[French 67]

Hello,
I am a happy French camper with a 67 RS coupe, fitted with a 350 sb.
The engine has had TFS twisted wedge heads (PN
304 0001) since 1998. I have always been happy with this product.
I am having the following problem:
Alerted by a pulsating noise made by un burnt gases popping through the
intake, I had a look under the valve covers and found that a rocker arm stud
broke on the exhaust side of cylinder #6 (passenger side).
At this point, I don't know if it broke because of the valve stuck closed,
which forced the rocker to push against the stud, or if this is due to a
simple failure of the rocker stud itself. Apparently, none of the valves of
cylinder n°6 are stuck. The pushrods check OK. Reversion seems to occur
during the intake phase, since the gases are unburnt .
The phenomenon occurred without warning, while cruising at 55 mph;
General specs of the engine:
Chevy small block, 355 ci, 10.5:1 CR
forged crank and pistons, chevy pink 5.7 rods, balanced.
Camshaft: comp cams nostalgia plus series, model L79+ , PN 12-671-4
cam specs:
275/282 adv duration,
229/236 at 0.050,
lift: .468/ .462
lobe separation: 112 (+4 adv built in)
rockers: comp cams magnum roller tip, 1.52 ratio
comp cams 7.900 " push rods (as per TFS recommendation, they are +.100)
The car is a week end driver only, and the heads have less than 15000 miles.
Transmission: TH 350 + trans pac / 2400 stall converter /final gear ratio
3.73:1 on 26.1 inch tires
I know the description is long but i try to provide you with accurate information.
Should I just mount a new rocker stud, reuse the TFS guide plate and try to
make it run as is, or do you think I should dismount the heads and check for
a bent valve and/or a broken spring ? Will I have to change the 16 springs ?
If so , which springs should I buy ?
In any case, which part numbers should I use, as for studs, guide plates,
gaskets, head bolts if necessary ? (are these parts available from Summit ?)
An idea , anybody ?

[BillK]

Frenchy,

I have seen studs break quite a few times for no reason whatsoever. I would measure the old stud and get a set of ARP studs the same length and replace them all. If you get some measurements, I can look them up for you.

Are you anywhere near Pau ?

[camaroman7d]

I know the early Trick Flow heads had a problem with the springs and the studs. A friend of mine had a set and they were breaking parts, Trick Flow sent him all new replacement parts. His were new at the time. I agree with Bill replace all the studs and be on your way.

[French 67]

Thank you guys [img]graemlins/thumbsup.gif[/img] . I will take the measurements of the stud and let you know.
Bill: I live in Lyon. It is 6/7 hours North East of Pau. Lyon is 100 miles West of Geneva, and roughly 290 mi South of Paris. Besides, I have been in Pau quite frequently when I was an airborne soldier.
Another question: ARP offers at least two diferent choices of studs, in 170,000 and 190,000 tensile strength. Which is the correct one for the street, the one that bends, or that breaks [img]smile.gif[/img] ?