Hello, I purchased a '68 coupe about 1 year ago and finally started working on it. Upon purchase, my wife and I drove the vette from NY to CA. It doesn't get any better. In Nevada it started missing in one cylinder. The whole drive was marked by trying to keep the engine cool. It overheated twice. The car got us home, where I removed the valve covers to find the 3 cylinder rocker arm not moving. I then disassembled the entire front end to prepare for a possible cam replacement. The engine was a dealer warranty replacement in its first year of life. The replacement casting number is 391478 which is consistent with the L79 option. I believe it is the original replaced engine. At some point the heads were replaced with World S/R (stock replacement) heads. The rocker arms were converted to Harland Sharp roller rockers. The intake is an Edelbrock Perfomer EPS with a Holley Carb, unsure the size. The carb is a vacum secondary, single feed, 4-barrel. The pushrod for the 3 cylinder was straight. I have no idea of the make of the cam, lifters or rods. Oh, the Ignition is an MSD. Question is whether to go ahead replace the cam, lifters and pushrods, and if so, which ones are the best to use. If I replace the cam, should I also replace lifters and pushrods to be correct? I am definitely planning on upgrading the cooling. The person who did all the modification did not upgrade the cooling. Advice is welcome. I suspect the cam lobe is gone. I was told that on the 327/350hp there was a design flaw which facilitates cam lobe damage. That person recommended I use a different engine. Is that accurate? There appears to be no burning that is present on examination. Any suggestions on intake, carb combos.
I am really excited to say the least about all of this and I think this is the place for the best advice. Is there a way to test compression manually. I think the compression is fine from turning the engine with the plugs in but I know it is a guess. I am not wealthy but I also believe if something is to be done it should be the best possible effort. Thank you in advance for any advice/suggestions. Jeff Rinek

 

Did you check for a broken valve spring?? You said the car started missing on one cylinder. If it was just missing and not knocking, clattering or locking up, you may just have a broken valve spring and no other damage. I'd check that before tearing the engine apart. If it's a broken valve spring, that cylinder probably won't have any compression and the rocker won't move much. Good luck.
Kenny

 

I would stick with the 327 they are great motors. Question what was the condition of the oil before you made that trip? Did the owner state there was any previous issues with the motor? I would suggest if you are going to replace the cam I would do the lifters and pushrods as well.

 

Thanks for the replies. The valve springs look good, no damage noted. Oil was changed immediately prior to travel. I bought this car from Cole Neadow, a senior member. A GREAT GUY! He checked it out really well and made sure the car was good to go. My gut feeling is that I lost a cam lobe during the last overheat. I am at the point of pulling it out hopefully today. I will change out the cam, lifters, and rods. Any suggestions for which ones. Any suggestions for an intake. I do not like the current set up of the Edelbrock ETS. Would it be a waste to put a double 4-barrel on? Again, thanks for any advice. Jeff

 

Update, I disassembled engine down to but not including cam. Everything looks OK so far, but I cannot remove the cam. Any suggestions?

 

Is there any chance you have a collapsed lifter?

cc

 

I got the cam out. It is a comp cam 12-242. From the kit advertised on the site, the entire kit was installed on the engine. A review of the cam showed two lobes gone, another two almost gone. It doesn't appear to be that good of a part, but I am just guessing. I have to change out the cam, and I am going to do the lifters push rods and rockers. Any advice appreciated. Thanks Jeff

 

Unfortunatly that is becoming more and more of an issue with flat tappet cams. What kind of oil was used when you changed it last. The cam selection depends on what you want to use the car for. The cam you mention is the XE 268 cam. A very popular cam for a 327 - 350 motor. The duration and lift are pretty good for a stock motor with stock heads. Something similar should work very well in your car. Hopefully not to much cam debris is floating around in the engine. Make sure you change the oil. Use an oil with a high level of zinc or put in an additive to keep the new cam alive. There have been numerous posts recently about the new oils lacking the proper lube for flat tappet cams.

 

Jeff will you be installing the cam yourself? I like the Edelbrock RPM manifold myself. About the type of cam. Any cam experts here want to give your 2 cents.

 

Thank you! Thank you! Thank you! The cam is a "comp cams" part 12-242. When I looked at the product page, it is pretty clear that the 'k kit' sold with the cam was used. That would explian the gold roller rocker arms, the timing stuff, and other part.
I am pretty convinced to put a hydraulic roller cam in. My concern was the valve springs. I called Comp Cams, they seem pretty nice. The tech said that in order to stick with the same performance profile of the cam I have, I could go with Comp Cams kit k12-423-8. He also advised that I would need to change the springs and retainers to the Comp cam 26981-16 spring. I am seriously thinking of a dual quad set up. I have always dreamed of one and at my age I will be running out of time. Can anyone offer any advice as to whether this is a good plan, or whether other cam manufacturers should be considered. I am planning on Edelbrock for the intake, and holley for the carbs. Any suggestions, advice or criticism would be appreciated. Thanks Jeff
PS, the tech advised of a device which can pump air into the cylinder to keep the valve up to enable changing springs and retainers with out having to remove the head. Has anybody done this with good results, what tools would it require. I am hoping I can do this myself. I am pretty well outfitted with a dedicated shop, air compressor. Thanks again

 

I have changed many a valve spring with the heads on. You just need an air fitting to screw into the spark plug hole. Plug in your air compressor and you are set. Just make sure the car is out of gear because it will turn the engine and put tha tpiston at the bottom. Take it from experience, take it out of gear. Once this is done you need a tool to take the valve spring off. I made my own but there are plenty of others out there. You just need to compress the spring enough to get the keepers out. Then release the tool and the spring will come off. If the springs have been on a while you might have to rap the top the the spring to "loosen" the keeper to retainer. These can be stubborn at times.

Make sure if you go roller to have a cam button so the cam will not walk on you and that you have the correct gear on the distributer.

 

Thanks for the advice. I will definitely be following it. Any suggestions for a good cam kit. The comparable Comp Cam Hyd roller is the 12-243. How is the experience with Comp Cams compared with Crane, Lunati, etc? Thanks for replying, Jeff

 

I have used Comp Cams for the last couple of cams that I have used but you can't go wrong with Crane and Lunati either. All 3 are good.