No towing power, any one have this problem?

[Boog]

You know if that cam wasn't degreed in right I suppose it could make it run out of steam early.

[mtdave2]

lets see...
new harmonic balancer

i did set the timing the redneck way, put in different springs, advanced it so far it wouldn’t start, tried just about everything timing wise, other than replacing the distributor its self...but i have been thinking about that!

gears, 411

to heavy? well maybe, but i have no power w/o the camper, wont spin the tires ect.

im guessing it may be the cam, or ?? if i cant come up with something else to try, ill take it to the speed shop and have them put a computer on it. perhaps they can figure this out.

i KNOW we put that cam in right.. we checked 4 or 5 times, and said it out loud to eachother.. no way did we put it in off a tooth.

[Roland]

Boog asked about several items including 12v to the new HEI. You answered all but the voltage to the new ignition system. Did you check that?

[mtdave2]

well, no, i have not put a meter to the wire. but, i ran the wire myself from the fuze box to the dist.

just for giggles ill gauge it. though to my understanding, an hei wont run at all if you dont have 12v.

[WorkinLonghorn]

What do the plugs look like?
Run it with the air filter off and listen for the secondaries opening.
Verify/reset true TDC and take off a valve cover and note the exact degree that the valves open and close (using a degree tape on the balancer),also check the lift and compare these to the cam specs.

My 2500 came with the original cab-over camper and the original worn out 350 with 3.73 gears and I ran it up and down the Calif.coast,up grades etc.with no problem at all.
I'd check out that cam.

[brothers69c-10]

Still saying you may need a stall converter. If you have a tach on your truck. put your foot on the brake and and pin the gas to the floor at whatever rpm the tires brake loose or the engine won't rev up anymore is the stall in your current torque converter. compare that with the power band range on the cam, intake, etc.

[mtdave2]

http://www.compcams.com/Cam_Specs/Ca...x?csid=95&sb=0

that is the cam... not sure how you tell where the power band is..but there you go.

after getting my truck back from the trany guy, i have noticed a vibration connected with rpms. around 2600 or so i get a rythmic vibration. if i shift into od, it stops.

i would say it was drive line angles because he did take my trany spacer out when he replaced the mount, but the angles still look ok. still i told him to put it back in. hope thats the deal.

also, the number one valve is ticking again when WARM! hum, finaly a symtom. we had a hard time getting that thing ajusted, now its out again. perhaps this may be the problem.

[mtdave2]

thinking about the valve ticking, it used to be it would tick when cold, that makes sence to me. once warmed up it would stop..

now, why would it tick only when warm?

[clinebarger]

I was under the impression that it only lacked power while towing. check out that valve noise soon chould be a flat lobe on the cam. seems to be a commen occurrence in the past few years.

[mtdave2]

we have been thinking that it had to be a flat lobe on the cam, but when i pulled the covers and watched the rockers, they were all moving the same. there was no tapping at that time..im really hoping i have a flat lobe..hhahaha ever hear anyone wish that?

[dwcsr]

I had a similar problem towing a trailer 2300lbs and a truck on it 3450lbs. It would not maintain 65 up hill. The throttle linkage was not opening the carb all the way.

I have a stock setup 350 TH350 so you should have no problem at 65 with 4k lbs

[69GMCLonghorn]

Man, you wanted suggestions, we're full of 'em!! it sounds like it's time to get a different set of eyes on that thing. Maybe it's something obvious (and hopefully simple) that none of us are thinking about...

[Old Chevy Mech]

I think its the cam, but I gotta ask What size fuel line are you running?
Have you verified full throw on the throttle linkage?

[mtdave2]

the carb is opening all the way.. size? um, well its orginal metal line with some same sized rubber to the carb.

i have a clear large fuel filter near the carb so i can see the gas is there. if it were starving for gas, i would at least have power from a start...and i dont!

there have been a few eye balls, and many brains thinking about this. all the motor heads think its timing, or the cam.

[Shaffer4]

probably a goofy suggestion, but are all the exhaust bolts good and tight? I've seen light and day differences between a sealed and a leaky exhaust...

[Old Chevy Mech]

I had to ask cause I once had a similar problem from the combination of 3 different things all working together. None involved the cam, but one part involved the timing.
It seems I saw in this thread somewhere you said it wouldnt smoke the tires empty? If thats the case then the problem is definately how the engine is set up and I agree that with those that say its the cam. In my experience even a poorly timed 350 will pull its guts out. It might overheat, ping like crazy, but it'll run. And since you are saying that its not pinging, not backfiring, not overheating, and not bogging from lack of fuel Its got to be when your valves are opening and closing.
You should be able to readjust the cam without pulling the engine.

[mtdave2]

well, this truck has ALWAYS been a dog. even with the original motor. runs nice an smooth, but just no guts. its like it has the tallest rear gear you can imagine.

after the heads and cam, i was expecting some power, but nota. Not much change at all. that’s the strange thing really.

im with you, it just has to be the cam. we will pull the whole thing out this week and see what we find.

have you all noticed that i have bad luck lmao

[68C15]

Originally Posted by mtdave2

its like it has the tallest rear gear you can imagine.

yet again I have to ask what it's like when you pull it out of overdrive. what are your RPMs both ways?

