Weird post-rebuild issues

-
MopaR&D

MopaR&D

Nerd Member
Joined
Jan 4, 2008
Messages
5,771
Reaction score
3,265
Location
Augusta, GA
I know I have another thread already but I didn't want to hijack it even more.

After rebuilding my 318 (reman'd #302 heads from CCH, Lunati Voodoo 256/262 cam, COMP double roller timing set, factory 360 4-bbl. intake, rebuilt Thermo-Quad carb) I've been having some weird issues while trying to get everything dialed in right.

First of all, there's noticably more blowby coming out of the valve cover than before (with the PCV disconnected), even though I didn't touch the pistons or rings at all when the engine was apart. I have yet to run a compression test but I'm not sure what to look for now with the different cam. Why is the blowby higher? I did a compression test before I disassembled the engine and it was around 95 psi on all the cylinders (except one with receded exhaust valves) with the throttle closed (I know it's supposed to be wide-open but I didn't know at the time).

Second, the carb is being a real ***** to get to run right. I've taken it apart at least three times just to get the floats/needles/seats to work properly and not stay shut while running. And those damn secondaries, whenever I tip into those things, the engine bogs down and then belches bluish-white smoke from the tailpipe (I thought gas was supposed to be black?!!). I then let off and slow down at which time my engine runs like the A/F mix is WAYYY off (misfiring, stumbling, etc.); I shut it down, check everything over, then start it back up and it runs fine (at idle and light throttle, of course). I'm sure the secondaries are way off because this carb came from an EGR-equipped truck 360. But why all the smoke? I even did it with the PCV hose disconnected from the valve and capped with a bolt but there was still some smoke when I hammered it.

Is my engine toast? Is my carb junk? I still have to get the kickdown linkage set up right too and the fan belt I got is too long so it squeals all the time. I'm still afraid for my engine though and I'd hate for the $1300 or so I spent on the engine to be wasted.

EDIT: Forgot to mention that it's still got the oxygenated 10%-ethanol Colorado pump 85 that I put in the car about 7 months ago.
 
Hey kid, you might wana take a loss on that fuel, get some fresh. How did this engine run before the mods? or are you relying on word of mouth on bottom end? I always thought blue smoke was guides or rings. You may have issues there. But mostly I think you got her overcarbed. That Quad is mostlikely 850 cfm. Seems a 600 would do better on your build. You can tighten up on the secondary air valve/plate, may help a little. And dont cap off your pcv system, your bad boy needs to breath8)good luck.
 
It didn't run very well at all before the mods. The old Carter BBD was really worn out at the throttle shaft bushings making a huge vacuum leak, the cam timing was retarded due to a slipped timing chain, and a couple of exhaust valves were receded far into the heads. But even with those issues there was almost no blowby when I disconnected the PCV.

I left the bottome end alone because I didn't want to risk messing something up, it ran fine before, and I didn't have enough money to replace any bottom-end components.
 
Some times when you recondition the heads it forces blow by past the rings because the valves are no longer leaking.

The thermoquads work nice with the small primaries but once they are messed up are not easy to get right. Maybe Demosizzler can give some tips on how to get it working right:

http://www.thermoquads.com/
 
your fuel is probably on its way out. The secondary sounds like it should be tightened up. I would tighten it by at least 3 full turns on the air door as a start. On the blow by... when you seal the heads up, and create more cylinder pressure, you place more stress on the rings... so naturally, you get more blow by.
 
Installing new heads on an old bottom end is generally a bad idea cause like the guys said it'll make more compression and force it by the weak/old rings. Your original compression reading of 95 lbs. was real low suggesting something (rings or valves) were worn pretty bad. When you did the compression test did you do a dry and wet test? That gives you an idea of how well the rings are sealing up. Helps you figure out if a low compression reading is from worn rings or valves.
 
fishy68 said:
Installing new heads on an old bottom end is generally a bad idea cause like the guys said it'll make more compression and force it by the weak/old rings. Your original compression reading of 95 lbs. was real low suggesting something (rings or valves) were worn pretty bad. When you did the compression test did you do a dry and wet test? That gives you an idea of how well the rings are sealing up. Helps you figure out if a low compression reading is from worn rings or valves.
Click to expand...

Well, here's the thing. I am at 7000 ft. elevation, most of the valves were leaky a little bit (no I didn't do a "wet" test though), and I definitely did the test with the throttle closed. Another member here did the same test and got the same readings but when he opened the throttle all the way the readings shot up by at least 25 psi. As soon as my neighbor gets back I'll see if I can borrow his compression tester and get a reading.

I did notice the gas in the fuel filter was kind of "opaque" instead of just clear. I poured a gallon or so of fresh 85 in the gas tank and sloshed it around a bit so it might get better but the stupid carb bowls still run out of fuel (at least one side does and it starts to run on four cylinders).
 

