[updated:LAST EDITED ON 06-Mar-02 AT 11:09 AM (EST)]sauerf100s(No Email Addresses In Posts!) I had this elsewhere, but I just found out I had this in the wrong place. I still haven't solved the problem.
I thought I knew a little about being a mechanic, but this one has me stumped. I just rebuilt a Ford 302 engine, to replace a 300 6-cyl. in a 65 F100. The engine is bored .040," fitted with Keith Black hypereutectic pistons and Total Seal rings, `decked, align honed,balanced and blueprinted. Rebuilt 69 302 heads with oversize valves, three angle valve job, ported and polished, screw in studs with guide plates, springs to match the cam (installed at correct height), and roller rockers. Cam is Blue Racer .472/.496 lift and 280/290 degrees duration. Pete Jackson geardrive timing set, set up at 0. Carter performance fuel pump, Holley 600 double pumper with 68/78 jets, 6.5 power valve, on a Weiand Stealth manifold, everything port matched. Ford Duraspark distributor fired off by a MSD 6-A box (Instead of Duraspark control module). Accel super coil with new Accel wires, cap, and plugs. Hooker headers, Flow Tech mufflers, 2 1/4" mandrel bent full-length exhaust. Behind the engine is a 94 Cobra T-5 tranny with a Hays clutch set, going to a 9" rear with 3:50 gears.
I set the timing at 10 degrees BTDC, and adjusted the valves at 3/4 of a turn preload. The oil pump was primed before installing the distributor of course. I'm trying to give you all the details, so maybe you can figure this out. The engine started and ran right off, and it was broke in at about 2500 RPM's for a half hour. Then I checked the carb float level and other carb adjustments, and optimized the timing by ear. After making final adjustments on the clutch cable, I took the truck for a drive. I just drove around town for the first 50 miles or so, and the engine ran great, but I never got on to it. I went back home, changed the oil and filter, and went out on to the interstate.
While going through the gears, the engine would run great to a certain RPM, and then just fall flat. Almost like it wasn't getting gas. Starting from a dead stop, it would have great power at first, and just fry the tires, and then all of a sudden it would lose power and barely run. If I let off on the gas when this happens, it will continue to run well, until flooring it again. The same thing happens if I step on the gas gradually. Runs great to a certain point, and then @#$%'s the bed. I have a glass fuel filter, and it stays full of fuel. I don't have any way of checking the fuel pressure. I have all 3/8" fuel line coming from the stock 5/16 steel fuel lines. At first I thought the fuel line was collapsing, so I rotated the fuel pump, and shortened up the fuel line and made it straight. Didn't do any good, same problem. I've tried adjusting the timing, checking the plugs to make sure the air/fuel ratio was close, and checking all the wire connections and clamps on the fuel lines. I'm going to swap out the carb tomorrow, but I really don't think that's the problem. At this point, I'm not sure if it's electrical, fuel delivery, or the Chevy valves in my heads (just kidding). I have no idea what the problem is.
If you can come up with some suggestions of what the problem is, you would really help me out a bunch. I've put a lot of time and money into this truck, and it really bums me out the way it turned out. I've had many projects in the past, but have always been able to make things right. Hopefully you can get back to me before I start banging my head against the wall.
Many Thanks,
Steve

 

