Thread: CAM question on 350 TBI

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Hello all, I am new here but I have found a lot of good info so far. I have a question regarding a cam swap in a 350 rebuild.

I have been helping my father rebuild his '82 CJ5 and he has put a 1989 Chevy 350 in it. When he purchased the cam he asked for a stock cam, but the guy at the engine shop gave him one that he said would help it breathe a little better, but would work fine. After giving him the new cam they ground a new timing mark on the HB that was offset by about 25 degrees.

We have set #1 to TDC and indexed the rotor accordingly, but we are unable to get the engine to fire at all. We have spark and fuel is being delivered properly.

Will a different CAM work with the stock ECM? Should we put the stock cam back in? Is there anything we are missing?


Thanks in advance,
Dan

There is nothing particular to a cam that would require
moving the mark on the balancer!!!!!! The mark on the balancer
indicates top dead center of the #1 piston. period.

Something smells fishy. There are two different balancer mark locations for Chevys and you must use the mating timing tab so they will line up. One style is 10 degrees from the key and the older style is 2 degrees from the keyway. Could those guys have mixed balancers and tabs and then tried to change the mark to compensate???

mike

Originally posted by yodasands
Hello all, I am new here but I have found a lot of good info so far. I have a question regarding a cam swap in a 350 rebuild.

I have been helping my father rebuild his '82 CJ5 and he has put a 1989 Chevy 350 in it. When he purchased the cam he asked for a stock cam, but the guy at the engine shop gave him one that he said would help it breathe a little better, but would work fine. After giving him the new cam they ground a new timing mark on the HB that was offset by about 25 degrees.

We have set #1 to TDC and indexed the rotor accordingly, but we are unable to get the engine to fire at all. We have spark and fuel is being delivered properly.

Will a different CAM work with the stock ECM? Should we put the stock cam back in? Is there anything we are missing?


Thanks in advance,
Dan

the cam should be ok. i dont understand why they marked the HB at 25 degrees. is that the mark you are using to set you TDC or did they tell you to use that mark for TDC?

Did you set the piston at TDC then line up your cam-crank timing marks. Then set in the distrub?

If you did, you are 180 degrees out of time. The cam/crank gear timing marks have to be- Crank gear mark up. Cam gear mark UP. Then install distrib.

Thanks for the replies.

Here is a picture showing the HB with the two marks.

Dan

Originally posted by yodasands
Thanks for the replies.

Here is a picture showing the HB with the two marks.

Dan

did he say that was the total adv?

From what I understand that is the new timing mark with no advance.

I am completely confused by this whole setup. When we try to start it like this we get a lot of gas blow back through the throttle body.

Dan

Originally posted by yodasands
From what I understand that is the new timing mark with no advance.

I am completely confused by this whole setup. When we try to start it like this we get a lot of gas blow back through the throttle body.

Dan

you are out of time. so you are using the new mark to set your dist. on #1. you cant change where #1 is any time you want to, so i dont know that that guy is doing. have you tried it on the old mark? or pull the valve cover and see if the valves are closed on either mark. unless he put that HB on your motor and found the TDC then he had no way of knowing where to put that mark. i dont think he meant for you to set your dist. using that mark. you need to be talking to him i think.

Thanks for the replies so far...no ignition to this point

Mike,
Here is the deal so far. We went and talked to the guy who sold us the cam. He said that the cam should work fine with a TBI engine. We then asked why he cut the new mark. He said that when the mark was cut they thought it was going into an older engine, and that for our application we should use the old mark.


So lets assume the cam is fine and will work. We spent the morning removing the left valve cover and setting the #1 cylinder to TDC. With both valves in the closed position. We then reindexed the distributor and verified the correct position of the plug wires. The ignition coil is new and passed all diagnostic tests. Fuel delivery is good. Spark plug gap is good. There is spark at the plugs, although, it seems a little on the orange side.

We are still not getting any detonation/ignition.

What could we be doing wrong? Is there anything else we could check?

It can't be this hard, can it?

Dan

which mark on the HB lined up to your tab, the new ,the old or none, when you had the valves closed? its kinda understood if yourer in time, have fuel and fire, its suppose to run. if youve got all of that, then maybe the plugs have stopped firing, you can kill a new set of plugs in raw gas in a min. if they are wet put a new set in. let me know where the timing mark was. what hes telling you about the mark dont make no sense to me. if you have the same HB and your timimg tab is at the same place on you motor then you cant move the mark. you can move it but its no good to you. but if you took the valve cover off and found TDC then you didnt need the mark. so i dont know.

When we got to TDC #1 it lined up with the old (original) mark. We did find out that the distributor did not have a solid ground, but we remedied that and still no go. When we pulled the plugs a few days ago there was a little bit of wet gas on a few of them, but not all. Not enough to run out of the holes, but enough to make the tips wet. Is this enough gas to ruin them?

Can the plugs throw a spark and still be bad?

Can you guys explain "gas washing" the engine? How long does it take for it to happen? I would say we have only cranked the engine for 5 or 6 minutes total.

What is the best way to keep the cylinders/engine lubed during this testing process?

Thanks again for the quick answers. Maybe we will stumble across a solution.

Dan

Originally posted by yodasands
When we got to TDC #1 it lined up with the old (original) mark. We did find out that the distributor did not have a solid ground, but we remedied that and still no go. When we pulled the plugs a few days ago there was a little bit of wet gas on a few of them, but not all. Not enough to run out of the holes, but enough to make the tips wet. Is this enough gas to ruin them?

Can the plugs throw a spark and still be bad?

Can you guys explain "gas washing" the engine? How long does it take for it to happen? I would say we have only cranked the engine for 5 or 6 minutes total.

What is the best way to keep the cylinders/engine lubed during this testing process?

Thanks again for the quick answers. Maybe we will stumble across a solution.

Dan

washing the rings down is when you keep trying to start the motor and raw gas gets on top of the piston and wash all the oil off and lower you conpression to the point the motor cant start. if you think youre washing the rings down you can get the comp. back with shoting a little motor oil back into in the cylinders, if the plugs are wet then they are not firing. id put a new set in. gas wont be running out of the hole i hope, if it does you got to fix that before it will ever crank. i cant get over the guy moving the timing mark and not the tab to. are you sure you was on the comp strock when you put the dist in?

I just wanted to update everyone on the progress so far. We finally broke down and had the Jeep towed to a shop. Upon further inspection the mechanic there determined that there was no compression and that the rods were bent. I am waiting to get a more detailed explanation. As far as the timing mark mystery the mechanic explained that it was moved because the new timing mark plate was in a different location than the stock configuration. Go figure.

I wish I knew more about this stuff.

Dan

Am I correct to summarize?

1. asked for stock cam, mechanic put in something else
2. never got engine started
3. mechanic says they ground new mark because of tab
4. mechanic says that there is no compression and rods are bent

This is the first motor that ever bent the rods before starting!!!

Here is your problem:

1. The mechanic

The mechanic that found the bent rods is not the same mechanic. He has been a friend for many years. He was the guy that we went to when nothing else worked. I would tend to agree about the other mechanic though.

Dan