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dual relief 7.4L forged pistons...

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Old 09-25-2009 | 04:12 PM
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Default dual relief 7.4L forged pistons...

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
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Old 09-27-2009 | 01:09 PM
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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.
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Old 09-28-2009 | 09:24 PM
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Try CompetitionProducts.com
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Old 09-29-2009 | 07:38 AM
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I believe these are the pistons you have. L2377's

http://www.flatlanderracing.com/trwchevy454.html
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Old 09-30-2009 | 06:29 AM
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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

Last edited by 1BIGJIM; 09-30-2009 at 06:33 AM.
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Old 09-30-2009 | 04:40 PM
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Originally Posted by Alan454
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.
I have that camshaft and I am satisfied with it. Its got a decent idle, not real radical, but it has excellent docking and slow speed manners. If I had known in time, I would have contacted RMBuilder for a cam, hes got a hell of a following around here ...

I have forged dual relief pistons, Im trying to remember what brand they are...
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Old 09-30-2009 | 05:04 PM
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I'm pretty sure you have a directional piston. They will face forward on either bank, therefore they have 2 valve releifs depending on which bank the piston is installed. BBC no not usually need exhaust reliefs.
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Old 09-30-2009 | 08:08 PM
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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.
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