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Discussion Starter #1
On my quest for a Cleveland head for my sbf 427 pump gas motor I have been told many times that giant intake runner heads are more for all out racing high rev motors.

Looking for a 240 ish cc intake runner I found the CHI 242's. But i noticed the smaller 220's with smaller valves flowed almost the exact same and better in some spots.

Does that translate in higher velocity speeds? What would be the advantage of the 240's over the 220's at this point?
 

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Stoker can use the larger csa or ^ larger runner... Your thinking right if you want a lower peak rpm for the sma'ller port. You should ask what's needed for CSA and CFM for your engine size & rpm peak ??<<. ;)

Then you've answered, your own___? Your on the right path.
 

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IMO it really depends on the application as to which would be better. Not just what the engine is, but its intended use, gearing, weight, converter, ect. the bigger head wont necessarily be better all the time for racing......as far as for a street engine, usually if its lower rpm then the smaller cross section port is usually a better fit. but with the correct valve timing a larger head can work well in that application also. the target cross section will depend on what rpm you want the engine to be in for its airspeed target. it also depends on the engines cylinder demand, and compression will determine how much lobe you can get away with. so it all plays a part.
 

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Discussion Starter #4
The head I was convinced by RCS that I need but cant afford is the rcs/chi 248 head.

The small intake runner/csa for a head flowing 400 cfm at around .700.

Hilborn (the intake i will be using) and TEA also suggusted 240-250ish intake runners.

So another question came to mind because the flow graphs on the chi 220 and chi 242 look almost identical, so what would happen if you took the 220 head and had ported it out a bit and maybe got it close to 240cc. If possible put some bigger valves in? Kind of wonder if thats what RCS did?

These 220 and 242 heads both come standard or with high ports. Im taking a guess here but if you you can get away with the high ports due to headers that they are preferred?
 

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Discussion Starter #5
Stoker can use the larger csa or ^ larger runner... Your thinking right if you want a lower peak rpm for the sma'ller port. You should ask what's needed for CSA and CFM for your engine size & rpm peak ??<<.




Then you've answered, your own___? Your on the right path.
So what kind CSA should I be looking for? Higgins told me they only measure csa because the runners are longer then normal causing port volume numbers to look much bigger.

So this would be a drag week build. Hilborn keeps telling me that their IR intake can make bigger cams idle and make mid range more useable.

I see pre-built pump gas street/strip 427-432 motors making 685-715 with OTB heads.

I am wanting 725-750 which seems to be around 400 cfm.

The more novice questions I ask the more I feel im feeling im getting closer to what I want.
 

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So what kind CSA should I be looking for? Higgins told me they only measure csa because the runners are longer then normal causing port volume numbers to look much bigger.

So this would be a drag week build. Hilborn keeps telling me that their IR intake can make bigger cams idle and make mid range more useable.

I see pre-built pump gas street/strip 427-432 motors making 685-715 with OTB heads.

I am wanting 725-750 which seems to be around 400 cfm.

The more novice questions I ask the more I feel im feeling im getting closer to what I want.
how hard to you want to turn it and what is the compression? to determine cylinder demand needed we need to know around how big of a cam you need/are expecting to run along with the compression. its the whole package, you cant just say 'this cfm' to make 'this hp'. it takes the correct cam, compression, and cross section to get it done. what are you thinking for intake? there are tons of heads on the market that dont flow anywhere near 400cfm with around a 2.5-2.6" cross section that will make the HP you want. the lower the compression, the less duration you can get away with, and in that case you will want a bigger head because nothing flows with the valve closed.
 

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Cross sectional area is what you should be looking at for your combo, also shape and then flow.


3.0 will get you 750 no problem , 360 cfm, thats with a small cam
 

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Discussion Starter #9
So my thoughts where to shift at about 7200-7500 rpm with a compression ratio of around 11:1. My thoughts where around .700 lift give or take, tight lash cam, stainless steal valves and tool and tool steel retainers. for a bit more durability.

