chevyguy7802

iTrader: (3)

Very nice!

Paint_It_Black

iTrader: (1)

71camaro I would fall over dead in my chair if TSP correctly answered all your questions!

blu00rdstr

Higher flow numbers often mean less power at lower rpm, and you'll need an intake to match for higher rpm.

black_z

iTrader: (4)

Jason 98 TA

iTrader: (4)

Guys I appreciate you going out of your way to move the original thread off-course. Here we are again doing the best we can to try to cloud & discredit the newest PRC cylinder head. I can't blame people for being negative about it, it's hands down the most powerful LS7 cylinder head available at this time!

We spend tons of time during the R&D stages of cylinder head development & testing. While you guys are reading magazines & getting "hardcore" information off the internet, we're dyno testing our cylinder heads on both chassis dynos & engine dynos.

In the future I will flow all the exhaust ports with a exhaust pipe to hype up the exhaust numbers so you guys can feel warm & fuzzy about it. The bottom line is a lot of time went into the development of both the intake & exhaust port on our PRC LS7 Cylinder Heads. I'm damn tired of people getting on the internet with absolutely no cylinder head knowledge, & attempting to discredit a really good product. You can argue all you want that big airflow from the LS7 cylinder head doesn't matter because the LS7 intake is a restricition, but I'll take the 30rwhp gains & 600rwhp LS7 power potential ANYDAY!!

The PRC cylinder heads are built with only 7cc's of additional material removed from the original ports. Your getting huge airflow gains with minimal changes in port volume! As a result you get throttle response that matches the stock heads with power potential that completely smashes the stock LS7 head.

The ports on our LS7 cylinder head were designed by one of the leading LS cylinder head guys in the country. These cylinder heads have pushed a pump gas 454lsx over 750fwhp & consistantly makes 30rwhp over a stock cylinder head. My personal z06 makes 605rwhp to the tire with our out of the box head & a ported LS7 intake. So I guess to answer your question, not every ported LS7 head only makes 15rwhp. You don't have to take my word for it, go search corvetteforum. We sell to tons of the vendors there & they constantly see 30+rwhp gains! I even had a phone call from a customer in Abu Dhabi UAE that made a additional 32rwhp after installing our cylinders heads.

I've personally never seen less than 30rwhp gains from our ls7 heads.

I guess I could sit here all day & discuss what magazines told you, but I've got a Pro Stock car to work on today! So in a effort to save time I've got a few results I found with the help of the trusty search button.

Here's my dyno sheet from my LS7 Z06


Here's the engine dyno results from stock LS7 heads to the PRC LS7 heads at a independent engine dyno shop!

http://www.texasquadperformance.com/lsx454.mpg

Testing was done with both cylinder heads using the same valves & set to 70cc chambers.

Dyno test with stock GM cnc ported LS7 cylinder heads:




Dyno test with Precision Race Components CNC Ported LS7 Cylinder Heads:

Jason 98 TA

iTrader: (4)

Question 1Here we go trying to hit on a few of your questions 71camaro. I don't know if this is your first ls1 cylinder head, or maybe ls7 cylinder head flow sheet you've ever seen but hopefully I can explain a few things to you. First off you need to understand a few things. Different flow benches read drastically different from one brand to another. Case in point the TEA flow bench. They claim 600 million cfm of airflow out of every exhaust port they ever flow. When I flow them on our superflow bench they typically flow right about the same as your typical ls1 ported head. Exhaust flow data is also drastically effected by the use of a exhaust pipe on the flow bench. You can vary the length of the exhaust pipes being used & also change flow data.

Now that I've given you a little bit of a magazine type lesson on flowing heads we will get down to the meat of your question. Would I like to see 75% flow? Sure but there's a lot of things that come into play when trying to reach a certain goal. The first & most important thing to keep in mind is we're using a stock LS7 casting. This is not a scratch built race head with canted valves for max hp potential.

