Inliners International Forums General Discussion Hi Performance Dyno day for a 250

Dyno 250 Predictions:
Some of you may recall I made some "Gonkulator" predictions of the 292 dyno tests before they were run. The predictions matched the test series fairly well, although I did correct the dyno data horsepower by about 4hp, that is my estimate of a correction to full open headers vs the (2" or 2-1/4 pipes I forget) used.

With that, the Gonkulator averaged same as the dyno overall, with a scatter (standard deviation) of 3% or 4%, ie a scatter of about 10 ftlb and 8hp or so.

So, on to the upcoming 250 dyno runs.
Run-for-run, my Gonkulator is predicting that the 250 will come in about 14% lower on torque and 6% lower on horsepower than the 292. We should be able to see this since 5 runs (as I count them) are repeat runs - the 250 will be dyno'd with exactly the same cam/head/manifolds as on a prior 292 dyno.

One reason the 250 hangs in there so well is that for most of its runs, the 292 only had 8.80 compression. I am calculating the 250's compression at 9.76 with the flat tops - Tom does that sound about right?

Especially fun will be the weber tests, I am predicting well over 300hp for the weber and the biggest cam planned.

With the 70cc heads it will be right at 10.03-1 for the compression with zero deck and a .040 gasket.

With the latest 12 port aluminum.Kirby/Sissle head,mild 250 build that Mike dynoed it & it made just over 300 - 310HP

IIRC? It was in a Hot Rod article?

MBHD

This should make for an interesting comparison. We are expecting to see over 300 with this testing.

MBHD
I think that is the June 2005 Hot Rod?
The 12-port fuelie 250 dyno'd at 315hp, my guess is about the same exhaust restriction as Tom Lowe's plan. Guessing the fuelie setup is about the same as weber power, adding tlowe's hottest cam would add about 20hp per the Gonkulator. Knock off about 5hp for compression (10.5 vs 10.0) so if the June 2005 Hot Rod engine had tlowe's cam and compression, it would have made maybe 315+20-5=330hp. I am Gonkulating about 310hp for tlowe's top dyno test, so that means the 12-port head would be adding about 20hp vs the ported, lumped, big valve stock head at this level of build. We will see!!!

I do expect to see over 300 hp.
The compression calculated was also 9.76, but will be lower because of the cylinder notching, should have caught those filings and CCed them(dang nab it).

Yes many of the same 292 tests will be done again and many are not. @ new cam's will be brought into the equation and a set of Langdons sweet exhaust manifolds and to kick it all off in the end , amild blow through turbo setup. Lots of work indeed.

Beater, Your coming , right?

Seriously, there will be some big time wrenching taking place, more hands always lighten the load. Tom

If you haven't closed it up already a little modeling clay can be used to reform the "missing" metal and then cc that.

True, It is not closed up. Just yesterday started balancing the crank. To start the rear 1/2 was nearly perfect and the front 1/2 was off by 18 gms on the non counterweight side! Talk about creative weight reduction. Tom

Tom, just stick a piston in a bore and cc it, then you can just subtract the difference in volume that an un-notched bore is from it. Its the same process you use to measure the effective dome or dish volume of a piston.

Going to work later, so been working on the 250. Crank is balanced to within 1/2 gram front and rear. Rods are also done. Those Crower rods are kinda heavy. 670 gms. But built like battering rams. To handle together has a sound like high quality wrench's have.
Will get the chamfer CC's figured in. Tom

Tlowe,

If you can open up your 194 head,by laying back the chamber wall for better airflow.

Then mill the head as much as possible to raise the compression.

Just a suggestion.

MBHD

Tom,

You still collecting money for the dyno day 250? If so, how much are you looking for and how would I get it to you?

Dodgy,
I am still collecting money for the 250 dyno session. There are a few ways to get it to me.
Paypal to tom@12bolt.com

or send it

Tom Lowe
3063 200th st
Dysart, Iowa 52224

All contributors will be added to the email list to share the info.


Still trying to narrow down to the dyno dates. Looking at the first and second weekends in April. Does that fit with anyone elses schedule? Got lots of fun tests scheduled.

