- This topic has 20 replies, 5 voices, and was last updated 11 years, 6 months ago by
.
-
Topic
-
Sorry this is a long read but I’m having issues. I’m not a mechanic but, me and a couple friends are replacing the head gasket on my Tahoe. We have got it all put together but, now it doesn’t sound right. First, it will not start. All it’s doing is backfiring. The weird thing is that it only seems to do It on the drivers side of the engine. It’s almost like the right side has nothing at all. When you try to crank it sounds like its rotating but there isn’t any combustion at all. (I’m not sure I’m wording this correctly). When doing the normal checks. There is new fuel. I’m at least getting it to the injection system and when we remove the plugs they are wet and smell of gas. We have gotten the motor to TDC. And then we dropped the distributor with out the cap on to make sure the distributor was lined up correctly. Then tightened it and put the cap on. We’ve double checked the wires to make sure they are correct. All of the wires are connected to their correct parts. The exhaust manifold is connected just not to the pipes. So we can make sure it runs and that we don’t have to disconnect later.
The reason we changed the head gasket was because a couple years ago the truck overheated. Since then the service engine soon light was on and everywhere I went to scan said the same thing. Cylinder 4 misfire. Later I learned that those engines are notorious for cracking the head when over heated. Once we got it a part sure enough cyl 4 cracked on the head. The block was fine. I was still able to drive it sparingly after the overheat so I’m pretty sure it was just the head. It never overheated after that or even had problems. Once I saw the head I ordered new stock heads from autozone, gaskets, pushrods, (because I dropped a couple when we removed them), plugs, wires, water pump, belts, hoses etc. pretty much everything I could that would be easy during all of this.
I have not checked the compression yet because none of us had a compression gauge with us. I plan to get one this weekend and check that too. I am hoping someone has run into this and at least give me a few ideas to look for. Thank you for any help you might be able to provide.
Oh and btw, if anyone else has to go through this. It’s almost just as cheap to buy a whole new motor from autozone or advance. I have probably about $1300 into it and the last time I checked a long block was another thousand and then you just had to bolt it on.
-
Replies
-
I look forward to the results of your last post. When doing work like that there are a lot of areas where things can go wrong. If you run into problems after the fact it’s always a good idea to go back over your work and recheck everything to make sure everything is plugged in correctly and back in it’s original place. Keep us posted on your findings.
I will sir. I’ve been busy with other household things and haven’t had a chance to get back to it! I will post once I get a minute or two to go over everything.
I did a 97′ not to long ago. Two things come to mind here.
First, if you didn’t adjust your pushrods you very easily could have bent one. They can be a little tricky to get seated right. Then there is a pretty specific procedure for adjusting the rockers. You have to do TDC and then you can only do certain intake and exhaust on certain cylinders rockers. Then you have to rotate the engine and you can do the other intake and exhaust rockers on certain cylinders. You are also supposed to “pre load” the oil pressure since they are hydraulic lifters they will change if you don’t have any oil pressure. You have to get these adjusted close or you will bend push rods and have problems running. I get them close by tightening them(with the engine at the correct TDC) and rotating the pushrod with my hand and then when engine is good I re adjust them. I take the valve covers off and have a set of rocker stoppers to put on the push rods so oil doesn’t shoot everywhere. Then with engine running I adjust the rockers. You can google “vortec rocker adjustment” and get lots of info. Also google “rocker stoppers”, well worth the 10 bucks or so to keep oil from flying all over.
Second, setting the timing on these is crazy. You mentioned using a timing light. No timing light needed, you HAVE to use an expensive scanner that will read cam retard. To set the timing you have to follow the procedure to get the distributor close. It has to be within +/- 2 degrees. Then you have to use the scan tool to actually “set” the timing. You can google this also, lots of info out there.
Ok guys so after a couple of weeks I finally had some time to work on it a bit. While I’m not done with it, it does run again. Lesson learned as well. I got to buy some new push rods and tools. I started checking the spark and had it all 8 plugs and the checker I got also said they were getting fuel as well. Next went to compression. A big fat zero. So I realized all along that my suspicions about incorrectly tightening the valves came true. We took number three exhaust pushrods out and almost couldn’t get it out! It looked like an s. So out comes the borascope and there was no damage that could be seen. We replaced all the pushrods even though some didn’t look bent. Tightened the valves in the correct manner. Btw that sucked, it took three of us all thinking out loud to make sure it was done in the correct order. Why can’t it be simple. All evens exhaust then intake or something like that. Anyway I digress. So put it all back together and first crank it starts right up. Let it run a few seconds and no probs. Now time to change the oil, reconnect the exhaust to the manifold and check everything again for safety. Thank you all for your help.
- You must be logged in to reply to this topic.