390 Timing
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Joined: Jun 2006
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From: Vacaville, Ca
390 Timing
Hello everyone
I have a 1970 motorhome built on a CS chassie that I have removed the entire motorhome part and built a 40" sleeper off the cab and installed a 10' flatbed on the chassie after cutting 5' off the frame.I have removed the 360 it came with and swapped in a 390 from a 68 f100. While the motor was on the stand I installed a crane truck cam CRN-343904 and timing gears,also installed Elderbock Performer intake with Holly 570 street avenger carb,Pertronix kit for the dist,and Dynomax headers. I fired it up yesterday and it lite right off.I set the timing at 6 deg advance but it seemed to have trouble holding there an stay running.Now I was running with open headers so would the lack of back pressure cause problems also do I need to make adjustements because of the cam and carb.If I set it at 8 deg advance it stays idleing and running much better. I would appreciate your thoughts and opinions..Thanks
I have a 1970 motorhome built on a CS chassie that I have removed the entire motorhome part and built a 40" sleeper off the cab and installed a 10' flatbed on the chassie after cutting 5' off the frame.I have removed the 360 it came with and swapped in a 390 from a 68 f100. While the motor was on the stand I installed a crane truck cam CRN-343904 and timing gears,also installed Elderbock Performer intake with Holly 570 street avenger carb,Pertronix kit for the dist,and Dynomax headers. I fired it up yesterday and it lite right off.I set the timing at 6 deg advance but it seemed to have trouble holding there an stay running.Now I was running with open headers so would the lack of back pressure cause problems also do I need to make adjustements because of the cam and carb.If I set it at 8 deg advance it stays idleing and running much better. I would appreciate your thoughts and opinions..Thanks
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Senior User
Joined: Jun 2006
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From: Vacaville, Ca
Originally Posted by 1975Ford
Try setting the timing at 12 degrees BTC. This works for me.
What type of vacuum are you running to distributor vacuum advance, ported or direct vacuum?
What type of vacuum are you running to distributor vacuum advance, ported or direct vacuum?
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The ported vacuum on carburator will have no vacuum during idle. When the engine is revved, the ported vacuum will gradually increase with the rpm's of the engine, and the vacuum should be noticable with the finger scale.
With the timing light, and with the vacuum hose plugged into the timing vacuum advance on distributor, make sure the engine timing is advancing.
Did you break-in the cam for at least 30 minutes?
With the timing light, and with the vacuum hose plugged into the timing vacuum advance on distributor, make sure the engine timing is advancing.
Did you break-in the cam for at least 30 minutes?
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Crane recommends bringing the engine to a 1500 thru 3000 RPM and getting the engine running fairly smoothly and vary the engine speed from 1500-3000 RPM in a slow, to moderate, acceleration/deceleration cycle. Using Shell Rotella T oil; Chevron Delo 400; or Mobil DELVAC oil for the break in period. Do Not use synthetic oil for 5,000 miles of the engine /cam.
Last edited by 1975Ford; Nov 8, 2006 at 02:11 PM.
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Vacuum Advance
Originally Posted by allwthrrider
Hello everyone
I have a 1970 motorhome built on a CS chassie that I have removed the entire motorhome part and built a 40" sleeper off the cab and installed a 10' flatbed on the chassie after cutting 5' off the frame.I have removed the 360 it came with and swapped in a 390 from a 68 f100. While the motor was on the stand I installed a crane truck cam CRN-343904 and timing gears,also installed Elderbock Performer intake with Holly 570 street avenger carb,Pertronix kit for the dist,and Dynomax headers. I fired it up yesterday and it lite right off.I set the timing at 6 deg advance but it seemed to have trouble holding there an stay running.Now I was running with open headers so would the lack of back pressure cause problems also do I need to make adjustements because of the cam and carb.If I set it at 8 deg advance it stays idleing and running much better. I would appreciate your thoughts and opinions..Thanks
I have a 1970 motorhome built on a CS chassie that I have removed the entire motorhome part and built a 40" sleeper off the cab and installed a 10' flatbed on the chassie after cutting 5' off the frame.I have removed the 360 it came with and swapped in a 390 from a 68 f100. While the motor was on the stand I installed a crane truck cam CRN-343904 and timing gears,also installed Elderbock Performer intake with Holly 570 street avenger carb,Pertronix kit for the dist,and Dynomax headers. I fired it up yesterday and it lite right off.I set the timing at 6 deg advance but it seemed to have trouble holding there an stay running.Now I was running with open headers so would the lack of back pressure cause problems also do I need to make adjustements because of the cam and carb.If I set it at 8 deg advance it stays idleing and running much better. I would appreciate your thoughts and opinions..Thanks
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