No towing power, any one have this problem? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mtdave2 · 10-05-2009, 10:02 AM

I just bought a camper rated at 4000 pounds. I was having trouble maintaining 65. the slightest of hills slowed me way down. I had the pedal almost floored to keep it at 65 on flat road. To say the least im a bit pissed, I had put the vortech heads on in hope of solving my power problem. Perhaps im just wanting too much out of the truck

Perhaps ill play with the timing a bit, and maybe go back to my original carb..

Here is the tread on the engine build
http://67-72chevytrucks.com/vboard/s...d.php?t=304830

Btw, the gear vendor rocks when towing.

dan42 · 10-05-2009, 10:03 AM

You might change your fuel filter too - just a thought.

71tahoe · 10-06-2009, 02:16 PM

Fouled plugs, timing, bad plug wires, vacuum leak, poor coil connection.

mtdave2 · 10-25-2009, 10:26 AM

its the orginial bottom end of the motor, we took it apart to change gaskets and seals, everthing looked good so we left it.

the top end got the heads, intake, roller rockers, and the cam above.

now i have added the below.

new plugs, accel wires, high pro coil, cap, rotor...aka new ignition system,

no vacuum leaks,

took the valve covers off, no sign of flat lobe on cam.

rebuilt the th350, shift kit, th400 converter.

having my org qjet rebuilt..

this is really starting to piss me off, this truck should be burning the tires off.

dan42 · 10-25-2009, 10:45 AM

Is the exhaust system appropriate for the engine setup you have? (i.e, too big, too small, etc.)

mtdave2 · 10-25-2009, 10:49 AM

ya, it has dules with a xover pipe and magnaflow mufflers. good thought though..

Old Chevy Mech · 10-25-2009, 11:27 AM

If you are nearly floored at times, did you verify that your linkage is allowing full throw of the throttle? If it is, are the secondaries opening?

What rear end is in the truck?

**Boog** · 10-25-2009, 12:08 PM

Dave I quickly looked through your posts and it looks like you have the GM HEI on it updated with new coil, cap and wires. That's good stuff. What condition is the mechanical and vacumn advance in on that unit? If the mechanical advance is somewhat siezed up it will definately be sluggish and drink gas. Also the HEI has to have a 12 volt power supply if that hasn't been changed already. How clean are the spark plugs running?
Yeah you are right your setup ought to be running great with plenty of power.

mtdave2 · 10-25-2009, 01:21 PM

mechanical advance is in good shape, i played with different springs, everything moves freely.

when i replaced the plugs, they all looked ok. nothing out of the normal.

compression was 165-175 , vacuum running at 16.

idle is nice and smooth, and it drives and shifts fine.. just no grunt

pumpkin · 10-25-2009, 02:10 PM

What cam are you using? Whats the outside temp? Whats the gears in the truck?

mtdave2 · 10-25-2009, 03:02 PM

cam http://www.jegs.com/i/Comp+Cams/249/12-235-2/10002/-1

head
http://www.jegs.com/i/GM+Performance...58060/10002/-1

411 rear end

mtdave2 · 10-29-2009, 11:48 AM

carb rebuilt.. nice to have the orginal one back on.

still no power..

guess it may be time to take everything back apart. perhaps i can find wtf we did wrong....

really have no idea what elese to do here.

brothers69c-10 · 10-29-2009, 12:15 PM

You may have used a th400 converter, but that may not still be enough. I have the same problem with my truck. I have a stock th 400 torque converter in place which is it about 1200-1400 stall on my truck. Looking back through my engine components and the powerbands that they are for i need almost a 2500 stall converter to get the power out of my truck. I figured this out also by putting the tranny in 2 instead of drive and i couldn"t believe the power at the high rpms.

69GMCLonghorn · 10-29-2009, 02:32 PM

Dave, I'll almost guarantee that your timing is not dialed in for your cam. Everything is probably functioning correctly, but it's just advancing enough or at the right time. If you have a timing light that measures advance, you should be running right around 40° of total advance in that thing. I had the same problem with my rig. I didn't know how to re-arch the distributor so I had someone else dial it in. I ended up with so much low end power that the tranny bearing were grunting in pain!!

mtdave2 · 10-29-2009, 03:06 PM

Quote:

Originally Posted by 69GMCLonghorn

Dave, I'll almost guarantee that your timing is not dialed in for your cam. Everything is probably functioning correctly, but it's just advancing enough or at the right time. If you have a timing light that measures advance, you should be running right around 40° of total advance in that thing. I had the same problem with my rig. I didn't know how to re-arch the distributor so I had someone else dial it in. I ended up with so much low end power that the tranny bearing were grunting in pain!!

i was convenced of that too... with the light, im at 11 btc at idol. 2000 rpm it jumps to about 25-30 mechanical, with the vac adv its 35 or 40.

i

**El Jay** · 10-29-2009, 04:27 PM

What's your rear gear?

