Help needed tuning Stromberg 4x2 NON-progressive on dyno, urgent!

I have my 291 DeSoto hemi on the dyno right now, and as you know time is money and I'm trying to use my money wisely! We finished up for today and need to get back on it tomorrow. Here's a short run down of the engine first of all.


(Copied from build thread)
The bore is now 3.800 inch, up from the 3.71875, making it a 303 now with Ross slugs checking in at 10.5:1 compression after CC'ing the chambers. The cam was a custom design from Donnie Johansen from the famed Howard's cams. It's a solid roller, .520 lift, 272 duration at .050, not a ton of lift but a LOT of duration and Isky 3/8" pushrods were used. 330 heads were used and port work was done to blend the seats and port match the Weiand 4x2 manifold. Carbs are all large logo Stromberg 97's. Rocker Arms were taken care of by Rocker Arm Specialist who did a GREAT job on them. Custom fabbed 1 3/4" primary headers with 3" collectors. Hot Heads supplied a lot of parts such as the 340 oil pump, bronze distributor gear, spark plug tube seals, balancer, adapter plate, bolts, etc... Toping off the flame is a Scintilla Vertex (10 degree advance built in) magneto rebuilt by Spud at Fuel Injection Enterprises, they do some NICE work and FAST. All 4 Strombergs are running together NOT progressively.

Now, we started off with the standard .045 jets and #65 power valve for base line. We got the engine to idle fairly well, but as soon as we started giving it gas, it fell on it's face, only made 184hp with a FAT 9.8 air/fuel ratio.

We changed the jets out to .035 still with #65 power valve. The engine would not idle at all, we constantly had to stay on the gas, but we made a pull this time and made 310hp with a 12.0 air/fuel ratio. The idle AFR was a LEAN 17.0 though.

Idle screws were backed out roughly 1 3/4 - 2 turns during this as well.

Now, I need the best of both worlds here. I need to get the idle set and the top end. What advice can I use to go from here. Change the power valves out? I rebuilt all the carbs, they're functioning beautifully, but honestly, I'm not a tuner of them. I need so help now.

Thanks guys.

-Brian

 

Anyone?

 

Put jet adjusters on the stock .045 jets and fine turn, much easier then swapping jets..The power valve should be ok because it doesn't come to the party till latter..
4X150 is 600CFMS..Using a basic formula 1.5 CFMs per CI, with that you need about 450 CFM..I believe that shutting down the .045 jets just little the engine will run strong..Your getting enough air just need the fuel to balance..
I helped dyno a 6x2 392 Hemi and told the owner to get the adjusters and bingo, dialed it right in..
Duane..

 

Also, I would pull the idle tubes and cut the small tip off. Set the air/fuel mixing screw 1 1/2 turns out..Are all idle adjustment screws set the same..I would have a goal of 875 to 925 rpm at idle, with that duration that might be just about it..
I hope this all helps..
LET me know..
Duane..

 

What is the total duratio ignoting the .050" starting point. My 270 degree cam is only 238 degrees at .050". Bill

 

Is this a race-only build?

That's way more duration than I'd ever try to run on a street 300" engine. With that much duration, it is going to be a bitch to try to get to idle and take throttle off idle.


jack vines

 

Thanks guys.

It's a street car, going in a '32 sedan.

I'll get the cam sheet tomorrow when I'm at the shop, I'll be there at 8am getting an early start on the dyno.

I'm placing an order for the adjustable jets tonight, I don't know why I didn't go with those from the beginning actually.

Strombergs97- how do you pull the idle tubes? That's the ONLY parts of the 97 that I've had trouble with, I usually just try to use a piece of wire to fish through there to clean them. I can see where cutting the small tip off would increase idle fuel flow.

 

We made 374hp today but there is Zero part throttle. This is what to figure out now

 

374? You poor poor soul!!!! That car is going to punish you hahaha!!!! I'm interested to see some details of the tuning process. I need to get my 4 97's rebuilt asap and running right. I've had a few set backs these past few months but now I am at the point that I just need to have them rebuilt I think. But I wanna hear all about the process of dyno-ing and tuning with 97's on a serious engine like that!

