[Ianstein]

I’m building a 383 LT1 motor using a solid roller cam. I went to set the valve lash and noticed as I rolled it over there is spot where it becomes extremely difficult to turn over and it makes a small “clink” noise when it hits that point. Before putting the cam in everything rotated fine with no extra drag at all. If I push hard enough I can get it to move past that point and it will roll over fine until it hits that point again. I’ve gone over everything and can’t find anyplace where parts are making contact. When listening to the noise, it sounds like it’s coming from the springs. I’m thinking the noise is from the coils of the inner and outer springs hitting each other. Does that sound possible? Is this a common thing?

Sorry for what little info I have at the moment, but any input would be greatly appreciated. I can’t seem to get my head around this one, and just need some ideas to help get me started.

 

[Jim Monson]

?????? Springs binding?????

Chris U may have a better idea.

 

[Martin Shows]

Probably a stupid comment, but is it possible that you have piston/valve clearance issues?

Martin

 

[Ianstein]

I’m going to pull the head off tonight and check the PTV clearance just to make sure. Although my thinking is that if the valve were contacting the piston or the spring coils were binding then it would stop up everything completely and I wouldn’t be able to push past it.

 

[BigS1975]

We had a 598BBC that did the same thing when we swapped cams.Degree'd the cam and it ran perfect.Still runniong somewhere in Nevada.I think we had to retard it 4* And the valves had plenty clearence after that.

 

[Martin Shows]

If it's a very light "ping" tht you're hearing, it could flex the push rod enough to roll on over.

Like BigS says, could just be a cam position issue, anything's possible. Maybe not though, may not have anything to do with your problem.

Martin

 

[suburban]

the rods might be hitting the cam lobes on a few cylinders. sometimes you need a small base circle cam

 

[AutoRoc]

the rods might be hitting the cam lobes on a few cylinders. sometimes you need a small base circle cam

Yeah...that would be bad. Much worse than Pushrods flexing. I had one cam that touched just one lobe to rod.....went to another to make it work.

 

[Ianstein]

well it looks like piston to valve clearance was my problem. The edge of the intake valves were just catching the edge of the valve relief in the piston. maybe .010 of the edge. Looks like a little bit massaging and possibly retarding the cam a few degrees should solve it.

Thanks for all the help guys.

 

[Martin Shows]

Glad you found it.

Martin

 

[jmarkaudio]

Thicker head gaskets. It will hurt compression though.

 

[billy438stroker]

I had the same problem with the diamond pistons im running for the brodix 201 heads....The 2.200 intake valve was barely scraping the inside of the valve relief...sent them back to diamond and they raised the relief 40 thous...And i also had the Bill Miller rods hitting 5/6/7/8 camshaft lobes....sent them back & they didnt hit when i tryed #5 that was hitting ' but thought i would check just to see how much clearance i had and only had 4 thou's...sent them back again and when i tryed #5 cyl again i had 83 thou's... they say they want u to have 40 / 50 ... some say they have ran them tight as 30 ' but i just wana be safe..So many people have engines break & most of the time the racer gets blamed for the break' when lots of times machine shops get in a hurry & look over soo much....

 

[BigS1975]

Glad you found it.

 

[blwilliams]

but thought i would check just to see how much clearance i had and only had 4 thou's...sent them back again and when i tryed #5 cyl again i had 83 thou's... they say they want u to have 40 / 50 ...

What method are you using to check your rod to cam clearance?
Not much room down in there to see what is going on.

Thanks in advance

 

[Ianstein]

I'm curious what you guys use to check the PTV clearance. I used to use silly putty (yeah the kids toy stuff) but either they don't make it anymore or no place here carries it. So I tried modeling clay instead, but it won't stay stuck to the piston like the silly putty used to. Just curious what you guys use or if there's some other methods I could try.

 

[Jim Monson]

I use a dial indicator. I install checking springs on a intake and exhaust vale and check PV clearance from about 20 deg before to 20 deg after TDC.