Wow, those pics of MG's heads makes me come the closest i've ever come to calling a cylinder head "sexy". Pure work of art.

Comparing the two also makes me realize the kind of port work that could go into the 18Xs. Those valve guide bosses look huge as cast. Just cutting those down could make some great gains. Speaking of which, any speculation as to just how far could one push these heads on a flow bench without ruining them?

 

I am really happy to see that this thread has become what it has, ITs served as wealth of info for a lot of people which is really cool. I find it really amazing just how many variables and possibilities there are when it comes to heads alone. Its definately answerd alot of my questions as well as many others that Im sure.

Bret, thanks for those emails, im surprised that both of those heads could be found for that cheap but that again proves what MG said that there are deals to be had.

The main reason That I want to go down this route is the fact that it might as well be done the first time around instead of doing it differently some time down the road. Im sure everyones been there, you just finish one setup and get it dialed in and your already looking to the next step up, I figure I may as well cut out the first step all together, granted it may cost more up front but the end result I feel will be much more rewarding. Like MG put it earlier discussing his car and his buddies GTS, Does anybody really need a street car with 600+ rwhp with a "soggy bottom end" lol or more, more then often not but its there and when it comes in you know its there. I can deal with a 7000-7500 rpm motor and have fun doing it just really comes down to me not wanting to spend the money on something the first time around when the setups going to change for the reason i mentioned earlier at some point down the road. There is more power to be had with 15* 18* head rather than 23* And i think thats well agreed upon, since im building the car the car just to have fun with and terrorize some of the locals im not holding myself to any 23* rules or regulations. My main concern is that the motor that is put together correctly and thats where knowledge and experience comes in and it makes sense to me to only ask those who are the best at what they do.

Bret, Im going to be coming out to bath to see Jason sometime in the next week or so to pick up some carpet and the rearend for my car so depending on what day it is ill let you know and i should be able to come out to the shop.

Thanks for all the info guys,
john

 

Going back to the beginning of the post, and comparing the STX and SPX versions (See this chart), I can see that the exhaust flow is substantially better on the Sread Port version. I was in particular looking at the numbers at .400, but there is a clear 20 cfm advantage across basically the entire range of lift.

Obviously using a spread port layout has connotations for header design/placement, although I'm not sure that really matters as a practical consideration, since I don't think that "off-the-shelf" headers are the proper solution for anything except the run of the mill aftermarket heads from GM, AFR or anyone else.

What I find myself wondering about is whether or not the additional exhaust flow is as desirable as I think it is. I have long believed that the exhaust flow of a head should be a higher percentage of the intake flow than you normally see, and I really prefer to see at least 80%. In this case the percentage is closer to 75%, but that is still a solid 5% better than the standard port.

Now, in the case of supercharging, I would want an even better percentage, but I wouldn't really bother with a higher end head like this anyway. I would simply buy some LT4 bare castings, let L.E. put in the biggest exhaust valves he could and slap on a blower.

But I look at THESE heads, these 18 degree ones I mean, and I think in terms of natural aspiration and higher revs.

Tha brings me back to where my curiosity is lying on this particular day; specifically the implications of the different exhaust flow percentages and how they relate to real world use.

 

I bet the 18Xs in any form would be absolutely BRUTAL with boost. Large, high-flowing ports and massive valves are things boosted engines really enjoy... moreso than NA engines, IMO, since port velocity and vacuum issues aren't as important. And the 18Xs give you all this in one nice, neat, affordable package. Give that pressurized goodness all the room you can

Brodix did their homework with this head. Like Bret said, i'd like to see these heads get more popular in street/strip engines.

 

Definately Im really looking forward to what this heads will do. Like I mentioned earlier about buildups progressing from one stage to another, I want to get this combo together and working properly for a few seasons and when it comes time for a refreshen go down the FI road (ATI D1SC) but thats years away and alot of money to boot plus i love NA,lol


-john

 

Well sure, but my question is centered around the issue of the different exhaust flow rates as a percentage of intake flow.

 

Lame,

From looking at the flow numbers here, I would choose the exhaust port layout depending on the exhaust pipe diameter that was best for the motor. So in a N2O or FI application I would probably lean towards the SP version of the heads. This is in ported form going off of the M2 CNC numbers. I would expect some really good flow numbers with any porting on these heads also.

The spread port layout would allow a 2" primary size where the STD would allow a 1 7/8" which is big enough for most applications using these heads.

I say this based on the E/I% and what cams would be needed here. Going to the SP heads you are more likely to see a reverse split cam and I just don't like those. If you need a reverse split cam (which I sometimes use) then I would be more inclined to throw more intake valve at the heads (if the castings will allow) and take some exhaust valve away from the heads to make more room for the intake valve. I could easily see a 2.200" / 1.560" valve combo in this on a 4.125+ bore. That's the difference between going about a engine build as a total design and crutching something based on cam choice.... It's a tug of war.

Honestly I think the only hold up on these heads in FI applications is the pushrod pinch point. That is where a 18* head with offset rockers really pays off. Then again these are better castings than more 23* stuff for a FI motor.

Bret

 

John,

Even with what I would consider a mild build up on a 400 based motor with a hyd roller cam, these heads put you in 600-650hp territory. Going FI after that would be scary. I think part of the reason that people do buildups in stages is that they find the point were they have too much power. These heads could very well get you there in the first try.

