As I said before man.... what you are looking at there is to not have pushrod pinch points that cause minimum cross sectional areas in the port.... That and I would look at a casting with a deep bowl to prevent excessivly high SSR velocities.

Bret

 

Boy, this thread has gone bonkers.

Good to see some activity in this forum. Things have been a little lethargic for some time now.

Where to start with all this?

Back to (well can't see back that far in the thread)... but someone asked about the old 18º NASCAR heads?
Well, as Bret mentioned... they all have very large port cross sections designed for 8k rpm and up. Even on a 383 or 396 you're looking at a head that needs to turn big revs. If you're not too against swapping a gen 1 engine in the car, then a 427+ ci engine could be built and it would love a set of large port NASCAR heads.

Now drag heads are a little more tricky. If a set was ported to work well on a heavy car with a little less gear/converter etc.. It just might make for a decent stroker street head. But you need to know what you're looking for here and... ask lots of questions and get as much documentation as you can. Better yet, ask someone who really knows.

If you can find an unported set... all the better cause you can build em just like you need to.

In regards to the theoretically ideal intake/exhaust ratio Lame eluded to..... guys, don't get too caught up into all that. The best race heads I've ever seen were less than 70%.
If you look at the shallow angle head's exhaust port you'll see a port shape and trajectory that is very efficient and that's what makes these heads move lots of exhaust out the engine at high speeds... even with a less than ideal ratio. Just look at those exhaust ports and tell me you wouldn't want to be a hydrocarbon molecule flowing through there. Don't blink.

Ok... yeah I have spacers on the motor and yeah, I was planning on having this whole engine out by now and get on to the new greatness. But my job keeps interfering with things. I've spent more time in Israel this year than I have in the states.
So, when I do get the engine apart, I will take some pictures and throw them up on my webshots account. I have all the parts for the new bullet but I don't have the time right now so.... things are coming along a little slower than I'd hoped. Patience, patience...

Oh yeah... not that anyone cares (you all know how much I like to talk about myself ).... I'm going to sb2.2's for the next build. No LT1 though. Sorry guys.

-Mindgame

 

I looked into the SP vs. the STD port versions more on a NA motor....

This is all theory based on a lot of data to back it up and some formulas I've stolen from Darrin Morgan at RMRE etc... but they seem to work.

I mentioned going to a bigger intake valve and a smaller exhaust valve on these castings.... Well if you throw in changing from a STD exhaust port setup to a SP one, then there is LOTS to be had here.

The M2 STD casting flow numbers are going to give you a really nice operating E/I% and changing the valve sizes on that version would really screw that up and you would need a major cam change in the motor..... Now if you go to the SP exhaust and enlarge the intake valve and shrink the exhaust valve along with changing the cam... you basically have the same TQ curve and 25-30 more HP.

Bret

 

Bret,

Yeah, I'm with you on the SP vs STD. The SP places the port in a less compromised position.

Do you feel strongly about the I/E% rule? Would you say that it weighs in heavier than port form?
I'm inclinded to think that port velocity is a bigger factor than flow numbers given the conditions the exhaust port works in.

Your thoughts?

-Mindgame

 

So mindgame what do you recommend for us less fortunate LT1 individuals using the stock style intake?? The 215RR head is awesome, but it won't work with the LTX intake. Are their any heads out there that can be converted and still potentially work with the LTX head. I would do the research, but heck if someone else already knows this, it makes my life easier.

Jose

 

Bret, you mention using a larger intake valve with a smaller exhaust valve on these heads. It seems to me this would raise the exhaust velocity which would help with scavenging or making a turbo spool that much faster. I see where this could be beneficial on a street motor that's kept under 7000 RPM. Are there any other benefits or detractors to going with those valves? Will the seats accept a smaller valve?

You guys are so making me want to sell my Pro 1 215s.

 

I'm a big believer in port velocity, especially having spent some time in the Oldsmobile world. But can we really discount 5% more flow? I mean... we're talking about 20cfm across the board in the specific case I mentioned earlier.

 

I would expect the following would be need to run these 18x heads on an LT1 engine.

1) Convert heads to reverse Cooling?

2). Make intake port spacers to bridge from the LT1 intake to the 18x heads?

3). Buy special pistons to work with the heads, special valve relief?

4). Major tunning to the ECM?

5). Get custom headers built for the exhaust?

6). Custom push rods.

7). Custom cam grind

Is that most of what would need to be done?

Or is the application easier than that?

I find the heads very interesting but the installation issue are over my head.

Thanks

Z28

 

For all the trouble you have to go through I think the AFR 220's are probably the best heads to keep your current setup, LT1/4 intake and keeping the exsisting exhaust.

Jose

 

Actually I could care less about the E/I% rule (it is Exhaust / Intake now isin’t it?) The problem I saw with Discharge Coef calculations based on valve size with those heads off the bat was that a STD port version will get crippled way to much with a larger Intake and smaller Exhaust valve that you really can't fix with the cam. I know what the seats will hold so therefore I figured WTF I have to run a custom header on these anyways lets go with the SP and see what happens. Well that like every other “street” motor always likes more exhaust flow to even out the exhaust duration with the intake duration and move the EVO later and improve midrange TQ, without causing excessive overlap. Kinda like on your motor ;-)

Do I look at effective E/I% based on calculations... yep, but actual flow numbers on the heads are just a guideline.

With exhaust port velocities over 1000 ft/sec and sometimes closer to 1500 ft/sec yeah I think velocity is the key here…. But there still has to be a point were to small is too little. Got any good formulas for that?

