I need more from my 351C

I'm not sure how close in physical size the FMX is to the C4 or C6. All the long-tube headers I see for sale for the 2V heads are for C4 transmission only. Mine has 2V heads but a C6 trans. I can get headers for C6 but only for 4V heads. (You can make a stock 4V intake work with 2V heads, but the exhaust ports are too different for 4V and 2V to be able to interchange.) I looked at shorty headers, but it seems to be too little power gain for the cost, so I just found new manifolds on eBay to replace my cracked ones.

For your carb, if you plan on revving it well past 5,000 RPM, even the 351C 2V can make use of more air than a 351W or any GM 350 engine, so the 750 carb could benefit you then. Mine never goes past 4,500 RPM, so I have a 600 carb on it and that's good enough.

what's the budget? and how much tear-down are you willing to do?

1st things first, the stock valves in the heads need to be binned ASAP and replaced with decent quality 1 piece stainless / single groove units. matching retainers, valve locks and springs to suit a new cam also. the valve guides will be worn and need servicing with bronze liners, then a 3 angle valve job performed. www.alexsparts.com is a great source for upgraded valvetrain parts, as is www.tmeyerinc.com but finding what you need in stock can be hit / miss. Get What You Can When You Can!

springs, retainers, locks, 30 day lead time

2V valves, after confirming size

as far as the cam & rear gears, they need to compliment each other as well as the torque converter in the transmission. the 'biggest' cam i'll recommend for a stock converter is something like the Comp Cams 268H. it'll even work well with the 2.73 gears. unfortunately getting a properly ground hydro-flat tappet cam and properly machined set of hydro-flat lifters these days is nothing short of a miracle. if you're not ready to $tep up and go roller, and i wouldn't blame you, i'd be prepared to send off any set of new lifters to be resurfaced by an outfit like https://egge.com/lifter-resurfacing/. going roller is no guarantee of a satisfying experience, hyd-roller lifters have been a roll of the dice for about the same time as hydro-flats. choice of engine oil is also critical when using hyd-roller lifters, Chris Straub of www.straubtechnologies.com has shared that the cSt (centistoke) of the engine oil needs to be 15 or less for hyd-rollers. he actualy just released a youtube about it

for a mild hyd-roller the Ford OEM roller lifters are an option but again, finding quality lifters is a crap shoot. the OEM system also requires drilling 2 holes in the valley surface of the block to mount the lifter retaining 'spider' so this should be done with the engine completely torn down so the drill & tap chips can be cleaned out

all 1973 351C's suffer 2 major drawbacks regarding their power output capability, retarded camshaft timing and low static compression ratio (SCR). both of these combined conspire to create a Dynamic Compression Ratio (DCR) that's in the toilet. DCR = cylinder pressure = thermal efficiency. if the engine doesn't make squeeze in the combustion chamber, it doesn't make power. as a general rule of thumb, 'big' cams close the intake valve later in relation to the position of the piston in the cylinder during the compression stroke and therefor generate less DCR than 'small' cams. big cams rely on high SCR's to make power. your 1973 351C came new with dish pistons and a barely 8:1 SCR. and a severely retarded camshaft aggravated by the new for 1973 crankshaft timing gear. off the top of my head, the 1973 8cc dished pistons with the Comp 268H cam will make about 6.5:1 DCR. that's a little on the soft side but will run with no tuning issues on regular gas. for reference, consensus is that about 8:1 DCR is max for pump premium. swapping to 1970-72 style flat top pistons only bumps the DCR to 6.7:1. hard to justify the expense unless you need to have the cylinders refinished anyway, which is probably the case if it's original stock bore after all these years?

while you're digesting all that, and all this,

do you have a timing light, dwell meter and cylinder psi gauge?

the 1st thing i would do is bump the ignition timing to 18* btdc and see if that makes a difference. 1973 came with a points distributor, out of spec points will kill performance, a dwell meter is needed to ensure correct setting. a feeler gauge can get the engine running but a dwell meter tells you exactly. and i wonder what the motor is making for squeeze, 4 hits on the gauge with the carb stuck open and coil wire grounded or spark plugs removed 

Tim Meyer just announced valves available, 

like i said above Get What You Can When You Can!

comments on comments, FWIW ... i've 'upgraded' from single exhaust to dual and lost significant low end response & drivability. Mike you didn't say what the status is of your exhaust system? large diameter tubing shines when the engine makes big power at higher rpm, small diameter tubing shines every where else and sometimes with no downside at all. diameter goes for both header primary tubes, collectors and exhaust pipes. bigger isn't always better, hardly ever is, usually Less Is More

same goes for carbs, your 625 AVS is a good match to your 2.73 rear gear. that gear will not allow any benefit of a big Holley. it'll use more fuel, make some noise and suck more than it does now. when the car runs so bad-azz that the carb is holding it back, you'll know it.

Brent didn't get chased away from the forum, wth would a forum owner chase away such a knowledgeable guy? there were behavioral issues that continued after many efforts to quell them, i honestly don't recall ATM (IHDRATM?) if Brent was banned or left on his own but but in either case it wasn't ever what the forum owner wanted. and some others chose to follow Brent to several other forums all of which no longer exist. that worked out pretty well, nope. enter fb, the forum never recovered but new members are still joining regularly. the forum connected fb page Clevelands Forever has been going strong from it's inception. Breaking News? the forum has a new owner. i don't know what the relationship is between Brent and the new owner, will Brent be back? IDK. that Brent would start yet another new forum of his own is IMO a bit laughable as the other one whittled it itself down to such a small clutch before going dark. my feelings aside, i have referred Brent some customers whether he's aware or not. enough on that sob

so whattaya thinkin Mike?