97 Jetting pointers??

[revkev6]

I have a Av8 that's been on the road for 25 years that has a couple carb issues i've been living with the last few years. when it's warm it doesn't want to start. when it's cold, I give her a couple pumps and she fires right up. I think it's draining fuel into the cylinders as it seems to start best when I floor it when it's warm. She'll sputter on a couple cylinders pouring some black exhaust as she catches on all 8. also, if I shut it off and restart it right away it starts fine... its only when its warm and sitting for 15 minutes or so it will give me trouble. it's got the stock A tank so I have a shutoff valve I use religiously.

so I'm planning to rebuild the carbs. one thing I have noticed over the years is the little chrome filters I have with the paper elements are extremely restrictive. if I pull them off, the motor is so lean it stumbles badly. I want to replace the paper elements with either a washable element or something like a frog mouth. speedway sells a K&N for 7.99 and there is another K&N element PN-E-3120 that fits a little better for 32.99 each.... anyone use either of these??

the motor is basically stock. it was rebuilt with an isky cam... the really mild one that is basically a stocker. she runs ok at the moment but the paper filter restriction thing nags at me.
I'm sure this has been posted before but I read this article about flowing the elements as well. looks like the flow bench backs up what I've seen on my motor.

http://www.stromberg-bulletin.com/air-filters-stromberg-97s/

I know this thing is jetted down pretty far. the plugs still look pretty rich... black as coal. I'd have to pull them to see the exact number but if memory serves it's a 43 main jet.

does anyone have recommended starting points for the carbs with either a K&N filter or no filter??

also, who makes a good rebuild kit these days?? up here in mass there is no such thing as non ethanol gas too.

any other pointers?? I rebuilt them and went through the mallory ignition about ten years ago but I'm no guru

 

[TerryOH]

2 or 3 carbs? Stromberg makes a good rebuilding kit! The engine is a flat head correct?? progressive or straight linkage???

 

[Bruce Lancaster]

Test it without filters and with standard jets or only one step down unless high altitude.
The little chrome filters are generally bad news, not just the filter itself but the tight fitting helmet as well. There may be good elements but the whole thing is just about right for a lawnmower. Better idea? Not sure if anything of real engine size can be fitted in and look good. Perhaps the small size of 4-barrel aftermarket filters, I think they are about 9".
The lean condition without filters, from what you have said, is just the downsized jets responding to flow without the choke effect of the filters. The filters will kill your piston rings, too...

 

[john in illinois]

I have had hot starting problems with a 97. I added 1/4" insulator spacer and it solved the fuel percolating problem. I think I got them from ebay. here is an example. You need longer studs.

http://www.speedwaymotors.com/Edelb...r-Carburetor-Spacer-Phenolic-Wood,139184.html

John

 

[uncle max]

Test it without filters and with standard jets or only one step down unless high altitude.
The little chrome filters are generally bad news, not just the filter itself but the tight fitting helmet as well. There may be good elements but the whole thing is just about right for a lawnmower. Better idea? Not sure if anything of real engine size can be fitted in and look good. Perhaps the small size of 4-barrel aftermarket filters, I think they are about 9".
The lean condition without filters, from what you have said, is just the downsized jets responding to flow without the choke effect of the filters. The filters will kill your piston rings, too...

As usual, Bruce is onto something...
Ever wonder why the Ford engineers designed the original aircleaners to gather air from an undisturbed, non-restrictive, non-turbulent, dead-air space?
As for jets and PV's, I've sent hundreds of carbs with .043 main jets and #69 powervalves, for 2x2 and 3x2 setups. It seems to be a good combo for most flatheads and altitudes, although every now and then I'll use .044's. Every motor is different.
For as often as I drive my car, I prefer velocity stacks. Aircleaners are over-rated...
Also: Model A owners using a gravity feed fuel supply find that the old style needle/seat combo is more desirable than the modern grose valves (S-Jets), unless you're using an electric pump and regulator. If using a pressurized (2-1/2 psi) system with an electric pump, the grose valves are the way to go!

 

[38bill]

Don't know what kind of a look you want but I used O'brian Truckers 4" on my pickup. They use a quality cloth filter and they are open sided so there should be little restriction. They have several different styles too. (I painted the tops of mine red)

http://www.obrientruckers.com/ecom/product/239/2368/

 

[revkev6]

2 or 3 carbs? Stromberg makes a good rebuilding kit! The engine is a flat head correct?? progressive or straight linkage???

2 carb, flathead with straight linkage

Test it without filters and with standard jets or only one step down unless high altitude.
The little chrome filters are generally bad news, not just the filter itself but the tight fitting helmet as well. There may be good elements but the whole thing is just about right for a lawnmower. Better idea? Not sure if anything of real engine size can be fitted in and look good. Perhaps the small size of 4-barrel aftermarket filters, I think they are about 9".
The lean condition without filters, from what you have said, is just the downsized jets responding to flow without the choke effect of the filters. The filters will kill your piston rings, too...

I agree on the jetting without the filters. this car was setup and tuned with them on it so it runs well with them.

