If i see another thread with this topic i am going to puke so i figured i would just create one with a somewhat 'searchable' title, and we can all agree to just link to this thread whenever one of these comes up again.

Anyway, one of the things that bugs me is when people say "the only real difference is the .3 bump in compression with the GSR head". Thats not entirely true. There are a couple more key differences.

As pointed out by many knowledgable indiviuals (Rocket, Max_CFM , myself ) most GSR castings are much better and suffer from less coreshift than their pr3 counterparts, especially the early B16 castings. Obviously the later 'R' castings were much better, but for whatever reason, the P72 stuff is consistantly quite good.

Another difference is the 'angle of attack' versus the two intake ports. While it maybe easy for someone who ports heads to hear the terms "high port" vs. "low port" and what not into visuals, most people dont understand whats going on there. Taking a cue from Rocket, i am not here to spill out all the good info, but simply lend a hand to those with a brain who really want to learn. Ive photoshopped the following images next to one another. On the left is a P72 port, on the right is a B16 port, both taken from relatively the same angle, both ported by myself. Just stare at the pics for a while and think.



This is my attempt at doing something good for the HT knowledge base.

 

good info. perhaps should be stickied?


now if only we could get a thread to answer the never ending " what's the highest compression ratio i can run on ___ octane?" this forum would be on the gravy train with biscuit wheels.

anyway,
good stuff.

 

Too many words to read! Which one is best? What cams are best for my motor? Who makes the best header? How much power will my engine make? What do you think my car will do in the 1/4? Is 13.5:1 ok to run on pump gas? Which swap should I get?


You should do a little head test to settle the P72 vs PR3 debate once and for all.
Port a GSR head and port a B16 head to give you the exact same flow numbers-an easy task, right?
Then bolt them onto your motor and dyno them. There you have the answer to the long running debate

 

Subscribed for future linking.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">
You should do a little head test to settle the P72 vs PR3 debate once and for all.
Port a GSR head and port a B16 head to give you the exact same flow numbers-an easy task, right?
Then bolt them onto your motor and dyno them. There you have the answer to the long running debate </TD></TR></TABLE>

Hmm.. If we pooled our resources, i bet we could do a real cool test, todd.

 

hmm, funny stuff is happening in my brain right now...lol, but thank you for the info. i greatly appricate it.

 

I'm down.

 

I would definitely donate to the cause.

 

some serious questions.

what exactly is "coreshift"? i hear this time a lot on the forums but what exactly is it? im pretty sure it relates to the casting process, but some more elaboration would be appreciated.

why did you add the guide "dividers" on the pr3 head and not the p72?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSRCRXsi &raquo;</TD></TR><TR><TD CLASS="quote">what exactly is "coreshift"? i hear this time a lot on the forums but what exactly is it? im pretty sure it relates to the casting process, but some more elaboration would be appreciated.</TD></TR></TABLE>


simple MSPaint illustration. Normal casting on the left, EXTREME example of coreshift on the left. Make sense?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSRCRXsi &raquo;</TD></TR><TR><TD CLASS="quote">
why did you add the guide "dividers" on the pr3 head and not the p72?</TD></TR></TABLE>

They dont really do anything. I had hoped they would aid in flow around the guide, but they really dont. Maybe they help with wet flow, but i havent seen it. Wheres RLZ to tell me wings are gimmicks? Actually the port on the right is very RLZ inspired (besides the guide boss fins) but i cannott go any more in depth.

 

Here is a recent flowchart for a stock B16(#4):

Please excuse the traced lines-I am no artist

Anybody have a stock GSR head I can test?

 

yea i figured they didnt do much. ive heard you and others state that, i was just curious that you did it to one and not the other.

i see what you mean by the core shift, how does that happen?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">
Anybody have a stock GSR head I can test?
</TD></TR></TABLE>

I have 2 in my possession right now. Lets do this.

 

subscribed for future results!

 

Let me borrow one to flow on the same bench-I will have it back to you in a couple of days. It would be a nice little comparison-stock for stock

 

Sounds like a plan. We'll take this to PM now.

 

great thread!

thanks Combustion Contraption!! and todd

 

subscribed.

 

the p72 Port look a lot better than the pr3. its bigger, and shape different. i never knew that

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bignewtCA &raquo;</TD></TR><TR><TD CLASS="quote">the p72 Port look a lot better than the pr3. its bigger, and shape different. i never knew that</TD></TR></TABLE>

its bigger, hmmm? How did you determine this? From your calibrated eye?

In any event, Todd has the GSR head in his possession now to flow test. Should be interesting.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">In any event, Todd has the GSR head in his possession now to flow test.</TD></TR></TABLE>
It is no longer in my possession
It is at a certain shop being cleaned in preparation for flow testing

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">
It is no longer in my possession
It is at a certain shop being cleaned in preparation for flow testing </TD></TR></TABLE>

Thats OK.

I traded the LS crank you gave me for a vintage 1964 VW Beetle water pump.

 

That is truely one thing I don't understand, head porting. Just from comparing those two pictures I can see like 10 differences between each of them. Do I understand the differences, nope and most people don't, but their is always 10 theories to support what they did.

Its truely a sick *** ******* art, that a lot of people TRY to do.......

 

big ups for steve and todd!

 

Wow! Finally you can see the difference between the 2. Thank you Combustion Contraption!