Typically ported LS7 intakes kill off about 35cfm from the stock intake. So for quick math we'll use the 600 lift area. The 385cfm at 600 number gets kicked down to about 350cfm after the intake is installed. If you flow the exhaust port @ .600 with a 1 7/8" exhaust pipe you'll typically see approx 255-260cfm of airflow. If you figure off of 350ish cfm of airflow from the intake & 255cfm of airflow from the exhaust you'll figure this head sits at about 73% or so. If you figure off the no exhaust pipe data than you see that that figure is about 68%. We'll discuss what can be done to compenstate for these figures in your camshaft question later in this post. While some additional airflow from the exhaust would be benificial, it's airflow that's pretty hard to come by. We're currently testing different seat angles to find some more airflow, but where we're at now is still the best head available & it constantly makes 30rwhp+!!

Question 2
The second question is really hard to reply to because it uses magazine B.S. that doesn't neccessarily apply to the real world. If you always received 2.2hp per cfm of air flow then bolting on 320cfm LS6 heads on a LS1 car would gain 80cfm x 2.2hp or 176hp. Do you realize how stupid that is? We typically see bolting on ls6 heads on a ls1 car is good for about 45hp. Given that the ls6 head flows a huge chunk more air than the stock head, then I'd say finding 30rwhp on a head that already moves over 350cfm stock is pretty damn good.

Question 3
The intake is definately a restriction on these cylinder heads. But what you have to understand is just because the intake is a restriction, it doesn't stop the cylinder heads down stream from making additional power. Case in point every ls1 car in the world. If you add a ported head on a ls1 car with a all around crappy intake you still see power gains. If the intake was the ultimate limit of hp then you'd never need to worry about who has a better cylinder head. Your entire goal would be to just buy a good enough head to flow at or slightly more than the intake allows. We all know that isn't the goal at all.

That being said a better flowing intake could be a big positive, but it all depends on how you get to that point. We've tested carb intakes & sheet metal beck intakes on our cylinder heads with interesting results. The intake changes power output drastically & modifying the intake can change power output characteristics as drastically as a huge cam change! That being said if you could create a intake similar to the stock LS7 intake with better airflow you'd definately see a power gain. Unfortunately it wouldn't be anything near that 2.2hp per cfm figure the magazines taught you.

Question 4

We've done tons of testing with camshafts in our LS7 engines specifically with our cylinder heads. We've had great results from installing our cylinder heads on just about evey camshaft companies have been selling for LS7 engines. The Stock ls7 head doesn't have the exhaust flow to keep up with even the stock intake port. As a result you'll see lots of split duration camshafts with wider lobe seperations in a effort to help the exhaust side of the engine. We engine dyno tested probably 20 different camshafts when developing our cylinder head & cam combos for the LS7 engine. I could go into further detail, but this should adequately answer this question for this application.

Question 5

The chamber volume can be modified by decking a cylinder head. Decreasing chamber volume does play into cylinder head airflow, but on the larger LS7 chambers we've seen little airflow changes by milling up to .035" That being said our chamber was built very similar to the stock chamber. As a result you can use off the shelf LS7 dome pistons with our cylinder heads! Compression at the end of the day is going to depend on way to many things than we can discuss in one thread. You'll have to carefully watch your camshaft, static compression, desired fuel, etc. when determing what compression you can get away with.... but you probably knew that from reading magazines.....

I believe that's the answers to all your questions Mr. 71camaro.

The ***** in your court Mr. PaintItBlack

Jason 98 TA

iTrader: (4)

Paint It Black & 71Camaro would you guys mind posting pics of your LS7 cars? I'm guessing by your posts your researching heads for your applications & not just trying to bust someone's ***** because you have nothing better to do.

Thanks

Jason

silverbeast

iTrader: (16)

Damn Jason,nice response,lol

Paint_It_Black

iTrader: (1)

I'm not going to try to derail your thread, but I will say I'm not satified with your answers on question 2 and 4, you didn't give any specifics. It was a nice response for not using any numbers.

So I'll just say.. I hope you sell lots of heads and I hope even the people I race with buy them!

And I'm not building an LS7, but I was considering LS7 heads for a stroker build, but I think I might want the H/C record now. And yes, I'm bored and have nothing better to do.

