I wish to thank all who have helped me on this site. you will never know what a differance you have made to me and my little F100.
I have been fighting a holley 500 on my 352 for over a year, simply cant make it run right, just when i think iv got it,it's eather to lean or to rich , i finally broke down and kitted the factory 350cmf carb and put it in and it runs great, good color on the plugs and all, go figure. but in running the normal tests my vacumm at idle is solid at 15. this is at 2300 feet at sea level it was 17. this seems low to me, I dont know much about the history of the motor except it was rebuilt with 22k when I bought it. It is not the original motor that came with the truck. it has the D8 heads and the exaust has plugs where I presume the smog pump nozzles would go. It runs strong up to about 2300 rpm and then the power falls off quickly, it;s not jetting as the oz sensor ( long story )
shows a 905mv reading indacating a slightly rich condition. I do know the former owner used it to tow a sprint car. it had a 3 speed with overdrive whih has been replaced with a C6. and 3.54 gears.
Could it have a cam that peaks about 2k ? and would this explain the low vacuum reading ? do I have what I have untill I replace it? Is their any thing I can check ?
Thanks agin for all the help, the motor runs great, it pulls strong from idle to about 2300rpm and falls flat, It has dual exaust ( flowmaster ) and the distro is recurved 10 in and all mech in by 2500.using vacuum advance and ported vacuum. pertronics ing with blaster 2 coil , spark is blue and will jump a 3/4 inch gap easyly.
not sure where to do now other than saveing up for a reman motor.

 

jav, it sounds like some kind of cork in the intake or exhaust to cause it to fall flat at 2300 rpm!! I am not aware of any cam with that low of an rpm range. IF it was dramatically advanced(in relation to the crank) that can cause poor high rpm power, althought 2300 is hardly high rpm! It will usually have higher idle vacuum also.

Have you performed a compression test? I think you meant D2TE heads? Does it surge, buck, hesitate, etc.? What is your complete ignition setup?

More questions than answers!!!!

 

Sorry I ment C8 Heads, havent run a compresion test But it uses no oil, doesnt smoak, no overheating, no blowback, none of the symptons that might lead me to think is has bad pistons or valves. I runs strong up to about 2300rpm then gets a bit ratty, not as smooth and It doesnt feel like its pulling anymore, to get much over 2500 I real have to put my foot in it. Like i said It had overdrive in it befor so i never noticed it. I never had to run over 2000 for any period of time, now that I have the C6 runin down the freeway at 60 is 2650 rpm. so it realy feels bad up in that rpm range. anything up to 2300 including towing it pulls strong.
Could the factory 2 barrol manifold be holding it back? I mean their are a lot of these truck-352-C6 combanations around do they all act like this ? is this the reason everyone seems to go with a 390 ?

no bucking hessatation or anything like that, just feels less powerfull after 2300, ing setup is a stock ford distro in the 10 slot a set of mrgasket advance springs. Pertronics modual, and Blaster2 coil, im running autolight 124 sparkpluges gaped at 49 thousands, Idle is smooth with no misses can actually Idel down to 350 rpm and it still idles fine. Base timeing is set to 12 degrees BTDC, using ported vacumm, all plates in the distro are lubed and move freely. Vacuum modual is adj to the max trow.

 

Did you check your points with a dwell meter? Also, .049" may be a bit too much gap, I run .035".

 

No points , pertronics igniter with Blaster coil, they recomend opening gap 10 to 15 thousands over stock, wil shoot a Blue white Spark 3/4 of a inch at idle. Pretty hot spark. But I guess I could try lowering the gap.

 

My first thought is that either the carb is not being pulled all the way open by the linkage or the mechanical advance isn't. Check to see if the throttle valves are opening all the way with the foot throttle and check the total mechanical advance (vacuum disconnected and plugged).

 

I don't think the 2V is the cause of your problem. When I moved here from the other side of town I sustained around 3600 rpm with a load, johnlaw was my only potential problem. I run motorcraft 2100 with a manual tranny.

