Hi All, In the process of putting my T-5 in, and all is going well there (I’ll be sure to take pictures, and maybe put together a “how-to” on it if anyone is interested). Since I have the car torn down, I decided to take one of my cylinder heads (D0OE 351W heads) that has had a “tick” to it down to the machine shop to see what they could make of it. Got a call the next day—8 bent valves, 8 new valve guides needed. These heads were remanufactured a year ago! So my question is, what could have caused this? I know I have plenty of clearance and there is absolutely no sign of the piston hitting the valve. My only thought is that, when I originally put the heads on I ran them for about 4000 miles with the valves hanging slightly open (since the heads are the “posi-stop” type where you torque them down, and had been milled an unknown amount, they were horribly misadjusted). It was to the point of getting pops through the intake and exhaust. I corrected this with a kit that made the rocker arms adjustable, but could it have been too late? I also have heavy duty springs on there (130# closed), but they were not always on there (changed those over from stock at about 4000 miles too). I plan on taking the second head down there, but I wanted to make sure before I put these back on that this was a problem that was created early on, and that it’s not anything I am doing wrong (i.e. wrong pushrod, wrong rocker arm (both of which are stock), etc.). If it matters my cam is 222* @ .050 and .498 lift (single pattern). Thanks!
No guesses on your valvetrain issue but if you need encouragement to do a "how-to" on your T-5 install I would really like to see that.
valve bending is caused by 2 major things. First and most common is lack of piston-valve clearance. There needs to be .100" intake .080" exhaust at the minimum with steel rods. You'll need more with aluminum rods as they stretch more. the other cause, and is a LOT less common is due to a cold rush of air/water etc into the hot engine. Usually it affects the intake valves more than the exhausts. If you've got 8 bent valves on one head, I'd be willing to bet that there is a clearance problem somewhere. I've seen 2.02 valves hit the cylinder walls, head gasket, etc. What was your piston-valve clearance when the engine was assembled? You will have to "clay" the piston to measure the actual clearance...guessing won't cut it. I thought I had over .200" clearance when guessing at my 393 last year, and the first time I mocked the engine together and checked it with clay, the valves hit the pistons @ 20 degrees before TDC (with trw flat-tops--4 valve reliefs). Switched to SRP's and the problem was solved. As a side note, I have a Kawasaki pushrod 22 hp v-twin (basically exactly the same as most american v-6's and 8's) and it's notorious for sticking the intake valve open due to bad fuel. When it does, the valve hits the piston, but does not show any signs of contact. I would doubt that the rockers or pushrods would have anything to do with bent valves, unless your valvetrain geometry is so far out of whack that the rocker tips are coming completely off the tip of the valve, and even then, usually the studs in the head bend before the valve does. Good luck, and keep us posted with your "clay" test
Without knowing more about what situation you have, think about this; at .498 lift with a tight valve condition; if the heads were milled even .020 putting the valves closer to the pistons, you could have the total .498 lift plus .020 would put the valves closer to the pistons (as if) the cam lift were .518 on unmilled heads. That is to close for my comford without knowing for sure what the actual clearence is. On the motor cycle example, I have already saw this on a double OHC Suzuki 4 valve engine where the intakes got so hot the stems went soft, stuck the valves open and got hit with the pistons. Didn't do much damage except to the valves because the pistons hit the valves head on and not at an angle like in a car engine , but enough to bend and loose seal. Ordinarly intake valves don't run hot in any engine unless some unusual conditions exist. In this case the air/fuel ratio was way to lean turning as high as 13000 rpm in a miget race car.
If you do the 'how to' on the T5, be sure to include the clutch install if you have no pedals, like in an auto car, if you can. I am thinking about this mod in my car. Thanks, Earl
Everybody is right. One question, did you start the engine without any exhaust manifolds or headers on it. I have seen bent valves from the cold air rushing into the open heads when the engine was running with the heads open.
I "clayed" up my engine today. Total clearance between piston and valve is .300". Had my dad look at the valves and he said the original rebuild on the heads was probably done poorly...got it done right this time. Thanks for the help!
.300 v/p with a 222deg .498 lift cam? You might want to double check that, cause it sounds way off, like too much. You do have to use a solid lifter to check, or come up with a way to prevent lifter from collapsing from spring pressure.
Yeah, i thought it sounded off too...the lifter was filled with oil, but i didn't know it HAD to be a solid lifter. Where can i get a solid lifter, or maybe i can just disassemble and hydraulic lifter and remove the spring and insert a steel tube or something. The valves fit very neatly into the pockets on the piston, so i figured that was why i had so much clearance.
Okay, rigged up a "solid" lifter, and my clearance is now .200 Glad i checked though. I guess i "need" a bigger cam now, don't I?