OK I did a compression test on a couple cylinders (got too dark out to do all of them) with the throttle open. On cylinders 1, 8, 4, and 2 and they were all around 110-120 psi. I especially looked at number 8 becuase before the rebuild it was low, around 60-70 psi and that cylinder had a badly receded exhaust valve; now it's up around all the others. Also all the spark plugs I took out were pretty black from carbon so I think the carb was running too rich. Really gotta get the idle down though.
 
MOPEkidD-3 said:
Well, here's the thing. I am at 7000 ft. elevation, most of the valves were leaky a little bit (no I didn't do a "wet" test though), and I definitely did the test with the throttle closed. Another member here did the same test and got the same readings but when he opened the throttle all the way the readings shot up by at least 25 psi. As soon as my neighbor gets back I'll see if I can borrow his compression tester and get a reading.

Ok. Nevertheless it's not a good idea to do because old rings, even if it shows good compression don't usually hold up well when you install new heads. I know this by trying it a couple of times when I was young.
Click to expand...
I did notice the gas in the fuel filter was kind of "opaque" instead of just clear. I poured a gallon or so of fresh 85 in the gas tank and sloshed it around a bit so it might get better but the stupid carb bowls still run out of fuel (at least one side does and it starts to run on four cylinders).
Click to expand...

Cloudy is usually a sign of water or some other contaminant in the system. It's possible that the contaminant is heavier than gasoline and sinking to the bottom of the bowl/bowls causing it to appear to run out of fuel. Sounds like you need to completely drain the system including the carb bowls and start from scratch.
 
IMO, that reading is low. Can you try suirting some oil in the cylinders and getting a reading? Also, this was done with the engine hot, correct? The cloudy fuel probably has water as said, and you can either burn it out, or drain it. I don't think it will hurt anything to run unless it's pinging like mad. An with 120psi, I doubt you could make it ping.
 
Even on a stock-compression 318 with a bigger-than-stock cam at high elevation? Damn, I guess I'll just have to drive around with a tired 318 for a while as I'm definitely not messing with this engine again for at least a year. I thought 120 psi was decent for an engine like mine.

Made some progress today though. Installed a new fuel filter and correct-size belt and fiddled with the carb a bit (tightened up air door spring, bent tang to reduce travel); it still stumbles a bit when I tip into the secondaries and starts to misfire above 3500 RPM or so but it's better than before. I think the primary jetting is still too fat though as it doesn't have much "oomph" on the primaries alone when I hit the gas (about the same as before the rebuild), but I adjusted the metering rods to lean out the part-throttle a bit.

I realized too that I have the wrong accessory pulley setup and need to switch to the non-A/C one I got but then nothing lines up with the P/S pump. Did non-A/C cars have different bracketry for the P/S pump than A/C cars?
 
MOPEkidD-3 said:
Even on a stock-compression 318 with a bigger-than-stock cam at high elevation? Damn, I guess I'll just have to drive around with a tired 318 for a while as I'm definitely not messing with this engine again for at least a year. I thought 120 psi was decent for an engine like mine.

Made some progress today though. Installed a new fuel filter and correct-size belt and fiddled with the carb a bit (tightened up air door spring, bent tang to reduce travel); it still stumbles a bit when I tip into the secondaries and starts to misfire above 3500 RPM or so but it's better than before. I think the primary jetting is still too fat though as it doesn't have much "oomph" on the primaries alone when I hit the gas (about the same as before the rebuild), but I adjusted the metering rods to lean out the part-throttle a bit.

I realized too that I have the wrong accessory pulley setup and need to switch to the non-A/C one I got but then nothing lines up with the P/S pump. Did non-A/C cars have different bracketry for the P/S pump than A/C cars?
Click to expand...

I don't think there's any diff. with ps setups on a/c vs. non a/c cars. How many grooves does your lower pulley have?
 
The original lower (crank) pulley has 3 grooves but they are spaced a little different than the 2 groove one I got. Right now I'm running the old 3-groove crank pulley and a different 3-groove water pump pulley, but the alt/water pump/crank pulleys don't match up exactly right and the belt keeps twisting or jumping off. If I put the other crank pulley on (2-groove) it will line up better with the water pump and alternator but then the P/S pump is too far forward (front of the car) and doesn't line up with anything. I was wondering if it would work if I just ran a belt off the water pump pulley directly to the P/S pump (bypassing the crank pulley) but I don't know if that would have enough strength to keep from slipping or anything.
 
I doubt you can run it off the water pump as it has very little belt contact driving it so it'd most likely slip. The power steering pump runs off of the groove farthest forward on a 3 groove pulley if I'm not mistaken. The 3 groove you have must be for the other style power steering pump if it doesn't line up. The old style pump was a Federal and it did use different brackets. The newer pump is the Saginaw. If you lay your 3 groove pulley on a bench engine side down and carefully measure from the bench up to the middle of each groove and let me know what it is and also let me know what you think it should be to work right I'll measure one I have here and if mine is what you need just pay me the shipping and it's yours. Hopefully that's clearer than mud. LOL
 
You must log in or register to reply here.
-
Back
Top Bottom