The quadrajet on my 85 was reaching the end of its useful life(Actually i think it reached it a couple years ago when the large crack appeared on the main body) and one of my buddies had what he thinks is a 1975 quadrajet laying in the corner of his garage. So i replaced it last night and got it to start. However after getting some sleep and clear head i went outside to finish up and realized that not even the vacume advance was hooked up and i seem to have a lot of extra vacume lines. So do i just cap them off? Should some be spliced together or what? Living in kansas there is no need to worry about emissions and it rarely leaves my property anyway. I just want it to be reliable and run good. Also its a 1985 k5 with a 305 and 700r4 everything stock(execpt the carb ofcourse) if it matters
CK5
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85 blazer with 75 carb vacume lines.
- Thread starter jkeys0218
- Start date
Look at the core support sticker, hopefully it's still there. Tells you what all the requirements are.
I can say (sounds like I had a very similar truck) that when I unplugged the EGR vac line, the truck surged at part throttle cruise, due to running lean. Needed to re-jet the Q-jet to "fix" the issue.
Some of the stuff, ignoring federal law, really isn't needed. The valve on the exhaust manifold and AIR are two that I think unnecessary for proper operation.
THERMAC (on the air cleaner) is apparently good to have in very cold weather to make sure the carb doesn't ice up, and EVAP is IMO the only "good" way to make sure the tank is vented properly.
Regardless, vac advance and PCV/breather are three lines you won't be getting rid of at all, and if you are that far into it, EVAP and THERMAC wouldn't be that much extra to keep. It's a matter of understanding it and making educated choices.
Other issue you might have is the 305 ESC. Running lean MAY start you running into the knock sensor under certain conditions, but the AIR and what not won't affect that. Ideally you'd be able to run vac advance off manifold vacuum (ported is for emissions, not performance) but again, with the way everything is plumbed, and the ESC, running it that way may cause issues.
I can say (sounds like I had a very similar truck) that when I unplugged the EGR vac line, the truck surged at part throttle cruise, due to running lean. Needed to re-jet the Q-jet to "fix" the issue.
Some of the stuff, ignoring federal law, really isn't needed. The valve on the exhaust manifold and AIR are two that I think unnecessary for proper operation.
THERMAC (on the air cleaner) is apparently good to have in very cold weather to make sure the carb doesn't ice up, and EVAP is IMO the only "good" way to make sure the tank is vented properly.
Regardless, vac advance and PCV/breather are three lines you won't be getting rid of at all, and if you are that far into it, EVAP and THERMAC wouldn't be that much extra to keep. It's a matter of understanding it and making educated choices.
Other issue you might have is the 305 ESC. Running lean MAY start you running into the knock sensor under certain conditions, but the AIR and what not won't affect that. Ideally you'd be able to run vac advance off manifold vacuum (ported is for emissions, not performance) but again, with the way everything is plumbed, and the ESC, running it that way may cause issues.
Thanks for all the info. Do you know where i could find a diagram that includes what pressure each line should be? Would i gain anything buy ditching all the unnecessary stuff or should i just keep it stock? Also any vacuum lines better th han others, likr ones that last longer?(I dont ever wanna do this again)
I read an article that talked about changing a esc dizzy to a regular one, it seemed pretty strait forward. Do you think i should do that since i got rid of the ccc? And since my ccc is gone( so obviously there's not anywhere to plug in that wire that went to it. I just have it tucked out of the way for now) shouldnt i be getting a check engine light? I know the light works whenever im starting it.
I read an article that talked about changing a esc dizzy to a regular one, it seemed pretty strait forward. Do you think i should do that since i got rid of the ccc? And since my ccc is gone( so obviously there's not anywhere to plug in that wire that went to it. I just have it tucked out of the way for now) shouldnt i be getting a check engine light? I know the light works whenever im starting it.
If you had CCC, all bets are off lol.
IMO, CCC was about the worst possible combination of vacuum lines and electronics possible.
