C2 L79 Engine problem - new problem!

[Ron Still]

Found out why the rocker arm came off, the stud is coming loose. It protrudes approx 1/4" longer than other studs, that's why the posi lock came loose. Where can I get the stud remover, reamer and installer referenced in serviced manual? Is this a big deal to do? Doesn't look to difficult IF have the right tools. Joe, would you happpen to have the part number handy for the oversize stud? (is it .003 over?)

Thanks,
Ron

[Duke W.]

Re: C2 L79 Engine problem - new problem!

Something else to consider. Why did the stud pull out? Does it have the OE cam and valvesprings?

Many engines get rebuilt with gorilla springs, even when using OE equivalent cams. This is a common cause of pulling studs, and if one pulls due to gorilla springs, the rest are on shakey ground.

Both the early and late OE valve springs will take OE cams to the limit of the engine's ability to make power even with massaged heads - 7200 with mechanical lifter cams, and I recommend the late, 3911068 springs. Equivalents are offered by Sealed Power, VS677, and I've seen them on the Web for about a buck apiece.

You can also buy Clevite equivalents from NAPA - just cross reference either of the two above part numbers at www.napaonline.com

Duke

[Clem Z.]

Re: C2 L79 Engine problem - new problem!

some of these studs go into the water jacket so make sure you drain down the coolant before you remove the stud. there are special studs out there in the after market that has threads on the bottom end. these are the ones without the hex and sold by pioneer auto parts. i have a special tap that i had made so you can thread the stud hole straight and install the threaded stud.i can loan you the tap if you want to go this route

[John H.]

Re: C2 L79 Engine problem - new problem!

Comp Cams makes a stud removal tool and tap guide, their #CCA-5306; available direct from Comp Cams, Summit also sells it.

[Ron Still]

Re: C2 L79 Engine problem - new problem!

Sounds like the recomendation is to use a threaded stud vs stock pressed in studs. I was looking at Summit and there are tons of different studs!! Anyone know which is correct for a stock L79? Also, as far as I know the valve springs are stock, not anything heavy duty. Maybe the reason the stud pulled up is the old girl is 41 now!!

[Duke W.]

Re: C2 L79 Engine problem - new problem!

I was recently consulting with an owner on an engine rebuild. I had strongly and firmly recommended OE springs, and I'm sure he gave these instructions to the shop that rebuilt his heads.

Somewhat by accident, it was discovered that the heads had some gorilla Comp Cams springs. The owner swapped them out with OE equivalent springs.

Studs don't pull out because the are "old". It's usually the result of higher valvetrain loading than what the press-in studs were designed for - like gorilla springs or severe valve float.

I would suggest that you closely inspect your springs and try to ID them. If you can't, pull one out and take it to a shop for testing and compare to OE specs. You should also review your rebuild documentation and verify that the part number of the cam is a real OE or OE equivalent L-79 cam.

Duke

[Clem Z.]

Re: C2 L79 Engine problem - new problem!

you will have to go to the auto parts because the speed shops only handle the high performance ones. you need the one without the hex above the bottom thread. the ones i have used were sold by pioneer parts. i bet even dorman has them. they look like these. http://cgi.ebay.com/ebaymotors/SBC-C...spagenameZWDVW

[Clem Z.]

the part john hinkley referred to

http://app.infopia.com/Shop/Control/fp/user/Shop/Control/Product/fp/SFV/32214/vpid/3459659/vpcsid/0/rid/125255

[Jim T.]

Re: the part john hinkley referred to

Pulled studs reminds me of a high school friend that was having trouble with pinned studs coming out in his solid lifter SB in 1964.

[Michael M.]

Re: C2 L79 Engine problem - new problem!

You don`t need a special tool to remove just use a deep well socket that fits over the stud and put a nut on and tighten up. It will pull the stud. Good Luck!

[Joe L.]

Re: C2 L79 Engine problem - new problem!

Ron-----

There are two oversize studs available. GM #3814692 is the 0.003 OS. GM #3815892 is the 0.013 OS.

However, I don't really recommend using these. Usually, you will get them in crooked. Whether, or not, you do, though, they will likely pull out again on you a lot sooner than you want them to.

I recommend the approach described by clem and others----install a screw-in stud. You MUST use the type that clem described and pictured. The type with the flanged base are better, but to install them you have to remove the head and have the stud boss machined down. Also, using the type that clem described pretty much maintains original configuration. In other words, done right it's hard to tell that the stud or studs have been converted to screw-in type. With the flanged type, it's obvious that a conversion has been done.

[Clem Z.]

NEVER drive to drive in a .003 oversize

stud into a head that has not been reamed. you will crack the stud boss. do not ask how i know this.

[Phil P.]

Re: NEVER drive to drive in a .003 oversize

clem,did you find this out on your 68z ? my 69 back when, pulled studs---drove in the .003 and yep, they pulled out after a few hard runs---i still have the non-dripper valve covers off of that car, they make interesting wall art for conversation---phil

[Ron Still]

Re: C2 L79 Engine problem - new problem!

Clem, thanks for all the great information! I ordered the screw in studs per yours and Joe's recommendations. Question about tapping the hole, how deep should I go drilling/tapping? Just to bottom of existing bore? I sure would hate to drill too deep!! Does the stud just screw down to end of threads (bottom threads)? How do you install stud, double nut on top threads? One more question, should I use Loctite on bottom threads?? Sorry for the million questions!!

[Clem Z.]

Re: NEVER drive to drive in a .003 oversize

i did it on a pickup truck engine where a stud pull up. that is when i had the special tap made to install a screw in stud. lucky for me the crack did not go into the water jacket as some stud holes are blind and some go into the water jacket