6.9 IDI

[dieselfuelonly444]

1979 F250 6.9 Conversion

Hello all, since my last post I have traded my '86 dually for a 1979 F250 351M 4x4 4 Speed. I did the trade with the intention of doing a 6.9 conversion into this truck. First off, I was wondering if there were any intensive modifications I'd need to make as far as the underside or engine compartment to fit the IDI in it. I'd assume not as it seems I have a lot more room in this truck than the 86. Also when I go to look at engines are there any specific things I should look for or try to avoid. Any ways to tell the year of the engine without checking a serial number on the block or if the owner doesn't know the year. Just trying to avoid any of the block heater problems with earlier engines. Also, if anybody would happen to have a 6.9 in Ohio or surrounding areas for around 500 or lower. Doesn't have to be running as I'll probably end up rebuilding it before I put it in my truck anyways. Thanks.

 

[icanfixall]

Every idi engine is drilled and tapped the same. So any part on the outside will bolt to any other idi engine be it 6.9 or 7.3. Now the truck and van engines have different oil cooler headers and different drivers side exhaust manifolds. So with that I can tell you the 7.9 engine serial numbers started at 509,*** and the turbo 7.3 engines started at 1,116,331. I can't tell you what 6.9 engines started at nor what block serial numbers to avoid but other will have that for you. A simple way to know if your looking at a 6.9 engine is the serial numbers will tell you 6.9 in the first few numbers. Then the non turbo 7.3 tells you its a 7.3 and the infamous turbo 7.3 says 7.3&. Hope this gets you started on the looking.

 

[dieselfuelonly444]

Okay, thanks for the info. I'll keep my eye open for a 6.9

 

[Knuckledragger]

The early blocks (83, mostly) have an "A" cast into the side somewhere, all others have "B" from what I have read. Otherwise, everything else is the same.

Putting the IDI in a gasser bay will actually not be too hard, since there is less wiring necessary. Mostly, you will have to accommodate the extra weight of the engine and probably have to fabricate some engine mount brackets. Unknown: crossmember location and depth. Bonus: if there is enough room, you can use the E series driver side exhaust manifold, which has less back pressure then the F series.

 

[IDIBRONCO]

The B block on the 6.9 and 7.3 is thicker behind the block heater. There is a small concave for oil dipstick tube clearance. They also use different dipsticks and tubes. The a block dipstick tube is supported by a bolt in the lower part of the head while the b block tube is supported by a bracket that bolts to the valve cover. Of course they can be interchanged so it might not matter what dipstick and tube you have on your engine. I do know that you have to use the right dipstick for your tube. IIRC, the dipstick and tube are longer on the b block.