With CCC gone, it *probably* will mean that even if you left the vacuum lines as they should be, it won't all work as designed in regards to fuel mixture, etc.
I would definitely swap distributors. I assume yours doesn't have a vac advance can, but I know around this time GM was running all sorts of odd combinations. In any case, probably just better to replace it with a non-ESC variant. Surprised that doesn't trigger the CEL (along with the unplugged MCS and TPS), but who knows what is up with that. It was a very primitive system.
I would keep EVAP, THERMAC, PCV/Breather, and vac advance. Cruise if you have it, as it's handy and very simple. Those are it I can think of that I would keep in your case.
Note that removing/disabling things like AIR, etc., depending on where you are, may make it impossible or very costly to sell later on down the road. Not saying don't do it, just understand the repercussions.
As to what hoses last longer, I can't really comment on that. Later on GM started using hard plastic hose with rubber ends, which holds up better long term than actual hose, but I'm not sure where you can get that, and then you'd need to figure out how to make rubber "ends" to connect to the fittings. Probably easy to do, just something to think about. Realistically many people are still running the rubber hose that the vehicle came with, so even 10 years would be a "short" lifespan for new vacuum lines.
IMO, CCC was about the worst possible combination of vacuum lines and electronics possible.
With CCC gone, it *probably* will mean that even if you left the vacuum lines as they should be, it won't all work as designed in regards to fuel mixture, etc.
I would definitely swap distributors. I assume yours doesn't have a vac advance can, but I know around this time GM was running all sorts of odd combinations. In any case, probably just better to replace it with a non-ESC variant. Surprised that doesn't trigger the CEL (along with the unplugged MCS and TPS), but who knows what is up with that. It was a very primitive system.
I would keep EVAP, THERMAC, PCV/Breather, and vac advance. Cruise if you have it, as it's handy and very simple. Those are it I can think of that I would keep in your case.
Note that removing/disabling things like AIR, etc., depending on where you are, may make it impossible or very costly to sell later on down the road. Not saying don't do it, just understand the repercussions.
As to what hoses last longer, I can't really comment on that. Later on GM started using hard plastic hose with rubber ends, which holds up better long term than actual hose, but I'm not sure where you can get that, and then you'd need to figure out how to make rubber "ends" to connect to the fittings. Probably easy to do, just something to think about. Realistically many people are still running the rubber hose that the vehicle came with, so even 10 years would be a "short" lifespan for new vacuum lines.
My main problem now is that when i bought it most of the vacumm lines were already broke. They hadn't been removed; just tucked away as to not get caught up in moving parts.so i have no idea what goes where. And i do believe i have a vacume advancd can( the silver thing just to the passanger side of the dizzy with the vacumm line going into the center?) Where should the other end of that line go? I really need a schematic of the vacumm lines if you know where to find one. A google search didnt find much.
I KNEW I had started to do something with those stickers! http://dyeager535.topcities.com/emissions/index.html
The '83 305 will probably be closest to yours.
As long as that can is part of the distributor, you are correct that is vacuum advance, but again with the ESC distributor, I'm not sure if it functions like a "normal" setup with weights too, or if it was all electronic. Pop the cap and see. I suspect it has the weights in it.
Contrary to what you may hear or read some places, you want the vacuum advance hooked to *manifold* vacuum. That will be a source that has vacuum even at idle. Either pull it from the carb if there is a port for it, or from a fitting on the intake. Q-jets usually have plenty of fittings to choose from.
You don't want any of the switches inline with vac advance, nor do you want it on a port on the carb that does not have vacuum at idle. GM used the ports they did on the carb for emissions purposes only, NOT to make it run best.
The '83 305 will probably be closest to yours.
As long as that can is part of the distributor, you are correct that is vacuum advance, but again with the ESC distributor, I'm not sure if it functions like a "normal" setup with weights too, or if it was all electronic. Pop the cap and see. I suspect it has the weights in it.
