More On Log Head Mods

[Anonymous]

Having a spare head and lots of reading has got me thinking about carby upgrades and I've got a lot of good ideas from you guys. First off though, I have a '75 head off of a 250 CI US made engine and I would like to discuss different options for carburation, particularly, in using fuel injectors coupled with a fuel rail and a throttle body. Do you suppose we could drill and tap holes in the log for the purpose of mounting injectors, and then mounting a throttle body on the carb hole. I got this idea from a recent magizine article where the guy built a big FE Ford engine doing this by using a regular intake manifold drilled for injectors with a throttle body mounted on the carb boss utilizing a Chevy module to control the injectors. He had very good success according to the posted horse power figures. After reading the article I thought this might be a super trick for our log heads. So for the sake of disscusion...I think the carb hole in my log is 1.75", and I think it would be fairly straight forward in adapting a throttle body to fit, but my theory is based on the maximum amount of air I can suck through this adapted throttle body and coming up with an injector size based on that figure. I then need to pick your brains for which computer to use and how to manage the set-up. Sounds easy, right?This has got to work well. Has anyone done it yet on a six?

 

[rbohm]

8) yes it can be done. in fact accel has injector bungs, raw fuel rails, etc to do what you are thinking of doing. in fact as i recall they even have bungs that are threaded along with injectors that are threaded, and fittings that clip to the top of the injectors so you can use an fittings and run hose to each injector.

 

[MustangSix]

I started down that path several years ago. The intent was to add injector bungs as you describe and use a Tempo throttle body which would simply bolt on in place of the carb. Then I came to my senses.

First, at the time there (1996-1997) there wern't really any cheap EFI ECU's out there. I would have had to use an expensive off the shelf aftermarket unit or hack a GM ecu. Today there's Megasquirt, but still, my conclusion would probably have been the same.

Second, even though the 1bbl-on-a-log is a compromise fuel/air delivery system, the real issue with the head is not delivering fuel. It's airflow. Log heads bite bigtime in the airflow department. You can port the thing till the cows come home but you very quickly hit an airflow impediment that either requires you to hack the log off or to adapt something else like an Aussie 2V head. Just swapping to a 2V head will net you 25 hp with no other changes to the engine. Swapping to EFI will not do that.

So the bottom line is, you will probably gain some efficiency, but little more power for your efforts. Engines are air pumps and getting air to flow decently thru them is far more important than tweaking the fule delivery. If I were going to retain the log (which is not really a bad design, btw) I would look at controlling fuel/air mixing more carefully by using a TBI instead.

 

[80broncoman]

I think if you open up the intake opening to take a larger throttle bodie like gezeer did to his, Then this could work well. if you can make a ford harness off of a 3.8 bent six work you could use almost any throttle bodie. the ones that come to mind are 5.0 non-HO (155-160hp factory) and of course 5.0 HO (225 hp factory) i think these would work good on a six. you would of course have to marry a TFI ignition to the dizzy.

 

[80broncoman]

I forgot something, you might want to look at a 4.0 jeep engine to see if the fuel rail and regulator can be of any use.

 

[rbohm]

8) i still think that using a megasquirt computer, and three tempo throttle bodies in a 3x1bbl settup like the offy would be the way to go. three injectors to feed six cylinders, and a/f distribution at its best in this case. you would see the same power increase the 3x1bbl carbs would give you, but since the throttle bodies would not be staged, you would get in increase down low as well, and likely better fuel economy as you can now tightly(fairly) control your fuel mixture.

 

[SONNY]

get yourself a 250 2v head from over here,while your at it get a tripple webber manifold and carbs.this will chew off your efi anyway.a stock 250 2v in australia had 170hp.

 

[Anonymous]

You need somthin like this
http://allclassifieds.com.au/c/ac?a=vi&i=1853622805

 

[Anonymous]

"get yourself a 250 2v head from over here"

I did. That's the reason I have a spare engine sitting in the driveway. However, I opted for the whole engine...

 

[Anonymous]

what are the bore spacings of a 260 and 223?

mabe a 223 cliffords intake will fit a 250 log with hacked off intake.

 

[CougarT]

I'll second 80broncomans thoughts and add the thought that you are looking for a MAF system, not speed density, if you you plan to adapt OEM stuff. If you buy aftermarket, well, anything goes. This would be true whether it's an AUS head or not.

http://www.slantsix.org/articles/dibias ... ersion.htm
This guy adapted a GM MAF system on his slant six.
Makes sense to me, 'cause the only (early, fewer sensors) MAF system for Ford sixes was the 300 '96 Cali version. (I stand to be corrected here, and would welcome knowledge of an adaptable Ford V6 MAF system).