I have a 355, I bought, guy apparently couldn't get running right. I tore it down found bent valves on a couple of cylinders. I examined the motor further found some very slight indention on the pistons from the valves. It has forged trw flat top pistons. Edelbrock aluminum heads w/ 64cc chambers, 1.5 roller rockers, comp cam .555 lift exhaust and intake, 306 duration, 110 degrees of lobe separation.

My question is what would cause this? Over revving, wrong springs for cam?

 

Are thre valve reliefs cast into the pistons?

 

Yes it has 4 eyebrows, I have 2.02 valves but it doesn't seem to be hitting on the edges as if they were too small. At least I don't think?

 

Cam could have been installed incorrectly.

 

How many ways can a cam be installed?

 

cam probably was installed incorrectly.. i run that same setup.. but with a 1.6 rocker for intake.. .592" lift.. and my quench is .040".. never was close to hitting valves.. and unless the springs are less than 100lbs seat pressure, then over-revving could have caused it.. my pressures are about 135-140 and i have taken my 385 to 6500rpm.. no problem..

 

I'm not sure I follow, Maybe I've been up too long. What do you mean by cam installed incorectly?

 

the cam could have been installed advanced or retarded. or over reved. causing valvefloat. more common in manual trans cars when someone misses a shift.

 

OK I get it now. It was set on the middle grove in the keyway. It had a double roller chain seemed to be in good shape. I think I'll put gears back on.

 

...or lined up on the wrong marks.

 

i would change out the timing set and make SURE you have the timing straight.. this cam has alot of duration and too much extra cam timing(advance or retard upon install) could be bad for your valves.. but if you can figure out which groove the crank gear is supposed to be on then you could reuse the timing set.. but if the valves were hitting, which it did, the timing chain could have stretched.. i would change it..

 

i would change it anyway. thats something i wouldn't cheat on. my cam is fairly large and very close to my rods. so i went with a gear drive. i don't want any timing chain stretch. at all.

 

Ok I need to ask a quick question, there are only one mark on each gear, are you referring to linning them up with Crank at 12 and cam at 12 and or the 12 and 6 positions. the latter is what I was planning on doning.

Ken

 

actually either way will work.. say you install it at 12 and 12, if you spin the crank once around, the cam will be lined up at 6 and crank at 12 again.. its a 2:1 ratio.. i would just line up the marks at 12 for the crank and 6 for the cam.. its the easiest

 

Then I'm confused, how can you install a cam incorect?

 

some timing sets have multiple keyway's. some have 3. some have alot. it's a ******* way of advancing or retading the cam.

 

Ahhhh...thanks for the info..makes since now.

 

Guys thanks for the replies, I'm planning on putting a set of pete jackson noisy gears in place of the chain. Based on that do you feel I'm OK with that much lift?

I just got my heads back from the machine shop, With new springs and valves, I told him the cam I have I think he said 130lbs seat pressure? Not sure though.

Also do I have a good chance of getting 350HP through my t56 to the ground? If not what kind of power will it put out, ruffly?

 

you have a chance.. which edelbrock heads do you have? what intake manifold? what carb? how much compression?

lift should be no problem if you install the cam straight up.. thats what i did.. the gear drive is up to you.. just a warning, it may get irritating after a while.. 130 seat pressure will be fine.. just as long as you dont take her up past 7k..

just on a really really rough estimate you will break 325 at the wheels..

 

Edelbrock performer rpm heads Straight plugs 64cc chambers 2.02/1.60valve ported/polished, 10.6:1, Edelbrock performer air gap Single plane intake, Demon 750 double pumper. Short tube headers 1 5/8 primaries, 3in exhaust.

 

a ported/polished set of rpms could be pretty good, depends on how much it helped.. compression is good

there is no such thing as a performer airgap that is single plane.. if it is a regular performer airgap, you are gonna choke the motor on the topend.. the rpm airgap will be sufficient.. vic jr. is optimal..

but from your combo, my guess stands.. anywhere from 325-350 should be a good estimate.. no one will truely know until you get on the dyno..

 

OK, I found another problem, I don't know if it was caused by the valves hitting the piston or the valve hit the pistons because of this. I counted 26 teeth broken it's a double roller timing set. It didn't have a brand on it. The crank gear is set on the square key-way, it has 2 other key-ways one is triangle shaped, the other is rounded at the top. What causes this kind of breakage? chain was fine as was crank gear.







Here is the engine I'm working on.





Thanks again guys for helping me sort this out.

 

looks like the comp cams timing set.. cost all of $35.. i run that one.. not sure which keyway its supposed to be on though.. call comp cams and ask them..

does it look like this one?? with the football shaped carved in it??



EDIT: i remember i installed the cam gear on one keyway without reading and my valves had almost ZERO clearance with the piston.. had to pull it and read the instructions.. just but a new one..

 

the gear drive is kinda noisy. i don't hear mine at all. unless i'm at idle. and standing in front of the car. i have 3" exhaust with 2 flowmasters at the rear. i also have 630 lift on my cam. so the cam is that much closer to the rods. the lobes barely cleared the cam bore opening.

 

No it doesn't have the football on it, all it had was 1-03 100k.
I wasn't planning on reusing it, I was going to install it and see if it was stretched when I noticed the broken teeth.

What do you think caused what? The teeth broke because of the impact or the impact happened because of the teeth and if so what broke the teeth.

I'm trying to pin point the problem before I put the engine completely back together.

 

Ok I'm not sure because I don't know what brand timing set I have, but I got on comp cams site, on their cams the square is retarded, which might make sense because it was the exhaust valves which were bent? Right? I can't think straight I might need another beer or 12.

 

i need another one for sure

it was probably the reason it bent the valves. the cam jumped time and the piston come up at the wrong time and... you know the rest.

 

Also I recomend you degree in the cam. I just had a custom grind that had to be adv 10 deg to get the intake center line to spec. And I thought it was the timing chain so I pulled one of my old cams out of its box and it was right on the money stight up.

 

exhaust stroke.. if it was retarded, the piston is coming up as the exhaust valve is closing.. the valve could have retarded too much from a timing chain jump..