One of the sites said to get a mcsa you took bore^2 × stroke x rpm x .00353 / (.55mach x 1116 fps)
For me that accumulates to 2.818 mcsa.

what about a 2.85 mcsa head? That particular one has an intake runner of 265 and flows particularly well.
 

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there are guys with heads that are smaller than that turning over 8k. i think the smaller head will be best for your low rpm application. if you want room to grow than run the bigger head and a smaller cam.
 

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So my thoughts where to shift at about 7200-7500 rpm with a compression ratio of around 11:1. My thoughts where around .700 lift give or take, tight lash cam, stainless steal valves and tool and tool steel retainers. for a bit more durability.

One of the sites said to get a mcsa you took bore^2 × stroke x rpm x .00353 / (.55mach x 1116 fps)
For me that accumulates to 2.818 mcsa.

what about a 2.85 mcsa head? That particular one has an intake runner of 265 and flows particularly well.
Take it.
Your cam guy can fill in the specs.
 

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i'd do a cost vs having work for bigger valves and port work. this from a guy who will make a head.

But to start with the port with say the 242cc runner is a win...u can use the area(csa) 4 the cubic inch size and rpm (also it"$ not as much work that wil be needed. Hell like it was said if U can get 360 cfm with the intake on, there goes your 750. Same rule applies for a 408 with Ls3 heads that flow 370ish and about 7500. 750 with all the small stuff: vac. pump, decent compression, crank scraper..... etc 2 fight windage- 700^ lift 250-260ish cam with a 4 inch arm works out to aroud 7500 rpm with any engine with that arm size used. Any. 360 to 370 cfm @ the piston = 700 to 800+ depending on compression/rpm/lift used.
 

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Will say this ER racing is a MF'er !!!!
Showed me how to set up a HD stud mount ls3 head. Zach Nelson winner of the EMC with SAMtech & winner with the 366Ls cid intake / NOS. Has a shop near me and we discussed what i have(to build), show i took them by. Was told basically i'm using my head with the set up. Told Zach i follow the right people. Zach made the custom harland sharps rockers for SAM and the 366 emc motor. Have a 5.3 aluminum block zach wants also.;)
 

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Discussion Starter #15
I have been looking and studying these 3 heads forever. The TFS 240's are there for reference and known for early flow numbers.

Are the 220's just a touch small, are the 258's too big. the csa vs flow numbers kind of imply to me the velocity may be ok on the bigger one.

Talked to some people about porting the 220's and they said you probably wont gain much.

CHI recommended the 242's or the c400's.

I talked to Jim at kontz and co and he said chi is good but he recommended a windsor and the monster brodix head hunters he helped design for my setup and that it would idle and drive ok.

RCS said their chi 248's are perfect for my setup but they want $6800 for a set.

TEA reccomended their 240's but said their 250's where too big.

CHI says they will put 11/32 guides in for no additional costs. Soon as i find out the exact valve length they use and can make sure there is off the shelf valves I can use i will be ready to order a bare set. Which ones i dont know.

 

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A 258 cc runner on a raised port, like the C400 is not real large. I have a 250 ish on a 388 and it peaks at 7600.
 

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^^^^^^^

C400 ftw
 

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Discussion Starter #19
I have been leaning back towards the c400. Because of a typo on one the distributors websites I thought it was a 285cc intake runner and had kind of dismissed it a month ago. CHI confirmed that it was a 258 after noticing runner size listed on their FAQ page and sending them a message.

Im actually excited to see that people kind of are agreeing with my thoughts on this. This has only been taking me months to decide and I been ready to order! Im sure i will miss out on some low end power and torque but Im ok with that.

Also helps that Jim from Kuntz and Co reccomended a monster 300+ cc brodix head hunter and when I asked about it being too big he said no. "Im 72 years old and been doing this a long time. Dont believe all you hear, especially on forums, most have never built a single engine." haha

I just hope they use a common valve length and I dont have to have custom valves or buy a complete head.
 

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We'll find you a valve that's no problem. Your thinking is right on c400 heads if in the budget. With room for more if need be.

Blanks<
2.225 valve head
.3110 valve diameter Hollow Stem
6.300 long
 
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