[65nss4spdGTO]

Originally Posted by Marty Palbykin

Calvin, A out of the box e head on stan sheldon's 1961 cat made well over 1200 hp at low boost. Unported head and manifold.
My recomendation would be a 3.00 main on a 3.75 stroke long rod of course.
Marty P.

Marty,

Why would you use a long rod, for a 3.750" stroke, somewhere around 7.100"?

Thanks.

Calvin Hill
Hill Performance
708-250-7420

[Tom Vaught]

I actually took some Intake Duration out of Jimmy Keen's Vortech Supercharged 347 cid Ford Engine because he was able to make the required rpm with less intake duration and as Travis mentioned ONCE the cylinder is full it is full. We were paying for the increased duration in other ways that was hurting our track performance. Jimmy was running a Power Glide. This is when we moved from the heavily ported "Street Heat" heads to the lightly ported Yates heads.

Tom Vaught

[Tom Vaught]

Just a Comment, I am very happy to see Travis posting on the Boost Forum.
Pulling for him and Rodney to be the First Pontiac Guys in the 5s.

Tom Vaught

[Travis Q]

Originally Posted by 65nss4spdGTO

The easiest way to increase VE in an NA motor is raise torque RPM.

If two motors each make 600 lb-ft., but one engine makes that same torque 500 RPM higher, that engine will make much more HP power.

So we put on bigger heads, longer duration cams and more valve lift.

How does valve lift effect boost power?

Calvin Hill
Hill Performance
708-250-7420

There it is! You moved the power band up in RPM, so by changing the heads and cam to suit, you moved more air through the engine and made more power.

If you leave the operating speed where it is, you don't see very much of a gain.

In terms of valve lift, I still say that once the cylinder is full it's full, so your valve lift only needs to be big enough to do that. Tough part is figuring out how much that is. I prefer to err on the big side with lift, and the small side with duration. I have not yet seen a degradation in performance from too much lift, only a degradation in valve spring life. So I tell people to put as much lift in the camshaft as they can stand.

I like camshafts that have pretty aggressive opening rates, and a little softer closing ramps with a lot of lift.

[Travis Q]

Originally Posted by Tom Vaught

I actually took some Intake Duration out of Jimmy Keen's Vortech Supercharged 347 cid Ford Engine because he was able to make the required rpm with less intake duration and as Travis mentioned ONCE the cylinder is full it is full. We were paying for the increased duration in other ways that was hurting our track performance. Jimmy was running a Power Glide. This is when we moved from the heavily ported "Street Heat" heads to the lightly ported Yates heads.

Tom Vaught

REALLY GOOD statement, Tom. Too much duration will hurt an engne more than not enough, from what I have seen. Especially true with a turbocharged combination. Especially with a supercharged combo, sometimes a little more cylinder head will allow you to make changes to valve timing events to improve performance on the track. This again goes back to our earlier statements about what a blower engine wants for an ideal cylinder head (increase in engine speed and decrease in blower overdrive) and what a turbocharged engne wants. They are definitely different.

[73 TRANSAM]

So if you have 4.5" stroker and spin it to 6500 rpm and a decent size single turbo, it will make more power than say 4.25" stroker. The bigger stroke will need more air than a 4.25 would at rpm below 7000 rpm right. Also is the reason for a lower stroke for turbo so that I won't stress the crank or the turbo don't like stroke? What about the rod ratio, I heard turbo engine don't like anything higher than a 1.59 rod to stroke ratio?Thanks.

[Travis Q]

Bigger engines at the same rpm level make more power, period. As long as you have the cylinder head to keep it full. The reason that I don't favor the longer stroke cranks is that they are not as strong as shorter stroke cranks, and put a lot more stress on the block (less rod ratio).

In terms of rod ratio, i've run ratios anywhere from the high 1.3's to above 2:1 and had no issues. The higher the ratio, the less the cylinder wall side loading.

The turbo doen't care. It has no clue what rod is in the engine.

[73 TRANSAM]

Travis,
Thanks for the info on the rod ratio as I got rid of my Scat 4" crank and my Manley 6.8 Pro I beam rod from wrong info from other sources. I will be running an IA2 block on the next build as I ordered one from Frank at All Pontiac last week. Thanks again.

[GTOGEORGE]

Interesting thread, can't believe I missed it.


