Old School chevy need help

**Street Fighter** · 02-09-2011, 03:27 AM

I have a 69 chevy truck with a 350 engine bored 30 over crane cam 278-467/494 lift, Rpm intake, 750 Holley carburator Vac.Headers,Stall and shiftkit in the 350 trans.The promblem I have had for a while is that the truck just want move out if you nail it to the floor at a stand still or below 50 mph It just sit there as if it has to make up it's mine to go.If I ease into it,it will do fine but nothing other than that.Tried changing carb,Disturator,wires, checked gaps on the plugs,and made sure there was a good 12 volts going to the disturator. What could it be? NEED HELP.

**Sarge** · 02-09-2011, 03:31 AM

Are you saying it "bogs" as in floods the bowls?

**pajeff02** · 02-09-2011, 03:41 AM

^^ Agree, need more information. Does the engine rpm jump up when you stab it, but the truck does not move? Or, does the engine stumble or hesitate rather than rev up?

**Street Fighter** · 02-09-2011, 05:39 AM

Originally Posted by Sarge

Are you saying it "bogs" as in floods the bowls?

Yes it bogs down once you floors it.

**Street Fighter** · 02-09-2011, 05:45 AM

Originally Posted by pajeff02

^^ Agree, need more information. Does the engine rpm jump up when you stab it, but the truck does not move? Or, does the engine stumble or hesitate rather than rev up?

No the rpms drop and it hesitates for a second than it takes off.It's bogging down.
could the fuel in the bowls need to be increased?

**fat50** · 02-09-2011, 08:15 AM

It sounds like you need to change or experiment with the vaccuum spring that opens the secondaries. slow down the rate it open them.

**pajeff02** · 02-09-2011, 08:19 AM

Could be a couple of things. When you depress the accelerator, the carb is supposed to give the engine an extra shot of fuel. I'm not a Holley fan, but my recollection is they utilize a power valve for enrichment that works off a vacuum signal. (Q-jets and Carters employ an accelerator pump that forces additional fuel into the engine).

If the power enrichment circuit is not set up properly, meaning your secondaries are opening and not enough fuel is getting to the cylinders in time, it creates a lean bog like you described. I believe that the Holley power valves can be "blown out" by a backfire and become inoperable. Again, Holleys are not my thing.

**Sarge** · 02-09-2011, 08:58 AM

Take the fuel level sight port on the side of the primary fuel bowl off. Fuel should just "trickle" out....or not at all or gush out. If it is not coming out at all your too lean and gushing out your too rich. You should just have a trickle like I said.

But before I did that I'd check some obvious/basics.
Is your throttle opening up all the way? Is the throttle sticking maybe?
Pull the air cleaner and you'll see four little holes on the choke tower. They are the acceleration and idle air bleeds. Blow some compressed air into them to insure they are not clogged with crap.
Get ahold of a vacuum gauge. Check your manifiold vacuum pressure. I'd just replace the power valve as part of the troubleshooting. Jeff makes a good call there.
Let us know.

**wheeliE-maxx** · 02-09-2011, 04:05 PM

Is your detent cable adjust correctly? It will bog like a mofo trying to go wot in 3rd at 50. I would trade that 750 for a qood later model q-jet ('78 or so) or a 600 holley or carter if you're prejudiced against rochesters.. Even with the best tuning, a 750 won't be as responsive as the other carbs on a mild 350

**Street Fighter** · 02-09-2011, 06:03 PM

Thank you all for your reponses I will be tryiing all of the things said and maybe something will get me back to the way it use to run.I tried a 650 double pumper That was brand new and I had the same thing happen. I have tried the 750 off my camaro and the same thing happen. the kickdown cable have been adjusted time and time again because I felt that was the problem, but the bog is still there.With the 650 there was no power valve to cause the bog, It flooded the engine when I floored it.But worked fine on my camaro. There is little difference between the cams truck 467/494 camaro 510/510.I feel that it's sometime thats going on with the truck it self.maybe it Is in the kick down cable. Still open to anyother ideals. I want to get this truck back to where it use to be. I have out run a lot of guys on my job and I want to keep it that way.The camaro have the same setup but a bigger cam as listed.

**wheeliE-maxx** · 02-09-2011, 06:09 PM

If it's not kicking down to second at 50, that's an issue unless you are running crazy short gearing. The bogging off the line is a tuning problem though. What heads, compression, and timing?
Secondaries could be opening way too soon

**Street Fighter** · 02-10-2011, 03:59 AM

Originally Posted by wheeliE-maxx

If it's not kicking down to second at 50, that's an issue unless you are running crazy short gearing. The bogging off the line is a tuning problem though. What heads, compression, and timing?
Secondaries could be opening way too soon

I have 10 to 1 flat tops
The total timming is about 30 degrees I say about because the timming tab I have on the engine only go to 16 .I have 350 vortec heads and 373 gears The vortec heads are 64cc .

**wheeliE-maxx** · 02-10-2011, 02:11 PM

get an adjustable timing light for sure. You could probably stand a few more degrees of timing if you're running premium. Maybe around 33-34. I would pick up a how to book on tuning holleys, the Cliff Ruggles q-jet book was a help to me for sure

**blue02Z** · 02-10-2011, 03:18 PM

yeah i concur that it is in the tuning of the carb. a quick and expensive fix is just to swap to efi

**Street Fighter** · 02-11-2011, 03:20 AM

Originally Posted by wheeliE-maxx

get an adjustable timing light for sure. You could probably stand a few more degrees of timing if you're running premium. Maybe around 33-34. I would pick up a how to book on tuning holleys, the Cliff Ruggles q-jet book was a help to me for sure

I have planed on getting one because I really do need one .Just how do they work? I will be getting a Holley help book this weekend.

**wheeliE-maxx** · 02-11-2011, 09:18 PM

Originally Posted by Street Fighter

I have planed on getting one because I really do need one .Just how do they work? I will be getting a Holley help book this weekend.

the knob "subtracts" timing. put the knob at 30* for example with 30* of timing, the light will flash at the 0* mark. Making sure your 0* mark is perfectly aligned with top dead center on #1 cylinder is good to do aswell.

**wheeliE-maxx** · 02-11-2011, 09:19 PM

Originally Posted by blue02Z

yeah i concur that it is in the tuning of the carb. a quick and expensive fix is just to swap to efi

that would need tuning aswell. The self tuning ones are over a $k to fix a one day tuning problem

**Street Fighter** · 02-13-2011, 01:10 PM

After thinking about this and reading the post made my you all, I need to know one thing, Why did the truck still bogg with a new 650 Holley evendoe it was a double pumper? and with my camaro's 750 which runs great on the camaro, if it's a tuning issue, not saying it's not, but tell me how this can be.

**cammed goat** · 02-13-2011, 01:18 PM

Brings back some memories of high school when a buddy of mine and myself tinkered with his dad's Dodge B250 Tradesman. We installed an Edelbrock Performer carb and it bogged. I can't remember if we swapped jets, but we changed the detent spring and he adjusted the timing. Woke the van up.

**pajeff02** · 02-13-2011, 01:51 PM

Originally Posted by Street Fighter

After thinking about this and reading the post made my you all, I need to know one thing, Why did the truck still bogg with a new 650 Holley evendoe it was a double pumper? and with my camaro's 750 which runs great on the camaro, if it's a tuning issue, not saying it's not, but tell me how this can be.

Two completely different engines. What is your vacuum reading at idle on both engines?