68oldscutlass

Hey guys. Have a 68 Cutlass with 350 and stock 4bbl manifold. Have a 750cfm Quadrajet on from Summit. Car runs great but getting real hot as I drive around town and even worse at highway speeds. Thinking timing might be the issue. Water pump is being checked next because everything else is new, even went with 4 core radiator (just need new top plate now to hold it down). Anyway I am wondering if I have my vacuum right. All I have set up is an HEI distributor and installed power brakes. Also there is the vacuum line from the trans. Can anyone helo tell me where I should be hooking these up and what I should be plugging up. I dont have the temp switch in the manifold like I have seen. That is plugged off. Lets see if this pic works. Thanks so much. I am very mechanically inclined just never understood the vacuum ad timing so well.

68oldscutlass

The top right angled port seems to be a vent. On the bottom back of the carb is a larger port so I was thinking power brakes go to that. I dont know. Help please.

68oldscutlass

See if this pic of my engine compartment works...

captjim

Yes, the threaded port at the rear goes to the brake booster. Hidden behind the vacuum canister on the carb should be a manifold vacuum port that is for the trans.

edit, here is a nice read on mechanical and vacuum advance,
http://www.corvette-restoration.com/.../Timing101.pdf

Edit, edit, just realized that your car will NEVER run correctly, that is a Chebby carb!! LOL

oldcutlass

You gotta clean that filthy beast! Trans gets hooked to manifold vacuum. Brake booster goes to the port in the manifold for full manifold vacuum also. Distributor can go to either manifold vacuum or ported, there have been many discussions on this. PCV goes to the big port at the front of the carb, also manifold vacuum. Then plug the rest.

rcrac3r

The following link will take you to a free online service manual for your car.

http://wildaboutcarsonline.com/membe...n_6C_6H_6K.pdf

It is the actual gm service manual scanned onto the site. This section shows where the vacuum lines are routed. Diagram 6K-10 has pics. Registration for the site is free as well.

oddball

Brake booster needs manifold vacuum and a pretty big connection. Usually that goes straight to the intake using a 3/8" hose, or to the base of the carb on the rear. Watch out - too much rubber hose will collapse at that size.
The tranny modulator goes to manifold vacuum. You can run that from the carb or from a connection right of the intake.
The distributor can go to manifold *or* ported vacuum. Pretty much your call on how you do your final tuning. I **think** the port on the base plate coming out towards the front right of the car is ported.

The PCV should go to manifold vacuum, usually on the carb, should be the large on on the base plate right under the fuel inlet, or maybe that large angled one above the fuel inlet.

Now for the problem - I'm unfamiliar with that particular model of qjet, so I don't know which outlet is what. That's not an Olds carb, and most folks avoid those later year models.

Do you have an evap canister? Probably not if it's a 68.

The only vent is the vertical one that's inside the air cleaner ring right in front of the primaries. Everything else is a vacuum connection and must either be connected to something or capped.

The temp switch is not essential. Overheating like that is probably not just due to timing though. Is the radiator in good shape? Good fan? No obstructions? I'd start with just basic cooling system checks.
Also, what's your definition of "overheat" and what temp thermostat are you running?

oddball

Sadly, this will only be partially helpful as this is clearly not a '68 QJet.

Hey, on that topic, I don't know that I've ever seen one with just a rear vacuum break. Plenty with just a front break, plenty with front and rear, but just one in the rear? Seems odd.

rcrac3r

I agree having an Olds Qjet would better but at least it will show what is connected to manifold vacuum, etc.

68oldscutlass

Brand new 4 core rad, new 160 tstat, flushed like hell, no air present, flex fan and original shroud. Running 180-190 sitting in garage. Once I start cruising temp slowly creeps up to 230-245. Not good. I have my original engine sitting in garage so Im gonna take off water pump, inspect then take off one on the car to see if there are any differences. I have no prob buying new one just curious if the blades are messed up or whatever and not keeping up.

oldcutlass

What is your timing set to? Is that carb running lean? Is the car surging at cruise? Seems you may have an airflow issue, anything blocking the radiator, like an aux trans cooler?

captjim

Couple of things,
1) is it an aftermarket flex fan or stock? Fan clutch?
2) With an HEI, disregard the OE timing, it should be 20 degrees initial at idle in park with vac advance not connected. If the timing is retarded, it can run hot.
3) have you varified that the engine is actually getting hot and not a faulty gauge?
4) What brand of stat? I resolved an odd problem once by using a Moroso (RobertShaw) stat. Relacement units from advanced, etc are more restictive.

68oldscutlass

Failsafe 160 tstat. Aftermarket flex fan in stock shroud. Fills entire fan shroud with only about 1/2 inch clearance. Maybe need to go back to fan/clutch. Was trying to get away from the weight. Not good with timing so I'll have to haves buddy come over. I have a timing light I think, just not sure what to do lol. Brand new gauges and everything else reads perfect. How else can I check temp without opening system? Thank you everybody. This site is extremely helpful. I'll post pic of fan in a bit, feeding the kiddies.

captjim

I would go back to stock clutch and fan, if you have it lying around.
You definitely need to verify timing.
If it really is that hot, the upper radiator hose should be very tight (a lot of pressure) and quite warm to the touch. Be careful.