1fast1slow

iTrader: (2)

Jason i am not satisfied with any answers... Could u retype a new reply no less than 9 paragraphs and repost. LOL just kidding. Bump for a great sponsor from a repeat customer. By the way... I usually CALL when i have questions, they have great tech support!

Jason 98 TA

iTrader: (4)

What part of number 2 do you not understand? Do you not get that if you made 2.2hp per cfm that we'd be bolting on 170+hp head swaps? Question 4 was answered as much as it needs to be. Just because I don't want to discuss everything we learn from the tons of R&D money we spent doesn't mean there wasn't anything to learn

I didn't expect you to like my responses, but all the questions were answered correctly. Sorry I didn't let you guys spend the rest of the day bashing on us, but there's only so much I can take of this B.S.

Thanks for the support 1fast1slow, but I don't think the guys are posting because they have questions, if you've read the other thread that was removed you'd find that most of these posts in this thread had nothing but malicious intent.

71CamaroLS1

First off, I should apologize for the tone of my two previous posts. No excuse, but I shouldn't be posting after 3 beers.

I should be clear about some other things as well. I am *not* bashing your product, which I think is great, or your company, which as I said I have done business with in the past and have recommended (particularly the LS1/6 CNC heads) to a number of local enthusiasts. I *was* and am bashing your decision to delete a bunch of posts. The particular irony of this discussion is that, if you read my now deleted posts, I was *defending* your product against magazine-style ignorance. And finally, my perspective on engine design does not come just from, or even primarily from, magazines. I'm an ME by degree, took ICE theory in grad school, and have been involved in a couple of dozen engine buildups for myself and others over a long hot rodding career.

I'll put up a pic of my '69 project after this post.

The answers you posted to my questions are pretty thorough and detailed, and I would think a prospective customer would find those answers quite useful. Some comments on the questions/answers, point by point:

1. Agreed that flow benches are not the same from brand to brand, or even user to user. More to the point of E/I ratios, it's a somewhat open question how well flow benches model the behavior of an exhaust port in a running engine. The "low" E/I ratio of the LS7 head is a function of the basic design, namely the choice to allocate more of the available valve space to the intake valve. Current racing engine research shows that, with the proper combination, such a tradeoff leads to more power. In other words, at least for naturally aspirated motor, the 75% E/I ratio is an old assumption which just isn't considered valid any longer.

2. Agreed, the 2.2 number is a very rough shorthand. And it makes an important assumption, which is that you can rev your motor to whatever RPM level is needed to max out the airflow - which is a good assumption if you're talking about an old-school 350 with a 190 CFM intake port, but not a good assumption for a 427 that starts with 350+ CFM intake. Bottom line, the out-of-the-box LS7 head flows enough already that really large gains from head porting are just not possible in streetable RPM ranges on a 427. Now, if we're talking 480 or 500 CID ... that's a different story.

3. The critical factor with the LS7 intake manifold is not flow per se, it's the tuning frequency, which is largely fixed by the basic dimensions and shape of the runners. The LS7 intake is designed to provide a significant assist to breathing through an RPM range centered on about 4500 - 5000 RPM, providing a nice big "bump" in the middle of the torque curve. But by the time you get over 6000 RPM, the intake tuning is starting to actively work against you, to the point that you can't move the HP peak too much past the mid 6000s, no matter how big the cam. As you point out, this can be changed with other intake designs, but those will inevitably trade off some of that mid range torque, which may or may not be what you want. I note that people do get a bit more HP by porting the intake, but actually it's not clear to me how much that is due to increased flow, as opposed to making the runner volume slightly larger and thus moving the intake tuning frequency up just a bit.

4. People on the previous thread made several comments about the LS7 design requiring "funky" cams to "crutch" the bad exhaust port. This is the wrong way to look at it - the LS7 requires cam designs that look much more like the cams for modern racing engines. Specifically, it requires earlier exhaust valve opening to aid with exhaust blowdown through the relatively small exhaust valve. Also, because of the negative intake tuning effect mentioned above, you have to move the intake valve close quite late if you want extended RPM and therefore higher HP peaks.

