I have owned 2 big block cars and both have had the cam lobes go. Is this common? I was told by an engine builder that they put 3 cams in one engine, each time the lobes would go during break in. I also had an issue with end play of the crank, the engine builder had to repair the block at the thrust bearing. He said that this is common with BB. I have had numerous small blocks and rodded the daylights out of them with no problems. When I get the car back I will be afraid to drive it, that's no way to enjoy this hobby. Hopefully I am an exception and not the rule. If this is normal you will probably see my car on E-Bay.

Randy

 

The first BB I put in my car to replace the NOM SB lost #5 intake lobe in about 1200 mi. The second cam didn't make the 20 min break in period; #5 intake lobe again. We only put in the outer valve springs in order to reduce the lobe stress. The cam in there now I'm afraid to look.

We checked oil passages, lobe/lifter bore alignment, you name it, after the first cam went.

 

OE cams and valvesprings rarely cause such problems. The problems start when you start installing aftermarket "big cams" and high force springs.

Duke

 

GM made about a bizilloin BB in all sorts of vehicles for a lot of years. If cams went south in most of them, they would have quit long before they did.

 

FWIW:
The cams that failed were from Comp and Crane. Both were selected on how closely they resembled the OEM 390 hp timing/lift.
I guess if you buy one over the GM parts counter that makes them better.

I've had one BB Chebby but there won't be any more.

I saved all the parts to change the car back to a SB again.

 

Done correctly or alternately left alone they are nearly unbeatable and all this with only one 4 bore carb. Any one that can`t handle a BB, will also screw up any other engine.

 

GM Big Blocks sometimes have a problem with lifter bore alignment.
This sometimes leads to cam problems.
They often need to be indexed (sleeved).
Aftermarket Big Blocks are more careful with lifter bore alignment.

 

I have heard the same rumors and that is why I got the "direct lube" lifters that have the .024" hole bored in them to directly lube the cam lobe. I have talked to guys that use them and they report negligable oil pressure drop using them. The other thing I have heard you can do is get the cam and lifters cryogenically dipped- for about $100 you can get them dipped and it is supposed kill any need to even break in the cam.

I have never used it though, so if Mr. Duke is still on this thread I would love to hear an opinion on getting parts cryo treated....

Matt

 

Direct lube lifters.

Who makes them? Where is the .024" hole, in the lifter foot I presume. Centered? Offset?

Normal cam lobe oiling is from crank throw off. A small hole weeping oil directly on the wear point should be an improvement.

 

I was going to use a crane cam blue print series because it is a direct replacement for the 435, it was mentioned in Corvette Fever. Based on the previous coment is there a better cam. The first BB that went south the cam was hydraulic with stock springs 200 miles on the rebuild. The second was a stock 435 cam, stock springs, and was an older rebuild. I told the engine builder I will sacrifice performance for reliablity, I am tired of spending mega bucks for these engine rebuilds.

Randy

 

Federal Mogul makes exact replacements for virtually all OE cams. I think their number for the L-71/71 cam is CS-165R, but VERIFY.

This cam probably has the grooved rear journal. If your block needs a plain rear journal, be sure to modify the rear bearing feed hole per the Chevrolet Power Manual.

Duke

 

This is not a problem endemic to big block design, it is the aftermarket cams that cause it. I had a brand-new Comp 280 cam in a 454 that flattented out several lobes on break-in. Took it out, sent it back to Comp, and they admitted it was a defect and sent us a new one. Against our better judgement, we put that one in also and it passed break-in and ran without a problem...

 

Duke, the cam did not have the groove cut. I thought all 65-67 BB had the groove in the cam. My engine was cast in Feb. of 67.

Randy

 

I have run many BBs in vetts and trucks, have taken them to 350,000 miles and never replaced a cam. The design is bullet proof. You have anouter issue other than original design.

 

Many of the name brand suppliers are getting their parts from China and we've had several lifter/cam failures, even with near stock rated springs, rockers, and cams. We now look for used OE solid lifters rather than buy new ones for the very reason you are running into. This occurs in both small and big blocks with some of the new cheap imported parts so your problems won't go away by going to a SB. It's just a roll of the dice on these import parts.
You need to find someone who actually builds racing engines and knows these details.

 

Hey 67L36- here are the lifters I got:

http://www.primediapowerpages.com/cg...rch/Run/100216

They are from competition products, but other companies sell similar products. The hole is right on the face of the lifter. I think big blocks don't get as much help from the splash oiling that the small blocks do, so I have heard that these are a big help especially for big-uns...

I am keeping my fingers crossed.

 

My understanding is that all '65-'66 big blocks need the grooved rear journal cam (along with a specific rear cam bearing). I'm not sure about '67. I've seen it stated both ways. It's also possible that a grooved or non grooved cam can be used in any year block as long as the proper rear cam bearing is used. I'm not sure.

There is some guidance in the Chev. Power Manual, but it does not cover the case of using a non-grooved cam in an early block - just what needs to be done if you use a grooved cam in a later block.

You need to consult with a BB expert like Clem Zahrobsky or Joe Lucia.

Duke

 

Big block chevys are not that complicated. The primary concerns are clearances between the valves and pistons and prevention of valve spring coil bind. Piston to valve a minimum of .100 and must be checked when changing a cam. Valve springs must have an additional .060 available at max lift or they may bind at operating speeds. The use of valve rotators are not recommended. Long slot or roller rockers are often required. Also check for adequate clearance between the rocker and stud at full lift and check guide height for possible interferance of the retainer and guide.
The 1965 and 66 engines are the ones that require the grove in the rear cam journal, without the grove will result in engine failure. As far as the rare lifter bore problem, just be sure not to use a worn out block.

Walt Knoch

 

..the Mark IV BB has a loooooong and proven history with very little maintenance. 350K+ miles on my last 454 before it's timing chain gave up the ghost. Cam breakin is critical (Moly paste is absolutely necessary for proper seating) as is quality steel.

Not to rant off topic, but what's been said above about imported steel goods is true. These days, most steel is poured/cast/manufactured overseas, imorted, then "assembled" in America (so it can proudly wear that "Made in the USA" label ). Often this "assembly" translates into nothing more than adding a small clip, a warning sticker, or reboxing for shipment. Chinese and Korean understanding of metalurgical properties and practices is in it's infancy (< 10 years), compared to the US and more recently Japan. Until costs of production, profit points and our economies find equilibrium, we'll continue to see importation of questionable steel. Likewise, opportunity is always in the margins, so until it becomes cheaper/faster/easier to once again fire up America's foundries & steel plants (highly doubtful), our only defense against junk imports (reproduction parts included) is stricter quality control and/or better educated consumers. The bad news is nobody is exempt; Federal Mogul to FedEx, Costco to Caterpillar - everyone is importing, assembling, wholesaling, distributing or retailing this stuff as a matter of survival. The good news is; taking lessons from Japan, those little guys are fast learners and should have the process down pat within only a few years - popping out top notch products of quality on par with that of the Honda's & Toyota's of the 90's. In the meantime, ask your FLAPS clerks for the Rockwell hardness certificate for every cam, balljoint, tierod and CV joint that passes over that counter