The Ford Barn

Dave in Denver · 09-21-2012, 10:05 PM

I replaced the engine my 30 Tudor due to the previous engine snapping its crank. This rebuilt engine is an inserted non pressurized engine with snyder head on top. The distributor is a petronix 12 volt and the carb is a new stromber 97 fed from a low pressure regulated fuel pump.

The engine was timed at top dead center and the started. once started the engine will idle, but when the accelerator is pressed it back fires out the top of the carb. If the accelerator is pressed further the backfiring gets worse.

I did a compression check and all cylinders read exactly 60#.

Might any of you have any ideas where I should look next.

Thanks,

Dave

J Franklin · 09-21-2012, 10:13 PM

Recheck the timing marks, they may be off.

ken ct · 09-22-2012, 01:26 AM

Sorry but in my opinion the 97 is a little over kill on a model "A". I think your flooding out the engine. ken ct.

George Miller · 09-22-2012, 07:15 AM

May be to lean. It all depends on a lot of things, Manifold, timing, cam, carb.
I would try a bigger jets.

MikeK · 09-22-2012, 07:35 AM

Factory 97 jets were 0.045 with a #65 power valve. Available jets go down to 0.033. You need a special jet wrench to remove them. You can check the size in place if you are careful with wire size drills. Vern Tardel has a book about Stroms. LINK

Jim Brierley · 09-22-2012, 09:53 AM

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Spitting back is caused by either too lean or too retarded spark. Check the operation of the accelerator pump. One 97 is definetly not too big for the A, I am running 3 of the 81's on my speedster with great success. Jets are stock.

MikeK · 09-22-2012, 03:45 PM

Quote:

Originally Posted by Jim Brierley

Spitting back is caused by either too lean or too retarded spark. Check the operation of the accelerator pump. One 97 is definetly not too big for the A, I am running 3 of the 81's on my speedster with great success. Jets are stock.

FWIW, so others reading this thread know, stock 81 jets were 0.035 with a #71 power valve. That's smaller than the 97 jets. The 40 & 48's had 0.048 & #63 PV. Stroms also do not like too much fuel pressure. 3psi is the absolute limit, even with the newer ball valves. Not enough float leverage. Holley 94's can easily take 5-7 psi, but are a PIA to set up multi, especially progressive, as their power valves are vacuum, not mechanical.

columbiA · 09-22-2012, 11:51 PM

A stock cyl head should have more than 60# comp.you should have a lot more than that with a 5.5 head.Seems like its running too lean to me.

09-21-2012, 10:05 PM	#1
Dave in Denver Member Join Date: May 2010 Posts: 67	backfiring through stromberg 97 I replaced the engine my 30 Tudor due to the previous engine snapping its crank. This rebuilt engine is an inserted non pressurized engine with snyder head on top. The distributor is a petronix 12 volt and the carb is a new stromber 97 fed from a low pressure regulated fuel pump. The engine was timed at top dead center and the started. once started the engine will idle, but when the accelerator is pressed it back fires out the top of the carb. If the accelerator is pressed further the backfiring gets worse. I did a compression check and all cylinders read exactly 60#. Might any of you have any ideas where I should look next. Thanks, Dave

09-21-2012, 10:13 PM	#2
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,979	Re: backfiring through stromberg 97 Recheck the timing marks, they may be off.

09-22-2012, 01:26 AM	#3
ken ct BANNED Join Date: May 2010 Location: stratford,ct Posts: 5,971	Re: backfiring through stromberg 97 Sorry but in my opinion the 97 is a little over kill on a model "A". I think your flooding out the engine. ken ct.

09-22-2012, 07:15 AM	#4
George Miller Senior Member Join Date: May 2010 Location: NC Posts: 2,975	Re: backfiring through stromberg 97 May be to lean. It all depends on a lot of things, Manifold, timing, cam, carb. I would try a bigger jets.

09-22-2012, 07:35 AM	#5
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: backfiring through stromberg 97 Factory 97 jets were 0.045 with a #65 power valve. Available jets go down to 0.033. You need a special jet wrench to remove them. You can check the size in place if you are careful with wire size drills. Vern Tardel has a book about Stroms. LINK

09-22-2012, 09:53 AM	#6
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,095	Re: backfiring through stromberg 97 Sponsored Links (Register now to hide all advertisements) Spitting back is caused by either too lean or too retarded spark. Check the operation of the accelerator pump. One 97 is definetly not too big for the A, I am running 3 of the 81's on my speedster with great success. Jets are stock.

09-22-2012, 11:51 PM	#8
columbiA Senior Member Join Date: Nov 2011 Location: B.C. Canada Posts: 1,746	Re: backfiring through stromberg 97 A stock cyl head should have more than 60# comp.you should have a lot more than that with a 5.5 head.Seems like its running too lean to me.