69GMCLonghorn · 10-29-2009, 04:42 PM

Quote:

Originally Posted by mtdave2

i was convenced of that too... with the light, im at 11 btc at idol. 2000 rpm it jumps to about 25-30 mechanical, with the vac adv its 35 or 40.

i

Ok, so maybe you need to set the timing the "ghetto" way... Bump it up until it pings, then back it off about 2-3 degrees. You can probably get another 5° out of it before it pings.

clinebarger · 10-29-2009, 04:54 PM

Lugging 10,000 pounds around at 65MPH is asking alot from a small block

1FAST68 · 10-29-2009, 04:57 PM

Quote:

Originally Posted by mtdave2

i was convenced of that too... with the light, im at 11 btc at idol. 2000 rpm it jumps to about 25-30 mechanical, with the vac adv its 35 or 40.

i

When you said 25-30 degs at 2000 is that what the light is saying? You should have close too 36-40 without the vac adv plugged in.

Also is you timing tab correct with TDC?

69GMCLonghorn · 10-29-2009, 05:11 PM

Quote:

Originally Posted by clinebarger

Lugging 10,000 pounds around at 65MPH is asking alot from a small block

It's not a light load, but in my other truck, I know my dad and I went over the scales at the dump at over 13,000 lbs... and that was with a 307, not even a 350.

clinebarger · 10-29-2009, 05:25 PM

Quote:

Originally Posted by 69GMCLonghorn

It's not a light load, but in my other truck, I know my dad and I went over the scales at the dump at over 13,000 lbs... and that was with a 307, not even a 350.

I agree its possible, but with a camper being taller than the truck catching all that air its hard to maintain high speeds with im guessing 300-350 ft.lbs.

68C15 · 10-29-2009, 07:21 PM

what is your RPM at 65? you mentioned a GV overdrive.

there's no replacement for displacement. you can achieve this 2 ways. build a bigger engine or wind up the 350 more.

capev86 · 10-29-2009, 07:33 PM

camshaft....is it a low rpm/rv type grind or a high rpm only piece of junk better suited to a honda than a work truck? back in the mid 80's my dad replaced the 350 in his 72 burb with a 305 out of a 77 monte carlo. he put in a camaro oil pump and an rv grind cam. we hauled our 71 holiday travel trailer all over the place with that little engine....a 305 has the same stroke as a 350, just more efficiently sized pistons. the mechanic/friend that did the job reinstalled the stock q-jet and put in hei. that and a cheap dual exhaust and it ran great. had stock 3.73 gears in the back.

ignition......gm's love dialectic grease.....my dad's current 87 tbi burb has that problem every year or so....not running bad, just absolutely no power...period, so he has to take it apart and grease it up....knowing that ahead of time could have saved $500.

done carefully, occassional towing gets the most out of any engine.....the extra heat generated will burn out all the carbon deposits. the original 350 out of my dad's 72 burb was clean as a whistle when the mechanic took it apart to rebuild it for another project....because we used it to tow the trailer for a short while before the engine swap.

PanelDeland · 10-29-2009, 08:00 PM

On the timing issue.There may be another problem you haven't discovered.It's very possible that the original Harmonic Balancer is on the engine and the rings may have slipped giving you a false reading(on timing).Just another thought.

68C15 · 10-29-2009, 09:39 PM

^^^^^
and a good one at that

10-05-2009, 10:02 AM	#1
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	No towing power, any one have this problem? I just bought a camper rated at 4000 pounds. I was having trouble maintaining 65. the slightest of hills slowed me way down. I had the pedal almost floored to keep it at 65 on flat road. To say the least im a bit pissed, I had put the vortech heads on in hope of solving my power problem. Perhaps im just wanting too much out of the truck Perhaps ill play with the timing a bit, and maybe go back to my original carb.. Here is the tread on the engine build http://67-72chevytrucks.com/vboard/s...d.php?t=304830 Btw, the gear vendor rocks when towing. __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban Last edited by mtdave2; 10-05-2009 at 10:02 AM.

