383 Flat top pistons.

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Rogue

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I've been looking into the Speed Pro forged flat top pistons for my 383. I'll have 2.14 intake and 1.81 exhaust valves. My question is, since the pistons do not have valve reliefs, will I need a piston with valve reliefs or should I be fine? If it will be ok, what ball park figure would max lift be on a cam?

Plans are max 450hp with reworked 906 cylinder heads.

Thanks
*Rogue
 
I'd be looking at a different set of pistons. I don't know what that company offers right off the top of my head, but I do know KB offers some really nice hyper-U slugs at a reasonable price that'll bump up the comprsion nicely and still letcha use pump gas with generous valve reliefs for big lift cams. Max lift on a cam won't be an issue for 450 HP and KB slugs.

OH, standard or .030, same price thropugh summit racing here --> http://www.summitracing.com/parts/UEM-KB162-STD/
 
I've read so many negative comments about KB pistons, I've become very wary when I think of their parts. I understand the hyperuetics are better than cast but not too much better and forged (the speed pro are) will be much stronger.

Am I wrong in thinking that the KB's are bad/not good?

I think I'll be going .060 over.

Thanks
*Rogue
 
The only bad thing about a Hyper U piston is there stiffer, whcih can equal fragile, in the case of to much nitros. It will need a specific ring gap. Ignoring this will have them break. If your an idiot, you'll break'em.

Gap the rings as per instructions.
Don't dump copious amopunts of N02 down it's throat.
 
If your an idiot, you'll break'em

Yeah. That's about it. They are much ctronger than factory cast. They are also more likely to break if you can't tune and decide to either use boost or NO2.. Or if you can't read instructions and install them or the rings incorrectly. That's where the bad rep comes from. Not the product, but the ignorance of the users. I've used many sets of them. They are my first choice for budget performance builds. But they do have thier limits and caveats. Not detonation can be allowed, and you have to pay special attention to piston to wall clearances (they get set vey tight compared to cast or forged) and the top rings must be gapped properly or they will overheat, butt, and rip the top off the piston.
 
rumblefish360 said:
I'd be looking at a different set of pistons. I don't know what that company offers right off the top of my head, but I do know KB offers some really nice hyper-U slugs at a reasonable price that'll bump up the comprsion nicely and still letcha use pump gas with generous valve reliefs for big lift cams. Max lift on a cam won't be an issue for 450 HP and KB slugs.

OH, standard or .030, same price thropugh summit racing here --> http://www.summitracing.com/parts/UEM-KB162-STD/
Click to expand...

You need to pick a different piston , that piece you linked LOWERS the compression on a 383 , it's got a SHORTER compression height than stock AND a HUGE 5cc valve relief .

If a person is set on using those hypers use the kb400 to get the compression at or better than stock
 
John, thanks for the foul mouth. thanks a million.

Been burned by Hyper-U's before?
How'd ya break'em?
 
rumblefish360 said:
John, thanks for the foul mouth. thanks a million.

Been burned by Hyper-U's before?
How'd ya break'em?
Click to expand...

sorry ..

The only burn I have with them was buying the JUNK before I really took a good look at their specs. After I realized how much they lowered the compression, because some moron that's never cc'd a stock big block wedge head, I sold them to someone else that wanted them.

I either use the speedpros or I have Dismond make me a piston in the CH and bore size I need .
 
Rogue said:
I've been looking into the Speed Pro forged flat top pistons for my 383. I'll have 2.14 intake and 1.81 exhaust valves. My question is, since the pistons do not have valve reliefs, will I need a piston with valve reliefs or should I be fine? If it will be ok, what ball park figure would max lift be on a cam?

Plans are max 450hp with reworked 906 cylinder heads.

Thanks
*Rogue
Click to expand...

That depends on the size of the cam you are going to be putting in it . Diamond has a forged flat top that has a CH almost the same asthe speedpro , has smaller valve reliefs, uses a 1/16" ring pack so you have more choices in rings and is lighter than a KB , they are a little pricey though.
 
Still wondering why you call them junk. You seem to be the only person calling them junk. While I would not call them a race piston by any standard, they still work and perform well from what I seen and read.

I'll have to pay more attention when I go posting links. A low comp. height slug, I didn't realized I posted.
 
Boy you guys did a fine job hyjacking the crap out of this thread and never really anwered the mans question. :angry7:
 
Rogue said:
I've been looking into the Speed Pro forged flat top pistons for my 383. I'll have 2.14 intake and 1.81 exhaust valves. My question is, since the pistons do not have valve reliefs, will I need a piston with valve reliefs or should I be fine? If it will be ok, what ball park figure would max lift be on a cam?

Plans are max 450hp with reworked 906 cylinder heads.

Thanks
*Rogue
Click to expand...

That Rogue is a loaded question and depends on a lot of variables. Obviously your concern is that at some point when approaching the overlap, where the exhaust valves are closing and the intake valves are just starting to open, you're worried about smacking the pistons with the valve heads. Using a flat top (no valve reliefs) piston you need to determine if you're going to be at 0 deck or below, at TDC. Don't make the assumption that the deck hasn't been skimmed at some point in it's past. Measure/measure/measure. You'll also want to get the reworked heads CC'd and with the head gasket figure out your comp.ratio. If I had to ballpark it I would say no more than a .510 lift cam with a 0 deck block and a true flat top piston and that's going to be pretty tight.
 
demon seed said:
That Rogue is a loaded question and depends on a lot of variables. Obviously your concern is that at some point when approaching the overlap, where the exhaust valves are closing and the intake valves are just starting to open, you're worried about smacking the pistons with the valve heads. Using a flat top (no valve reliefs) piston you need to determine if you're going to be at 0 deck or below, at TDC. Don't make the assumption that the deck hasn't been skimmed at some point in it's past. Measure/measure/measure. You'll also want to get the reworked heads CC'd and with the head gasket figure out your comp.ratio. If I had to ballpark it I would say no more than a .510 lift cam with a 0 deck block and a true flat top piston and that's going to be pretty tight.
Click to expand...

I apologize, I wasn't trying to make it difficult. :snakeman: I appreciate the help and when I get the block to the Machine shop, I'll have them measure everything.

Thanks
*Rogue
 
rumblefish360 said:
Still wondering why you call them junk. You seem to be the only person calling them junk. While I would not call them a race piston by any standard, they still work and perform well from what I seen and read.

I'll have to pay more attention when I go posting links. A low comp. height slug, I didn't realized I posted.
Click to expand...

I call them junk because of the very poor design and the added expense required to make them zero deck, in the end you still end up with barely 9.0 compression, if you are lucky, because of the huge valve trough.

I don't even consider the 162 for any build unless the requirement of the build is a low compression POS, in that case they fit the build nicely.
 
Rogue said:
I've read so many negative comments about KB pistons, I've become very wary when I think of their parts. I understand the hyperuetics are better than cast but not too much better and forged (the speed pro are) will be much stronger.

Am I wrong in thinking that the KB's are bad/not good?

I think I'll be going .060 over.

Thanks
*Rogue
Click to expand...
The machinist doing my 383 is using speed pro flat tops, as he prefers them over KBs. I'm also using the 906 heads
 
Rogue said:
I've read so many negative comments about KB pistons, I've become very wary when I think of their parts. I understand the hyperuetics are better than cast but not too much better and forged (the speed pro are) will be much stronger.

Am I wrong in thinking that the KB's are bad/not good?

I think I'll be going .060 over.

Thanks
*Rogue
Click to expand...

They, in my opinion, are bad because of their design. Hypers have their place , in a 383 Mopar isn't one of them .... :munky2:
 
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