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I just got my 66 Gal back about a week ago from the engine re builder. He turned it into a 390. Bore to 030, flat top pistons, and a mild cam. I do still have my stock exhaust manifold and pipes so I know that will help some but my throttle response is garbage! I do also have a new Holly 600cfm 4 barrel. The throttle response feels the same as it did before the rebuild. Before the rebuild it was on its last legs. Smoked, hardly accelerated, not good.

Now Im trying to figure out if this is normal for a FE engine or the rebuild was junk? I know FE's are not known to be terribly fast engines but I was excepting a little more then that. I think with the rebuild it should be around 300 hp. It feels like 90hp. Any suggestions?
 

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What ignition system and where is the timing at?

Timing can make a HUGE difference in throttle response.
 

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ive had best luck with similar setup at 15 degrees btdc and vac advance hooked up to manifold, not timed port. try that. also, verify firing order.

holley.... 4160?
 

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Make sure your total timing is at around 36-38 degrees at around 3000rpm. Your initial timing will be once it is at idle. Do this with the vac advance disconnected.
 

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I would expect it to be timing related too. If it is a Pertronix distributor or stock Ford, they deliver with very slow curves. The timing curve, as said above, makes a HUGE difference.

As far as curves, a mild 390 usually likes 38-40 total (no vacuum), and 12-14 initial, all in by 2800 or so. I then use ported vacuum (dead at idle on top of that). 36-38 is fine too, but if you don't have tight quench and higher compression, they like a little more.

When you check it, check it at various RPM from idle until it stops advancing, a dial back light or timing tape is required and report back, once we know where you are can give better recommendaitons.. Wouldn't be a bad idea to check TDC with a piston stop first too.
 

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If it isnt fixed after messing with the timing please describe the poor thottle reaponce better.
Is it a bog where the car slows before getting going again?
Or is it is it flat when giving it more throttle. You can here the throttle is open but you get no acceleration and the engine never picks up.
Or does it actually misfired and pop until letting back off the throttle?
 

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If it isnt fixed after messing with the timing please describe the poor thottle reaponce better.
Is it a bog where the car slows before getting going again?
Or is it is it flat when giving it more throttle. You can here the throttle is open but you get no acceleration and the engine never picks up.
Or does it actually misfired and pop until letting back off the throttle?
I'll have time to mess with the timing and carb tomorrow hopefully. At this point, I drove it around the block today because I put an aluminum radiator in it, and had to floor it to get it up to the 40 mile speed limit. It doesn't sou d like it's reveling, just slowly accelerating. It just feels like it doesn't want to go, like a bog.
 

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Dang, new carburetor, new ignition, new engine. Same old spark plugs?
 

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1970 Ford XL Sportsroof 390 Fe
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Bro I have a 390 Fe engine in my 1970 Ford XL, I rebuilt the engine in 2020, and I stated running it in October or 2020 after a rebuild. I’m about to be running it for a year. Anyways bro, the acceleration could just be because of bad timings, because mine runs very good on the highway. Timing is difficult to find with these engine. I saw on google people put it 15 degrees forward or 5 degrees back but it just depends on what your engine wants. And as for the smoke, it’s probably because of the value seals. If he replaces them, then he probably used the rubber valve seal which hold oil on them longer than the other ones that are aluminum or metal type material. Or could just be that your exhausts are rusted or have a hole. My vehicle smokes every morning but once I drive it close to a mile, then all the smoke disappears for the rest of the day. You have to let the engine break in.
 

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1970 Ford XL Sportsroof 390 Fe
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Bro I have a 390 Fe engine in my 1970 Ford XL, I rebuilt the engine in 2020, and I stated running it in October or 2020 after a rebuild. I’m about to be running it for a year. Anyways bro, the acceleration could just be because of bad timings, because mine runs very good on the highway. Timing is difficult to find with these engine. I saw on google people put it 15 degrees forward or 5 degrees back but it just depends on what your engine wants. And as for the smoke, it’s probably because of the value seals. If he replaces them, then he probably used the rubber valve seal which hold oil on them longer than the other ones that are aluminum or metal type material. Or could just be that your exhausts are rusted or have a hole. My vehicle smokes every morning but once I drive it close to a mile, then all the smoke disappears for the rest of the day. You have to let the engine break in.
 

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If it’s an automatic, do you have the kick down set up correctly? Some cams don’t like running through stock exhaust. Does it rev in neutral? Is the carb set up correctly?
 

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I was having similar issues with my 390 in my 64. I eventually bought an msd pro billet distributor, 6al box, and blaster2 coil, and msd plug wires. I sent the distributor to Faron Rhoades for a custom recurve. I also swapper to sniper efi. Game changer.. my 390 moves the ole 64 pretty good now.

BC
 

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i'm wondering if the rebuilder timed the cam correctly?

that aside, assuming everything is assembled correctly, there's no reason it shouldn't run well when tuned reasonably well, not even perfect. If its struggling to get to 40 mph there's something obvious thats missing. also, simple but might be over looked, is the choke opening up when the car is warm? if its hanging shut might explain a lot of this.

I drove mine to work the past 2 days, 80+ mph easy on the highway smooth as glass, carburated and running 14.2-14.8 afrs at light throttle with nice roll on throttle response w a 600 carb.
 

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So after checking everything it was still crazy slow with terrible response. I took it back to the shop and they found 2 bent rods!!! They are fixing it but now I'm reluctant on their ability. I probably drove it about 15 miles, all of which were very slow. Hopefully it's fixed when I get it back and have no other issues.
White Gas Tool Boats and boating--Equipment and supplies Metal
 

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That's what scares me. The builder said it may be due to bad gas. Not sure if I buy that. I don't think they will own up to anything. Any ideas as to what I should look for?
 

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That's what scares me. The builder said it may be due to bad gas. Not sure if I buy that. I don't think they will own up to anything. Any ideas as to what I should look for?
I’m just a backyard mechanic, but from my perspective bent pushrods come from incorrect cam timing, incorrect rocker arms, incorrect rocker arm studs (or installation), or improper rocker arm gap. There’s always the remote possibly of a backfire.
Good luck. Please post the actual reason.
 
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