 

bad ass - good for you - will watch tomorrow

Basically it sounds like you have a lot of air at idle (4 carbs) and low vacuum to suck idel fuel. Good luck man - going to be a rippin little engine that could

 

is there a reason for going non-progressive?

You've got a lot of carb and duration. progressive linkage seems like the logical way to help part-throttle.

 

The 10 degrees advance built in is confusing me. Are you running a ton of initial advance?

 

Go back and reread Duane's post about the idle RPM. With that much duration, you may not even get it to idle at his 875~925 goal. With that duration, even with 8 idle tubes, you probably need MORE tube opening.

The poor part throttle is probably due incorrect A/F at idle, which goes way lean when you give it part throttle. Get the A/F good at idle.

And I would suggest at least trying idle screw settings of 1 to 1 1/4 turns, and then crank the idle positioner screw in further, so you are getting more air around the throttle plates at idle. This should help the transistion to part throttle.

Jon.

 

Video feed of it running would do all of us some music to listen to.........please!!!!!!

 

A little info from today. 2 carbs had poor flowing accelerator pump discharge jets, so I tore all the carbs down, put them in the solvent tank, THOROUGHLY recleaned them all, and flowed each of them before putting them back on, they all flow perfect now. We base lined with .037 jets in, made 366hp, little lean though with 13.2-13.5 AFRs, went step by step to .039 and make 374hp, 12.6-12.8 AFRs. Part throttle was still giving us fits, so we put in .042 jets for the final pull, made 368hp with a little fatter 12.3-12.6 AFRs, part throttle SLIGHTLY better, just leans out when you tip in throttle.

Total timing on all the pulls was 37-38 degrees. Anything less and it dropped power like a rock, any more and it mould decrease as well, so that was the sweet spot.

We worked on idle, the magneto is suspect for idle issues. The engine likes to idle around 1300 RPM, 22 degrees of timing, with 14.0 AFRs, as the idle drops, so does the timing. It will drop to 700 RPMs with a slow weak idle and only have 8 degrees of timing, way less than what is needed.

We have a 14.0 at 1300 RPM, read my results from today. Is there a way to richen the idle circuit without the main jets? I read what he said about cutting the tips off the idle jets, would that help?

Idle screws are 1 - 1 1/2 turns out now.

Someone at the shop mentioned a trick they used to do was drill another hole about the 2 air bleed holes so that when the throttle plate was cracked open it had another source of air as well. Have you ever heard of this?

The AFRs at idle are 13.5-14, wide open throttle is 12.6-12.8 on the dot.

Initial timing at 1300 (idle for now) is 22 degrees.

This manifold won't allow non-progressive, there's no plenum to balance the carbs out.

There's basically no vacuum! It's a ripper though!

Patience, I'll get into more on what we did later on.

I'll see if I can get a new one up soon.

 

378 HP on 303 cubes? EGADS! I'd be happy to get that with my 341 with Hilborn injection on E-85. Got my roller cam from Contreras Cams today. A real thing of beauty. If you want an iron gear on it just ask. That way you won't need to run a bronze gear on the oil pump shaft.

 

Hello, the idle jets are inside the body, you have to take the air horn off, you will see the two brass, one on each side, a small flat screw driver will remove them..Look at the end and you will see where the tube tappers, cut that off, just that much will improve idle, you can even drill them larger, this will help at first acceleration..
Again, with the jet adjusters you can really fine tune the 97s into the demand of the engine. With the engine on a dyno the analysers will tell you what you need to do, open or close..
Let us know..
Duane..
ps..make sure all the air bleed holes are clear on the emulsion tubes. The two air holes that you can see when looking down through the 97, just behind where the emulsion tubes come out, make sure they are clear..Very Important..