Contrary to what you may hear or read some places, you want the vacuum advance hooked to *manifold* vacuum. That will be a source that has vacuum even at idle. Either pull it from the carb if there is a port for it, or from a fitting on the intake. Q-jets usually have plenty of fittings to choose from.
You don't want any of the switches inline with vac advance, nor do you want it on a port on the carb that does not have vacuum at idle. GM used the ports they did on the carb for emissions purposes only, NOT to make it run best.
Thanks for thoes diagrams. Mine seems more like the 85 350. I might run by the library on my way home. They have a lot of original service manules( like the one the dealer ship had). Im sure they'll have an 85 blazer. Im assuming it will be one book that covers all the engines.
Service manual will cover all for that year, yes. As I recall though, they didn't cover vacuum lines at all. Could be wrong, but I don't remember it. There was normally an "emissions" manual supplement, but still don't think the vacuum routing was listed there. I think that's why the core support stickers are so clamored for still.
big reaper
1/2 ton status
I know my chiltons manual has all the different vacuum diagrams in it. It came in handy since when I got my blazer the engine was in the back in pieces and I had to reconnect everything to pass CA emissions.
That might be a better bet.
Then again, from that core support sticker, you still don't know what vacuum port got what for vacuum, you'd still have to check each port on the carb, so if planning to do away with a bit of the emissions stuff, I'd just run what needed to be run off of the port that gave me the vacuum signal I needed.
Then again, from that core support sticker, you still don't know what vacuum port got what for vacuum, you'd still have to check each port on the carb, so if planning to do away with a bit of the emissions stuff, I'd just run what needed to be run off of the port that gave me the vacuum signal I needed.
This morning i went and roamed around the local truck salavge ( like i often do on saterday mornings lol) i noticed a new mid 80s k5 in the lot. So instinctively i headed strait to it. Looking around the inside it seemed everything was exactly like my 85. Then it hit me; maybe the vacumm lines are still intact! So i poped the hood and... There wasn't even an engine. However there was a core support stick! And it looked to be exactly like what o needed so i snapped a picture on my phone. And comparing the picture to whats left of mine its a perfect match. But that spot in the upper left with the three letters that identify it was gone so i dont know what it is labeled as. So if any one has the same problem as me with and 85 305 pm me and i can send you a picture of the sticker. I kinda went crazy and hooked everything up like the picture with all new lines even though that wasnt the plan. So now shes running "good" is there anything that i should remove for better preformance? I dont care about emissions but i dont mind them on there except if it's taking power. There are to 4 port male plugs in the front center just a little to the drivers side, are these both just manifold vacumn? Also not really vacuum related but my carb outlets didnt exactly match up to the picture of a 75 carb(which is what i have) but looked like the picture(an 85) so i compared it to the 85 that i puled off of it. And sure enough the base plate matches up perfectly to the 85. So a 75 qjet with an 85 baseplate? Is that a comon thing to do?
Nothing emissions actually robs power. What robbed power was the terrible catalytic converters they used back then. Obviously there were all sorts of changes based on emissions that didn't help, but the single largest change was from gross to net HP numbers in 1972.
But in an '85, low compression, horrid heads, weak cam, and bad exhaust all make for poor power production. You can actually increase power and clean up emissions from those numbers with the parts available today, as long as you aren't in an emissions area lol.
There were only maybe three substantially different Q-jet castings (I'll say early, later, and then CCC although there were more subtle variations) and of the three pieces (air horn, float bowl, and throttle body) the throttle body didn't change much at all. Top two pieces changed quite a bit based on the year/variation of carb.
But in an '85, low compression, horrid heads, weak cam, and bad exhaust all make for poor power production. You can actually increase power and clean up emissions from those numbers with the parts available today, as long as you aren't in an emissions area lol.
There were only maybe three substantially different Q-jet castings (I'll say early, later, and then CCC although there were more subtle variations) and of the three pieces (air horn, float bowl, and throttle body) the throttle body didn't change much at all. Top two pieces changed quite a bit based on the year/variation of carb.
Opening a whole other can of worms with those questions.