GTO George

[Tom Vaught]

Originally Posted by 65nss4spdGTO

I'm still struggling with this. I've thought about it quite a bit today, my conclusion turns to engine size, RPM and boost pressure. So lets push this head number one to the extreme. I know that NA, that style of cylinder head will make around 1.25 HP to Ci. So we are looking at an engine making around 550-575 HP. Add 13-15 lbs of boost, the engine should make around 1200 HP?

Now take an engine that makes 1.75 HP to Ci with the same cubic inch, we are looking at around 800 HP NA.

Why wouldn't a smaller boost amount make the same power as our target?

Calvin Hill
Hill Performance
708-250-7420

Couple of things needed to be added to your "equation" that I touched on before:

Going by your post above:

"So we are looking at an engine making around 550-575 HP. Add 13-15 lbs of boost, the engine should make around 1200 HP?"

1) What is the Boosting Device?

With the turbo you might hit the 1200 hp number. With a Supercharger we have a couple of problems: You said that we made 550-575 naturally aspirated. I will give you the benefit of being at seal level conditions of 14.696 PSI on the pressure and 60 degrees F on the temperature.

You add a second atmosphere of air to the engine, but this time the air has been compressed by the boosting device so right off the bat you will take a hit it the HP number if you are not running an inter-cooler. Less dense air without the inter-cooler.

Then if the boosting device is a Supercharger we have to subtract out the horsepower to drive the supercharger (which I posted earlier is at least 100 horsepower).

So you can't "add" 13-50 psi and expect to double the horsepower to 1050 or 1150 hp because you have not taken into consideration the horsepower to drive the supercharger or the need to add the inter-cooler plumbing.

Course if we change the engine parameters at the same time with a better V.E. engine design that makes more hp naturally aspirated and increase the rpm of the engine, then maybe even with paying for the drive losses we might hit our 1200 hp goal.

So using your simple math, "doubling the hp" does not take in to account a lot of real world changes that also might need to occur. BUT your example of changing the V.E. of the engine and then needing less boost pressure hits the nail on the head.

Tom Vaught

[BruceWilkie]

Originally Posted by Travis Q

Bigger engines at the same rpm level make more power, period. As long as you have the cylinder head to keep it full. The reason that I don't favor the longer stroke cranks is that they are not as strong as shorter stroke cranks, and put a lot more stress on the block (less rod ratio).

In terms of rod ratio, i've run ratios anywhere from the high 1.3's to above 2:1 and had no issues. The higher the ratio, the less the cylinder wall side loading.

The turbo doen't care. It has no clue what rod is in the engine.

Good pointson rod ratio and crank strength.

I have a little bit more that deserves discussion. First is its quite true that longer rods reduce side loading. Not only is this less wear its less load on the ring package. The second thing that goes along with that is piston rock. Too long a rod moves the piston pin up high. You dont want to sacrifice ring position and you dont want to add a bunch of skirt length to control piston rock. IMO the 3.75" to 4" stroke and 6.8 rod is not all that bad. I think it might be the best compromise.

Here is something to think about...its an ABSOLUTE EXCEPTION but indicative of the strength in a shorter stroke... Vin63 has used a cast 1969 400 N crank at HP levels exceeding 1800 and rpm exceeding 8500!!! Supercharged Alky 15% nitro... in a stock block!!! Blocks dont last long...but havent broke bad enough to ruin the crank...yet!
This year he has switched to a forged crank figuring he's more than pushed his luck on cycle life. I'm following this progress...I'm interested to see affect on block life with the change a more flexible crank brings... I can not type what I feel this change will do.
BTW his 455 crank life was measured in feet and rather embarrasing...but probably related to a very high nitro load more so than the crank.
I cant empasize enough about exception...kids dont try this at home lol! It does validate a few of Travis's points though. It also leaves one to wonder just what level of prep and all that was done that allowed the 400 crank to live.

[Elarson]

Fascinating thread. I've re-read all of it a few times. Although not specific to turbos, here's a couple of bits of interesting trivia:

1) the blown nitro NHRA big show cars are rumored to be making something north of 8000 hp. Although it is pretty tightly held info, a tremendously reliable source has suggested to me that the blower (alone) takes something approaching 1500 hp to turn.

2) with any boosted engine, it becomes more and more important to build the engine with durability in mind, and let the boosting method make the power (thinking in terms of the previous discussion about stroke, rod length, etc.). We were discussing the Boss Bird engine with Bill Miller (back when it was still in the planning stages) and he had this to say...."With blown nitro, a lot of the things you guys are used to worrying about just don't matter".

