When I degreed my cam a while back my ATI damper hadn't arrived, so I decided to continue with the buildup, installed heads, etc. I bought a piston stop that screws into the spark plug hole to determine TDC on the adjustable timing pointer. This stop screws a further 1 1/2" into the chamber.

Question: Is there a danger of a valve hitting the stop while turning the engine over for the checks? Valve lift is just a tad over 0.700" on intake & exhaust. Since the checks are done on # 1 compression TDC, I'm more concerned about the intake valve.

Thanks!
John

Yes there is...take out the pushrods......be careful! :eek:

Generally you use low load springs for that test. I guess you could release those valves, get TDC like you're doing and readjust the valves afterwards if you're worried.

I had a problem with one of those. I was turning the motor over and over and I thought I would be able to tell once I hit it. After a few cranks on it I thought something was wrong. Cranked it back and removed the stopper to see that it was bent. It didn't "stop" like I thought it would. I was scared I bent a valve but it checked out ok. It didn't hurt the piston luckily.

Thanks guys, I figured I might have a problem. I'll undo the shafts on the intake and exhaust rockers after I detrmine #1 is on compression. I'll also do a "dry run" with the piston near TDC to see when I can expect the piston to touch the stop.
Knew I should have waited for the damper.... graemlins/clonk.gif

Yeah usually better to use a dial guage with the heads off but depends on what you building. Shine a lite in there and you can see when you're getting close then run your plug in there. Some of the "older" guys weld a stop on. Dont beat your piston up with that though.

Shouldn't both valves, more or less, be closed at or near TDC or am I missing something?

On the compression stroke that is?

Guys, aren't you not supposed to crank the engine over with the starter?

I'm pretty sure I read somewhere to turn it manually, that it's not a good idea to use the starter.

I think the valves are closed for the most part when the piston is at deck height whether it's compression or exhaust.

Slowpoke,

No way I'd use a starter to do this check. much to dangerous.

jobberone,

You're right, both valves will be closed as you come up on the compression stroke. That wasn't my concern. It's when you turn the crank backwards to bring it back up to TDC once again ( so you can get two readings and split the diff) that had me worried. The intake would be fully open as you start to come back up, the exhaust would just be opening as you come back to TDC and the intake would be closing; remember, we're turning the crank backwards. Since the piston stop would still be in, that's when the concern for valve contact becomes an issue. As mentioned, I'll get the #1 piston on the compression stroke, then undo the rocker shafts with the valves closed. Hopefully, I'll be able to fell the resistance to the stop when I lightly touch it, then do the same in "reverse".

John

Turn engine over by hand (OBVIOUSLY)

Take those rocker arms off!

YES, you can and will bend a valve even turning it by hand with a big block. "Trust me." (it was a few years ago - 2am - forgot to back off the rockers.)

66 283,

Read and fully understood. You MUST be a diehard hot rodder...assembling an engine at 2am, I'm impressed... smile.gif

The important lesson is: MAKE LISTS of specific tasks if you are going to work all night or you will forget things and make mistakes.

I think all true hotrodders pull all nighters regularly - when I'm trying to get my car back together every winter i spend at least one all nighter per week and maybe 3 nights to 2am (4 hrs sleep).

ALL my transmission or converter swaps in the last few years took place between the hours of 10pm and 5am.

I'll get plenty of sleep when I'm dead.

I've looked for one of these piston stop tools so that I could confirm my balancer is marked correctly but I can't seem to find one. Where do you guys get'em?

66 283

lol graemlins/thumbsup.gif Couldn't agree more! I usually try to pack it in by midnight or so; after that, I can't read my notes on what to do next! ;)

1967talldeck427,

I tried the speed shops around here, most didn't know what I was talking about, or didn't know how to order one. Went to my friendly GM parts guys, asked them to order #12364087 and it was there in two days. :D A quick question for you, did you use standard headers with yout td 427?

John

i used off the shelf hedmans. fit wasn't too bad, just had to make a couple small dings to clear everything (would have to go look to see exactly where, dont remember) i really didn't have that many problems installing the tall deck. except of course you will need at least a 2" cowl hood.

1967talldeck427,

Thanks for the info, I'm hoping I'll have enough floorboard clearance with the tall deck and the 0.300" raised exhaust ports. Just in case there is a problem I also ordered the big block frame mounts to give a little added clearance.

Thanks again,

John

John,
If you went to a speed shop and they didn't know what a piston stop tool was, or how to order one I would cross them off my list of possible sources for your parts. They should consider calling themselves something else besides a speed shop as well. These tools are pretty basic necessities for anyone doing performance engine work and should be in stock at any shop that insists on identifying themselves with the "speed" monkier.
In the good old days piston stop tools were not available commercially. We made our own by taking the porcelien (sp?) out of a spark plug and welding a bolt in the center of the plug. For a piston stop for use when the heads were not installed, it was a piece of angle iron - you get the picture.

FWIW, How I did mine was turn the balancer until it was near TDC then install the stop, turn the crank until the piston hit the tool then marked the balancer. I then removed the tool and turned the crank the oposite direction until I was near tdc then installed the tool and kept turning until it stopped, the distance between the two marks is TDC.

Lee

I forgot I posted here. I was cranking mine by hand. NOT with the starter, but I did not back the rockers off :D