I have a stock 1955 T-bird 292 and have upgraded to 1957 intake manifold, carburetor and distributor. I'm also considering upgrading to rebuilt 1957 "G" heads and a Clay Smith cam with 272 duration and .446 lift based on 1.54 :1 rocker ratio. I believe my stock '55 292 has a 1.43:1 rocker ratio. The upgrade to '57 intake, carb and distributor seems to run fine. I'm wondering if the "G" heads and new cam will cause me any problems considering the lower lift 1.43:1 rockers?
As always, thanks for your expert help.
Steve



Steve

It will be fine.  The heads will be a better match to the intake and are higher compression.  The cam will provide more lift than stock, even with 1.43 rockers and you can always install 1.54s later.


Lawrenceville, GA

My 55 TBird was bone stock when I bought it. Other than being converted to 12 volts, it was as built.  The first thing I did to the engine was install a set of "G" heads, a 57 "B" manifold, 57 exhaust manifolds, a Holley 465 and a 57 distributor.  The "G" heads came off a 1957 engine with the high ratio rockers.  There was an immediate improvement in the performance and drivability of my car.   The engine that came with my car was a Frankenstein   I didn't know it until a freeze plug fell out of the block leaving me on the side of the road.  When I pulled it apart, it had a welded crankshaft, mismatched pistons and a timing chain that looked like it would fall off just sitting there.  I started over and built a new engine around the original block. My new engine has a couple of improvements that I think are worth considering. 

Ditch the stock push rods and install a set of tubular push rods.  My engine had two bent pushrods in the galley when I took it apart. Install a new timing chain and gears.  I used a Cloyes roller timing chain set.  I am running an Isky cam, but a stock 57 cam will do for most people. Finally, make sure your distributor is working correctly. Old distributors are notorious for sticking advance problems. 

If you build a decent engine using these parts, I believe your YBlock will put out a solid 250 HP.   That may not sound like much, but my 55 is a joy to drive.  It has a manual transmission with O/D and is very lively.  It's one of the best old cars I have ever owned.

55 e Bird:  If  you are buying that replacement Clay Smith cam thru Mummert, I believe he has replaced some or all of his lineup with other cams. Some or all are from Isky. If your car is on a Fordomatic, U need to be a bit carful what U choose. At least one person who used the cam U are considering,  said it was a bit marginal on idle quality with that cam. Depends on how fussy you are about idle quallity or RPM. By the way, Mummert has one on his current list he calls the 57 + cam.  (not to be confused with Ford spec stk replacement cams, which are pre '57 spec..) ..  


Paul

I can offer some input into two of the Isky cams.  I considered two cams for my TBird, Isky parts numbers 301444 and 301333. I called Isky and they helped me sort this out.  Both cams are a good choice for a street car.  301444 has 260 degrees of duration and .245" lift.  301333 has 270 degrees of duration and .448" lift.  Isky says both cams will work with stock valve springs and a stock converter.  I have stock "G" heads on my car and the cam installed without issue.

I believe 301444 is a better choice for an automatic car with a stock converter.  I chose the 301333 cam because my car has a manual transmission and a 4.11 gear.   The 301333 cam has a noticeable idle. It's not the worst cam I have had, but it has a significant lope. The low end response is great.  Mid range torque is outstanding.  The pull in 2nd gear and 2nd gear O/D is amazing for such a small engine.   I never rev my engine over 5,500, so I can't comment on high rpm performance.  

If you are going to run a big cam in an automatic car, you need a looser converter.  From my personal experience, something around 2,000 stall is about right for the street.  I ran a 5,000 stall converter on the street years ago.  I was like driving a car with a light switch, all on or all off.   Loose converters run hotter.  You may need an additional cooler for the transmission.  Hope that helps someone.