Ok first refer to this thread here for background.

http://www.g2ic.com/forums/showthread.php?t=162128

Now my question is I am trying to make a decision on cams. I am pretty much set on the buddy club spec 4. I know that I need a higher compression than what my RS machines pistons provide. The RS machines pistons will give me a 11:0 flat compression because they are US spec pistons correct? I called buddy club myself and the employee told me that for my setup I would have to have atleast 11:5-12:0+ compression for the spec 4 cams.

So...I have a spare B18A longblock I'm still trying to sell. Should I try to package my RS machines pistons with this block and sell it off? Then should I take that money and look into some higher compression forged pistons? (I have a wet nitrous kit on the side just in case I need more power)

Basically I just want to get to the minimum 11:5-12:0 compression needed. NO 12:5+! Reason being is that I know that minimum compression alone is kinda pushing it on a street motor. We have 93 octane available here. Also I am just really stuck on the spec 4 because with my motor plus ARP hardware I am gonna take it to 9,000rpm...with capable valvetrain also of course. I search alot and don't post often at all. I saw the spec 3+ will die off and the spec 4 will not. I am basing this information mainly on dynos I've seen, especially na200whp.


ANY SUGGESTIONS APPRECIATED THANK YOU

 

Use a 2 layer HG and flat bottom valves. You should be at approximately 11.5:1 compression with those two products.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jdmegmong &raquo;</TD></TR><TR><TD CLASS="quote">Use a 2 layer HG and flat bottom valves. You should be at approximately 11.5:1 compression with those two products.</TD></TR></TABLE>

Can anyone confirm this? I knew about flat face valves before but I didn't think it would make that much of a change.

So a second question has arose. If I keep the RS pistons does anyone think they will be able to handle nitrous reliably or would I need forged pistons? I'm not even sure yet if I will use the kit on the motor but if I do it will be setup to a safe 50-75 shot, none of this 100+ big shot.

 

Alright, I found out I had my numbers wrong and my RS machines pistons will only yield me a measly 10.6...wayyyy to low for the spec 4 cams. So I did some searching and found out that my best option are JDM P30 pistons!

It looks like these will yield me around a 11:3-4 correct? But I need oversized so the .20 oversized translates to around 81.5mm which is the size I need. Do I have the sizing right? ...or maybe the oversized I saw were .25? ****...help me out.

guess the RS pistons are for sale!

 

bump for some help.

Now I know that any Bseries (cept b20 but to low compression) oversized oem pistons are still to small for me.

I contact RS and for 1. the ctr pct replica will be to much compression and 2. everything else they have are us spec replicas which arent enough compression.

I guess I have to go aftermarket forged is my only choice. can anyone recommend me something? my piston size needed is 81.5mm and the same compression I mention earlier.

 

Keep the build simple. I would personally use RS machine pr3 or p30 81.5mm pistons, flat bottom valves, and a 2 layer HG. That should net you 11.5-12.0:1 compression. You need to factor in your head being milled and if the block has been decked also.

What are you planes for the motor?

You also said you had a spare LS block. Ls/vtec might be another option. I have had both a semi built gsr and a semi built LS/vtec. Both were good motors.

What kind of HP are you looking for?

for a .10 overbore that translates to 81.25mm bore. You can still use oem pistons

for a .20 overbore that translates to 81.50mm bore. RS machine/aftermarket pistons needed.

 

Ummm, I got some sort of bad news for you. Those aren't ITR rods you have there. Those are just GSR units.

If you plan to run nitrous, you need to open up the ring gap slightly to compensate for the increase in heat. I guess you don't NEED to, I should say you SHOULD open up the ring gap.

The USDM P73's in a B18C block only gets you 10.6. Stock ITR levels. You can increase it further by using a GSR head (worth .2), and also using flat face valves. The omni valves should yield around .4 in compression alone. The 2 layer will further bump the compression levels, but I wouldn't do it personally.

As for 10.6 being "way too low" for spec 4 buddy clubs, I have to disagree.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid93Eg &raquo;</TD></TR><TR><TD CLASS="quote">Ummm, I got some sort of bad news for you. Those aren't ITR rods you have there. Those are just GSR units.</TD></TR></TABLE>

Gah I don't care...heck I may buy ITR rods just so it can all be the real stuff.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid93Eg &raquo;</TD></TR><TR><TD CLASS="quote">As for 10.6 being "way too low" for spec 4 buddy clubs, I have to disagree.</TD></TR></TABLE>

Call buddy club and ask them, I did.


I didn't think the RS b16 pistons would be enough from using the cspeed calculator...but then again from searching everyone says that thing is messed up. It says with my setup, b16 head, pr3 pistons i'd be at 11.2:1

Well unless a local shop gives me a deal I can't pass up on forged pistons looks like I'll be getting the RS pr3 81.5mm pistons.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Daft_Soul &raquo;</TD></TR><TR><TD CLASS="quote">

Gah I don't care...heck I may buy ITR rods just so it can all be the real stuff.</TD></TR></TABLE>

ITR rods are actually quite a bit different. Worth more then getting "just so it can be the real stuff"..

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Daft_Soul &raquo;</TD></TR><TR><TD CLASS="quote">
Call buddy club and ask them, I did.</TD></TR></TABLE>

Woah there tough guy. I didn't know Buddy club was the end all of knowledge when it comes to engine building. How many engines you built in your time? How many years you been doing this? Do you always take Buddy Clubs word as gospel? I'm telling you I have used these cams with compression around your level with excellent results. If you want to tell me that according to Buddy Club, they won't work... so be it.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Daft_Soul &raquo;</TD></TR><TR><TD CLASS="quote">I didn't think the RS b16 pistons would be enough from using the cspeed calculator...but then again from searching everyone says that thing is messed up. It says with my setup, b16 head, pr3 pistons i'd be at 11.2:1</TD></TR></TABLE>

Yes, with USDM PR3 pistons, you will be around 11.2:1. C-speed is fine for the most part, but doesn't take into account the piston to deck height changes some of the pistons (CTR) have. This is why a lot of people think its "OK" to run those CTR slugs in B16's, B17's, etc on pump gas without any issues.