just bought a 97 active thunder 454 mag carb.running 66.7 mph with 23p mirage.want to go faster and not sure what i should do 1st.motor is all stock.motor is also spinning 5100 rpm.should i prop up?was thinking of building a 496 this winter but would like to pickup some mph this summer

if you are running at 5100 and trimmed properly i would try a labbed finished 25p mirage that should put you at around 4900 and that is good with a 454 and you should pick up a couple mph. but you will lose some low end and mid range.

Congrats on your A/T!

Yes, try props---------AND (if you have some spare bucks) I would add a decent breathing aftermarket exhaust system like a Stainless Marine or GIL or something comparable.

The aftermarket exhaust system isn't going to help much with a stock engine, BUT as you modify your engine with more hi-perf parts you will notice an increase in power. Besides, most aftermarket exhaust manifold systems are made of aluminum and will be much lighter than the stock Merc HEAVY cast iron system you now have, plus it will dress up your engine and give it some rumble/thunder.

Adding hi-perf induction parts (heads, porting, intake manifolds, cams, cubic inches, etc.) aren't going to do you any good unless you have a good breathing exhaust system to handle it. Hope this helps---have fun!

A big wallet for all the money you will be spending

get your super chargers first

anyone know what the stock compression is on 454 mag?what should my oil temp be?after along run it's 280-300 i think its too high

I think you are right, 300 is to high. There are many threads on the topic, do a search.
160PSI for a stock engine. Kind of depends on all cylinders and the difference between them.

I wouldn't run your oil much hotter than 240 degrees.

You need to tell us for much money you want to spend if you want us to help you spend it!

I would wait and put the money into the new motor. Buy things that can be used w/the end product. Like a good exhaust. Don't pay 4 it twice and accumulate a garage full of parts that were never effective. Decide what the ultimate goal is and then buy parts that can be used now and then. Don't reinvent the wheel.

Buying props, unless you ultimately luck out and get a set that will work on the end product why spend the $'s this yr?? Just my .02, been there done that.

what is it? 25 /28/32? we want to know. pics?