All Small Six Engine changes, rpm limit and cam specs

[Dragonlich1961]

I'm looking to install a new camshaft in my 61 ranchero. Currently it has a comp cams 260h. (Don't remember exact specs). Reason for wanting to install a new cam is I recently acquired an aussie head and 3 sidedraft weber intake. The carbs will be replaced with efi throttle bodies from borla, 2900 series. The new head setup will allow for much more air flow than my current e8, 32/36 adapter setup. With the new head, I also acquired some yellow Terra 1.65 rockers, which reguire new lifters.

I would like to match the new cam to the head to make most use of it. I know the head will support much more cfm, and therefore more rpm. What is a safe limit for these engines? Engine is rebuilt with ARP hardware at all 3 critical points.(head and main studs, rod bolts). Using a stock 68 block .020 over, with stock 68 rods(with arp), t5, a/c, 3.73 rear, header.
Thanks to super4ord for the head.

 

[aussie7mains]

Yella terra! First off, stick the 2v head on a 250, dont bother with small cubes, the head is really designed for that much displacement, yes the 200 might rev better, but overall you will be happier with the torque the bigger cubes will give you, this is especially true if you run a slushie (auto). Dont know why you would run the EFI rather than weber/delorto, the diffeernce in performance will be small, I would guess the cost will be about the same, not counting the fun you will have setting up the electronics!!! As to camshafts, crowcams here in Australia do a line in cams for precrossflows, IMO if you thinking of a slushie then the 63602 would suit, if your going manual trans then the 63651 is more for you. As to maximum safe rpm, if the USA engine is a good as the Australian one (not known) then a 200 could go 6000rpm and 250 5500rpm on stock stuff without too much problems, keep in mind your not a racer, and you will only see full power, full rpm very infrequently, fatigue is what kills most engines. lots stress for a long time= blown up! Crowcams:-https://www.crowcams.com.au/Portals/0/Crow2020/CrowCams2020.pdf?ver=2019-12-18-095023-240

 

[Dragonlich1961]

Yella terra! First off, stick the 2v head on a 250, dont bother with small cubes, the head is really designed for that much displacement, yes the 200 might rev better, but overall you will be happier with the torque the bigger cubes will give you, this is especially true if you run a slushie (auto). Dont know why you would run the EFI rather than weber/delorto, the diffeernce in performance will be small, I would guess the cost will be about the same, not counting the fun you will have setting up the electronics!!! As to camshafts, crowcams here in Australia do a line in cams for precrossflows, IMO if you thinking of a slushie then the 63602 would suit, if your going manual trans then the 63651 is more for you. As to maximum safe rpm, if the USA engine is a good as the Australian one (not known) then a 200 could go 6000rpm and 250 5500rpm on stock stuff without too much problems, keep in mind your not a racer, and you will only see full power, full rpm very infrequently, fatigue is what kills most engines. lots stress for a long time= blown up! Crowcams:-https://www.crowcams.com.au/Portals/0/Crow2020/CrowCams2020.pdf?ver=2019-12-18-095023-240

Usually I am a fan of bigger cubes, but a 250 does not fit well in my chassis. And have a running driving 200 in the car now. Efi is part want, part need. I want to push my abilities, and to have the ability to daily it. Need because the efi throttle bodies are almost 2 inches shorter then the carbs and are required to clear the shock tower. Carbs ( no stacks) clear the tower by 1 inch.

 

[aussie7mains]

I have a 65 Falcon "ute" with a 250 crossflow in it, here they and the pre-crossflow fit easily, where is the problem area? As to carb clearance, you could always run something like the crossflow EFI, which arches over the rocker cover, or run downdraft carbs/efi. The difference between a single downdraft (Holley for instance) and a isolated runner 6 throated setup, on the street would be minimal, and probably not justified expense wise. It looks like you want to challenge yourself, thats fine, just a HF. Have you considered the Argentine head, it would give more room on the LHS. Of course the crossflow would be better still, but a bit ut there" for you guys. IMO the 250 would be worth the trouble to fit and get right. This is my ute, is your engine bay that different to this?

 

[Dragonlich1961]

Engine bay is similar, I belive hood hight changes a little. A cross flow 250 could be made to work, how ever finding one in America is harder then the 250 2v head. Plus the 250 is not as supported over here in the states.

 

[pmuller9]

As Aussie7mains posted, 6000 rpms for a short period of time would be fine.
If you want to make power to 6000 rpm then you would be looking at a cam with a maximum .050" duration of 230 degrees.
Anything in the upper 220s would be fine.

The Schneider 145H has a 230 degrees .050" duration.

145H Ford 144-250 Hydraulic Lifter Camshaft

145H Straight 6 Hydraulic Lifter Camshaft <br /> RPM Range: <font color="red">2500-6500</font>

schneidercams.com

If you don't mind a solid lifter cam the Schneider 137F has a 228 degree .050" duration.

137F Ford 144-250 Solid Lifter Camshaft

137F Straight 6 Solid Lifter Camshaft <br /> RPM Range: <font color="red">2000-6000</font>

schneidercams.com

If they don't have cam cores for the 200 six then see if they can grind your Comp 260 out to upper 220 degree .050" duration.

 

[bubba22349]

I have a 65 Falcon "ute" with a 250 crossflow in it, here they and the pre-crossflow fit easily, where is the problem area? As to carb clearance, you could always run something like the crossflow EFI, which arches over the rocker cover, or run downdraft carbs/efi. The difference between a single downdraft (Holley for instance) and a isolated runner 6 throated setup, on the street would be minimal, and probably not justified expense wise. It looks like you want to challenge yourself, thats fine, just a HF. Have you considered the Argentine head, it would give more room on the LHS. Of course the crossflow would be better still, but a bit ut there" for you guys. IMO the 250 would be worth the trouble to fit and get right. This is my ute, is your engine bay that different to this?

View attachment 14563

Hi aussie7mains, the main problem we have here in fitting the US 250 Six Block into the 1960 &1961 cars is the 250's Block is1.661 inches taller than the 200 Six Block. The pre 1962 Falcons and Comets chassis also have a smaller Transmission tunnel so all most all of the 250 Six Transmission combos are the bigger SBF V8 Bell Housings with a 157 Tooth Flywheel or Flex Plate for a tighter fit needing a lot of Hammer work to the lower section of the Firewall and tunnel to fit the those big bells in. But yes they can be fit into them and dropping the front motor mounts down about 5/8 to 3/4 inch helps too.