68oldscutlass

Water pump seems brand spankin new which is what I thought. Tested thermostat on stove. 160 stat didn't budge til 172, fully open at 180. Tested 4 times same result. Hooked hose up to inlet hole on timing cover abd just let run for an hour. Little pieces of what looks like paper towel came out here and there. Tiny little pieces. That probably what clogged up my old rad. So I'm gonna put back together with no tstat and straight water just to test. Cabt keep spending money on antifreeze. Flushed it 6 times already. Will put stock fan and clutch on too

68oldscutlass

Can't put pics up when I use my phone so I'll do it from work tonorrow

Octania

what's your definition of "overheat" and what temp thermostat are you running?
===============
covered I guess


The temp switch [TVS] is not essential.
=============
au contraire, mon frer... that depends
the factory did not put in "extra" stuff that does no good. It is however meant to alleviate overheating a idling due to retarded timing. Ports D.C.MT are Dist'r, Carb [ported vacuum], Manifold Tap. Sends ported vacuum to the dist'r below activation temp, full vacuum above activation temp. That said, you may find that hooking the dist'r to manifold tap directly, which will obviate the need for the TVS, makes for better driving and less overheating. Such was the case for my high compression heavily cammed HEI equipped 403. Put the mech adv. kit in the HEI, and then set total timing to 36 degrees with vacuum disco'd at dist'r and plugged, and engine at 3k rpm. Reset idle and adjust carb. Note where the static timing is during idle now. Probably about 20 degrees. Reconnect the dist'r vacuum and reset carb and idle speed again. Watch it be happy.


Overheating like that is probably not just due to timing though. Is the radiator in good shape? Good fan? No obstructions? I'd start with just basic cooling system checks.
==============
all good things to do, but part of my investigation process on the 403 From Hell was to run it very retarded- like zero BTDC. NO *****. Left in the dust by a late model Chevy family car. Top speed maybe 60. Severe overheating from a 2 mile road test. Timing alone can indeed do that.

rcrac3r

Going back to the clutch fan for now would be the best idea IMO, as long as the clutch is in good shape. When you fill up the coolant do you run the engine with the rad cap off? Letting her heat up with the cap off will "burp" out any air & you should see it running through the rad. Just need to be carefull when doing that though. Usually I will run the engine with the cap off, keeping an eye on the level. you can tell when the thermostat opens as the level in the rad suddenly drops. Then I rev the engine up a bit, may need help with this part, then top up the rad & put the rad cap on before letting her go back to idle. It may just be a combination of air lock & the fan not putting enough air through the rad.

ihengineer76

Just out of curiosity, have you pulled the plugs to check lean/rich mixture? And were you running the car as shown in the picture? Just checking because there were more than a couple things to catch the eye.

68oldscutlass

Thanks guys, will post pics later of fan with shroud and engine set up. No car wasbt running at the point of that engine pic. Figured it was easier to ask with that pic when it was nice and neat. Will check plugs also. Gonna need to find someone that knows timing and vacuum cause that's just not my thing.

68oldscutlass

Pic of the fan set up with shroud and the engine with all lines run

photo3.jpg?t=1343820812

photo-11.jpg?t=1343821096

Creativeindy

Umm I personally wouldn't have put the Brake Booster hose on the front and the PCV on the rear but whatever floats your boat. THey are normally reversed on most peoples cars.

Creativeindy

If it were me I would eliminate the obvious if it's overheating. Start with checking to make sure you have flow in the radiator and good flow. With no thermostat and the cap off that baby should be flowing like no ones business. If it is flowing well and you verified this then when you drive it gets hot it could be a couple things. First I would check to make sure the fan is working properlly to keep it cooled. I have always had bad luck with those flex fans on both of my cutlass's. I would check to make sure nothing is obstructed in front of the radiator eliminating the ability for it to get adequate air passing through it.

Timing if retarded can cause it to run a tad on the warm side so you need to make sure that is checked as well. Vacume hoses and such will make it idle and run rough, I'm no expert but I don't think it would cause it to over heat if you had a vacume not hooked up. That is over course unless the transmission isn't shifting out of first and you are cruising around in first doing 40 MPH LOL

Start with the obvious, check flow, obstructions, guage working properly and timing set right.

68oldscutlass

And that is why i am here my friend. I will reverse immediately. Didnt think there would be a difference from the front or back of the carb but I trust you on this. Like I said I know nothing about the diff types of vacuum or timing. I did all you see myself and can usually figure stuff out but that is chinese to me.

Creativeindy

There may not be any difference in vacume that is supplied from the base outlets on the carb in front or back. They very well may produce the same amount of vacume as I have no idea myself on that one as i've never tested it or inquired. I just know that factory, and on most peoples cars, the booster goes to rear since it's closer and the PCV goes to the front eliminating long vacume lines. However the way you have it could work just fine. I seen that and thought I would share what little imformation I could with ya.

