Main Menu

Camshaft replacement problem...too tight

Started by chargerdon, November 21, 2018, 08:08:10 AM

Previous topic Next topic

0 Members and 1 Guest are viewing this topic.

chargerdon

My 74 360 engine was built less than 2,000 miles ago, by a professional engine shop several years ago.   im in process of replacing the Mopar 508 camshaft which is too hot for the street, with a Lunati 703.   

In disassembling the cam, i got to the point of pulling it out...  BUT it wouldnt budge unless i pryed on it and i couldnt turn it by hand without putting the sprocket back on and putting a lot of strength.   This is certainly strange, you would have thought that a professional shop would have properly "sized" the bearings.

Ok, so i pryed it out till it cleared the back bearing and then it slid out normally the rest of the way.   

Putting in the new cam ran into the same problem...i.e once i got the cam into the last journal/bearing in had to push hard to get it to start and then had to tap it in with a rubber mallet.   It wont turn by hand either. 

I cant figure this out...   but.. called Lunati and they simply recommended using emory cloth to polish the rear most bearing...and retesting and keep doing it until it can be turned by hand easily.   That a good snug fit is fine, but it should rotate easily..tech felt i needed to take off about 1/2 of a thousands to get to this point.   

Any thoughts or recommendations before i do this???   

Another question..the thrust plate that holds the cam in ...should the bottom oil grove be intowards the block, or on outside facing me?   I didn't notice when taking it off...   

1 Wild R/T

Take the old cam, using a die grinder with a cut-off wheel make a single cut across each bearing journal 90 degrees to the length of the cam, it's a good idea to keep them all in line and add a paint dub across a lobe to indicate that line ....  You now have a bearing sizing tool.... Insert it back in the engine with the grooves facing up & rotate it one full revolution...  Pull it back out & clean the shavings from the groove & repeat....  Usually 4-5 revolutions & the bearings are shaved enough on the high spots to cure the problem...

Oh, while it's nice that they think it's the rear bearing it's pretty obvious the guy suggesting that doesn't know what he's talking about..... Each bearing front to back is a different size so the bearings never get tight till the cam slides into all five bearings...

Brads70

I had a similar issue with my cam, I ground down the one journal on the cam about a thousand.


Strawdawg

I think this can be a common problem after installing new bearings.  Reaming as suggested above should be all it takes
Steve

chargerdon

Thanks guys...i ended up sanding down the back most journal and its still tight...but i think acceptable.   Here is another question.

To reinstall the rocker arms the shop manual says: "Install the rocker arm with notch on end of rocker shaft towards the front on the left bank and to the rear on the right bank".    Can anyone tell me Drivers side and Passenger sides for the notch...   Or in other words in the manual when they refer to left bank is that the drivers side....or passenger side !!!     

73440




RJChallenger

I hope that fixes your issue of the camshaft  being tight and won't cause any engine damage. If it were my motor , I would try to find out exactly where the tight spot is and only scrape the high spots on the bearings. High spot blue ink. Camshaft bearings are held in place by interference fit.They are soft and can be distorted when installed. usually always requiring a little scraping.The camshaft with gear should be able to turn by hand.Any tight spots with the bearings and camshaft means no or very little oil is in that spot. As for your plate look to see if there evidence from the bolts leaving marks? the camshaft rubbing the plate etc. I would think to the inside of the motor to allow oil to escape.Good luck

RUNCHARGER

You still don't know where it is tight. That's why Wild's suggestion is the best course of action. It could be one bearing or all of them, his suggestion makes sure you don't end up with a tight one somewhere. The bearings get progressively smaller so none of the journals will be tight going in until the last position, then they all could be tight.
Sheldon

chargerdon