Jose,

Good to see you over here… I’ve heard a lot about you from Geoff Chadwick.

Some heads to look for more flow in a STD 23* SBC head is an All Pro 220. Then again my first choice would be to go to another intake manifold and a elbow setup.

I never really thought about it in terms of Turbo Motors…. A small exhaust valve is going to have less area to transfer heat from it to the exhaust seat so you would want a better material in your seats and valves here.

Let me think about this one some more before I say if the extra velocity is going to help. Extra cylinder pressure and more NA VE is going to help turbo spool as much as anything.

I see where you are coming from but sonic choke is a condition that comes from excessive port velocity. That’s the case in the intake not the exhaust.

On the example I gave before with the bigger intake and smaller exhaust in a SP head. I was expecting about 68% average E/I%, where the standard valve sizes and M2 CNC port give you about a 75% E/I% average. You have to realize that with that comes a GAIN in intake flow of 6%, and a loss in exhaust flow of 5%. Basically flowing the same as the STD exhaust port with a 1.600” but more intake flow. In NA motors that means more power.

I like to see as much intake flow as a head can physically handle. Then get me the most I can get with the exhaust valve I am given. That’s why I switched to the SP exhaust in my large valve example, to gain a additional advantage of 3.5% in E/I% ratio (going from 65% to 68%)

See your quote for answers.

It can be over your head but this is something where you either have someone build this if you don’t get it, or you have someone get you the parts together so you can pull this all off.

Bret

 

I talked to Bret, MG, and others about these heads early last year before they started to become popular. If i had the $$$, those heads would be in process of LT1-ization. Seems some info has come around since then though, finally. And since then i've gained a lot of info about using them on the LT1 block. My best source was KTamez though (moderator on this board), who actually built a LT1 with 18X heads (like i stated earlier). I still have pics on my computer showing the completed engine, intake to oil pan, installed in the car (camaro). He used an EFI converted HV1801 intake (the TALL version). He said that the HV1800 intake would probably fit better with less headache, even though you loose some plenum volume. And it all wasn't as expensive as you might think. Get the right pistons in a good shortblock and sort out the header issue and you should be set. It's still a good chunk of change though.

If anybody knows where Kurt is, maybe point him to this thread?

 

Jason,


you said that you have the pics on your computer, post them up if you have a webshots account or email them to me and I can host them for ya.

JPMuscleZ28@hotmail.com


-john

 

Thanx to Fast Caddie for the quick PM to try and get me in here. I guess I can poke my head out of the ground for a few minutes....

Just some quick insights, I'm by no means as technically savvy as many in this forum when it comes to alot of the intricacies of cylinder head tech, but I can say I firmly believe that if the 18X's should suit a LTx combination, if you're stubborn and refuse to move on to Gen1 Block. Personal reasons for this can be due to class rules or just because you think its cool. Thats all personal. For a stretch of time there were LTx motors being built with numerous different head combos, all the way up to SB2s.

Its my rather simple minded opinion that the LTx block loses its useability with anything more then then the 18Xs and even then they are probably overkill. The RPMs necessary to make most other larger cylinder heads work as they are designed and capable of, exceed the LTx blocks stability, to keep positive ring seal, among other bottom end issues. Also take into account the need for aftermarket engine management, Intake manifold restrictions, etc, etc....you soon find yourself no longer actually needing anything LTx based (block included).

About my 396 which is now gone. Sadly it was a project that never came to fruition. The Engine began as a simple 396ci 210AFR LT4 Intake motor, that I then decided to step up with, before ever firing the motor it came back apart and the 18X heads were added, along with Single Plane 1801 Intake as mentioned by Fast Caddie. As the entire project began to come close to finish (chassis included) I decided to sell the chassis, and for safety reasons among other things buy a full chassis car, and run NHRA Top Comp/Top Sportsman. At which point I thought it would be fun to be one of the VERY few using a small block, or EFI. The engine then came apart again, to rebuild using a Dart block to help withstand the strains it would be put through trying to make 1100-1200hp with nitrous in order to just qualify for the field. At which point it was found to have multiple issues, some being poor workmanship in machining/assembly, others being specifications not to my previous request/requirement. The motor was reassembled with the Dart Block, and then sold, as a lost cause, chalking it all up as several lessons well learned. I had already aquired a much larger engine simplifying the racecar operation altogether.

Suffice to say: A 632ci, 18* Big Chief Headed Engine, and a Good Chassis car, made for a string of 4, easy, low maintenance 7.40s at over 180mph last weekend in Seattle.

Back on topic, a couple points made earlier in this thread by others (such as Rich Krause), the LTx combination for all intents and purposes can be great, and make more power then any sane person needs in a stock chassis'd car, even more true in a "street" car. But to get to these levels, I don't believe the exotic heads, and crazy combinations are even remotely needed. Going back to my first paragraph, these combinations make for great bench racing, and forum threads, but for all feasibility, it just isn't needed.

As also mentioned before, know your end goal, and plan accordingly. Proper planning will net you more power, better reliability, and cost less money in the end. Take it from a guy that couldn't make up his mind on what he wanted to do.

Good luck all........

 

A friend of mine runs the exact same combination in a split window Corvette tube car. I believe he's run 6.80s around 200 to date on a 400 shot.

 

Sounds cool. My Father has a 63 Vette. Little but more serious (ie expensive) motor, and runs 7.1x's. Both cars are just on motor, and both use PowerGlide Trans'. A lenco or a liberty w/ a clutch would be a take a nice 2-3 tenths right off the top.

Where and what class does your buddy run?