Yep,
Remember the posts about URY and his "too tall" stacks??

I decided to post the data from my latest engine combo as i try to find the perfect stack arrangement for it..

Guys wanting a cheaper, reliable TIV engine will love this one because it has a ton of torque and awesome smoothness. It does NOT have ported heads, so its almost 1,000.00 cheaper than some of its bigger brothers and makes torque very similar, but does not have the RPM range.. Ultimate daily drivin, short shiftin, 901 abusin power- plant..

Anyway, look at these plots and descriptions for this engine here
http://www.shoptalkforums.com/viewtopic.php?t=80579

I plan on replicating this exact test on the next 10 engines I dyno and see how port work and cam changes effect the results.

The results from this engine do not follow suite with my earlier findings, but almost all those tests were done on high revvin engines....

Wow, the 6" stacks are sort of a wierd curve? I like the results on the 2.65's though! Cool stuff Jake!

Thanks!
Yep, the 6" stacks are all over the place....

Thats what i have seen before, but typically they make a bigger impact up top in the powerband and hurt power more there. My guess is that these test progress to higher tuned engines I will yet again see this.

This engine has a slow piston speed, and high velocity heads with a huge split in the duration between intake and exhaust on the cam. The tuning is effecting my results with this one, but thats why I'm doing more of them back to back.

The tests are fast and easy because it only takes a few minutes to swap them out and unless they effect jetting no other changes are made..

One of my costomers with a 1750 356 and 44's will like to hear about this. Thanks again. This sort of testing rocks!

The 356 is a totally different world...

The best stacks I ever found for them were around 3" tall...

Jake,

About a month ago I took your advice and changed my 6" to 1-7/8" from Aircooled.net.
And I reinstalled the K&N filters.

Do I feel a change?...not really, but my engine needs a overhaul anyway.

I'm glad I was able to spark your interest in doing these tests.
Once again you come through with real world, tested, and verified info.

Now can my daughter use this for her science fair project? I bet she'd be the only third grader with a velocity stack comparison.


Paul

That would be cool!!

The higher the engine is tuned, the more you will notice the changes from the stack variations.

Thats why I'm gonna do this more..... The next 10 engines I have lined up is a very good mix of sizes and tuning from a 1911 clear to a 2563....

Did you change your jetting after you changed the stacks??

No I didn't but I'll look and see what I'm running now and what sizes I have.

Paul

BTW, I was kidding about the science fair thing. We're going to do a compairson between fiberglass, wood and carbonfiber. We're going to make F/G and C/F the same size as a wooden paint stiring stick. We'll put a weight on them and see which one bends the most.
Simple.

Check on the jets...

That sounds cool.... for the science fair..

Safer than mine, I made some home made napalm from the old styrofoam stuff and melted my desk the first time I showed the teacher....

She thought it was gonna be a volcano!

Thanks for showing that. Now people won't look at me wierd when I take the 6 inchers of their car and throw them across the yard.

that's hilarious jake!


they took all the fun stuff out of chemistry sets about the time i was born... still managed to blow some beakers up.

Brett, I had you in mind as well when I did the testing..

I'm gonna play with a bunch more combosand I just found my 4" stacks a few minutes ago while looking for my spray gun to paint the interior of the new shop!

Damn place looks like the OR at the local hospital! Its so bright inside that I'll need shades to assemble things!

The decks are super glossy epoxy and the walls are 3 coats of the same paint used on the underside of Delta aircraft.... every bench is stainless steel.. Its bitchin!
BTW, I guess no one noticed those NOS foggers in the manifolds.....

You should see what it did when I sprayed the juice to it!

Just curious:
Is there interaction between the stack height/size and the
intake manifold height/size?
I ask because I seem to remember that either SCCA or PCA
had some new rules for Carbs that require the use of the Pierce
manifolds which are shorter than the CB ones.

--- bill

absolutely... We are fighting with SCCA right now about the manifold situation... The Pierce manifold is still too tall for high revs and it is not the correct size under the butterfly for a 40mm carb, its like 48-50mm!

everything changes when the manidfold length changes, the CB manifold is a great street manifold, so I'm using it for the base for the testing..

I'll have 4 production engines to test this on very soon, as well as manifold length..

I'm running 2" stacks on my race engines. I think I got them from PMO, same place I got my good manifolds.
I hope to have some more soon, to send down to you Jake.

You didn't show the 1.7" stacks in your pics. Are they the cast plates that have no bell shape?

No, they are the stock dellorto stack....

Thanks for the work on the manifold stuff with SCCA Chris..

BTW, when are you sending down the rest of your goodies?

Speaking of stacks.....does anyone have a line on some "interesting" stack cover/cleaners? Frankenstealth has the typical water shields...but since it is a rustypieceofshit and will never see the rain....it also does not have a top....I would like to dress up the intakes.... <_<

Hey Jake of the different stacks I make 90% are 3.5 inches tall don't know why but thought i'd pass it along

Hijack Alert
URY914 said:

I used to work at GE Aerospace, and I remember them making an antenna boom out of unidirectional graphite fiber - epoxy that was effectivly the dimensions of a 4" diameter pipe, 28 feet long. My understanding was that they hung 60,000 lbs off of the end of this thing (fully cantilevered) as a proof load

End Hijack

Harvey