Yes, you can hollow out a cat. On a stock motor as bad as the mid 80's, I doubt it will make enough difference to notice. I am not a fan of hollowing converters, I would prefer to simply replace it with the newer style converters that are almost no hindrance to flow, yet still work. Even a properly running vehicle will smell, a catalytic converter can make the vehicle exhaust less of an issue, which even if you don't care about the environment is a good thing in my book. I don't think I'd worry about it either way unless I was in the process of changing the exhaust, and/or building the motor up.
Yes, you can swap heads without pulling the motor, but new heads on an old block can lead to head gasket sealing problems. I haven't put old heads, and I think some of the thicker head gaskets do a better job of sealing in cases like that, but thicker head gaskets ruin "quench", which is important for efficient combustion, and keeping knock to a minimum.
As to new heads, Vortecs are the common upgrade, but along with those heads, you are now talking different rockers, perhaps different pushrods, new intake, etc. You can buy aftermarket heads that are good as well, but they cost more than the Vortecs.
Yes, you can hollow out a cat. On a stock motor as bad as the mid 80's, I doubt it will make enough difference to notice. I am not a fan of hollowing converters, I would prefer to simply replace it with the newer style converters that are almost no hindrance to flow, yet still work. Even a properly running vehicle will smell, a catalytic converter can make the vehicle exhaust less of an issue, which even if you don't care about the environment is a good thing in my book. I don't think I'd worry about it either way unless I was in the process of changing the exhaust, and/or building the motor up.
Yes, you can swap heads without pulling the motor, but new heads on an old block can lead to head gasket sealing problems. I haven't put old heads, and I think some of the thicker head gaskets do a better job of sealing in cases like that, but thicker head gaskets ruin "quench", which is important for efficient combustion, and keeping knock to a minimum.
As to new heads, Vortecs are the common upgrade, but along with those heads, you are now talking different rockers, perhaps different pushrods, new intake, etc. You can buy aftermarket heads that are good as well, but they cost more than the Vortecs.
So really i just need a new engine lol
I plan on swaping for a tbi 350 in the not to distand future anway so unless is a simple fix more a noticeably different amount of power id just be wasting my time.
I plan on swaping for a tbi 350 in the not to distand future anway so unless is a simple fix more a noticeably different amount of power id just be wasting my time.
If you are going TBI, yes leave it alone lol. TBI will work great as long as everything in the motor is stock, and the fuel pressure is optimum. When you start changing hard parts (cam, heads, exhaust, intake, etc) you will need to look into PROM tuning.
Many people aren't happy with the stock TBI power output, the TBI rigs I've driven that have decent gearing and small-ish tires seemed to have decent power to me. As with everything, it can always be improved lol.
Many people aren't happy with the stock TBI power output, the TBI rigs I've driven that have decent gearing and small-ish tires seemed to have decent power to me. As with everything, it can always be improved lol.
MrSchaeferPants
1/2 ton status
One question though, with the new '75 carb and your TV cable for your 700r4 hooked up, how's your shifting, and if you've been up to speed, torque converter lock up.
Well it doesn't have any tvs and i never really liked thoes big radios with the screens but im assuming youre talking about a different tv cabel lol. I dont know any thing about transmissions so your gonna have to dumb that down a lot. And as far as shifting goes i havent got to dtive it except around back to get it out of the way. Probably never went over 6 maybe 7 miles an hour
MrSchaeferPants
1/2 ton status
Your first post said you had a 700r4. TV or throttle valve cable is what tells your 700r4 to shift. A carb off a 75 never used a 700r4 (they came out in 82), so if it doesn't have the bracket for it, or if you never hooked it back up, you will have major shifting problems and eventually burn out your transmission. Just wondering if it did have a stud on there for a TV cable. That 75 carb could have came off a boat, car, or truck with a th350, th400, sm465..etc.
http://coloradok5.com/forums/showthread.php?t=255404
It's not related necessarily to your question, but you posted you have a 700r4 and I'd hate to see something happen from not knowing about potential problems from a carb swap.