10-05-2009, 10:03 AM	#2
dan42 Registered User Join Date: Feb 2007 Location: Cali Central Coast Posts: 5,191	Re: No towing power, any one have this problem? You might change your fuel filter too - just a thought. __________________ '67 SWB Fleetside ZZ4/350/Tremec 5-speed/4link/Scott's IFS - and fun as heck! SOLD Click here to support the board Philippians 4: 6-7

10-06-2009, 02:16 PM	#3
71tahoe Registered User Join Date: May 2006 Location: Jonesboro, AR Posts: 916	Re: No towing power, any one have this problem? Fouled plugs, timing, bad plug wires, vacuum leak, poor coil connection.

10-25-2009, 10:26 AM	#4
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: No towing power, any one have this problem? its the orginial bottom end of the motor, we took it apart to change gaskets and seals, everthing looked good so we left it. the top end got the heads, intake, roller rockers, and the cam above. now i have added the below. new plugs, accel wires, high pro coil, cap, rotor...aka new ignition system, no vacuum leaks, took the valve covers off, no sign of flat lobe on cam. rebuilt the th350, shift kit, th400 converter. having my org qjet rebuilt.. this is really starting to piss me off, this truck should be burning the tires off. __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban

10-25-2009, 10:45 AM	#5
dan42 Registered User Join Date: Feb 2007 Location: Cali Central Coast Posts: 5,191	Re: No towing power, any one have this problem? Is the exhaust system appropriate for the engine setup you have? (i.e, too big, too small, etc.) __________________ '67 SWB Fleetside ZZ4/350/Tremec 5-speed/4link/Scott's IFS - and fun as heck! SOLD Click here to support the board Philippians 4: 6-7

10-25-2009, 10:49 AM	#6
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: No towing power, any one have this problem? ya, it has dules with a xover pipe and magnaflow mufflers. good thought though.. __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban

10-25-2009, 11:27 AM	#7
Old Chevy Mech Keepin it runnin! Join Date: Oct 2007 Location: Deep River, CT Posts: 1,036	Re: No towing power, any one have this problem? If you are nearly floored at times, did you verify that your linkage is allowing full throw of the throttle? If it is, are the secondaries opening? What rear end is in the truck? __________________ 1970 K-5 4X4 Blazer 1970 K-20 4X4 Long Bed "Liberty Means Responsibility, that is why most men dread it"

10-25-2009, 12:08 PM	#8
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,514	Re: No towing power, any one have this problem? Dave I quickly looked through your posts and it looks like you have the GM HEI on it updated with new coil, cap and wires. That's good stuff. What condition is the mechanical and vacumn advance in on that unit? If the mechanical advance is somewhat siezed up it will definately be sluggish and drink gas. Also the HEI has to have a 12 volt power supply if that hasn't been changed already. How clean are the spark plugs running? Yeah you are right your setup ought to be running great with plenty of power. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

10-25-2009, 01:21 PM	#9
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: No towing power, any one have this problem? mechanical advance is in good shape, i played with different springs, everything moves freely. when i replaced the plugs, they all looked ok. nothing out of the normal. compression was 165-175 , vacuum running at 16. idle is nice and smooth, and it drives and shifts fine.. just no grunt __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban Last edited by mtdave2; 10-25-2009 at 01:24 PM.

10-25-2009, 02:10 PM	#10
pumpkin Registered User Join Date: Apr 2006 Location: East Sooke B.C. Canada Posts: 543	Re: No towing power, any one have this problem? What cam are you using? Whats the outside temp? Whats the gears in the truck?

10-25-2009, 03:02 PM	#11
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: No towing power, any one have this problem? cam http://www.jegs.com/i/Comp+Cams/249/12-235-2/10002/-1 head http://www.jegs.com/i/GM+Performance...58060/10002/-1 411 rear end __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban Last edited by mtdave2; 10-30-2009 at 11:33 AM.

