All Small Six 250 Engine Build

[pmuller9]

I have contacted schaferstephen about a set of autotec pistons on 300 inch rods and have agreed to purchase them when the banker cuts loose funding next month (please don't anyone buy them out from underneath me.) These are custom and have the .912 pins

As you already know the 300 six .912” pin connecting rod is the 1965 to 1968 forging number C5TE.
Have you located a set?

 

[twentyover]

As you already know the 300 six .912” pin connecting rod is the 1965 to 1968 forging number C5TE.
Have you located a set?

The pistons are already hung on rods. They were in an engine and have run time on them

 

[zunepuh]

Am considering undertaking a 250 engine build using the 2,5 rods and 3332 pistons. The target car is an old English sportscar that came with a 2.9l engine that was overweight and oversize. And underpowered. The plan would be to make the swap keeping the body pretty much uncut so it could go backward if I ever lose my mind. A requirement is that the car have a manual transmission.

Trying to find a flywheel for a 250. Unlike the 200's, it seems these are unicorns. I understand they are the same diameter as 302 wheels- is the crank bolt pattern different, a different balance factor, or what? What makes them unique?

In a fever dream, if I follow thru with this plan and am unable to find a flywheel, I thought maybe, while browsing ideas like bmw auto accessories, start with an automatic flex plate, have an aluminum disc machined to the correct diameter, and cut so a steel clutch surface is installed. I've gotta cut down on the pizza before I go to bed

Hello. The 250 flywheel uses the same bolt pattern and 157-tooth diameter as small-block Ford V8s, but it is neutral (internally) balanced, unlike most 302 flywheels which are externally balanced (28oz/50oz). That balance difference is what makes dedicated 250 flywheels rare and not directly interchangeable.

 

[twentyover]

Ref post #39, I managed to divert some coin the CFO's piggy bank and bought the piston/rod assemblies. Started looking for a local performance engine builder, found one in Kirkland that would talk to me. He wasn't interested in helping me with my bizarre intake ideas, but gave me the name of a retired machinist who did express an interest, so I busted the head off yesterday and will strip it tomorrow. I'll get it cleaned and pressure checked, then get it over to the machinist after he gets back from a vacation after Memorial day.

The engine shop was pessimistic about re-using the piston/rod assemblies, so I'll continue to disassemble the engine and get the block, crank, and piston/rod assemblies over sometime in June

Anyway, Mo Later

 

[twentyover]

Are the 200 and 250 pans interchangeable? The reason I'm asking is that my proposed application requires a rear sump pan that I understand was available on Foxstangs w/ 200, but the 250 was never available in that platform. I am also aware that Ford widened the pan rails on some long stroke engines (thinking Cologne V6 here) when they stretched the stoke.

Options are to hunt for a 200 Fox oil pan or get a front or rear sump pan and graft that sump to the 250 pan. I'll need to relocate the pickup, but that's a problem for future me

 

[aussie7mains]

Just modifiy the original sump. Our cortina sixes had a rear sump and pickup pipe for oil pump. I dont think Australia 250s and your 250s have the same sump bolt pattern. As to a head, Argentine? Or ditch the lot and go crossflow. You could still use your rods and pistons.

 

[drag-200stang]

The 250 pan is wider. The oil pumps are different, the bolt pattern is different and the 250 pump, pumps more volume. the pickup on the 200 comes off the bottom, the 250 comes off the rear side. The 200 pickup tube is too small.
Just fab the pan as needed and get a SBF V8 rear high performance pickup and mod to fit.
A member has grafted a rear sump 200 to a 250, but then you still have a stock pan with no oil control improvements and mods to get the pump area to fit
When fabing the pan make sure that the pump is in place and figure for the pickup.

 

[twentyover]

Twin HS8 might be better on a 250ci engine, theory says the carbs should be centred between cylinders 2-3 and 4-5. The 2 inchers are hard to find, 1 3/4 easier, MGB has them, tiny mechanical cam might be approprate. You could also try a header design I came up with. It works with the siamesed 3/4 exhaust port. Numbers are pipe OD in mm. length doesnt matter much, just what fits.View attachment 29560

HS8's would definitely be better suited for the 250 than the HS6, but are uncommon and expensive in the US. The only thing that I know of that came with them here were Jaguars, so add a zero to the end of any dollar amount we're talking about to get a good set. On the other hand, HS6's and HIF6's came on Volvo B18 and B20 engines, so are much more plentiful. Replacing the single barrel with two barrels of 1 3/4 each should provide as much venturi area as a direct mount 2 barrel, so I don't think I'm giving much away there. As an aside, HS6's came on MGc's (and various Triumphs), the MGB used a pair of HS4 or an HIF4 carbies. Agree 'centering' between 2-3 & 4-5, perhaps biasing toward 2 and 5 a little as much as physically constrained.

Regarding your proposed header design- have you had one built this way?

 

[aussie7mains]

HS8's would definitely be better suited for the 250 than the HS6, but are uncommon and expensive in the US. The only thing that I know of that came with them here were Jaguars, so add a zero to the end of any dollar amount we're talking about to get a good set. On the other hand, HS6's and HIF6's came on Volvo B18 and B20 engines, so are much more plentiful. Replacing the single barrel with two barrels of 1 3/4 each should provide as much venturi area as a direct mount 2 barrel, so I don't think I'm giving much away there. As an aside, HS6's came on MGc's (and various Triumphs), the MGB used a pair of HS4 or an HIF4 carbies. Agree 'centering' between 2-3 & 4-5, perhaps biasing toward 2 and 5 a little as much as physically constrained.

Regarding your proposed header design- have you had one built this way?

No i have not built any like this, I gave a way pre-crossflow engines years ago, however I have run them in the past, and feel that this design should work ok, and would retain that special sound that these engines have. It should be too hard to make them, ive done many header type things and the simple ones work very well on street engines. I did make a manifold for two 13/4 Skinners to a 250-2v engine I was running in a 70 Falcon, it seemed to work pretty well even though it was never really tuned, cant remember what carbs they were, some sort of pomme thing. GM here used CD Strombergs on some of their cars, the XU1 Torana was one of them, this worked very well for them. Look it up if interested.
The 250 was a strong engine and not too bad on fuel, we never had emissions on them here, they were phased out before emission began. Our later crossflows were emission engine.