From what I'm reading the only real changes have been the carb and the tranny, the carb is back to stock.
Have you tried plugging the vacuum to the tranny, brake booster and other potential leaks?
How about swaping a set of breaker points in place of the pertronics to see if there's any change?
That's all the simple stuff I can think of at the moment. Could be the P.O. advanced the cam knowing it would be run with an overdrive? Gave me enough excuse to see if this link is still active:

downloadable degree wheel

I'd save indexing for last. Hopefully you'll get lucky before then.

 

Its not the camshaft, imo. As with what Putt, said the smaller camshafts have higher vac readings. As, for 2300 thats strange cause peak power is at around 4000 but thats about right for peak torque. back in the day i could pull 4000-4100rpm in third gear with a 390, 3.50s, c6, stock cam.

What kind of plugs are those? I work with autolite 45's, they are the base spark plug nothing fancy. The .049 is fine but about .005 high.

 

are you sure your tach is right??? I'd verify that first

 

I hate to say it---but your problem my friend sounds like it's your ignition!!!Try throwing a good set of points--heavy spring tension---accel sells them for 25$ set the dwell between 28-32 degrees--set timing--check dwell again.A friend went thru 2 of those pertronic's on his 455 olds jet boat --coughed and sputtered all summer until i installed the simple point distributor with quality parts and correct ballist resistor and wiring-----it reved so high the dummy over-reved and destroyed that 455 olds---keep your head--keep your toy ---Fortyford

 

I think Bear's comment is worth checking out. My step-son recently acquired an International Scout that was weak on power. I learned the previous owner had changed the carb...checked it out and sure enough the throttle was hooked up such that the throttle wouldn't even half open. Fixed that easy enough and the scout was like a different vehicle.

Tracy

 

Persuant to a previous discussion about Pertonix, do you have it hooked up WITHOUT the ballast resistor in between the Pertronix and the ignition switch?

 

A friend with a 428 in a one ton work truck had a similar problem...we checked every thing we could think of and more...it started good,ran good,until it got to a certain rpm and it was like a limiter would kick in...I was laying under the truck just sort of hoping the answer would come to me, and it just seemed like the exhaust was kind a puny.So for the hell of it we put on a new system,bigger,dual,turbo's...and hey!! Now it's running really good! But I was still curius and cut open the old pipe.It had been made with a double wall and the inside one had rusted away enough to collapse in chokeing it all off and yet it still looked sound on the outside. I have also found a similar problem once with a gas line,we took the line off and gas was coming through but when we'd step on the gas it would choke up.When enough gas flowed through it would make the little "flapper" close,starving the engine...I use fuel injection hose now,and just don't trust hose or tubing so much...hope you find your problem without creating too long of a story also..

 

Is it possible that there is an internal short in the distributor wiring that is causing a problem after the points plate moves enough??? Maybe try running it without the vacuum advance hooked up to see if it changes. A good point about the fuel line and exhaust tubing, they can collapse on the inside and still look fine.

 

Ok a follow up, I pulled the 124's and replaced them with 45's gaped at 35 thousands, that brought the rpm up to 3000 without loss of power, I do get a kind of tiny surge at around 2500 but it seems to run fine,I then started advanceing the timeing a bit at a time till it pinged under hard acceleration and then just backed it off till it stoped. now it accelerates hard, and pulls fine up to 3000 I wont go any further cause I have no need to. Funny It seem the 2100 runs a lot leaner ( on the ox sensor ) then the holley 500 did, yet the plugs are burning better than with the holly, I had tried several differant power valves 4.5 , 5.0 , 6.5 ,7.5 , 8.5, 10.5 and none of them worked correctly along with lots of jet changes, 74,73,72,71,69,67 And never could get the combo right.
It looks like the 2100 is leaner in the normal circuit but the powervalve circuit seem to add more fuel then the holly did under load. Oh well more wasted money. should have just kitted the 2100 the first time.:P
Thanks for the Ideas.
The pertronics unit is wired correctly
The exaust sysem is less then a year old
I probally bought a bad holly, new, holley wasnt much help, They said to drill holes in the throttle plates cause I was getting vacumm at the ported output even at Idle, guess what , it already had holes in the throttle plates.
I get no vacuum at Idle with the 2100 it works like it should.