Eric

[Tom Vaught]

Originally Posted by Elarson

Fascinating thread. I've re-read all of it a few times. Although not specific to turbos, here's a couple of bits of interesting trivia:

1) the blown nitro NHRA big show cars are rumored to be making something north of 8000 hp. Although it is pretty tightly held info, a tremendously reliable source has suggested to me that the blower (alone) takes something approaching 1500 hp to turn.

Eric

Eric, a piece of data crossed my desk one day that had to do with NHRA Big Show engines. It basically had some accurate data on a specific power producing unit and what kind of horsepower was required to make that unit work in its design envelope.

I would say that your tremendously reliable source was telling you the truth based on my info.

Tom Vaught

[Travis Q]

Originally Posted by 73 TRANSAM

Travis,
Thanks for the info on the rod ratio as I got rid of my Scat 4" crank and my Manley 6.8 Pro I beam rod from wrong info from other sources. I will be running an IA2 block on the next build as I ordered one from Frank at All Pontiac last week. Thanks again.

Here's a little more food for thought on this subject:

One of the fastest turbocharged combinations right now is the AJ481X. This engine has a 4.125 stroke, and a 7.100 rod, for a ratio of 1.72.

Another very fast turbocharged combination in Outlaw 10.5 has a 6.8 rod along with a 4.875 stroke, for a rod ratio of 1.39.

You can make just about anything run, but I prefer the longer rod/stroke ratios, so long as I don't get the bobweight too high for the intended rpm range, or have a block deck height package that puts the piston/pkin design in left field.

[Travis Q]

Here's one more thought:

Long stroke cranks make LOTS of torque. Lots. So much, in fact, that it can be totally unmanagable in any application. Shorter cranks allow you to move the torque curve around to a more usable range....which is normally higher rpms. And this is OK, because the engine is smaller, and as a result requires no more cylinder head than the larger engine at less rpm. Hope this makes sense, becuase in our (currently) cylinder head limited Pontiac world, it's best to figure out what the desired engine speed range is, and then back into an engine size based on what is available in terms of cylinder head.

[GTOGEORGE]

Like Travis said you make just about anything run in a boosted application................I think it's more important to learn how to seal the head to the block, since we do have heads that flow the numbers (Warp 6) to be competitive and billet heads to last.


GTO George

[70 bird]

I have been over to my bosses, Doug Kalitta's race shop and have seen the blower dyno test cell. It has a pretty hot sbc just to turn the blower. That might give you an idea of how much power a blower can take.

[Tom Vaught]

Ideal Billet head in my mind would be a BAE-8 style head, if you could fit the design onto a IA-2 style block (since it uses a 4.181" bore chamber). BAE Heads have years of actual race time at the top of the sport as related to the other guys components on the head. EVERYTHING in the Head Design was designed for boost.

That being said, that is not going to happen so then the "Fall-Back Plan" would be, can you get the Warp 6 head to perform as well as say a BAE-5, BAE-6, type head?

A Complete set of "KNOWN DESIGN" BAE-5 "like New Heads" are selling for $5,250.00

http://www.racingjunk.com/Drag-Racin...der-Heads.html

Doubt if you could get the basic Warp-6 castings for that money much less finish them with similar components.

BAE 5 Cylinder Heads complete with Victory Titanium Valves, 1359 PAC Dual Valve Springs and Manton Titanium Retainers. Heads have a manufactured date of 5/27/2010. All parts have only 3 full Runs since installed new in Oct. of 2010. These heads are in "Like New" condition.

So figure out how to mount a BAE-5 Head on the Pontiac Block and go racing.

Tom Vaught

[GTOGEORGE]

Doesn't matter what head you have 10 studs won't seal it.

GTO George

[Scott Roberts]

The warp head would give you a chance to get on the track with the big boys but not win. You could win some races but would be plagued by the sealing issue. We went out and ran with hemi powered cars and beat a lot of them but never won
on a final round. We torched a cylinder in the semi finals and had to smash the electrode on the number 6 hole ( making it dead) and run on 7 cylinders in the finals one time at a funny car shoot out...still went a 4.30 but lost to a 3.90. It can be done but its a lot of work , time, and money....thats why got rid of the car..
The Pontiac just isnt there....