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Discussion Starter · #1 ·
I have a .030 over 351W crate motor in my 70 Mustang. I want to upgrade the cam since the one in it now is very mild (.480 lift I believe).

Problem is I have no documentation on what pistons it has, other than what the build sheet says "TRW Hypereutectic Pistons (Compression ratio 9.5:1)"

I need to find out if these pistons have valve reliefs to see if I can go bigger on the cam, but I don't really want to tear it down to find out, because if there aren't reliefs, I may decide not to mess with it until I can do it right and re-do the shortblock.

I have heard that some shops have little fiberoptic cameras that can fit in through a spark plug hole to look around in there. I wonder how much they would milk me for that if I pulled the plug for them and all they had to do was point the cam in there?

I also thought about trying to point a flashlight in the hole along with a digital camera, but that doesn't seem like it's going to work.

What do you guys think about cutting reliefs into the pistons if they are not there to start with? (as this sites tech article suggests doing).

Do you guys think that aftermarket TRW hypers would typically have valve reliefs? I sure hope so!
 

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I'm about 99% sure they would have them. Even if they do, you're STILL going to have to check piston/valve clearance, which means removal of the heads.
If it was MY engine, I would not just rely on the word of others....too much money invested in it to do that.
 

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they have reliefs but valve lift is not the determining factor in PTV clearance. Its all about the timing events. Take the heads off and check PTV clearance.
 

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Discussion Starter · #4 ·
Thanks guys. I would definitely never install a cam without checking the ptv clearance, but I appreciate you looking out for me.

My point was that if there were no reliefs at all, I would probably just live with it being a very mild motor for now and just save up my coins for when I could afford to rebuild it properly, but if it turns out the pistons do have reliefs I am going to see what I can do with making some changes to the top end (cam, heads, intake).

What I was looking for was for someone to say either that they probably do or probably don't have reliefs. Your answers are what I was hoping to hear, but I know I'll have to crack it open to find out, and even then you have to check ptv clearance to know for sure if you are ok to run.

I'm working under the advising of a pro Ford small block builder. I am going to buy some parts from him, but do all the work myself, and he's going to help me along the way when I have questions. I'll probably be bugging you guys too


Thanks again for the help!
 

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Here's something you can try: Air up a cylinder and remove both valve springs and in their place put a couple of weak hardware store springs. Reassemble the valve train. Now turn the engine over slowly by hand and every 5 degrees or so push the valves down about 1/8" with your hand. If you hit the piston, measure more accurately to find actual clearance.
 

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And theres not much point in checking 360 degrees of engine rotation (remember the engine rotates twice in a cycle, 720 degrees,) since the piston isn't even close. Just start checking clearance once you see a valve moving until it closes fully.

Or get someone to hold the valves open and spin the engine slowly by hand until you hit it, then check actual clearance.
 
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