Lower end is all balanced, next to hone block, reclean it and assemble it. Tom

Tom, what's your best guess as to the difference in the cast iron Langdons vs the Clifford tube headers?

Kerry,
I think it really matters to the rpm the engine will see. They will be very close in power upto around 5k and then the headers will come out on top. Difference being 10-15 hp.

To be sure this idea is to be tested.
Planning on testing Langdons cast iron manifolds against headers with a moderate cam or 2.

Also plan on comparing Offy and Clifford intakes again, a bunch of street worthy cams and some not so street worthy along with lumps vs no lumps too.
Even have a fully divided head to mate with a divided intake. Lots of stuff planned and not going to be enough time.

Thankyou to all contributors! I am putting together another sheet with the planned runs (current stuff) and will redistribute it out by the end of week. Tom

Here it goes. Dates are picked.
Fri, Sat, sun April 2,3,4 and the remainder Fri, Sat, Sun April 9, 10, 11.

Anyone interested in helping, contact me.

A email was also sent out to contributors, if you did not get a email from me, contact me.

This is going to be fun, I can almost hear the roaring now. Tom

Had a guy moment, wife took care of that. She reminded me Easter is on the 4th. So no dynoing that day. Still planning it to be a go for the other dates. Tom

Here is a correctly laid back chamber on my aluminum cyl head.



Any thought on this?

MBHD

Sorry Hank, The "194" closed chamber head is not in the cards for the 250 tests. It was proven without a doubt to me that with the same work done to a open chamber head , the open chamber produced more power. The average guy doing port work on his head will not know what is needed to be done for the "194" head to wake up.

I think you are better to start with a open chamber head to start with.

Maybe you could supply that aluminum head for testing. I will provide shipping. Thoughts?

Tom,
sorry to hear you will not be testing the 194 head.
I thought the tests were going to be the same heads tested w/the 292?
Now with you having custom higher compression pistons ,running the small chamber head should show more torque, & you are also running larger camshafts that require higher compression will also complement this small chamber cyl head.

You do not need to the cyl head work yourself. Sure it cost $ ,but that's what it takes sometimes to get the most out of a cylinder head.
That is why there are professional shops that can do this type of work.
Like Sissels,Larry,A.K.A. twisted6 & others.
Twisted6 has done a small chmber cylinder head for a record holding Camaro in it's class.
They made no other changes other than swapping out the big chamber head to the small chamber 194 head & saw a .3 seconds faster in the 1/4 mile.
This same 194 head actually flowed a bit better than the open chamber head that was on there. But that is not where the .3 seconds faster came from, it was mostly from the torque increase from the increased compression, I would think,maybe Twisted6 will chime in on this,as he is directly involved w/the car & knows better than I. Larry?

The port lay out is pretty close to the same if not indenticle as the big chamber head.
The only major difference is the chamber wall is too close & shrouds the valve
With that being said,,,
You need to find a way to properly unshroud the small chamber head to flow equal to the big chamber head.
As I mentioned ealier,the ports are the same. So,it's not the ports that is limiting the airflow.
It's the chamber wall too close to the intake valve.

Do you have old hacked up small chamber heads to try some more serious unshrouding?

An average guy will not know how to work on there heads & get them to flow good,if you do not know what you are doing to a cylinder head,you can actually lose airflow/CFM.

Not trying to scare anyone from working on there own cylinder heads hear.
Are average guys sending you there cylinder heads for you to do the work? If so, why,it's so simple to work on correct?
Plus you need the correct tooling etc.

I can't tell you have many times my friends cylinder head shop have recieved cyl heads that have been ported @ home & basically detroyed the cyl head,& or just absolutely killed the airflow.
Customers even try to do certain machine operations @ home.
Then they send there heads to my friends shop to do a valve job.
Some are so bad,the shop refuses to do any work on there heads.

I do know how to port heads,I know what a good flowing port should look like,but I do not have the experience to correctly do a high performance valve job,I leave that for my friend.
My friend is much better porting than me & has much more experiences on different chamber shapes & what type of porting is needed for best overall CFM numbers.
Not sure why you are asking to borrow my cylinder head as you already have 2 or 3 of the 12 port heads?

