[KO]

bore size dictates intake valve size which in turn dictates maximum HP potential, the ideal displacement for the maximum HP per CID is much smaller than 500 inches when it comes to the Pontiac V-8.

I'm looking into NHRA Super Stock SS/CS which is 10 pounds per CID, cast iron heads only single 750.the Chevy guys are running the cast Bowtie head (heads must have OE casting #). I think a good OE Pontiac head should be better.

[S/st 54]

Originally Posted by cgeise

I see all this back and forth about 2.3 - 2.5 - -2.7 per cid. but I see so very few trying to get there ? The reason they don't is two fold - or three depending on approach. First for a lot of guys is the expense, there is a point that the dollar per tenth of improvement gets astronomical -- I have a chart some one did and it gets really crazy at the upper limits. Second is just plain "WHY" Id say 98% of us are some form of bracket racer or index racer, you could probably count on one hand the number of guys running true heads up, so where is the need??? I admit that SOME of the information gathered doing this kind of thing trickles down to the mass's -- but it takes a long time and some of it is not applicable to bigger engines. The last is -- it is just easier to build it bigger -- stress it less and make as much or more HP. A 400cid at 2.5 per is a 1000 hp and a high maintenance bitch to run and take care of. A 560 cid at 1.8 is over a 1000 hp and way easier to build and maintain. So - for the four or five guys that want that small engine stuff. I get it --kinda, but for the mass's I think its big muscle that seems to be the way the majority of the racing world is headed.
And we haven't even talked about power adders :-))))))))

Well said Curt! Hmmm I think there is someone else that agrees with you on the cubic inch thing....



http://rehermorrison.com/tech-talk-2...-displacement/

http://rehermorrison.com/tech-talk-6...of-the-giants/







And hay Curt ! Best of luck to you and Clint this year!

[Chad Speier]

The engine that just made 2.50 hp/cid was a 4.04 bore and had a 2.180 valve.

Who woulda done that! A Comp racer.

[dci]

I agree 100 % Curt. I am just trying to shed some light on what it would take to get to this level of HP. The good thing about discussing or debating this level of performance. Is that it will broaden everyone's knowledge base and hopefully improve their own program. I think that magazine articles are good for getting the basics, but that some times is not good. I know they have limited space and resources to get the point across, but I also know that people take what is in black and white as gospel. So I thought perhaps taking a given cubic inch, and a realistic HP level for the traditional Pontiac engine. We could expand on the magazine articles we all read and get some more insight into what it actually takes to build this type of engine. Like you stated, bigger is better and less expensive (not cheap). I guess I am just trying to get people to think for them selves and not rely on the uninformed and partial information to guide them. I truly believe it will help our small group of Pontiac loyalist rise to another level.






Don Johnston
DCI MOTORSPORTS INC.
330-850-5050 shop
330-628-3354 cell
Designer of the DCI Tiger Heads and the NEW DCI Ram Air 5 Heads !!!!!

[pastry_chef]

Originally Posted by dci

Chad, If that 349 needed 9600 rpm to make that level of power. What rpm do you speculate a 500 cu in would need? With the assumed optimal csa for this engine of course.

If the power level goal is 2.50 HP/cu.in, at the same efficiency (MEP) a larger engine would need the same RPM.

In theory, its more difficult to obtain the same efficiency with larger displacement.
If less efficient, then you would need to spin to a higher RPM.

Gives insight as to how challenging it really is!!!

[Tiger Paw]

Don, there may be a way to get the pushrod out of the port on V heads and still maintain the same layout. Had you ever considered a cam follower arraingment like that used in Ilmor Indy car engine raced in the 90's. Those followers can be narrower that a round lifter and lifter bores arent used anyways. probably could be retrofitted to any block. It's only time and $$$ !

[J.C.you]

Originally Posted by Tiger Paw

I think the problem area for a 500ci Pont is the needed port crosssection to achieve the desired port velocity will run into a pushrod. You can't move the lifter lobes/bores enough laterally and still not hit the lobe/lifter on the other side of the engine. Compare your cams to a even a stock BBC. Pro stock cams are montrous in every dimension compared to a Pont.

You need to think smal CI so you can get the pushrod out of the port to get 2.2 and up.

I had to design and machine our own cores for my 500" comp engine after some clown here in Detroit moved our lifter bores to a place where no one had cores available. I've been down this road.

you had them moved perpendicular to the deck then? How long ago would this have been?

[BruceWilkie]

Originally Posted by Stan Weiss

First let me correct myself that should be 139.5% VE




Exactly, if we look at a 572 ci engine, bore = 4.375", stroke = 4.75" at 8400 it will have the same mass air flow at 124.8 % VE.

