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Went ahead and swapped to a Chevrolet Performance 350HO 330HP crate engine.
Car runs great UNTILL the Air Con is switched on: then there is an obvious and annoying hesitation every time the compressor kicks in, and that is now every 3 to 4 seconds.
with the old engine this didn't happen.
replaced compressor and clutch, still feel the shudder.
Do you mean you swapped out your (original) L82 for another SBC crate engine?
I can't help much with A/C questions (my 80 doesn't have it anymore), but I am curious about your upper radiator hose routing. Can you post some more photos?
EDIT: Do you have the dual gauges to check the high and low side pressures? Rapid cycling could be from overfilling the system.
Last edited by Bikespace; Feb 25, 2021 at 08:21 AM.
You can buy a solenoid that kicks the idle up slightly when ever the ac compressor kicks on that will prevent that problem. It mounts to the carb and is wired in with the compressor. Easy fix.
You can buy a solenoid that kicks the idle up slightly when ever the ac compressor kicks on that will prevent that problem. It mounts to the carb and is wired in with the compressor. Easy fix.
Agree. This solenoid was standard on the 1980 cars with AC (pretty much all had AC). I disconnected mine after I disconnected the AC. The only L48 items left from my engine are the block, rods and crank. When the day comes that I have days on end to tinker, I have an 80-85 L82 reconditioned short block assembly just waiting for me to build my dream engine. For now, I have all of my dream pieces on my L48 block. Lots of fun (see signature).
Agree. This solenoid was standard on the 1980 cars with AC (pretty much all had AC). I disconnected mine after I disconnected the AC. The only L48 items left from my engine are the block, rods and crank. When the day comes that I have days on end to tinker, I have an 80-85 L82 reconditioned short block assembly just waiting for me to build my dream engine. For now, I have all of my dream pieces on my L48 block. Lots of fun (see signature).
I didn't realize this was a thing. All 1980 Corvettes came with A/C standard, but it seems that only those with automatic transmissions got the idle control solenoid. It must have gone missing from my 79 auto.
Holley sells one at Summit dont know if its correct or not?
Those are nice crates, make good torque. Neighbor has one feels pretty good.
Its no powerhouse but not a slug either.
I suspect the solution to your problem may lie in all three of the suggestions here. If you no longer have the idle speed solenoid, you should find one. I have mine set to bring the idle up to the AC off setting when the AC is running. This means the idle runs around 950 rpm when the AC is on but the compressor cycles off. Even if the solenoid is not operational I don`t have a `shudder`when mine kicks in. That may be due to timing too retarded and possibly an incorrect charge of refrigerant.
Ok...so here is some food for thought.....I have a 1971 Dodge Demon 340 in my garage that I just installed Classic Auto A/C on.......it is a Sanden Compressor. The engine is a pretty hot .030 340 with 73' 360 heads, ported and a 240@.050 cam with .525 lift...RPM Performer and a 750 Demon carb....TTI step headers.....just a nice setup. I charged the A/C on this Monday. When I kick the compressor on....the RPM moves maybe 100 RPM.....timing set at 20 degrees initial and 35 total...no vacuum advance, no idle solenoid. The point is that this is a hairy little engine and it barley even knows the compressor is there.......it has a lot of initial timing.
I bet the OP $100 that he needs about 10 degrees more timing at idle......need to check it and adjust the total and curve as well. The 330hp engine is a mild setup.....it should not even flinch when the compressor is turned on.
I will have to check the timing I'm not sure where it is set right now
and that solenoid must be magical the shudder is really a pain thanks anyone got a Pic to help the search?
@Bikespace yes I swapped the factory motor with a Chevy Crate engine
Do you have a way of testing your AC charge pressures? I use one of these (link), with the appropriate R12 adaptors for a C3 (not that I have a C3 with working AC, which is why I have an R134a manifold).
But, yeah, timing is the low-hanging fruit. Email @lars for the proper timing specs to follow.
Last edited by Bikespace; Mar 26, 2021 at 08:24 AM.
The other thing is take the compressor and see if you can move the drive by hand.....right up front. If it is very hard to turn then you are on to something.......
At idle (700-800 rpm) the compressor isn't spinning fast enough to show if the problem is load/compressor related......but at 2500 rpm running down the highway, it sure will be.
I got two compressors for 90's Silverado's last year brand new from Four Season's and you could not spin them by hand out of the box......Four Seasons's assured me there was no issue, just tight tolerances and when I installed it, it started making noise in about 5 minutes. I was PISSED. Sent it back to Rock and got another, this one was the same way.......they would NOT refund my money. So after having the truck sit for a week at my house, I punted and got a re-man in town at O'Reilley's......you could spin it by hand and it is still on the truck 9 months later. Food for thought.
Jebby
Last edited by Jebbysan; Mar 26, 2021 at 09:02 AM.
I didn't realize this was a thing. All 1980 Corvettes came with A/C standard, but it seems that only those with automatic transmissions got the idle control solenoid. It must have gone missing from my 79 auto.
i know 79 manual does NOT have it and idle is 900 rpm, auto supposed to have it and idle 700 rpm (you assume theoretically with solenoid and with and without ac on)
if it were mine and i am an expert at breaking r4 compressors..
- clarify 134 or r12
- post pressures at idle and 2500 rpm high and low
- note if compressor cycling at all
- verify belt is TIGHT
- what is your idle and what is your transmission?
- compressors area CRAP SHOOT.. other than leaking, i went NEW only Napa professional not remanufactured. (they even warranty'd my leak, free exchange)
- you noted every 3-4 seconds.. that to me is cycling compressor, could even be low.. or very high on high side and restriction in orifice
i just returned a rock auto china rebuilt alternator.. it charged but could not believe it dropped rpm at idle 110.. i put new bearing in old one and it drops 50 rpm and recovers faster (rear defogger on) so i'm leaning compressor for whatever reason
Last edited by interpon; Mar 26, 2021 at 09:34 AM.
Now it sounds like a compressor issue. You can’t compare the Sanden to the oem as they are very different designs. The oem compressor definitely requires more torque to spin, but it should not have that significant of an impact. Modern ac on performance vehicles, including Vintage Air, provide a provision to prevent the compressor from energizing during WOT.
1980 L88 Engine Swapped 350 Chevy performance
