dual relief 7.4L forged pistons...
#1
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From: Omaha, NE
Does anyone know where on earth I can find a set of forged pistons for my 454's that have two valve reliefs in them like the stock pistons do? Everyone keeps telling me that the one relief (intake I believe) is good enough and that unless I have some radical cam (which I don't) I don't need the other relief. These same people say that unless I am turning over 5000 RPM I don't need to balance it. I don't care, it is getting balanced anyway - well as soon as I can find a set of pistons to balance with! Reliefs and balancing points may be true, but I am the kind of person that likes to do something right the first time - maybe even a little anal. I can find pistons with dual reliefs - but they are hyperutectic, not forged. Aside from having pistons cut, does anyone know where I can find what I am looking for? 454ci/7.4L Chevrolet V-8, .030 oversize, forged with dual reliefs. I have tried Jegs and Summit. Any leads would be appreciated, can't start the engine work on the starbord until I find a set. Then once she is done, I will do the port to match! Also, maybe I should start a new thread, but wondering if anyone knows lift, duration, and separation of a stock cam - I am looking at a comp cams marine extreme 270 roller and was curious as to how it compares to stock...
Thanks for reading!
Dustin
89' Pachanga32 Twin Merc 7.4/330
Thanks for reading!
Dustin
89' Pachanga32 Twin Merc 7.4/330
#2
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Note sure those exhaust reliefs do anything as the seem to be cut at the wrong angle for the exhaust valve. I have them on my engine also and am going to replace with forged.
Take a look a few threads down and I have the 7.4L 330 Hp cam specs posted. I am considering the XM270HR also, although I am also looking for something closer to 230 deg exhaust duration which is the general rule for maximum duration for stock exhaust. I just purchased an EMI exhaust system, with short ss risers but it turns out they also recommend 230 deg max.
Take a look a few threads down and I have the 7.4L 330 Hp cam specs posted. I am considering the XM270HR also, although I am also looking for something closer to 230 deg exhaust duration which is the general rule for maximum duration for stock exhaust. I just purchased an EMI exhaust system, with short ss risers but it turns out they also recommend 230 deg max.
#4
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Joined: Jun 2004
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From: Omaha, Nebraska. Boat on the Mighty Mo! Longest river in the USA!
Spunner, are you at Dodge Park?
I am starting building two new engines for my Pachanga. I don't know if I will use the 454's (built by previous owner). I have been looking for a pair of 502 then thinking of selling the 454s. I have built several 496 strokers in the past and they worked great!
Personally I would not worry about the two valve relief. But I recommend talking to RMBUILDER about a nice roller cam. And, yes I would get it balanced
I am starting building two new engines for my Pachanga. I don't know if I will use the 454's (built by previous owner). I have been looking for a pair of 502 then thinking of selling the 454s. I have built several 496 strokers in the past and they worked great!
Personally I would not worry about the two valve relief. But I recommend talking to RMBUILDER about a nice roller cam. And, yes I would get it balanced
Last edited by 1BIGJIM; 09-30-2009 at 06:33 AM.
#6
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From: Granite City IL
Note sure those exhaust reliefs do anything as the seem to be cut at the wrong angle for the exhaust valve. I have them on my engine also and am going to replace with forged.
Take a look a few threads down and I have the 7.4L 330 Hp cam specs posted. I am considering the XM270HR also, although I am also looking for something closer to 230 deg exhaust duration which is the general rule for maximum duration for stock exhaust. I just purchased an EMI exhaust system, with short ss risers but it turns out they also recommend 230 deg max.
Take a look a few threads down and I have the 7.4L 330 Hp cam specs posted. I am considering the XM270HR also, although I am also looking for something closer to 230 deg exhaust duration which is the general rule for maximum duration for stock exhaust. I just purchased an EMI exhaust system, with short ss risers but it turns out they also recommend 230 deg max.

I have forged dual relief pistons, Im trying to remember what brand they are...
#8
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From: Omaha, NE
RHM 253, you are da man! Finally it makes sense. Yes, they are directional and the dual reliefs have nothing to do with the exhaust. I feel so much better now that I know this because I said to heck with oem today and bought a set with one relief anyway
Thank you for making sense of it.
Thank you for making sense of it.