My aluminum head has 2.08 intake valves & flows 320 cfm @ .600 lift.
It has street porting ,not an all out full on comp port job,w/bigger valves.
Still a work in progress,it's not done yet.

Seat angles,seat widths,throat shapes,air entry into the port are all very criticle.
This stuff you do not learn overnight ,or in a year,it takes a lot of R&D work.

Not trying to rag on you,I think it's just a better idea to send your heads to a professional cyl head shop than to possibly screw up a cylinder head.
Two cents thrown & then some,sorry for the ranting everyone.
I just know HP & torque all starts w/the cylinder head & to get a great cylinder head working ,most will need to send to someone that knows what they are doing.
I would like everyone to show up/beat up on those V-8 thingys.

Peace!

MBHD

Update.
The dyno has another V8 going on it to break in a cam. He says it will be off on Fri. So the 250 is slow getting in place on the dyno. Hopefully Sat will be a run day. I will also perform runs during the week. The following weekend will be a all out thrash to test as many combos as time will allow. Sat and Sun are scheduled that weekend.

Getting all my ducks in a row and keeping fingers crossed that all goes smooth.
Lots of cams, intakes, carbs, and exhaust to be done. Tom

Goodluck w/the testing & trashing ;-)

MBHD

I second that!!

Me 3

Been working on the weber intake and throttle mech. It has to pull from the side. It has been fully assembled, just needed to make a bracket for the dyno to hook to.
The engine looks good and hope to get it bolted down on fri and get it all hooked up for sat. Start it on Sat. Parts will be flying then. The following weekend will also be a fury of wrenching.
There is so many things to keep track of, feel like I'm getting married or having a kid.

Tom

I sent Tom a writeup with a bunch of computer "Gonkulator" predictions for all the runs. Gonkulator says the low-boost Turbo (mild cam) will NOT make the most horsepower, but rather the webers and biggest cam, 16hp more than the Turbo. But the Turbo computes to make the most torque by far, 66ftlb more than the Webers.

Just for fun I computed each of the dyno builds in my own 63 Nova SS. Street build, 200-4r and 3.25 gears.
Mildest (stock+4v+headers) computed to 16.02 at 82.1.
Hottest cam and webers computed to 14.38 at 95.7.
Turbo / mild cam, the winner, computed to 13.72 at 98.1.

Soon we will know how the computer Gonkulator fares vs the dyno!

Good luck again Tom.

Duece,
Hoping the 250 dyno beats the Gonkulator! Engine is not running yet, but will be in the morning.Your calcs came close last time.

My real work kept me away and could not get enough done tonight. It is bolted down, valves lashed, oil in. Intake/ exh need to go on. The main part is I have to modify the dyno for the 6. The water tank is on the pass side infront of the cam. I move it and all the water valves, ect to the drivers side for the 6's. It takes about 1/2 hr for this. Tom

What damper is going to be used on the 250?

MBHD

Day 1 on the Dyno is done!
Tested 3 cams, 2 intakes and 2 carbs.
Put another rumor to rest.






Offy intake will not perform better than a Clifford. I know this will raise some eyebrows, but it is true. Tested a 390 4 bbl, Truck headers, 1.84 lump head and Clifford 264 hyd cam with both intakes. Clifford produced more tq across the entire RPM range( 2500-5600).

Here are some #'s so far.
Cam 2 Mild street cam 240hp @ 5000 274 tq @ 3800
Cam 3 moderate street cam Offy 252hp @ 5000 278 tq 4100
Cam 3 " " Clifford 269 hp 5500 283 tq 4400
Cam 4 Moderate street cam Cliff 280 hp 5900 283 tq @ 4100

Next goes on a bigger 1.94 valved head, expect more power. Then test the weber intake, the turbo setup and a divided port intake/ head. Lots more fun to go! And no burns.

Have 5 more cams to test. 2 that are bigger solid lift units. Expect to see rpms to 7000.

Will run a few times after work this week and next Sat and Sun if needed. Tom

Glad it all went well.

I would hope you are running a stub stack, or something to help smooth out the airflow into the carb.

