Horse power I never knew I had shows up unexpectedly

[ozkiwi]

I have had a rebuilt quadrajet sitting in it's plastic wrap in my workshop for over a year.
I only bought it as a back up while the Australian dollar was up against the USD as my old one seemed fine.The original started to leak so I thought I would install the spare and rebuild the original at my leisure.
I have a crate 330hp HO with a roller cam,1 5/8 long tube headers running into a 2 1/4 true dual exhaust and a elderbrock performer inlet manifold.
No rocket ship but a nice street setup.
First off the old carby was barely bolted down with all bolts finger tight which cannot be a good thing.
After the install my lumpy idle was gone????I thought it was the cam making it idle like that !
Driving down the road I noticed how smooth the engine was and how responsive the it was to throttle input.
The shock came when I floored the peddle off the lights and my little mouse roared for the first time I know it is only 330hp but it felt like the thing jumped in the air when it launched I must have been driving around on about 100hp less and I was happy with that.
Only a tired 305 the truck came with for comparison so it felt good to me but surely the shop that installed the HO would have noticed something was amiss as they have installed a ton of these engines?

Here's a question how does a carb change effect the the change points for a 700R4 because now my truck will pull hard all the way till 5500rpm through each gear until top where it used to change at 4000 unless I held it manually in each gear?

[Titomars]

Both the vacuum modulator and the throttle valve cable will effect shift points.
Now that you don't have a huge vacuum leak, that will change the modulator's vacuum signal and how it moves it's control valve in the valve body.

[ozkiwi]

Originally Posted by Titomars

Both the vacuum modulator and the throttle valve cable will effect shift points.
Now that you don't have a huge vacuum leak, that will change the modulator's vacuum signal and how it moves it's control valve in the valve body.

Thanks.I obviously no jack **** about quadrajets,700r4s and how they work and honestly I don't really want too but hard to find an honest mechanic here in Australia.I am learning fast because every time I pay a professional to do the work for me I have to redo the job to get it right.

There is a vacuum hose running off a T connector at the carb down to a cylinder on the gearbox on the passenger side which I assume the must be the modulator you are talking about so understand what your saying.This started to make a whistling noise a while back and when I dropped into a transmission specialist he said the transmission needs a rebuild based on that noise and a minor leak out of the rear seal.Now that noise has gone along with the vacuum leak at the carb so guess that lack of correct vacuum
may have caused it?
I have found a youtube vid for TV cable setup so I won't pick your brains on that.

thanks for your help

[Slammed84]

Aren't quadrajets 750 cfm's?
I think I read that in Chevy High Performance a long time ago

[67swb72klb]

I would check the adjustment on the TV cable to make sure it is right if it is not the trans will have a short life

[enaberif]

Originally Posted by Slammed84

Aren't quadrajets 750 cfm's?
I think I read that in Chevy High Performance a long time ago

750cfm or more harder to find 800cfm which I run on my truck

[Bishops Trucks]

I had the same motor in a 1971 long bed I lowered 6" in the back and 4-1/2" in the front. It was backed up with a TH400 with a street/strip shift kit. Those motors are no slouches. I know I must have put almost 200,000 miles on the motor between the 2 trucks it was in. Keep the oil changed and usual maintenance and it will serve you very well.

[Titomars]

Originally Posted by Slammed84

Aren't quadrajets 750 cfm's?
I think I read that in Chevy High Performance a long time ago

Actually if I remember correctly there were 2 sizes. The most common one was about 735 cfm. and the harder to find one of 785 cfm. The 785's were used on Buick, Olds, and Pontiac 455's and GMC MHC with the 455.

[ozkiwi]

Originally Posted by 67swb72klb

I would check the adjustment on the TV cable to make sure it is right if it is not the trans will have a short life

https://www.youtube.com/watch?v=0jiSIoks7Jw

As long as this guy knows his stuff it seems pretty straight forward.