OTOH I always believe that you start off with the right castings and go from there. An aftermarket block, 18X heads and a single plane is a good base setup to start from.

Part of me doesn't know if it's prudent to put 650hp in a 20 year olds hands, well unless it's Jeff Gordon years ago. BTW a D1 setup will be chump change to you if you do a 650HP NA motor.

BTW I like your quote in your sig by Short.... Question is who do you look at when you look at whose going fast? Is it Overton or Kaase? Quinn or Anderson? That's always been my caveat to that rule.

Bret

 

I guess if you use the LTX intake though your stuck with a AFR220 head as the largest, or maybe the AFR227. Any chance the 18X could work with an LTX series intake?? I am doing a new motor now with my current T88, but I'm going to a larger unit/setup soon. I am running a set of AFR LT4 heads that are fully worked to the max right now, but they won't supply the air I want for the new setup.

 

Mindgame is the man to ask here.... I know he has some pictures that could help us here but will he post them?

Bret

 

Bret, I agree with you 100%. The D1 thing is more or less fantasy a guess i could call it whether or not it ever happens doesnt matter, I find myself daydreaming every now and then what kind of car I could put together with 50 grand but that is as far as it will probably ever get.

I dont argue you about questioning whether or not a motor like this is in my hands is a smart idea or not being only 20 and ive wonderd the same thing about myself but Myself and alot of respected individuals( Family friends employers) around me wouldnt label me as the stereotypical 20 yr old now wether people believe that or not is up to them but I feel that I am much more mature person than I perhaps should be by societys standards. hell the vast majority of my friends are in their mid 20s whether or not thats a good things I dont know but it has helped to look at the world in a much different way and perhaps grow up much quicker than normally....


As for shorts quote there, I feel that its more of a general Guidline to most people and it holds very true. I think that there is more to the idea tho, its not just looking at specific set ups that people are doing but the way they go about putting them together, the work that isnt seen in the background, all of the testing, tuneing, trial and error. Sure its impressive to see how their setups perform at the track but I feel the more amazing thing is to look at is what they did to get there. In my case tho im a big fan of what Overton is doing, He is i feel one of the best at making all of parts and components of an engine work together best they can NA. He shows how hard work and determination can pay off. Sure if your going FI its still complex as hell but you can just turn up the boost and make more power( until it grenades) where as NA is much much harder when your trying to squeeze every possible hp with what you have...

thats kind of my take on things,

-john

 

I agree with you on what Joe has done is impressive.... it's the work that goes into getting the car to work as a system. It's not his job like it is for WJ and Anderson at every NHRA outing, but I bet it feels like one sometimes.

The cool thing is that the average guy with the determination and help from the right people can get there.... Obviously knowing everything there is to know about the motor, suspension, tuning and car setup is really hard to do. There are guys out there who do a bang up job specializing in those exact things..... and when you get into motors we even start to specialize in parts of the motors. We have guys out there who can get in a tune your ECU in for you, guys who can setup full suspension systems under a car and engine builders, head porters, cam guys who can give you the power to get the car down the track.

I make my comparisons the way I do because I'm a motor guy. You don't see me in the suspension section or even in the FI section much. I'm a NA motor guy for the most part, I care about what Kaase puts into his motors and what the guys at DEI, RCR, Rousch, Yates, Ferrari, BMW etc... are doing on their motors. Can I use pneumatic springs and DLC coated cranks in my stuff.... Nope but it helps you form ideas of what works and what to try next and gives you a better understanding of how the motor works. OTOH better spark plug placement, better head port shapes, piston/chamber designs etc... I can use and apply into things.

You can either be a jack of all trades or specialize in a smaller group of things. Either way I really think that there is only so much to can take in over time and only so much you can do. Just gotta pick WHO can help you with what and what you are going to learn on your own.

Bret

 

Bret,

My lines of thinking are definatly moving along yours for the most part, obviously I dont have the knowledge or understanding that you posess but thats why you are one of the best at what you do, so congrats on that.

I didnt mention it before in my last post since those were the list of names that you gave me to choose from but you are definately part of that list and im sure everybody would agree that you are one of the best at what you do. Going along with that imn not sure how many engine builders of your caliber would be willing to share their knowledge like you do through these forums with us. That in and of itself shows what kind of person you are. So Thank you for that....!


-john

 

Hell I still don't think I'm good. I just like doing this. Then again for the most part I don't think I get to fully extend my knowledge on most motors due mostly to $$$ constraints. You wouldn't want to know what my next idea brewing in my head is... I still don't know if I can do it, but I think it can be done and will pick up power in pump gas powered motors.

Bret

 

Mindgame, I need pics .


We are definitely going to push the LT1 limits. Our customer has made 1012rwhp with a 355 LT1 using stock castings ported by A.I. and our PTK kit with a PTE-88 on 24psi. Now I am pushing my personal vehicle to hopefully beyond those #'s with maybe the motor that is in the car now. But with the new setup (new motor) I hope to push into the 1200+ range. Heads at that HP range become a big concern for us since the better the flowing the heads the less boost will be required to reach the #'s we are looking for. Right now my current setup will need at least 20-21 psi to get close to the 1000rwhp range.