As far as the intakes go,,,I would suggest people to try them both out & see what the diferences are. That type of testing would be real world,put it on the street testing.

I have tested both intakes,with many different carbs.

The Offy is the hands down winner also better for mileage.
Now if you want the better top end power by about 3000 + RPM,then yes,, the Clifford would be the one to use.
Just my two cents.



MBHD

Hank,
Have not used a stub stack on this engine yet, did on the 292. Will with the bigger cams.

The Clifford had 4 lbs more tq @ 2500 rpm and 19 more @ 5600 rpm.
How is that not more usable on the street? This is a real world test. Another thing, the engine was more efficient with fuel. Also shown in the BSFC #'s. The tq is there...


You also say people should try both intakes and decide. I agree. Who can afford to have both? That is why the dyno testing is taking place. To put #'s with modifications done, to be logical with parts used, and dispell long held misconceptions about building these engines for the street.

A 280 HP 255 inline 6 is no slouch, especially with a modest cam and a reasonable build. With the next head 10-15Hp will be welcome. Got my fingers crossed. Tom

One of the reasons for the clifford to have run better is the Lump ported head. If you wanted to do a better/fair test try it with out a lump ported head.

JM2¢ on Clifford vs. Offenhauser:
The Clifford 42-4501 has larger plenum volume, which means more mass available to any open valve with the same carburetor flow, but also a weaker signal from the intake valve to the venturi at all times (of course, when engine speed is high enough this fades out).
The Clifford also has a larger radius between the front and rear runners to the plenum, which will improve flow at higher speed.
As either engine size or RPM go up, the Clifford will have a bigger power advantage.
I know it's not within the goals of this test (can't do everything - only the ones that would be helpful to most builders), but IMHO where space permits the Clifford might benefit from 1 or 2" spacers between the runners and the ports (of course, this makes it much wider, linkage and fuel line problems, etc.), and also perhaps a 1" spacer under the carburetor (especially a 390, etc.).

The Offy 5416 looks like what they made out of plumbing fixtures in 1940 to add a second carburetor - and before they were willing to admit that the factory manifolds weren't that bad as to contour and design (just too small). The smaller plenum permits leaner jetting and better mileage at low to moderate speeds with no loss of response.
With a small engine at moderate speed (194, stock cam) the power difference will be small.

Can you pick up cylinder to cylinder mixture distribution differences? Any manifold may also change which runners are favored as RPM varies, etc.

When the 292 was ran. There were temp sensors in every header tube. No differences were found with either intake , cam, carb combo. The even fuel distribution was surprising. So on the 250 I got lazy and only hooked up 2 sensors. One on front and one on rear. No difference in temps seen this time either. Tom

That's a great point as when I ran my tests w/the two manifolds,w/just the adaptor plate, I also tried using 1" open hole spacer,1", 4 hole spacer,2" open & 4 hole spacers.
I did not have any lump ports.


MBHD

That is exactly what I am saying,,,,you would need to try these manifolds out on the street,,,your street car engine does not start out @ 2500 RPM.
I realize you cannot start the dyno pull idle or @ 1000 or 1500 RPM,but cars or trucks can, & that is 1 part of the reason a dyno is not a tell all absolute truth.
Even a chassis dyno is not real world driving situations,you can simulate road driving conditions,but it still is just a tool & should be used as such.
When you actually drive your vehicles from idle & up on the street or track,it will be a different condition than a engine or chassis dyno.

MBHD

With you running this dyno testing it does not dispell all misconceptions,& like I said you cant prove any misconceptions unless you are pulling from idle to 2000 or so RPM

I have always said the Clifford makes more power in the 2000 + rpm range. Nothing is being proven different to me in these dyno tests,@ least not so far ;-)

Yup - stock Powerglide + tall gears needs power at 1,500 RPM for daily traffic. Even many stick drivers don't use 2,500 until their doing parkway speed.

All of that testing was done in the first 292 dyno tests 6 months ago, and the Clifford was still superior then, as it is now. Lumps or no lumps, it matters not. As panic pointed out, the Offy is a much older and cruder designed intake, the Clifford is/was designed in more recent times with a more performance minded clientele in mind..