Ok, after killing myself getting my new crate 300 to work with the old pollution controls, I had enough. Stripped it and went with the offy intake, 390 holley, new distributor for a 75 f250 and an Ignitor 2 electronic conversion, vaccum advance. My truck is an 85 f250. My timing used to be 9 degrees btdc. Has this changed now with the new parts?? Where should I be timing it now with the new setup??

By the way, WHAT A DIFFERENCE!! This truck is an animal now.

 

what is it supposed to be set at? i know the EFI 300s are 10* BTDC. i would try advancing it 2* each time to see what works best. then take it for a drive and see how it runs and hear for any signs of pinging or pre-detinionation (SP).

 

your right. According to the sticker in the engine bay, it was supposed to be 10*. But theat was with the other ignition and all the pollution controls in place. Thats why I asked for those that have this setup, was the timing kept the same or changed.

 

my 85 300 is set @10 bdtc. With a duraspark dist. from a 79, 1 bbl w/no emissions from 78, no egr carb spacer, and a manual choke. (efi exhaust/walker pipe/2.5"exhaust too). this is in a 79 bronco. I too have wondered about the timing differences between tfi and duraspark. I've thought about this as the block and internals should be the same until 87, when they switched to efi and the head change, however, the moment the spark is produced between the tfi and duraspark can't be exactly the same, therefore what would the timing be judged from? My haynes and chiltons don't agree either.

 

Yea, I was going thru some older haynes, and back to I think 73 they were still calling for 10* in a 250. Now in 71 which was just a regular vaccum advance dist and coil, they called for 6*. I experimented with both settings, and found no apparent difference. I am set at 10* as of this writing, and unless I find otherwise, I will keep it there.

 

I have a copy of the Ford shop manual for my '77. For the 300, factory timing is at 10* +/- 2*. Before I removed the stock manifolds and carb, my truck wouldn't run at anything other than about 15*. When I put the Clifford intake, Holley 390 and Clifford shorty headers on it, I reset the timing to 10*. BUT, it still idled pretty rough, so I bumped it up a little, and I think I ended up at 12*.

All this to say that I think it depends on your engine and how it is worn internally. Whereever you can get the right idle with maximum manifold vacuum is where you should leave it!

 

I've heard that you don't want the timing set for maximum possible vacuum, but that it's better to advance timing to achieve maximum vacuum, then back it down 1Hg. (Someone with more experience ought to confirm this, since I don't know for sure)

 

thanks red77 for the info. I will compare timing to vaccum in the next couple of days and see what happens. I got it at 10 right now and feels good, but has a hesitation at startup and thru the entire drive cycle. What i mean is that I still feel it when at cruising speed. Just touch the throttle, and it hesitates then takes off. I think the new holley just isnt tuned right.

 

On my 1981, the emission sticker says to adjust the timing to 6º BTDC, with the advanced unplugged and blocked. With the vaccume advance plugged back in it reads around 10º BTDC.