Gutless now
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From: Laramie,Wy
Gutless now
I just finished swapping out my cam and fired it up and broke it in. At 35 min of running I let my foot of to let it idle and it sounded like my exhaust manfolds were off and died then my truck would not start or run. After playing with timing and that fun stuff finally got it running and sorta driving. But it was gutless. My question is those people that are running a summit racing 3500 cam or similar what timing are you running. I am at 8 degrees Btdc and does not feel right. It is back firing during start up and will not idle. I do know carb needs rebuilt as I think the back firing has trashed it. Thanks for any ideas of what else to look at and the timing info.
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From: Arkansas
I don't know the specs on your summit cam, but I have a cam with .5" of lift and I can run 15-18* with it, I am experimenting still trying to find the sweet spot.
Did you change the valve springs? Lifters?
Your 8* is WAY off, and would make it very hard for it to idle right. I would bump it to 15*, then reset your air/fuel on your carb and see if that don't make a huge difference.
Also, be sure to change your oil, very important step in the break in procedure. I changed mine immedietely after i ran it for 20 minutes so all the crud would come out with the warm oil.
Did you change the valve springs? Lifters?
Your 8* is WAY off, and would make it very hard for it to idle right. I would bump it to 15*, then reset your air/fuel on your carb and see if that don't make a huge difference.
Also, be sure to change your oil, very important step in the break in procedure. I changed mine immedietely after i ran it for 20 minutes so all the crud would come out with the warm oil.
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From: Laramie,Wy
I still have factory springs but did change the lifters. I planned on changing mine at 100 miles just to be sure it has the zinc it wants. I will try moving the timing to 15 and see what happens thanks.
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
Two things come into play.
Ignition timing -and- cam timing.
8* BTDC ignition timing should be okay with that cam.
With my recurved distributor I can only run 12* static before I start to run into detonation on midgrade pump gas.
Your having retarded ignition timing will not cause the engine to backfire through the carb.
How did you install the cam?
What timing set did you use, and what marks?
The Summit 3500/3501 do NOT want to be installed advanced beyond '0'
A performance cam with more duration and overlap will bleed off some pressure at low speeds and can tolerate more advance.
These R/V - Towing cams are not that way at all.
Ignition timing -and- cam timing.
8* BTDC ignition timing should be okay with that cam.
With my recurved distributor I can only run 12* static before I start to run into detonation on midgrade pump gas.
Your having retarded ignition timing will not cause the engine to backfire through the carb.
How did you install the cam?
What timing set did you use, and what marks?
The Summit 3500/3501 do NOT want to be installed advanced beyond '0'
A performance cam with more duration and overlap will bleed off some pressure at low speeds and can tolerate more advance.
These R/V - Towing cams are not that way at all.
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From: Virginia
The Ford valvetrain is not adjustable. So when you put in a aftermarket cam, it may work, it may not work. The valve lash needs to be checked. So what you need to do is run the engine around to TDC on #1 cylinder, take the valve covers off, and the go over to #1 rockers, loosen the bolts, and while wiggling the pushrods, slowly tighten the bolt till the play is just taken out of the pushrod. Then while looking at the ratchet, see how many turns it takes to tighten the bolt. You should be in the range of 3/4 to 1 1/2 turns to tighten the bolt. 3/4 of a turn you are barely pushing the lifter plunger down, over 1 1/2 and you are pushing it so far it's getting ready to bottom out. Less than 3/4 you will get alot of ticking in the valvetrain, more than 1 1/2 and that valve will not be closing all the way.
When you get done with #1, turn the engine crankshaft 1/4 turn, and then check the next cylinder in the firing order.
When you get done with #1, turn the engine crankshaft 1/4 turn, and then check the next cylinder in the firing order.
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
Well, there's no way to mix up a timing set with only one keyway.
Something is very wrong
Are you sure that your harmonic damper hasn't slipped?
i.e., with cylinder #1 at TDC on compression are the timing marks at zero?
Have you tried it with the vacuum advance disconnected and plugged?
I know when I first installed a 3500 there was so much vacuum I had to get a Crane adjustable advance unit and dial it back.
My truck was showing almost 60* advance with the stock advance unit on the distributor.
Something is very wrong
Are you sure that your harmonic damper hasn't slipped?
i.e., with cylinder #1 at TDC on compression are the timing marks at zero?
Have you tried it with the vacuum advance disconnected and plugged?
I know when I first installed a 3500 there was so much vacuum I had to get a Crane adjustable advance unit and dial it back.
My truck was showing almost 60* advance with the stock advance unit on the distributor.
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From: Laramie,Wy
I will check the damper but I don't think its slipped. Would to long of push rod make my carb back fire. Last night it stacked a 2ft flame out the carb with the ignition timing at 3 degrees. The vacuum advanced is plugged and I have not even had it plugged in after starting this mess of adjusting the timing
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pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
3 degrees with no vacuum advance added?
I think your cam timing must be far off or the valves are far too tight as Dave suggests.
There is no way the intake valve should still be open when the plug fires.
Are you sure the plug wires are in the correct order?
(sorry for the stupid question)
I think your cam timing must be far off or the valves are far too tight as Dave suggests.
There is no way the intake valve should still be open when the plug fires.
Are you sure the plug wires are in the correct order?
(sorry for the stupid question)
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Joined: Dec 2012
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From: Laramie,Wy
Plugs are in the right order and got my carb rebuilt. I retightened the rocker arms and it is running well except I can't get it to idle. Should I not run vacuum to the dizzy and see if that helps. Also with that how should I adjust my carb to accept the new cam? Thank you for the help.
pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
Glad to hear you got your valve lash sorted out. 
Where is your advance set right now? (without vacuum)
What does it show when you connect the vacuum?
Your sig says you have a 4180.
There's not much you can adjust except the idle mixture.
Tune with a vacuum gauge, or just a tachometer.
I used to set my 4180 1/8 turn out from highest vacuum.
I would work each side (back and forth) in small increments and then reset my throttle stop for 800 rpm if they got too high.
Where is your advance set right now? (without vacuum)
What does it show when you connect the vacuum?
Your sig says you have a 4180.
There's not much you can adjust except the idle mixture.
Tune with a vacuum gauge, or just a tachometer.
I used to set my 4180 1/8 turn out from highest vacuum.
I would work each side (back and forth) in small increments and then reset my throttle stop for 800 rpm if they got too high.
Senior User
Joined: Mar 2013
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From: Arkansas
Sounds like your A/F idle mixture is off a bit. Do what Jim recommended, you can set it off the highest idle, or the best way would be to get a vacuum gauge and set it off highest vacuum you can achieve, that should smooth out your idle.
I am a little worried that you didn't change valve springs though......
I am a little worried that you didn't change valve springs though......
Senior User
Joined: Mar 2013
Posts: 258
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From: Arkansas
Just because you got away with it doesn't mean anything....cam companies don't say to replace the valve springs for no reason. Not saying it is the problem, just saying it is an important item when performing an upgrade like this, and for good reason too.