Stan

Stan as the stroke gets longer, the valve lift rate "wants" to be greater due to piston speed. Two motors same displacement with heads of same flow capabilities but different bore and stroke... the longer stroke motor isnt likely to acheive as high a VE as the shorter stroke motor... it certainly WONT if you use the same cam and rocker ratio... and making rod length ratio equal or different wont make much if any difference.

Keep in mind bigger bore motor could run bigger valves and be made to flow more than the smaller bore could... again same displacement, the bigger bore motor now has the potential for even greater VE.

VE is king in making power per cubic inch.

[Jack Gifford]

Originally Posted by cgeise

... Id say 98% of us are some form of bracket racer or index racer, you could probably count on one hand the number of guys running true heads up...

Either I'm in the 2% or I'm not one of us! So keep these discussions going...

[dci]

Pastry chef, I agree the rpm's will need to be high. That is why I chose the cubic inch I did. It's not to big, but it still big enough to make the 2.3 goal. With a 4.400" bore we can use a big enough intake valve to flow enough air to reach the rpm's we need. I think that on that bore size. An inline valve type head could accommodate a 2.350" - 2.380" valve and still be far enough away from the cylinder to be efficient. That valve is a little bigger than the 52% rule, but I'm not sure that the old 52% rule is still being used any more.Especially since everyone found that shrinking the exhaust valve does not hurt the HP. By shrinking the exhaust valve down it makes more room for the valve package.


Tiger Paw, The time part doesn't scare me. It's the money part LOL. I have not considered that arrangement for my heads, but I am always open to new idea's. I still need to prove to myself though that the way I have my port designed now it will be a limiting factor. I am not so bull headed or blinded though that if someone has a better idea that I will not consider it. I have a port that we have been developing in my 5 heads right now that has about 4.5" csa. at the pushrod or opening. It sounds really smooth on the bench and does not back up. So I am really anxious to get it on an engine to see how the port performs. Unfortunately though it is going to have to wait for now since I was chosen for the engine masters challenge (not enough time and money LOL). We think this port is way to big to operate within the rpm range of the challenge. I know everyone is all cranked up about the pushrod being in the port, but until I have tested and tested and tested for myself. I cannot let it rest.

Bruce, When do you think you will get your software functional again? Do you by any chance have the software to determine intake and header spec's?


Don Johnston
DCI MOTORSPORTS INC.
330-850-5050 shop
330-628-3354 cell
Designer of the DCI Tiger Heads and the NEW DCI Ram Air 5 Heads !!!!!

[65nss4spdGTO]

Originally Posted by Transporter

Wasn't someone offering a 9.2 Pontiac block? in aluminum?

That is what you need, hell it would probably bring Marcella back!

The new IA-II iron block is cast at 9.500" with enough deck thickness to get very close to 9.200". This information is based off the two blocks I've had in the shop and sonic tested the decks.

The projected build I have for this project is right around 425ci engine with a 425CFM cylinder head.

Calvin Hill
Hill Performance
708-250-7420

[Tiger Paw]

JC, I had design my own cores in 2000, and moved the intake lobes roughly .375 fore and aft. Exhaust lobes then needed to be moved about .150 to provide clearance for the moved intake lobes on the opposite side (as best I can recall). If you want more of the story PM me.

[Stan Weiss]

Originally Posted by BruceWilkie

Stan as the stroke gets longer, the valve lift rate "wants" to be greater due to piston speed. Two motors same displacement with heads of same flow capabilities but different bore and stroke... the longer stroke motor isnt likely to acheive as high a VE as the shorter stroke motor... it certainly WONT if you use the same cam and rocker ratio... and making rod length ratio equal or different wont make much if any difference.

Keep in mind bigger bore motor could run bigger valves and be made to flow more than the smaller bore could... again same displacement, the bigger bore motor now has the potential for even greater VE.

VE is king in making power per cubic inch.

Bruce,
There are a few sub threads going on here. With the 572 I was talking to Curt about large ci engine for bracket racing.

For the 2.3 thread 575 * 2.3 = 1322.5 HP

Bore = 4.375 - Stroke = 4.75 - Rod Length = 6.7 - RPM = 8400
Piston Speed is 110.83333 Feet per Second
Piston Speed is 6650.00000 Feet per Minute
Maximum Piston Velocity 11090.732 FPM @ 72.362 Degrees

Bore = 4.44 - Stroke = 4.03 - Rod Length = 6.7 - RPM = 9600
Piston Speed is 107.46667 Feet per Second
Piston Speed is 6448.00000 Feet per Minute
Maximum Piston Velocity 10579.730 FPM @ 74.498 Degrees

Because of the difference in RPM, there is not that great a difference in piston speed.