Rickman48

When fuel was reasonable, I'd advance my timing 'til I got 'ping' and back it off a little, after filling up with mid-range.
Performance and mileage off-set the dime at the pump, but my wife would forget and put regular in it - it would overheat big time.
You might have a lean condition - check the specs on that carb!
Another thing would be to check for the spring in your lower hose - new hoses usually don't have them - they collapse at speed - A MUST HAVE!!!

68oldscutlass

I 100% do not have the spring in the bottom hose. If that is the cause of all of this then A. Holy crapness and B. awesome cause its cheap lol. I definitely had a clogged radiator though from pieces of what looks like blue shop towel. Guy must have shoved it in the water pump so nothing got in. Great but I never looked. New rad, getting another thermostat, flushed the hell out of the engine with garden hose for an hour, putting fan clutch back on. Should be good then definitely going to get carb and stuff looked at. She idles and runs soooo smooth so I am hoping that is all good to go. Updates to come but obviously would love any other thoughts.

68oldscutlass

Ok just ordered AC delco lower hose with spring...

68oldscutlass

Been cruising around 25 minutes. No thermostat, fan clutch back on. Mainly water with 1 jug 50/50 antifreeze, metal pipe in lower hose to keep from collapsing until my new one with spring comes. 165 is the highest she's gone so far. Stopped at home depot for something so see how high is gets from sitting then going again. I think it's fixed. I don't mind no thermostat cause I took out the heat and everything anyway. Now just gotta check timing and vacuum anyways to get peak performance.

68oldscutlass

Maybe it's just me but how are you guys "knowing" when it's 20 or 30 or anywhere in between degrees?? My timing marks are from zero to 10. At idle it seemed to be right around 10. Put vacuum advance on a more powerful vacuum port on carb and advanced timing past 10, adjusted idle and car feels sluggish as hell. The port it was on ( bottom left) barely sucks anything. I gotta get a vacuum gauge but I'm just stumped on how you know what it is past 10 degrees

ihengineer76

You need to get a timing light with a degree dial or an electronic one. You set the light to what degree you want it at then line the timing mark up with 0 degrees. You can get a decent one for around $100.

68oldscutlass

So the $ 40 one I just got that just has an on off switch is useless?

ihengineer76

No, its not useless. Another option is to get degree tape for your harmonic balancer. I'm personally not a big fan or it because half the time it falls off after a while and ends up God knows where. If you go that route, whatever degree is on the 0 mark is where your distributor is. You can get the stuff through most auto parts stores or online. Make sure the surface of the balancer is very clean before you put the tape on.

Octania

1) I just bought a dial back timing light offa epay for $40 and it's great. The $100 ones have tach built in now.

2) Timing TAPE on the balancer is a good way to make do with a regular timing light.

3) GOOD LORD PEOPLE... LOOK AT THE ENGINE PHOTOS above. Do you NOT see an obvious problem?!?!?

oh, and
4) No, you won't see much suction at the PORTED VACUUM nipple on the carb, it is above the throttle plates when at idle... only exposed to vacuum at cruising conditions.

3b) Think we found yer cooling problem there

68oldscutlass

Cooling problem has been fixed. Octania what's the obvious problem? Would like you to share rather then keep me guessing. thabks

allyolds68

If you "fixed" the cooling problem by removing the thermostat you haven't fixed anything

dancutlass

I'm not sure, but is the fan installed the wrong way round?

Octania

Just noticed another snafu in the first photo.
Two holes in the intake just to the front of the carb, LH side, One goes thru. No bolt in it = giant HUGE intake leak. Yet, strangely, we have a bolt "plugging" the blind hole at the right rear where a coil used to go... *sigh*

As for the overheating issue, sure I will go ahead and point out the obvious after giving y'all ONE more chance to look at the photos above.

Hint: Does your engine turn clockwise as viewed from the flywheel end or from the fan end... and what does an ARROW mean to you?

PS I engineer fans for a living.

"I'm not sure, but is the fan installed the wrong way round?"
==============
worse than that
I will guess that if the fan clutch has been reinstalled, the flex fan is no longer in place
and, NO, you do not "cure overheating" by t'stat removal! You get unregulated flow with that plan.

no, a fan will blow the same DIRECTION if the prop is reversed [flipped over], just horribly inefficient.
What we see above is a REVERSE ROTATION fan as for say a serpentine belt system.

GOTTA pay attention to that arrow.

Your flex fan was pushing air fwd, against the oncoming air due to driving.

Use the correct factory ENGINEERED shroud, fan, and fan clutch for best results. Pulley diameters matter also, as does the exact water pump casting, due to many variations in their designs.

Oh, and, y're welcome.

allyolds68

Nice call Chris....I had to actually go downstairs and pop my hood to confirm the obvious

68oldscutlass

Guys, the thermostat was reinstalled yesterday. Stock fan clutch and fan back in place. Great call Octania, even though I'm picking up on a huge amount of sarcasm/talking down to here! I appreciate the great knowledge. Makes sense why it was getting worse while driving on highway. Fan was pushing against everything I bet. Car runs 180-190 all day long now, max. Trying to follow you on what you are seeing unplugged and plugged. Being that I'm obviously spun around here, are we looking at the picture and going right to left or right side is still passenger side by your terms. Just wanna follow your knowledge dude