First of all, I want to thank everyone for the suggestions. I tried swapping out the carb for the Carter AFB I have on a truck with a 352. It ran exactly the same. Then I replaced the short hose under the rear of the cab. It had cracks in it, and started to leak as soon as I touched it. I thought I found the problem. NOT! I went for a drive, and it was a LITTLE better, but still cut out at high RPM's. I tried loosening the gas cap too, but that didn't do anything. I went back and checked all distrib wire connections. All were tight and clean. To to hit on some of the comments and suggewstions I got so far: My MSD has no rev limiter. It's the 6-A type. The vacuum advance seemed a little stiff before I installed the distrib, so I cleaned it and lubricated it first. Is it possible to be too loose? At idle, my exhaust smells a little rich, but that's the way a double pumper always has been on any of the engines I've had. Maybe that's a sign of being jetted too rich. I've played with the idle mixture using a tach/dwell to get best RPM at idle. Still smells rich. Funny thing is, no black smoke when I hit the gas hard. And the plugs appear to be burning real clean. Since the original carb is a double pumper, the secondaries open as I push down on the gas more. It has progressive linkage. I'm kind of confused by Mark Covill. First you say to set the timing with vacuum advance plugged (which I always do) Then you say that there should be no vacuum at idle. HUH? The port where I had the advance hooked to at first has nothing at idle. Another truck I have was this way too, and I could never get it to run good at low RPM's. Once I connected the advance to the bottom of the carb (low vacuum at idle), it ran a lot better at idle. So I applied this theory to the built 302. It too ran better at idle. It got rid of the slight misfire I had at idle also. I've played with the timing a lot. I advanced it until it wouldn't hardly turn over while trying to start. Then I retarded it until it wouldn't barely idle. I went back to a happy medium, and it seemed to like that the best.I know all about setting the float level on Holley carbs. I've been around them for over 20 years, and that was one of the first things I learned. I always have a tuff time getting the jetting just right though.
I AM using a Melling high volume oil pump. I always have in the past though, and never had a problem. Maybe it's a problem now, since I installed a windage tray. This may keep more oil down in the pan where it belongs. I don't know about that theory though. It sounds great while cranking to start. It doesn't even go a full turn before it fires. And once it's warm, you don't have to hit the gas. it starts just fine, so I don't think the valves are being held open. I think the only thing bad the high volume pump would do is heat the oil up a little bit.
Base timing was set at 10 deg BTDC. Idle speed is 800 RPM's. My timing light is an antique, so I have no way of knowing the timing at any speed bu idle. At least I ruled out the carb. A mechanic friend said there is a screen on the end of the fuel pickup in the tank. It may be gummed up. He's seen that before. The 3oo with the single barrel carb wasn't pulling enough gas for it to be a problem. I'll let you know if that was the problem tomorrow.
It looks like I'm writing a book. Thanks Y'all. Steve

 

OK, Maybe I'm not explaining the problem good enough. When I nail the throttle, the tires will just shred and the engine will scream for the first few seconds. If I short shift, it'll fry the tires in the first two gears before it begins to die. If I still keep the pedal to the metal, it will keep running. Just not very good. Then if I let off the gas just a little bit, it begins to run fine again. I have a T5 five speed with 3:70 gears, and at 70 MPH in third gear it still runs good. Any more RPM's then that and it starts to run poorly. I know I'm not overrevving the engine yet.(I have no tach yet) I really still don't know what the malfunction is. When I say let off the gas a little, I mean only a quarter of an inch or so. Maybe a half inch at the most.

 

I am running a similiar setup as you. Differences are I have '70 351W and a C4 auto... same basic engine build up 'cept my cam has a tick more lift.. not much... same fuel pump, same carb... don't have your problem... I take it you are running the stock behind the seat gas tank with the top of the tank pickup... I had a problem early on when I was running an electric fuel pump that required me to "modify" the gas tank to feed from the bottom (long story).... so maybe that is why I don't have your problems... the clogged pickup as your friend says sounds like a possibility based on everything else you are saying.... (I would not suggest taking my tank modification route as it led to many other modifcations to make it safe until I can relocate the tank to the rear frame rails)...

Other than that this is a head-scratcher...

Bill in 'bama
'64 F100 Shortbox ('70 351W/'76 C4)

 

Well today I swapped out the distributor with a rebuilt points type Autolite with a Pertronix Ignitor to see if the distrib was at fault. At first the truck wouldn't even run, but I hooked up the MSD as if there was still points in the distrib. I didn't want to fry anything, not knowing, so I eliminated the MSD for now. It started right up, and had a little crisper throttle response then before. That told me the curve was a little better on the 2nd distrib. The original problem is still there though. If I get time tomorrow, I'll pull the tank and see if there's crud in the bottom of it. That seems to be the popular opinion of what the problem is. I wrote MSD to find out how to connect the Pertronix to it. I suspect the same as I had the Duraspark distrib, but MSD's cost too much to just try different connections.

 

Hey Steve,
What I was talking about is straight out of the holley web site as far as the "0" vacum for the distributor. The distributor vacum advance port should have no vacum indication until the throttle is opened. It's ported just above the throttle plates in the bore of the carb body. Hence it shouldn't have vacum. This is in theroy mind you. It is possible to have a vacum reading on it due to the throttle plates being set just short of bypassing the idle circuit.
Just out of curiousity did you degree the cam when it was put in? Maybe the internal timing is off? I know stupid question but it does happen.