 

Could you put in leaner power valves and increase the main jets? That would help the low end mixture. At that idle rpm, it is probably not even using the idle circuit.
I know a guy that has run on just one 97 with that manifold on a DeSoto. It has been fine for 12 years ar so. The others come in on demand.
Have you checked the delivery tubes for damage. Most all the 97's I have worked on had the main jets tightened too much which collapsed the bleed holes in the tubes. Makes them run rich.
I would try a distributer as a check. A lot of 97 problems are found in the ignition. Espcially runing rich.

 

Andy is correct about the the holes at the end of discharge,(delivery, emulsion) tubes. Lots of time they get crushed..Also some tubes have two holes and some have four, look for the four and make sure both sides are the same..
The idle tubes should bring that Hemi up to 1k or a little more RPMs by them selves..
CUT THE TIPS OFF AND IF YOU HAVE TO, DRILL THE TUBES A LITTLE LARGER..
Duane.
Try it, you might like it.............

 

You need to shorten the advance degrees in the mag..38°-22°=16°/2°=8°..If the engine likes to idle at 1300 the advance shouldn't start till 1400 with 8° in the mag to give 38° total and you want it in by 2500-3000...The reason for doing this is idle tuning, when you make a carb adjustment and the idle speed changes so does the timing which affects the adjusting making a catch 22... x2 on thats a lotta cam!!

 

Thanks Duane,

All the emulsion tubes are perfect, no crushed tubes or holes, all have the 4 holes. When I rebuilt all the carbs I took care of that and no neanderthaling the jets into place.

Air bleeds are all clean and debris free.

I don't have any more dyno time so I'm going to have to wait until the car is running to get the engine sorted out. I'm going to try the idle jet trick, I like that idea.

When I get the car running, I'm going to put a wideband O2 in each collector to tune the AFRs in as best as I can, it's nice to have access to wideband tuning equipment.

Andy and seb, I'm calling Fuel Injection Enterprises tomorrow to see if I can get the mag worked on. I'm going to tell Spud what is going on and see what he can do. I looked at the sheet he sent me when it was rebuilt, but doesn't say anything about the advance being locked or anything about degree.

 

That is what I was going to recommend. Try switching to a 71 power valve, and increase main jets back to .044 or .045.

I have a high compression, big cam 331 with 4 Stromberg 97s running non-progressive linkage, and that's what worked for me. Runs like a scalded ape and was able to do a 5000 mile round trip last year.

 

I'm willing to try anything with it, I appreciate the input Brian, I wasn't sure if your car was progressive or not.

We'll see what happens.

-Brian

 

jee-zues!!!

 

Probably still has more in it too honestly.

 

The 71 power valve is real small. The P.V. opens when the accelerator pump pushes down on the tang of the P.V. then it will join the party..I would think that the Hemi would want more fuel when getting close to WOT, so it would need a larger P.V...The P.V.is the last thing that comes to the party..\
That is my 25 cents..
Duane.

 

Some guys still don't get it... When everything inside a 97 is in good working order, the powervalve starts to open the moment you stab the gas, due to the hydraulic action of the accelerator pump, and becomes fully open at the bottom of the stroke. When you step on the gas less violently, the built-in relief valve in the pump takes over for a smoother transition. This is why it's critical to marry the jets with the pv's.
Try .043" main jets with # 68 powervalves.
Adjustable jets will make you crazy trying to figgerout the baseline.

 

Max, your first part is correct, I agree, .043 and 68 is a good balance, the ????? is will it work with his Hemi, each engine is different. I'm a believer in adjustabe jets when it comes to lots of carbs, I find it easier to adjust and fine tune, better then swapping jet till you get the right combo....
Duane.

 

I have a set of .041, .043, and the stocker .045 jets right now. I picked up a set of #71 power valves to see how the engine likes it. If I need to go bigger, then I'll get different ones. I just remember how much the engine liked the bigger main jets at idle and part throttle, I have a feeling the significantly smaller power valves will help this thing run like it wants to.

I'm going to wait until the car is all together and running before doing any more testing. I sent the adjustable jets I had back, they just looked to be a huge pain in the ass, and space is tight to begin with, so adjustment was going to be a bear anyways.

Thanks to EVERYONE who has chimed in with advice, I greatly appreciate it!

-Brian