10-29-2009, 11:48 AM	#12
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: No towing power, any one have this problem? carb rebuilt.. nice to have the orginal one back on. still no power.. guess it may be time to take everything back apart. perhaps i can find wtf we did wrong.... really have no idea what elese to do here. __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban

10-29-2009, 12:15 PM	#13
brothers69c-10 Suburban Hick Join Date: Aug 2008 Location: Altoona, IA Posts: 810	Re: No towing power, any one have this problem? You may have used a th400 converter, but that may not still be enough. I have the same problem with my truck. I have a stock th 400 torque converter in place which is it about 1200-1400 stall on my truck. Looking back through my engine components and the powerbands that they are for i need almost a 2500 stall converter to get the power out of my truck. I figured this out also by putting the tranny in 2 instead of drive and i couldn"t believe the power at the high rpms. __________________ Mathew 1947 Chevy 3600 1951 GMC 100 1969 Chevy C-10 396/500hp TH400 lowered 4" 1968 Imapla Custom 396/325hp TH400 "Grandmas Car" 1976 Crew Cab 4x4 diesel http://67-72chevytrucks.com/vboard/s...d.php?t=488505 1978 Chevy K-10 454 1983 S10 4x4 "Bumblb" (Grandpa's truck) 1993 Chevy S10 V8 conversion 1990 Ford Probe Gt 1992 Dodge W-150 "Old Man's Truck" 1992 Pontiac Grand Prix SE 1992 Mercury Grand Marquis-Mercruiser 2000 Ford F150 (Currently my mother drives this) 1946 Farmall H with Stan Hoist loader 1965 John Deere 110 1961 Wheel Horse " Rat Tractor"

10-29-2009, 02:32 PM	#14
69GMCLonghorn Registered User Join Date: Dec 2006 Location: Porter Ranch, CA Posts: 978	Re: No towing power, any one have this problem? Dave, I'll almost guarantee that your timing is not dialed in for your cam. Everything is probably functioning correctly, but it's just advancing enough or at the right time. If you have a timing light that measures advance, you should be running right around 40° of total advance in that thing. I had the same problem with my rig. I didn't know how to re-arch the distributor so I had someone else dial it in. I ended up with so much low end power that the tranny bearing were grunting in pain!!

10-29-2009, 04:27 PM	#16
El Jay Gone to greener pastures Join Date: May 2007 Location: Gateway to the Delta Posts: 7,354	Re: No towing power, any one have this problem? What's your rear gear? __________________ '69 Chevy 1/2 T LWB Stepper: Daily Beater '72 GMC 3/4 T Fleet: Another Daily Beater '72 Plymouth Gran Coupe: ? "Ah women. They make the highs higher and the lows more frequent." Friedrich Nietzsche "Never kick a fresh turd on a hot day." Harry S. Truman GUN CONTROL: Never having to say, "I missed you." Always fire two warning shots into your attacker's chest area before putting a bullet between his eyes. Paraphrased from Louis Awerbuck



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10-29-2009, 04:54 PM	#18
clinebarger Senior Member Join Date: May 2009 Location: Fort Worth, TX Posts: 6,370	Re: No towing power, any one have this problem? Lugging 10,000 pounds around at 65MPH is asking alot from a small block

10-29-2009, 07:21 PM	#22
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	Re: No towing power, any one have this problem? what is your RPM at 65? you mentioned a GV overdrive. there's no replacement for displacement. you can achieve this 2 ways. build a bigger engine or wind up the 350 more.

10-29-2009, 07:33 PM	#23
capev86 Registered User Join Date: May 2009 Location: Eliot, Maine Posts: 1,314	Re: No towing power, any one have this problem? camshaft....is it a low rpm/rv type grind or a high rpm only piece of junk better suited to a honda than a work truck? back in the mid 80's my dad replaced the 350 in his 72 burb with a 305 out of a 77 monte carlo. he put in a camaro oil pump and an rv grind cam. we hauled our 71 holiday travel trailer all over the place with that little engine....a 305 has the same stroke as a 350, just more efficiently sized pistons. the mechanic/friend that did the job reinstalled the stock q-jet and put in hei. that and a cheap dual exhaust and it ran great. had stock 3.73 gears in the back. ignition......gm's love dialectic grease.....my dad's current 87 tbi burb has that problem every year or so....not running bad, just absolutely no power...period, so he has to take it apart and grease it up....knowing that ahead of time could have saved $500. done carefully, occassional towing gets the most out of any engine.....the extra heat generated will burn out all the carbon deposits. the original 350 out of my dad's 72 burb was clean as a whistle when the mechanic took it apart to rebuild it for another project....because we used it to tow the trailer for a short while before the engine swap. Last edited by capev86; 10-29-2009 at 07:34 PM.

10-29-2009, 08:00 PM	#24
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,992	Re: No towing power, any one have this problem? On the timing issue.There may be another problem you haven't discovered.It's very possible that the original Harmonic Balancer is on the engine and the rings may have slipped giving you a false reading(on timing).Just another thought. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

10-29-2009, 09:39 PM	#25
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	Re: No towing power, any one have this problem? ^^^^^ and a good one at that

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