 

I didn't degree the cam. Didn't have a degree wheel at the time. I'm thinking of replacing my Pete Jackson geardrive timing set with a true roller gears and chain, cuz the darn thing sounds like I'm running a supercharger at full boost, even at low RPM's. When I do that, I'll borrow a friends degree wheel and check things out (I already have the timing set and gaskets). I really don't think that's the problem though.t seems like if the internal timing was off that bad, it wouldn't run so good at most other engine speeds. Maybe I'm wrong. I did check vacuum with a gauge today. At idle I have a pretty steady 15 lbs. It fluctuates just a half pound or less sometimes.I know this is lower then most stock engines, but I hope that it's normal for the cam that I'm using. Anybody know if this is normal vacuum?

 

What is the rpm where it starts messing up? If you had some way of measuring this, I am thinking of an experiment. Run it down the road and record the rpm and see if it is consistent. Then with the truck sitting in the driveway, rev it up and see what rpm it is cutting out. If it will rev much higher in the driveway (no load on the engine), I would guess it is still a fuel delivery problem, since the fuel demand is much higher pushing the truck down the road.

What I think would be interesting is if the rpm where it screws up is the same for both cases. That would lead me to believe it may be a valve train problem. I see you have guide plates and probably adjustable rockers. I wonder if the rpm would increase if you turned the adjustment back(loosened) on the rockers say 1/2 a turn? Maybe the valves are floating off the seats for some peculiar reason.

 

[updated:LAST EDITED ON 07-Mar-02 AT 02:18 PM (EST)]My 351W pulls 52 engine vacum (24 Hg). I am told this is high. The interesting thing is that most HiPo articles state that you should obtain the highest vacum possible. Also when you do do the road and parked test try to keep the vacum gauge on the engine. Major fluctuations will show floating valves. Try to keep that in mind when the engine starts acting up. I thought there were "quite" and "noisey" gears available? Anyway. I had many problems/discoveries on my engine before I got it right. Sucks when you buy a truck that someone else said was "perect". Hopefully your problem is something simple and was over looked.

 

I'm almost ready to do the unthinkable and buy a Chevy. I'm one step from pulling my hair out. Today I mounted a clean gas tank from a truck I'm restoring in the back of my truck. Hooked it up, and put some good gas in it, and went for a drive. Same problem. I think that this safely eliminates the fuel delivery problem. It's really weird. If I creep up on the RPM's, I can get almost WOT and still run smooth. As soon as I try and get that last quarter inch, it starts to run rough and lose power. If I let off on the gas a little, it picks up power. It's worse if I nail the gas hard all at once. I'm thinking that vacuum has something to do with it somehow. I guess it could be valve timing, but it doesn't seem like it would start and run as good as it does at every other throttle position if that were the case. Maybe I just need to put a little slack in my throttle cable so I can't get WOT, and don't worry about it. Not. I'm not giving up until it runs the way it should. Any ideas?

 

Are you getting enough fuel pressure when it starts cutting out? It sounds like you are just losing the fuel delivery at the top end. In reading some of these posts and reviewing the Ford Windsor Small-Block Performance manual, if the engine has been modified significantly, a proportionately higher pressure fuel pump is in order to meet the higher demand.

Just a shot in the dark from a shadetree mechanic (and the tree is more the size of a sagebrush)!

Good luck!

Roy

 

I noticed today that the steel fuel lines on my 65 are quite a bit smaller in diameter then on my 70 (that I robbed the gas tank from)The 70 is a 302 truck, while the 65 was a 6 cylinder truck. I'm thinking maybe those Ford engineers knew what they were doing, going to a bigger fuel line. I'll be looking for some steel gas lines tomorrow to try that next. Can't hurt. Just for the hell of it, I did another compression test and leakdown check. All cylinders were within a pound or two of 175, and tested between 2 and 3% leakdown. That's the tightest engine I've ever had, between my machine shop, and those Total Seal zero gap rings.

 

I'm no expert by far but here's a guess. Is it possible that when you wromp on the gas the socondaries are slamming open and flooding it while when you ease into it they are opening slower and not flooding.
I've never had a double pumper so I'm not real sure of the setup.
Clint

 

[updated:LAST EDITED ON 09-Mar-02 AT 08:15 AM (EST)]I feel I eliminated the possibility of the carb being the culprit by trying a different carb. I think I mentioned I tried a Carter AFB that I run on a different truck with a 352. Exact same problem. But thanks for the suggestion.