after a year of running my car without cruise control, its time to reinstall it.

The engine darely pulls enough for power brakes, what are my options looking like for cruse control?

i'm thinking since i run pretty stiff throttle return springs, i'll have to lighten that load quite a bit. and run a vacuum can....

I run like 8inhg at idle..... with no vacuum can...

got the stuff to put a vac can in just never actually got down to installing it...


so what problems will i run into?

 

Cruise isn't required to work at idle..... fortunately.....

You should have 20-25 in. of vacuum under any conditions where cruise is appropriate. I've never yet had a problem with it, in any situation where I've tried to use it; except when the motor had too much power for the adjustment range of the cruise, and the cruise would detect that the car needed to speed up and yanked on the throttle, but the car sped up so fast that it would overshoot the set speed; at which point the cruise would completely let go of the throttle. So I'd be driving down the road with the cruise alternately flooring and letting go of the gas. Kind of funny, but useless. Yours might do better, since it looks like all you've got is a 350; much smaller motor than I had, and a whole lot less torque.

 

unfortunately my 355 is not stock in any way except a 70's nickel block... sledgehammer crank, 6.2" rods anmd forged pistons are a short list... i ran a 13.3 at 119, with an amazingly slow 3.11 60ft...

i just need to be able to have it hold the throttle when i'm driving to the track...

 

Torque goes mostly with # of fuel molecules burned per engine cycle, which goes mostly with cubes. Somewhere in the 1 - 1.3 ft-lbs per cube neighborhood usually... affected by compression, but not by a HUGE amount.... crank brand and rod length don't affect it too much.... cam & heads affect what RPM it occurs at, but the actual amount still pretty much is what it is..... a 350 has 350 inches of torque, a 400 has more, a 454 more still, etc.

I think it'll be fine. It's actually one of the easier things to get to work on a modified motor, as long as you have the right hookup on the carb, and the motor makes a reasonable amount of torque within the range of RPMs that you'd use the cruise in.

 

well the cam is 234/244 @.050... with .520/.544 lift.... not too small but my torque definately is not too low down low.... and it has ported RHS vortec's... aftermarket castings...

i'll see, i hope i have time off tomorow to give it a try, i'll just weld on a new peice to my exixstic throttle cable to hold the cruise control cable... not hard at all...

when the car had tpi, it would also do the whole floor it and let go thing, but i;ve been told that was because it was designed to give it like 65% throttle if it wasn't picking up fast enough so the tranny would downshift... makes sence to me, but in an aftermarket carb setup and modified tranny that wont always work...

 

I don't think it takes much vacuum for cruise control to work. I used to tow a 3500# boat behind my very under-powered 4.3L V6 GMC Jimmy with the family aboard. It took a lot of pedal in Overdrive to hold 70 MPH. Cruise control would work until you hit a long uphill. Cruise control would hold it far enough open it would unlock the converter, sometimes downshift to 3rd and then...... it would slow down. Not enough vacuum to operate the cruise control. It would close the throttle more an more until it finally reached a "balancing point" where it had just enough vacuum to run the cruise control but couldn't open the throttle any further.

Here's what I found interesting..... about the time the cruise control ran out of vacuum there was also not enough vacuum to operate the various HVAC doors under the dash. Air would stop blowing out of the vents and start blowing out at my feet. So I guess if you've got enough vacuum to oeprate the HVAC vents you probably have enough to run the cruise control. Give or take. Just a rough rule of thumb I learned.

Camaros default to blowing air out the Defrost vents without any vacuum. My Jimmy defaulted to floor vents. Just FYI.

Note HVAC vents typically have a one-way valve and vacuum reservoir so they still work when you go WOT for a while. My old Jimmy had leaky lines so it would react almost instantly to low manifold vacuum. You might want to remove the one-way valve from your HVAC vacuum line (temporarily) to simulate what my Jimmy was doing in order to have a meaningful "HVAC vs. cruise control vacuum test."

In short- I think you'll be OK unless you're lugging the engine at too low an RPM, below the cam's normal operating range.

 

my cam seems to like nothbing less then 1700rpm, and even there power is scetchy....

but at the speeds i am talking about, i can disable the lockup, and 2000rpm, a muhc better for my cam speed can be achieved... at 65mph lockup is at 2krpm.... IIRC....