That was intended to be a joke

The engine has never had a rebuild to the best of my knowledge and currently has 59,000 miles (on the odometer). Runs strong, does not smoke or burn any oil. I have not taken it to the redline (maybe 6000 rpm tops) in first gear.

It really bogs off the line when I floor it. My gut is telling me it's the carb, but will look at all possibilities.

 

Again, which carb do you have on it?

Lars

 

Holley 6239

 

I have a similar setup, 70 LT1 shortblock, 3:70 rear, Holley 780. Over the years/decades, at least in my case, the primary accelerator pump arm on the throttle shaft developed a large amount of wear in the area that rubs against the nylon cam that activates it. Check for wear in this area and if necessary replace the arm and cam.

 

Thanks! I'll add it to the list.

 

That's a 780 Holley vacuum secondary with secondary metering block (not plate), so it's a good carb. But it shouldn't hesitate or stumble when you nail it, so you have a setup problem.

First thing you want to do is a good solid baseline setup, which includes verifying the jetting is the correct 68/73 with 6.5/8.5 power valves installed. Also, make sure you have at least an .025 squirter, if not bigger (I'd use a .028 to .032).

Set up your primary/secondary throttle blade openings as outlined in my setup papers: you need both primary and secondary openings at idle to be equal, and you need to verify no more than .020" transition slot exposure on the primary side. Any more than .020 will produce the stumble your describe.

Set your float levels with the engine hot and running. Right to the bottom of the plugs with slight slosh coming out the plugs.

Make sure your accel pump has no slop in it and that the spring loaded rod slightly compresses the accel pump arm at idle for an immediate pump shot with the slightest throttle movement.

Make sure idle mixture screws are equally adjusted and set for best manifold vacuum.

...and make DARNED sure your timing is set right: You should be running about 16 initial with 36 total and a functional vacuum advance hooked up to manifold vacuum in order to produce about 30-32 degrees of timing at idle.

E-mail me if you need the carb setup papers. With things set up as outlined, the car will not stumble, and will smoke the tires by sidestepping the clutch at 2500 rpm. If it doesn't, send me a plane ticket and I'll come set it up for you.

Lars

 

Thanks for the advice. I talked with a good mechanic today who I trust to do this type of work. I'll print off your recommendations. I PM'd you with my email for you to send the setup papers. If all else fails, you may have earned a trip to Ohio!

Ken

 

I don't do PM, IM, Text, LinkdIn, Facebook, Twitter, Messenger, PayPal, or whatever the other in-vogue crap is. I do e-mail and phone calls:

Lars
V8FastCars@msn.com

 

Just got your e-mail. Info sent to you. Good luck with the setup and tuning - contact me with any questions.
Lars

 

I bought two new Z/28 camaro's 69 and 79 both had 3.73 rear. 69 had E-70 15 good yrs that measured 27 inch in diameter. Both ot these cars showed 3000 rpm at 60 mph. Either you have non stock really big diameter rear tires, no 3.70s or bad tach.

 

The cheapest deal i could come up with was sprint. The small phone has a text message on it. Have not leaned how to use it or will even try. Had a computer since 2000 don't know how to use it. I bought it to e-mail with look up web sites and on three forums. Other then that i know nothing about computers care not to learn, Send me back to the 1960s with modern medicine of today and i would be good to go. I don't need a computer to drive the car or truck for me, braking system, traction control. Why don't we just get in a new vette push a button on the dash let the car drive itself. That way we can 100 percent take the abilty to drive something away from ourselfs. I want my 66 back with no PS, PB, PW, PD, A/C. Problem is i see the price on a 66 427/425 hp or any C2 i want to puke. I remember what i sold my 66 for in 1978. I seem to be not the only one out there that prefers the 1960s.

 

Sounds like your full of "SYNERGY" and those "ISSUES" need to addressed by an MBA

 

Yeah, I'm full of something, alright...

 

Beer???

 

Ok, here is what I have learned so far:

Looks to be 3:70 rear end. Found a conversion table that indicated that at 82 mph with this setup I should be turning 3700 RPM. At 41 mph, it should be 1850 rpm.

Here is my results:
41 mph 1900 rpm
60 mph 3000 rpm
82 mph 3700 rpm (approximate, since I didn't want to take my eyes off the road long enoung to confirm exact, but it was over 3500 and less than 4000)

Looks like it's a 3.70 gearing.

"Nervousness" test:

Three attempts to at 3000, 3500, and 4000 rpm. First two, bogged down for a second, then took off, no rubber lost. At 4000, I was able to get a small squeal, but nothing drastic. I'm by no means a mechanic, but from all I have learned here, looks like it is probably a carb problem somewhere.

Ken

 

Hard to imagine the carb could be THAT bad: A 4000 rpm banzai launch should smoke the tires if you had a coffee can with a calibrated leak for a carb. I was able to smoke the tires on my 2.3 Pinto autocross car with 85 horsepower if I did a 2500 rpm drop... You might have problems not related to the carb, like a cam installed 1 tooth off, for performance at that ****-poor level. If you'd like to verify if you have a carb problem or not, send me the carb and I'll put it on my 500-horse '64 small block and try it out. If it runs fine, you don't have a carb problem. If my car falls on its face, I'll fix the carb for you.

Lars

 

Well im no where near as good nor may i ever be as good as lars on a carb but i would think you have some binding in the rear end or the some major brake drag, see if your wheel is hot to the touch after a short drive , I had it when I first bought my car one of the brake lines collapse and it wouldnt spin the tires to much.

But the falling on its face,
I know you said you checked timing might want to check the firing order 5 and 7 wires can get mixed up easily.

By the way Lars may take you up on that offer for a carb issue have the holley 750 street avenger can remember number but here it is
I had a problem with bog and eventually took it off for a smaller 600 holley and no more problems arose

 

Any progress?

 

Not yet. My "tuner" didn't have time this week to look at it.

Lars sent me his carb setup guide. We will be using his settings for timing and carb setup and see what happens. I'll keep you posted.

Ken

 

You already had an offer from Lars to ship him the carb for testing and/or repair. Why do you still need a "tuner"? Put the carb in a flat-rate shipping box from the post office and send it his way. He always does quick turn-arounds and you will then know the carb is good.

Sounds like a 'no-brainer' offer to me....