how long can I limp along a low compression engine?

[hpcbmw]

Got my 67 GMC out of storage and am getting it back on the road. I don't want to put a new engine in til I get the body work and paint sorted out, which will probably be a couple years. In the meantime, I'd like to have it running and drivable.

It runs ok, but backfires out the carb when romping on it off idle. It's a sbc 283 with about 100k miles. It was rebuilt in 1980 or so and has been in the truck ever since. I don't have details on the build anymore (bought the motor from a friend who rolled his 66 chevelle right after having the motor rebuilt). I think it was a pretty stock rebuild, but recall that he might have put in a mild cam. It had a quadrajet, but I replaced that with a used Edeldbrock 500 a couple weeks ago. The QJet never ran that smooth, so I hoped the Edelbrock would be better. The carb change has made little difference. The engine has smoked out the exhaust pipes (not to bad) and smoked out the crankcase vent (pretty bad) for the last 10k miles or more.

I checked the compression and got the following: left bank 115/130/120/85, right bank 95/100/90/100. When I squirted some oil in the low cylinders, the compression when up on average 10 psi.

Can a tired engine run somewhat smooth and reliable for a year or two while I work on the paint and body? I'll only drive it maybe 1000 miles a year or so, but want it reliable enough to drive 100 miles at a time. I'm thinking of putting HEI, but is that just polishing a turd?

Thanks for any ideas/advice.

[Dave Severson]

Hard to say how long it will last, but if you don't pound on it a lot it should be able to survive while you do the body work.... Keep an eye on the spark plugs and replace the ones that are oil fouled....

[rspears]

Can't argue with Dave, but I'd go after the power train and chassis before paint. Getting the body straight first is perfectly OK, but if you get your paint all done before you attack the chassis, engine & tranny you're going to have a hard time not messing up your paint as you work, and you're not going to be able to enjoy your truck nearly as much if it's not running 100%. Too many guys pour money into "bling", then get frustrated because it keeps breaking down, or draws laughs when they're driving around town leaving a trail of oil smoke, and end up selling the project for a song. Just my $0.02...

[edward g. p.]

I would not be afraid to drive that truck across the great U.S. of A. right now. Probably has another couple 100,000 miles in her. You need a few supplies is all. Which would include spark plugs, oil, coolant and tools. Drive it gently and good luck to you.

[IC2]

With two low cylinders, and not next to each other, would probably drive it 'as-is' for a while, take anothe comp. test. You might find that a valve was not seating well (carbon) or a top ring or two were also gummed up (also carbon/rust/crud)

[shine]

my guess would be running fat for a long time , very little use , cylinders most likely washed down. get it tuned and put some hwy miles on it. like said it will likely run forever.

[powerquest 257]

Installed new manifold, carburetor, MSD ignition and coil, new plug wires, replaced fuel pump and battery. Engine will start and run at higher rpms but stall out and die.

[hpcbmw]

Thanks for the input. I'll try to get it on the freeway and put some miles on it and see how she runs. I've got lots of bodywork to do, including rust repair on the floor pan, plus some suspension work i want to do before the motor. I'll put in a new motor before getting final paint. Is it worth the HEI distributor, just to stop messing with points? Cheap HEI from Summit, plus plug wires, is about $150. I guess I could use the HEI on the next motor I build (it will be a pretty mild build). Would some "gunk stop smokin" or similar oil thickening product help or harm things?

Shine - by "running fat" do you mean the carb is to rich? What effect will that have? It's smelled rich when running for along time, but that could just be the oil burning. I'm planning on spending some time tuning the edelbrock to make sure I'm not running rich.


Thanks!

[jerry clayton]

Well, threr several angles to look at--first points----why worry about messing with points--you don't need to worry or change to an hei--just put new points/condensor in and set gap (dwell) properly and you will be good for the trip----

Second----with everything else coming down to bodywork or engine first-----with the fuels you have out there now, you will lose the exhaust seats within a tank or two of gas and even now they could be the reason for the uneven compression readings---

[firebird77clone]

You can get a decent HEI off eBay for less, Hell I've got a couple for a 350 if they'll work for a 283 I could help you out. And yes, it's WAY worth it just to get rid of points. You will need to run some 12AWG to properly feed power.

[rspears]

For where you are in the process I'd probably just throw a new set of points in like Jerry said, and run it. Once set the points shouldn't give you any problems, it'll get you by while you're repairing the body, and a little highway driving may just smooth things out a bit. Nothing wrong with swapping to HEI, but you're looking at the dizzy and plug wires (different connectors) and I doubt you'll notice any difference with the stock 283. Money can be spent where you see more value. If it's indeed running fat (main jets rich) that could be a big part of your problem, including maybe some carbon deposits that might affect your compression.

[hpcbmw]

I'll probably do like you guys suggest - put in new points and condensor, check the jets and settings on the carb, and drive her til she stops. If I come across a good deal on an HEI, I might pick it up, but the extra $60 for new plug wires is kind of a deal killer, and I'm not a fan of re using someone else's used plug wires.

Thanks for the suggestions.

[glennsexton]

The HEI will definitely transfer to your new build.. As to the low compression - slap a quart of Hiltons Hyper-Lube in place of your oil when you change and you'll be pleasantly surprised. You can probably drive it for years as long as you're gentle and remember to check the oil often..

[stovens]

Never heard of hilton's so I looked it up Glenn. Cool stuff by their description, as well as their Hy-per Lube Zinc! Might have to check it out!

[glennsexton]

I've used the Hiltons for a long time after a friend in the industrial supply business turned me on to it for use in gear boxes as well as engines. It's about 7-8 bucks a quart and sure seems to help the older engines that I seemed to attract for a while! Much better than STP or Motor Honey

The Hy-per Lube Zinc is kinda spendie ($16.00) but works well and is definitely worth the price when firing up a flat tappet for the initial break in.