Looking to buy a 85 Crew cab...need opinions and help

[1986Silverado]

Found an 85 crew cab today, didn't really notice if it was a 1ton or 3/4 ton. It has the 454 with th400 setup. I drove it and here is where help and opinions are needed. It seemed as if it was missing and actually backfired thru the exhaust when I got on it and when I was parked and revved the engine up.....could needing a tuneup cause this or could it be more serious as in burnt valves? Also noticed a problem with the tranny when I drove it. I pulled out of the lot and it took a long time to shift and when it did, boy did it shift! Like to have caused whip lash Anyway I only drove it maybe an 1/4 of a mile and turned around to head back and this time it did not want to shift, so I dropped it from drive to 2nd and back to drive and it shifted......need a tranny rebuild? The owner told me it had been sitting for a couple of months and I was the first to drive it in that time......would that cause any of the above problems? Also while sitting there idling it seemed to miss/pop ever so often, not cosistent just every few seconds, also seemed to be idled to low, or it may have just been cold. Help!!

[sdkid]

Low engine vacuum could cause the delayed shifts. Low vacuum could be caused by a variety of problems, including serious engine damage. See if you can you have it checked out by yourself or a mechanic before you make a final decision.

[1986Silverado]

I have a vacuum guage and compression tester.....could I do this and how, not real familiar with big blocks. What would I look for?

[dark-star]

you should check to make sure but it should have a th-400 or old style 3 speed and yes vacuum makes a huge impact on shifting, check to see if there is vacuum at the modulator on the transmission housing, a lot of the time the rubber rots right where it goes into the mod. no vacuum no shift/late shift no down shift etc... a good tune-up might cure the engine issues, could even be bad gas from sitting, how many miles on the motor? i myself would consider going to a later model this day in age and taking advantage of a TBI truck (87 and newer) much better power but more $$$. most crew cabs are full tonners, the best ones are the ones marked with the camper special tag with dual rear wheels, they have a monster sway bar for stability with heavy loads and still drive and ride decent! john

[SanitysBane]

all big blocks have a random miss in them, you can richen the hell out of the carb to make it not have it, but 1)gas millage goes down, and 2)your ET will slow down too. low engine vacum can also becaused by larger cam, also i would check the rubber line first, probally just needs to carb rebuilt.

[N2TRUX]

Before you going looking for vacuum leaks, check the fluid level in the tranny....

[1986Silverado]

What compression reading should I look for?