5. The LS7 seems to have a very efficient combustion chamber that will tolerate higher cylinder pressures without detonation. The cam design - particularly the intake valve close point - has a big impact on just how much compression is desirable.

I will reiterate, I think your product is great, and I think your company philosophy of delivering high performing products at very attractive prices is a refreshing change from the "whatever the market will bear" philosophy of so many big-name vendors.

Paint_It_Black

iTrader: (1)

Could you mention anything about flow and velocity in these ports?

(Port velocity = (CFM * 2.4) / CSA)

And how that changes cam selection? (IVO AND IVC?)

Or would that be giving away too much like you said for giving numbers for question 4?

And what are your thoughts on a I/E ratio goal?

71CamaroLS1

Here's a pic of the '69 before we blew it apart and sent it off to body/paint jail (sigh). Believe me, after what I've already got invested $1k for a pair of heads ain't much. Whether I actually *need* more power, or whether you'll still take my money after this, are still open questions

Jason 98 TA

iTrader: (4)

Forgive me for being so defensive. I think if you reread the post there were a lot of way off course replies. It was better to start over & get back to talking about the PRC head. That's what this thread is about ofcourse...

I guess we will have to disagree on #2. I have installed these heads on stock ls7 engines with a camshaft & seen the huge gains possible from this swap. I'll take the 30rwhp with only minimal port volume changes wouldn't you? I guess I'm reading this as you saying heads aren't any good on a ls7 engine even though they gain 30rwhp. Honestly I'll take the 30rwhp that pushed me over 600rwhp & use it to bust everyone else's heads cam z06's a$$.... But what do I know I've only got 30 hours of engine dyno time testing these things. You guys are probably right...

Paint it black I appreciate your interest in our cylinder heads & what testing we've done. If you'd like you can call & order one of our camshafts & dyno test it in your LS7 vehicle. I think you'll find our camshaft & cylinder head combos make really great power in the LS7 engines.



If LS7 ported heads don't work how did my car get from the 560 mark to past the 600rwhp mark? Maybe I just dynoed it at LG, or maybe the heads really do gain power....

71CamaroLS1

I guess it comes down to whether you'd consider 30HP to be a "really large gain" (my words). On the old-school motors, I wouldn't even think about building a performance motor without seriously upgraded heads, and I would get way more than 30 HP. On the LS7 - well, it depends on your goals. It's certainly 30 HP you can't get any other way, and the expense is reasonable. And the gains are in line with, or better than, what the competition is getting from their ported heads (although compression increases blur the pure porting effect in most vendors' tests I see).

Jason 98 TA

iTrader: (4)

I understand what your saying 71. I think what your overlooking is the fact that 30hp can be gained by a cylinder head that cost less than the factory head does. So basically a customer can buy the PRC head fully ported, make 30rwhp over the stock head & save a few hundred bucks. How can you beat that!?!?!?! Compression does effect it alot, that's why I did all my engine dyno testing with stock size chambers to rule that out. I understand you can fudge numbers that way, but guys want to see the products do what you advertise. I know if I tell someone they can get 30rwhp from a head swap that they won't be calling me saying they didnt' see it! Could I claim 40rwhp? Sure some people have seen it with decking, but is something I can promise a customer they will see everytime? Nope... That's why 30rwhp is the quote even though they typically do a little bit more!

71CamaroLS1

That's a very good point, one which I overlooked since I bought a complete LS7 crate with heads already, um, attached Anybody who's starting a 427+ inch build from a shortblock would be silly not to look at your complete assemblies.

Jason 98 TA

iTrader: (4)

No worries we offer complete cnc porting of your castings for about $900!! For 30hp that's a decent value. Keep in mind FAST intakes cost $1200 or so for 15hp!!

71CamaroLS1

If you look at my sig, you'll know I'm all too aware of that! And $1200 is not considering the extra $500 to replace the sticking FAST TB with something that works.