[budman k20]

Hi,
I re-read your post and build and these are my thoughts. I would think you would have more than 16" of vacuum at idle with that cam. The cam seems right for towing and is very close to stock. I don't know the stock cam specs but your current cam is very close to stock and I dont think you would feel a seat of the pants change over stock. Have you sprayed water around the carb base and intake gaskets? If you have an increase in idle speed doing this it would indicate a vacuum leak. A vacuum leak makes for a lean mixture... which = loss of power. My gut tells me you may have tightened the valves a little too tight. The engine could idle fine but when you get it wound up the lifters can pump themselves up and not allow the valves to close all the way. Causing the engine to run like it has much lower compresion. As far as you running the wrong converter, the converter would not affect the power output of the engine after you get the Longhorn moving. It also sounds like you are getting too much advance too quickly. A common problem with HEI. And from years of pulling with SBC's you need to be in drive when you are pulling your camper. My personal experience has shown I never get better mileage pulling anything much over 1500 lbs in overdrive. A loose timing chain could be the reason your timing readings are so variable. Did you put in a new timing chain? I may have missed it but I did not see it in your build list? Anyway a lot of details to cover. Good luck with troubleshooting your power issues! FYI I still have my dad's 71 Longhorn and have many fond memories pulling a big camper trailer all over the country with it!

[RustyParts]

I had a similar problem once, turned out to be a restriction in the exhaust system. Had a defective muffler, ran pretty decent at part throttle but performed like it had a govenor kicking in at higher RPM's. Pretty easy to check out. Good Luck.

[mtdave2]

Originally Posted by 68C15

yet again I have to ask what it's like when you pull it out of overdrive. what are your RPMs both ways?

65mph 2300 or so in od, 3000 out, no dif in power.

[mtdave2]

Originally Posted by budman k20

Hi,
I re-read your post and build and these are my thoughts. I would think you would have more than 16" of vacuum at idle with that cam. The cam seems right for towing and is very close to stock. I don't know the stock cam specs but your current cam is very close to stock and I dont think you would feel a seat of the pants change over stock. Have you sprayed water around the carb base and intake gaskets? If you have an increase in idle speed doing this it would indicate a vacuum leak. A vacuum leak makes for a lean mixture... which = loss of power. My gut tells me you may have tightened the valves a little too tight. The engine could idle fine but when you get it wound up the lifters can pump themselves up and not allow the valves to close all the way. Causing the engine to run like it has much lower compresion. As far as you running the wrong converter, the converter would not affect the power output of the engine after you get the Longhorn moving. It also sounds like you are getting too much advance too quickly. A common problem with HEI. And from years of pulling with SBC's you need to be in drive when you are pulling your camper. My personal experience has shown I never get better mileage pulling anything much over 1500 lbs in overdrive. A loose timing chain could be the reason your timing readings are so variable. Did you put in a new timing chain? I may have missed it but I did not see it in your build list? Anyway a lot of details to cover. Good luck with troubleshooting your power issues! FYI I still have my dad's 71 Longhorn and have many fond memories pulling a big camper trailer all over the country with it!

wow lots of good stuff there, thanks.

yes, new chain went in with the cam. we had problems with number 1 valve. im thinking you may be right, we may have over tightened it. guess we will find out Wednesday when we start taking it apart..

[mtdave2]

Originally Posted by RustyParts

I had a similar problem once, turned out to be a restriction in the exhaust system. Had a defective muffler, ran pretty decent at part throttle but performed like it had a govenor kicking in at higher RPM's. Pretty easy to check out. Good Luck.

i did take a look at this, everything seems to be flowing fine.

[Boog]

Without going back through all 48 posts I'll ask if the fuel pressure has been checked. Low fuel pressure will let it run good from idle up to a point where it seems like it hits a wall and cannot go on. Collapsed rubber hose or intank strainer maybe?
Example: my 97 Burb all of a sudden wouldn't pull itself past 47 mph, floored or not, not towing anything. Started fine and ran fine up to that point. New filter fixed it.

also note: the HEI will run with less than 12 volts, just not with as much power.
Dave you said the truck was a dog from start before the engine build and still is. So run over the list of parts that were reused from the original engine and give them a look over. And without putting a dial indicator on that cam you don't know if they sent you the right one or not.

[jeffspower]

I just read this for the first time. Read every post. If there are no lobes going flat on the cam, and the lash isn't set too tight... I'd be reading the plugs. It could be too lean. I know some will say that if it is too lean that it should ping, run hot, etc. but they don't always. Too lean robs power big time. If you was one tooth off on the timing chain, your idle vac. should be low, which it isn't.

I went thru this on a 500 Caddy I put in a '80 K20. The first time down the road after installing the fresh mild cammed engine it was gutless. I made a nice little 80 mile unloaded trip to break it in, and it used 20 gallons of gas! I pulled a few plugs and they were white as new. I think I went up 3-4 jet sizes in the Qjet, and the mileage at least doubled and power was at least decent. I know you had 2 different carbs on it with no difference, but don't rule it out... both could be too lean for your combo.