VE is king up to the point it is maxed out then the only way to increase HP is to add cycles (RPM)

Stan

[Tiger Paw]

Don, I understand completely and would do the same in your shoes. Good luck with the Challenge and hope your heads meet your goals.

[Stan Weiss]

Originally Posted by dci

Pastry chef, I agree the rpm's will need to be high. That is why I chose the cubic inch I did. It's not to big, but it still big enough to make the 2.3 goal. With a 4.400" bore we can use a big enough intake valve to flow enough air to reach the rpm's we need. I think that on that bore size. An inline valve type head could accommodate a 2.350" - 2.380" valve and still be far enough away from the cylinder to be efficient. That valve is a little bigger than the 52% rule, but I'm not sure that the old 52% rule is still being used any more.Especially since everyone found that shrinking the exhaust valve does not hurt the HP. By shrinking the exhaust valve down it makes more room for the valve package.


Tiger Paw, The time part doesn't scare me. It's the money part LOL. I have not considered that arrangement for my heads, but I am always open to new idea's. I still need to prove to myself though that the way I have my port designed now it will be a limiting factor. I am not so bull headed or blinded though that if someone has a better idea that I will not consider it. I have a port that we have been developing in my 5 heads right now that has about 4.5" csa. at the pushrod or opening. It sounds really smooth on the bench and does not back up. So I am really anxious to get it on an engine to see how the port performs. Unfortunately though it is going to have to wait for now since I was chosen for the engine masters challenge (not enough time and money LOL). We think this port is way to big to operate within the rpm range of the challenge. I know everyone is all cranked up about the pushrod being in the port, but until I have tested and tested and tested for myself. I cannot let it rest.

Bruce, When do you think you will get your software functional again? Do you by any chance have the software to determine intake and header spec's?


Don Johnston
DCI MOTORSPORTS INC.
330-850-5050 shop
330-628-3354 cell
Designer of the DCI Tiger Heads and the NEW DCI Ram Air 5 Heads !!!!!

Don,
I have Larry Meaux PipeMax software which does headers / exhaust systems and also intake lengths. If you need some numbers run.

Stan

[J.C.you]

Originally Posted by Tiger Paw

JC, I had design my own cores in 2000, and moved the intake lobes roughly .375 fore and aft. Exhaust lobes then needed to be moved about .150 to provide clearance for the moved intake lobes on the opposite side (as best I can recall). If you want more of the story PM me.

Ok, that is a eiieeiie arrangement then.

[Tiger Paw]

JC, That is correct. Nice looking engine, love the exhaust port trim. Are those headers for your car?

[BruceWilkie]

DCI ....Bruce, When do you think you will get your software functional again? Do you by any chance have the software to determine intake and header spec's?

Originally Posted by Stan Weiss

Don,
I have Larry Meaux PipeMax software which does headers / exhaust systems and also intake lengths. If you need some numbers run.

Stan

Same here...

but with xp support expiring soon and current pc long ago maxed for memory capacity I've not reloaded software. (had to crash my system as granddaughter maybe decided to ignore security warning and fixed me up with a virus that affected windows load. Fixed her moms laptop up with same bug. We caught her at 4am try'n to get on Debs laptop a few days later... long story but intent was malicious and coached by her dad!)

Eight years on same box(with upgraded replacement parts) I cant complain. But time to shop and decide... Might just build what I want. Most store bought stuff uses cheap or marginal components these days. Built one yrs ago when Windows 3.1 was at its best. Was quite the rocketship back then. I'm rather rusty these days and havent tried or had the need to recertify my A+ certification in 9 years.

[Chad Speier]

Here are a few numbers I come up with from the program I use for everything.

Model Engine
500 CID
1250 HP
8000 peak RPM

4.50in² flowing 655 cfm = 100% efficiency
To achieve goal you will use 3.60in² and 524 cfm of that head

4.50in² flowing 555 cfm = 84% efficiency
To achieve goal you will use 4.25in² and 524 cfm of that head

4.50in² flowing 524 cfm = 76% efficiency
To achieve goal you will use 4.50in² and 524 cfm of that head

[dci]

Interesting Chad!!! How accurate do you think that program is? Does your program use it's own flow analysis or do you need to plug the numbers in?


Don Johnston
DCI MOTORSPORTS INC.
330-850-5050 shop
330-628-3354 cell
Designer of the DCI Tiger Heads and the NEW DCI Ram Air 5 Heads !!!!!