I have had hot starting problems with a 97. I added 1/4" insulator spacer and it solved the fuel percolating problem. I think I got them from ebay. here is an example. You need longer studs.

http://www.speedwaymotors.com/Edelb...r-Carburetor-Spacer-Phenolic-Wood,139184.html

John

this motor did not always have hot start issues. I'm guessing something is leaking down.

As usual, Bruce is onto something...
Ever wonder why the Ford engineers designed the original aircleaners to gather air from an undisturbed, non-restrictive, non-turbulent, dead-air space?
As for jets and PV's, I've sent hundreds of carbs with .043 main jets and #69 powervalves, for 2x2 and 3x2 setups. It seems to be a good combo for most flatheads and altitudes, although every now and then I'll use .044's. Every motor is different.
For as often as I drive my car, I prefer velocity stacks. Aircleaners are over-rated...
Also: Model A owners using a gravity feed fuel supply find that the old style needle/seat combo is more desirable than the modern grose valves (S-Jets), unless you're using an electric pump and regulator. If using a pressurized (2-1/2 psi) system with an electric pump, the grose valves are the way to go!

I am fairly certain it has 43 mains but I have no idea what the powervalves are. i have a stock 8ba fuel pump on the motor that I rebuilt when I did the carbs. I have standard needle and seats in these carbs now.

thinking I will grab a couple gasket sets from stromberg along with S-jets, 44-45 main jets and 68 powervalves. another thing I think I should check is the cross shaft for play. they haven't been bushed but were very tight last I checked.

anyone else second the 68 powervalve in a mild flathead with 2 97's??

also any other reasons the motor would have this hot start issue now?? I always turn the fuel off at the tank when it's off. I know if I leave it on overnight it will wash the cylinders with gas. I've had to change the oil more than once because of my poor memory.

 

[Bruce Lancaster]

"I agree on the jetting without the filters. this car was setup and tuned with them on it so it runs well with them. "
I think this is very dysfunctional! You are effectively trying to tune out driving with the choke on! A cork in the inlet is never good, and the choke versus jetting issue probably changes a good deal at higher airflow...I would expect this to richen up at high speeds, where the car runs fairly well over-rich...but is still drowning in too much gas. Which will rapidlt wear out your rings, besides the loss in available performance. If it is tuned to run against a restriction...I say it is tuned wrong. Fix the poor thing, don't try to compensate for a bad condition!

 

[deuce_roadster]

After having a cheap defective condenser cause my avatar roadster to backfire blowing gas and fire up into the air cleaners and set both of the K&N air filters material on FIRE, blistering the paint on the hood and burning some wiring off the top of the engine--I threw them away along the side of the road and use paper filters now. The OIL on the K&N filter material made the fire worse and very hard to put out. Could have lost the whole car.
Learned that the fire extinguisher needs to be where you grab it quickly and not in the trunk, a few seconds can make a big difference.
My 2c on K&N.

 

[revkev6]

"I agree on the jetting without the filters. this car was setup and tuned with them on it so it runs well with them. "
I think this is very dysfunctional! You are effectively trying to tune out driving with the choke on! A cork in the inlet is never good, and the choke versus jetting issue probably changes a good deal at higher airflow...I would expect this to richen up at high speeds, where the car runs fairly well over-rich...but is still drowning in too much gas. Which will rapidlt wear out your rings, besides the loss in available performance. If it is tuned to run against a restriction...I say it is tuned wrong. Fix the poor thing, don't try to compensate for a bad condition!

the entire purpose of this thread is that I agree with you!!!

I raced minisprints with carbs and midgets with mechanical fuel injection. these carbs are by no means rocket surgery, but I don't want to spend more time than I have to tuning it on a configuration that I know literally hundreds of guys on this forum use. btw, this motor will never be a very hot motor as it's minimum bored (.030 I think) with the mildest isky cam you can get 77b I think??

in reality I should put the effort into this motor and do a little more maint. she needs the valves adjusted and I should probably pull the heads and replace the gaskets. If I go that far I should pull the cam and go a little hotter... never ending cycle. hard part is I have to lift the body to pull the head.

 

[Bill OH]

I have a 221 with duel 97s and Isky 3/4 cam. I was advised to run 43 main jets. I used 65 pvs. Motor ran lean unless on wot. Not acceptable. I installed 45 mains together with the 65 pvs and motor would bog on wot. Disconnected accelerator pump linkage and motor ran fine on just the mains at wot. Lack of an accelerator pump raised some issues. I then installed 71 pvs (81 stromberg pv?) and motor ran very well - no bog. Preceding all of the jetting, I blocked the heat riser with core plugs and put 5 gaskets under the carbs. The linkage is unison. To sum up, I am running 45 mains, 71pvs, 5 gaskets under the carbs, core plugs in the heat riser, Edmunds oval air cleaners, unison linkage, 5/16 cu line from tank to mechanical fuel pump and 5/16 neoprene line between cu line and fuel pump. Engine starts without hesitation hot or cold and has excellent power. My elevation is about 550 ft above sea level - Nothern Ohio - Home of the Ohio State Buckeyes!!! Hope this helps.