Extrudehone is an abrasive putty that polishes the inside of anything, but does not always remove material in the right places.  If you want to send something to them for that process, it is best to take a 6" long carbide and remove any bumps, lumps, shapes you want removed prior to sending to them.  I have flowed several intake manifolds, EFI plenums that had been extrude honed, and the flow was not even between ports, only polished.  Last time I checked prices, it was $350.00 minimum for one piece, and you had to sign a waiver if you wanted them to make more than one trip through the ports, in case the abrasive made holes in a thin spot.  A set of manifolds was $700.00 plus shipping both ways.    Joe-JDC

JDC

There used to be an outfit that flow-ported and coated iron manifolds to make them more efficient.  Probably much more expensive than headers, but I always wondered what happened to that company

https://www.extrudehoneafm.com/industries/automotive/

____________________________

I think the smaller carbs tune better for a "street driver" - I've got one of the smaller, early Demon, 4160 pattern carbs on my engine and it has worked well. It could use a smarter slotted style opening in the intake and a more clever adapter/isolator - but it starts and drives well as it is. In my experience, the "seat of the pants" dyno rules - and the 600 cfm size Holley was just a step too far - I couldn't tune it to get the right torque curve to throttle feel (stocker cam).

Port matched, ceramic coated '57 exhaust manifolds will be a good simple upgrade (along with up-sized exhaust tubing). The "Jet-Hot" coating I had done to the iron manifolds was a really good return for expense - and came back fairly quickly too.   

 
 Steve Metzger       Tucson, Arizona

I tried the 600 cfm 390 GT Holley carburetor on my TBird.  Ran into a small amount of clearance trouble with the coil and I had to make a new fuel line. Other than that, no issues.  To be honest, I think it runs better with the Holley 465 cfm.  The bigger carb seems a little stronger in the upper RPM  range, It drives better with the 465 around town.   It's hard to beat the torque and drivability of the 465 on the street.  I guess that's why Ford used it on the 57 312s?

There used to be an outfit that flow-ported and coated iron manifolds to make them more efficient.  Probably much more expensive than headers, but I always wondered what happened to that company, and if anyone has had dealings with them lately (?).  Sure would be simpler, especially for those wanting to retain a more original appearance.
BTW: My Bird had 2” exhaust installed when I obtained it, but everything was rusted out. Buying aluminized OEM replacement parts (except for the glasspacks) was just more expedient on a car with an unmodified engine, and the open exhaust likely more than made up for the smaller pipe sizes.

6 VOLTS/POS. GRD. NW INDIANA

The stock down pipe, between manifold and muffler, is 2". from the muffler to the exit, the pipe narrows to 1.75." You could keep your manifolds and go with 2" mufflers and pipes, or go with 2 1/4" from down pipe to exit, while still retaining manifolds. If desired, you could later install headers, with only the down pipe between header and muffler needing to be replaced. 

I'm going on vacation next week.  When I return, I am going to rebuild my "S" code Holley and put it on my iron manifold.  I'll post my results.  Next, I think I'll work on the exhaust. I hate to scrap the 57 Thunderbird manifolds, but the stock pipes are pretty restrictive. My exhaust system is from NPD.  The tubes are small and made up of numerous pieces held together with clamps. It's noisy too and not in a good way.  As 55 TBirds go, my car performs well.  It could be better,

Phil: Black Tie brings up a point.. will an aluminum intake on your engine hurt low end power?.. In the recent cylinder head tests printed in Y-Blk magazine, c/w a Mummert aluminum intake, the "score" for the engine with stock. "G" heads, up to 3500 rpm, was identical to the engine with aluminum heads!  If you're not planning to run over 5000 rpm...is it worthwhile ??     


Paul

My experience with the Blue Thunder intake has been great. I replaced my port matched E intake and carbs with the Blue Thunder and a 750 Holley. Engine has Mummert heads and a custom grind Isky cam with Sharp roller rockers. Night and day difference. Better torque in the 5000 rpm range.

have a 600cfm holley4v  on a292.040 over bore,56merc reground cam,works great,lots of power,dual exhaust,with heat riser on drivers side,works great on cold starts, purchased the carb from holleys used website(warranty carbs repaired and resold) at very good price. have used this setup for 4years. myn is in a 1949 mercury  f47