Flathead tuning

[Popastruck]

Hey all. I need some help. I have a 1953 8ba rebuilt 30 over with 4” crank Max 1 cam Offy aluminum heads and Speedway three duece intake with 3 super 97 carbs and progressive linkage. Timing is 6 degrees initiall and 32 total all in by 2900 rpm. When I hook up the vacuum gauge the needle is erratic at idle (600 rpm) if I increase the rpm to say 900 the gauge evens out around 18. If I increase idle to 750 the needle waves between 14 and 18. There seems to be a slight miss sound at the tail pipes. Sorry about the long explanation but I don’t know what to do next?

[Kurt in NJ]

Check compression. Look at how the plugs are burning. Try blocking off the end carburetors so there is only l one to worry about

[Popastruck]

Compression test 1/135 2/137 3/140 4/135 5/130 6/128 7/138 8/130. Center 4 plugs are a little rich and outer 4 plugs are clean. Truck is not on the road yet so just short drive down the street and back

[drolston]

I have the same setup except for a Schneider 248F cam, which is slightly milder than the Max 1. Both good street cams. In perfect tune and no sticking valves, I still get flutter on the vacuum gauge at 650 rpm idle between 14 to 16 inches. With these cams it is never going to be rock steady at idle.

Is it correct to assume that your end carbs do not have idle circuits, or if they have them, they are closed? All idle adjustments must be done on the center carb with the throttle plates on the end carbs adjusted so that they are both absolutely and precisely fully closed. Absent that precision, there is a vacuum leak that makes idle adjustment futile. If you have the cheap progressive linkage, get the expensive one. Take the tops of all carbs off leaving only the cast iron base and linkage. That way you can see the throttle plates and make the linkage adjustments to get precise closure of the end carbs. Be sure to use throttle return springs on the driver side of the throttle shafts of all three carbs. The linkage must operate very freely. Any misalignment may cause binding that could prevent reliable closure.

Another warning on those 9Super7 carbs: double check the float level. I have those carbs and the float was way off on all of them. Carefully heed the warning on how to make adjustments. If you bend the tab without protecting where it joins the float from stress, the float seal will fail and sink the float, flooding the engine. I also replaced the needle type float valves with the Grosse ball type float valves. Less prone to stick closed and less susceptible to debris. I learned all of these lessons the hard way, but now the performance is great and reliable.

[Popastruck]

End carbs do not have idle circuits. I wondered about the float levels ? I do hav an electric fuel pump as back up. Runs on stock pump now. I spent a lot of time on linkage so it wouldn’t bind. I guess I will have to check float levels and maybe disconnect end carbs altogether and try tuning with just the Center carb

[Popastruck]

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So I did a little more checking on my flathead. Linkage was not working properly. Now both front and rear cars are closing all the way. I disconnected linkage so just dealing with main carb for now.
The miss or popping is from cylinder #4. If I pull cyl 4 plug wire the miss or popping goes away? There is good spark at the plug. Any ideas?

[corvette8n]

Sticky valve?

[danliveshere]

Popastruck, try swapping the spark plug out of 4 & if you don’t have another just swap it with number 3, does the miss now go away or the miss is in number 3? Sometimes a good spark does not actually mean a good spark plug under compression.

[cadillac512]

Regarding timing...The 6 before is ok especially with your cam, but 32 is higher than a flathead likely wants. 25 all in by 2500 is usually a good setting. May have to modify the distributor to get it done.
As for the misfire, have you double checked firing order? Flathead has a couple cyls swapped compared to later Ford.

[Bored&Stroked]

You do not want 32 degrees of total timing - I'd try about 24 or so. I have not run any flathead over 26 degrees total.

[Ol' Ron]

Never had any luck with Stromburg carbs I;d install a stock holley carb on it and go for a ride.
Gramps

[grumpys hot rods]

Originally Posted by Bored&Stroked

You do not want 32 degrees of total timing - I'd try about 24 or so. I have not run any flathead over 26 degrees total.

Bubba would say that Flathead is not a small-block Chevrolet.
I think Bubba says 28 degrees at full out is max if my memory is correct.
I think that 24 degrees would also work.