Gm 3400 dohc timing belt question on a 1995 monte carlo

drifter · Post by **drifter** » Sun Feb 10, 2008 5:32 pm

We changed a belt on a 95 monte with a 3400 dohc.We replaced all the pulleys & belt first when we had it done it seemed ok.Then we took it for a test drive and i noticed the idle was high.Took it apart again and religned it up i felt the two cams near the firwall were not correct.So now its all done and i think its correct but when you rev it up and the idle comes down the belt whinnes like its to tight.I told the owner drive it and it might goaway when the belt works in.She also calledme and said it seams worse on fuel but she complained about the worse fuel before we did the belt.Is it possible that all the cams are not aligned up correctly and still have 20" of vacum at and idle in park?

Procision-Auto · Post by **Procision-Auto** » Sun Feb 10, 2008 5:55 pm

The only way to know for sure is to degree the cam.

The idle surge could also be a vacuum leak. Check the hoses for cracks,
or loose fit.

Cogburn · Post by **Cogburn** » Sun Feb 10, 2008 6:05 pm

I believe they make a tool to hold the cams straight in that engine(all 4 at the same time) . I always let somebody else do them because they are noted for numerous comebacks even when properly done,and the aren't any fun to do. One of GM's better ideas.

(GEE my lifters make noise...I swear they never made a peep before...please replace them for free...thank you).

drifter · Post by **drifter** » Sun Feb 10, 2008 6:49 pm

The idle dosent surge up and down at all.The first time when we put it together the idle just seemed a bit higher then i thought it sould be.Thats why i checked vacum and it was only 18" in park and i pulled it apart again and moved the 2 cams on the one head and now it has 20" in park this car has 120000 miles on it so i wasnt sure if its possible to still have 20" of vacum and have one cam out a tooth or not?

And as for the belt whinning i hope that goes away

nhrastocker · Post by **nhrastocker** » Sun Feb 10, 2008 7:37 pm

Did you use the proper tools and procedure? It is not an easy job to do. The good thing is that you do not have an interference engine the later engines are interference and if you install the belt incorrectly it will bend the valves. Also, did you install a new tensioner or kept the old one? If you kept the old one, you needed to fill the tensioner with Mobil 1 oil and bleed any air. The incorrect procedure in re-filling the tensioner can create the belt noise. Many times you have to also replace the idler pulleys and even the cam gears and locks for the gears.

drifter · Post by **drifter** » Sun Feb 10, 2008 8:58 pm

No i didn't take off of the valve covers to use the special tools to hold the cams.I just took off the front cover and aligned the hard to see paint marks.But my question mostly is can and engine run good and have 20" of vacum but the cams not be aligned 100%??

MileHighMan · Post by **MileHighMan** » Sun Feb 10, 2008 9:00 pm

drifter. Whats your scanner say? I'd think if you were off by even a tooth anywhere, and she's bitching about milege, the C/E light would be on. Maybe not. I do know this though, usually when a cam is advanced, they idle like crap, when retarded they idle smooth, but are down on power, or mileage. I know you don't want to hear this, but I say you need to tear it down again.

I've never heard about refilling a 12 year old tensioner, but that does'nt mean it can't be done. Good Luck. Dan.

nhrastocker · Post by **nhrastocker** » Mon Feb 11, 2008 12:00 am

MileHighMan wrote:drifter. Whats your scanner say? I'd think if you were off by even a tooth anywhere, and she's bitching about milege, the C/E light would be on. Maybe not. I do know this though, usually when a cam is advanced, they idle like crap, when retarded they idle smooth, but are down on power, or mileage. I know you don't want to hear this, but I say you need to tear it down again. I've never heard about refilling a 12 year old tensioner, but that does'nt mean it can't be done. Good Luck. Dan.

Refilling the tensioner is an option in the factory GM manual. I used to have even the GM training VHS video that showed the complete removal, overhaul and installation of the engine. Although I always put a new tensioner, it showed how to collapse the tensioner, put a pin to hold it in position and fill with Mobil 1.

v8Fiero · Post by **v8Fiero** » Mon Feb 11, 2008 10:40 am

those cam gears are not degreed so if you accidentally loosened a cam gear by accident they most likely changed degrees slightly, I would highly recomend taking the valve covers off and re-setting the timing. the 1994-95 cam gears move very easily since they do not have locking keys like the 91-93 gears do. so they will change setting easy without you even knowing it. good luck, those timing belts are a major PITA to replace and tune correctly.

gn69z28 · Post by **gn69z28** » Mon Feb 11, 2008 6:25 pm

is this the same engine that was in Lumina Z34.it had a specific name given to the engine but I cant remember it.if it is the same engine then I did one but I dont want to confuse the problem untill I know if its the same engine.what do they call this engine other then 3.4 dohc..

drifter · Post by **drifter** » Mon Feb 11, 2008 6:33 pm

Yes this is the same engine is the lumina i did not loosen the cam gear bolts at all to do the job

gn69z28 · Post by **gn69z28** » Mon Feb 11, 2008 6:59 pm

ok,here's the way it's done.you heed to remove the valve covers..the cams have flats on them that a special tool goes on..its just a flat bar with a hole in the middle.easy to make.put crank on TDC and turn front 2 cams so that the flats are up.then put bolt thru the flat bar(tool)and snug it down to hold cams with bar resting on the flats on the cams..the bolt will go between the cams.do the same with the rear 2 cams to hold cams in place..with all 4 cams held with the 2 bars(tool)put timing belt on.release tensioner and remove the 2 flat bars..now here is where it gets interesting..rotate the engine 180 degrees.so now the flats on the cams are pointed down.gently clamp something(I used small vice grips) on the cam sprockets on the front 2 cams so they wont move when you remove the belt again..because you now have to rotate the 2 rear cams 180 degrees so the flats are up again.put the flatbar (tool) back on the rear cams and put belt back on and do the tensioner thing over again..this is why I used the old tensioner untill this last step..when this engine is in time ,at TDC 2cams have flats up and 2 cams have flats down.thats why this thing is a nitemare to put a belt on.and it will run with 2 cams 180 out.I found out the hard way..I had to read the manual serveral times to figure it out..hope this helps..if I can help any more just let me know..its been 10 years since I did one but that procedure is stuck in my head forever because it was so strange..let me know how it runs..

gn69z28 · Post by **gn69z28** » Mon Feb 11, 2008 7:05 pm

i need to make a correction..when I said rotate engine 180 degrees,I meant 360 degrees,or 1 complete revolution. so that the cams rotate 180.sorry for any confussion.

jemsman3 · Post by **jemsman3** » Sat Jun 14, 2008 7:42 pm

i recently got a 1995 monte with the 3.4 dohc.it had a new timing belt and ideler pulleys.it starts very hard(kick back on the starter) has rough idle and it sounds like a grinding or bearing noise when it does start.the timing was gone through 3 times by two different people.the mechanic says he thinks a bearing is bad behind the front cover plate.any comments.

jake197000 · Post by **jake197000** » Wed May 18, 2022 3:23 pm

i think its called a dual twin cam.we drop the engine when we do them

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Gm 3400 dohc timing belt question on a 1995 monte carlo

Gm 3400 dohc timing belt question on a 1995 monte carlo

Re: Gm 3400 dohc timing belt question on a 1995 monte carlo