to go often depends on what the track is like and who you are racing.
The R sport valves are large but tend to be shrouded. I've got a couple of R sport heads that I got to analyze or use, and ended up not using any ---- yet.

John
v-performance.com

I think you told me that when you showed it to me in KC.
(We need to get together again!)
If you ever get tired of it, let me know!!
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George Downs Bartlesville, Heart of the USA!

The head got shaved down a ridiculous amount by the previous owner. Something like 12.5 or slightly above on top of a 2 liter bottom end. I guess they were running it on 105 - 110 octane race gas? In any case, it will only work on pump gas with some dished pistons now, which add about 12cc's of volume to the chambers.
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'63 PV544 rat rod, '93 Classic 245 + turbo

how do you post big pictures like that?

I used the html 'img' tag.

Replace ( and ) with < and > in the following, and enter the URL of the picture in between the quotes (leave the quotes, though):
(img src="")
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'63 PV544 rat rod, '93 Classic 245 + turbo

The better heads first appeared in '73 models here in Australia. We got A,B & E versions but not the F. The difference is the short size radius is larger which makes for better flow after porting. If you look at the exhaust port from outside in, the floor of the port tapers upwards roughly 6mm. On the earlier heads it was only 3mm, for my own heads I build them up to 10mm with brass.