I have a shop manual for my '69 F250 and it has the following for cam specs...

Lobe LIft int/exh .2470/.2490 & Theoretical Lift int/exh .427/.430

but nowhere can I find the duration information. Does anyone know what the duration of a stock 390 is?

I'm looking to replace the stock with a slightly lifted cam with a slightly longer duraction, but I don't konw my starting duration.

Thanks for your help

Cheers, Doug

 

Stock advertised duration will be less than 250 degrees. Anything above that is where you want to go. A 250-260 degree range is considered to be an improved stock type cam. 260-270--RV type, 270-300 is what most high performance cams are.

 

Baddad, Thanks for the tip. I'm considering the Competition Cams 252H, I think that falls within your numbers.

Cheers, Doug

 

Old TRW catalog specs are as follows

Int. valve lift .428 duration @.050 193 degree

Exh valve lift .431 duration @.050 199 degrees

Overlap @ .006 cam lift 51 degrees

Lobe centers 113* intake / 111* exh

Timing events @ .050 lift Int Exh
open close open close
BTDC ABDC BBDC BTDC
17* 29* 31* 12*

I hope this helps Hotwrench

 

HotWrench - Exactly what I needed. Thanks, I going to save this somewhere for my future projects as well.

Thanks again, Doug

 

If you've got an 8 to 9 to 1 comp ratio the 268H ought to work well for you also.

 

Here's the specs I have:

Intake lift: .427"
Exhaust lift: .431"
Valve duration, seat-to-seat: 256/266
IVO:13
IVC:63
EVO:63
EVC:23

Here's some other good cam specs I found:
http://web.ics.purdue.edu/~stanchfi/fe-camshaft.html

 

Kurt- Awesome Chart, I had been thinking of using the CompCam 252H with:

Intake lift: .468"
Exhaust lift: .468"
Valve duration, seat-to-seat: 252/252
IVO:20
IVC:52
EVO:60
EVC:12

But now seeing my starting point, I'm thinking the 268H would be better:

Intake lift: .494"
Exhaust lift: .494"
Valve duration, seat-to-seat: 268/268
IVO:28
IVC:60
EVO:68
EVC:20

Thanks again for the charts and tips. If you have a suggestion on a different cam, I'd love to hear. Also, I'm still seeking some more opions on my Distributor. I'm kind of leaning toward a Mallory, but your thoughts would be nice.

Cheers, Doug

 

I'd look at something in the Xtreme Energy line. I think the following one would be good for what you're doing:

XE262H
Intake lift: .513"
Exhaust lift: .520"
Valve duration, seat-to-seat: 262/270
IVO:25
IVC:57
EVO:69
EVC:21

I'd look elsewhere than Mallory for a distributor. I had one of their Unilite distributors. Almost every time you hook up the wiring, the module burns out. Then it's another $45 to replace that. I'd go find a '75 or '76 truck with the Duraspark setup.

To really, really, do this cam thing right, you'd have to increase the compression ratio. But it'll run fine with that cam.

 

OK, This cam looks like much bigger than I was thinking, but someone else suggested I increase compression ratio as I drive mostly over 5700'. What range of compression are you thinking 9:1?

I'd like to keep it a daily driver and not die everytime I hit the pump. Low end torque and a descent cruise power @70mph is what I'm looking for. I have a 3.54 w/31" rubber, so keeping the revs in the torque would be nice.

This distributor your talking about, it must be rebuildable, becasue how will you konw if you get a good one from a pick-n-pull? What engines can I get the Duraspark from so that it will mate with mine? Only 390's? Is there markings of model numbers, etc I should look for of the body of the dissy?

Thanks again.

 

A duraspark from any FE will work. Basically, you're looking for a '75 or '76 truck, with an FE. Look for one with a magnetic pickup where the points would be, some extra wiring, an ignition computer, and a coil. Get the whole system.

If the distributor is froze up, or otherwise worn out, you can get a replacement at the parts store.

Compression somewhere between 9 and 9.5:1 would most likely be adequate. Check out the KB / Silvolite number 1116 pistons. They have a 9.5cc dish, and the compression would be somewhere between 9.25:1 and 9.75:1, depending on the head gasket. At your altitude you might consider something toward the upper end of that range, especially if you dont get down out of the mountains that much.

 

Do you have any pictures of this ignition computer? I've not looked into this at all. Is there a website with information about the dura-spark or is there an aftermarket making replacements and I'll checkout there stuff and then go the pick-n-pull.

Also, the set-up of this system seems a little more complicated than a electronic (points replacement)system, is it? If there is some reference material I should read let me know.

Thanks tons

 

You know, I did some research a while back, and thought Duraspark would be the way to go. Now I'm not so sure. After looking for your wiring diagrams, I found a few older threads on here and other sites that say the Duraspark modules can burn up.

Now I'm not really sure what to do. Everything I read about the Pertronix points replacement seems to be good. You might consider one of those and an aftermarket ignition box.

What does everyone else think here?

 

The aftermarket electonic module are the ones that keep needing replacing.
The Motorcraft electronic module are the best suited for Duraspark II ignition and are the most durable.
The Motorcraft electonic module with the blue grommet at the module is the one of the best module for Duraspark II ignition, the blue grommet is located where the wiring goes into the module, and try finding one of those.

If you can find a donor truck with the Motorcraft electronic module, wiring harness from the module to the distributor and coil.
Then just purchase either a new or rebuilt distributor with stator and reluctor.

Any truck with the electronic ignition will work. I have used the wiring from module to distributor off the trucks with 6 cyl. I perfer using the Duraspark II setup, but Petronix will work too.

 

I killed my original DuraSpark module by nursing a bad battery and letting the alternator's voltage "spike". I figure. Anyway bought a BlueStreak in 1979 and it's still in there going strong.

I modify the crap out of everything, it's what I do, I can't help it. :/

A few years ago I wanted to move the vacuum reservoir (tha canna tomatas;) back out of the way but figured, it was blocking the radiant heat from the engine from hitting the ignition module. :/ Hmmm....

I moved my module to the otherside of the hood hinge (otherside of the square humpy part of the fender apron;).

I never claim my crazy ideas are any good for anyone other than me. :)

But the point is... get a BlueStreak or some name brand of DuraSpark module and it'll outlast you if you don't mess around and screw it up yourself.

Like don't disconnect the battery terminal while the engine is running.

I figue my bad battery did that for me.

Alvin in AZ