505 build on it's way.....but problems of course

[PeteyDaMan]

Hi all,
I've been lurking around this site for years but never posted much. I recently started my 505 build with a 78 RB block. I had it bored .030 over, decked, line honed and final honing with torque plates. That came out perfect.
The stroker rotating assembly I got from Eagle. That went in fairly straight forward as well. I had a little bit of an issue with the King main bearing being a little tight but was quickly solved by getting a set of their -.001 undersized bearings. I file fit the rings, installed the pistons to the rods and put them into the block, all with no issues.
Where I'm at now is the cam. I picked up a Comp roller cam and lifters from Summit (part# 23-712-9) along with ARP cam bolts (ARP 144-1001) and a summit double roller timing set. Here's where the problems started. The cam is a 3 bolt design and supposed tapped to accept a 3/8 x 16 bolt. For the life of me, I couldn't get the bolts in more than 2 turns before the bound up. I didn't want to try and force anything so I checked the ARP bolts and they are spot on. Then I looked at the threads in the cam and they looked terrible. They weren't machined right at all.
I called Comp cams tech line and they confirmed the cam is supposed to be tapped to a 3/8-16 thread. I then called Summit Racing and they were quick to offer me a new cam with no questions asked and paid for shipping the old one back at no cost to me (great customer service).
So yesterday I get the new cam, and guess what. It's got the exact same issue with the threads. WTF!!
I'll be calling Summit again today to return the second cam but now I'm not sure which direction to go. Do I take a chance on a third Comp cam? I'd really rather stay with a name brand hydraulic roller cam from a reputable source. Any suggestions?

thanks guys!

 

[Hemirunner]

There were lots of cores that got out with 3/8-24 fine threads rather than the 3/8-16 that most have. And if your clearance was tight and you put in a .001 undersize bearing, it's now tighter....

 

[PeteyDaMan]

There were lots of cores that got out with 3/8-24 fine threads rather than the 3/8-16 that most have. And if your clearance was tight and you put in a .001 undersize bearing, it's now tighter....

I'll try a 3/8-24 to see if it works, thanks
and I went with looser bearings to gain the extra .001. I didn't just slap them in without checking. everything was checked with a mic and a bore gauge.

 

[moparnation74]

I found out recently with an engine build that Comp Cams cores are supplied by CHINA and shipped here and ground in the US.

In that build we had a cam issue and when finding that out. We went with an american ground cam...

 

[PurpleBeeper]

Interesting. That would be a pretty simple fix. Summit really needs to do a full comp cams stock inspection if there's a known problem....just sayin'.

 

[PeteyDaMan]

ok, I just got off the phone with Summit. They agreed to have someone pull a new cam off the shelf and see if they can thread the same ARP bolts into it. If it works, they'll ship it off, if not, they'll let me know what the next steps would be. Can't ask for much more that that.

 

[1967coronet440]

ok, I just got off the phone with Summit. They agreed to have someone pull a new cam off the shelf and see if they can thread the same ARP bolts into it. If it works, they'll ship it off, if not, they'll let me know what the next steps would be. Can't ask for much more that that.

Always been happy with summit customer service, top notch

 

[not so famous bob]

There were lots of cores that got out with 3/8-24 fine threads rather than the 3/8-16 that most have. And if your clearance was tight and you put in a .001 undersize bearing, it's now tighter....

-----------------
on the bearing thing , absolutely not so !

 

[Hemirunner]

-----------------
on the bearing thing , absolutely not so !

A .001 under bearing is meant for a .001 under crank so is thicker, reducing clearance. Just as a .010 under bearing is for a smaller journal. A .001 over bearing (sometimes referred to as X or extra clearance bearings) are thinner, increasing clearance. So unless King has gone against the rest of the industry or the OP meant something else... if you take out a standard bearing and put in a .001 under, you've reduced clearance.

 

[PeteyDaMan]

A .001 under bearing is meant for a .001 under crank so is thicker, reducing clearance. Just as a .010 under bearing is for a smaller journal. A .001 over bearing (sometimes referred to as X or extra clearance bearings) are thinner, increasing clearance. So unless King has gone against the rest of the industry or the OP meant something else... if you take out a standard bearing and put in a .001 under, you've reduced clearance.

As I previously stated, I put in thinner bearing (X bearings) to increase clearance. I mis-typed -.001 instead of +.001.

 

[PeteyDaMan]

So the winner is (drum roll please) Hemirunner with the suggestion of fine threads. I went and got some 3/8-24 x 3/4 Grade 8 bolts and go figure, they threaded right in. Just as an FYI, I had called Comp Cams tech line and they insisted, vehemently, that the threads HAD to be 3/8-16. So much so that the tech yelled then proceeded to hangup on me.
I'm very tempted to call him back, LOL.
So now I can move onto degreeing the cam to see if they f**ked anything else up.

thanks all for the help and suggestions

 

[Garys1969RR]

Glad you found the problem. I would definitely call Summit back and let them know about the problem of having 2 different thread pitches on their cam, and save some other guy from having the same issue.

 

[Hemirunner]

So the winner is (drum roll please) Hemirunner with the suggestion of fine threads. I went and got some 3/8-24 x 3/4 Grade 8 bolts and go figure, they threaded right in. Just as an FYI, I had called Comp Cams tech line and they insisted, vehemently, that the threads HAD to be 3/8-16. So much so that the tech yelled then proceeded to hangup on me.
I'm very tempted to call him back, LOL.
So now I can move onto degreeing the cam to see if they f**ked anything else up.

thanks all for the help and suggestions

We first saw the fine thread cores show up about 10 years ago and reported it back to Comp Cams then. I'm not sure why they wouldn't have told you it was possible. Glad to hear the mystery is solved.

 

[PeteyDaMan]

Glad you found the problem. I would definitely call Summit back and let them know about the problem of having 2 different thread pitches on their cam, and save some other guy from having the same issue.

I have let Summit and Comp Cams know. Summit said they'll see if they can put it in the part description. Comp still insists this has never happened before. I was on a chat with them yesterday. The tech said he was going to look into it then never responded again. Go figure.

 

[Hemirunner]

I have let Summit and Comp Cams know. Summit said they'll see if they can put it in the part description.

The problem with this is that you might get a 3/8-16 core the next time. No way to know. They buy "semi finished cores" and then finish grind them to the various specs. They're supposed to have 3/8-16 threads but on occasion, a batch of fine thread cores get into the mix.

Comp still insists this has never happened before. I was on a chat with them yesterday. The tech said he was going to look into it then never responded again. Go figure.

We reported several to Chris Padget over the years. He works for Crane Cams now.

 

[bm02tj]

I would not use grade 8 bolts as they grow at a different rate with the heat cool cycle
just use grade 5 or check with ARP and get their advice