OK so i put a 355 into my camaro a while back and for some reason it just doesn't seem to crank out much power...i have a 9:1 compression and i believe its a roller (spelling), it also has a basic 14x3 element with a k&n high flow, its got an aftermarked edle. intake manifold, and its a tbi, i know its history and its got aftermarket heads. it used to be my uncles friends and he was suprised that i couldnt even light the tires up. he knows it has WAY more than that in it he told me it was turnin his car easy...im not a car expert by any means it just seems weak i still am runnin a 305 everything else like the chip and everything and stock exhaust. but i have a pair or headmen longtubes and a true dual with h-pipe and moroso's coming in soon when weather breaks. something just doesnt seem right when my buddies impala with a v6 is beating my car i take care of it and everything. any thoughts?

i really just come down to being stumped because my lack of knowledge im expecting the exhaust and headers to help seeing as im using the stock 305 system but do i need different injectors will a tune do it i mean whats my best bet here im tired of getting beat by crappy mustangs, or am i just expecting to much

Sorry for any spelling errors

 

How do you know that?

Which one?

What ones?

A clue right there.... that being one of the WEAKEST parts of a 305 TBI. You need the 350 injectors and chip, and to GET RID OF every single piece of the 305 exhaust, from the head to the back bumper. That garbage throttled the already otherwise throttled 305 that came in there, and completely chokes a bigger motor to death.

Mistakes, all of it. "True duals" gains little to nothing on most setups, and causes other problems that make it a step backwards, like, scraping the ground and getting torn off or smashed flat. Don't do it. Chassis-specific "shorties, and a 3" single, is MORE than enough for a 350 with TBI on it.

What cam is in it?

 

youre going to need a 350 computer ,knock sensor ,injectors,and a reprogrammed chip to make it run right at all. some of these other fellas on here have more experience than me will chime im sure. good luck with it tho.later jimmy

 

ill have to look for some of the stuff my uncle knows all of it. but i just know its 9:1 for sure he told me that and he knows the engine i think he and his friend built it i just bought it...and i already have the duels and longtubes because i got a good deal on them...as far as the ecu thing and injectors what do i need to do to make it work...like do i go to a junkyard and pull a chip and put it in and steal the injectors or what the hell do i do to swap it over lol i am not that good with engines i know basics but im just a lil lost on this one..and if i switch the injectors and the chip and exhaust will that make a huge difference? i just think its an edle. tbi intake manifold i believe i cant remember the heads i have to check...

 

Problem is, EVERYBODY "just knows for sure" what their compression is; and about 99% of the time, they're wrong.

This is NOT something you can look up in the catalog. If that's the basis of this estimate, then it's probably WAY high.

In order to ACCURATELY determine the CR, you need to know the volume of the valve reliefs in the pistons; the ACTUAL MEASURED chamber volume of the heads; the head gasket thickness; and the "deck clearance", which is how far below the deck the pistons are at TDC. This last is affected by several things: stock blocks usually have the pistons about .025" below the deck, but the tolerance is pretty wide, so it could be anywhere from about .020" to .030", and may vary CONSIDERABLY from side to side or from front to rear on either side. MOST "rebuilder" pistons, including virutally ALL cast ones, MOST forged ones especially such as TRW/SpeedPro except for racing-specific high-$$$ ones, and most hypereutectics, locate the pistons an EXTRA .020" below the deck.

To give you a look at how much variation this can create:

350, .030" overbored, .039" head gasket such as FelPro 7733PT2, 76cc heads such as 882 or 624, TRW or cast stock (15cc) dish pistons (.045" deck clearance) with 6cc valve reliefs: 7.7:1

Same as above motor except flat-top pistons (TRW or cast, 6cc valve reliefs): 8.3:1

Same as above (flat-tops) except 64cc heads such as double-humps: 9.3:1

Same as above (flat-tops, 64cc heads) except with ZERO deck clearance: 10.3:1

Get the idea? Those last 2, with the extra deck clearance and without it, are where most people go wrong "guessing" their CR. The TRW/SpeedPro catalog doesn't help, because it lists the "compression height" for their pistons; problem is, what they list is the "nominal" height for the motor the pistons are for, but NOT the actual, as-manufactured height of the thing in the box.

I'm betting, the CR is NOT really 9:1.

If you don't get this right, then it's impossible to pick a cam, and you can easily end up with a motor that makes FAR less power than you "think" it's "supposed to". Worse yet, you can buy a bunch of parts and assemble them, and the guy in the far lane can buy the same parts and assemble them too, and he can KICK YOUR BUTT by doing the right machine work to optimize things like the CR.

Yes you can just go to the junkyard and get the injectors and chip from a 350 truck or Caprice. Might not be perfect or ideal, but it'll be AHELLUVALOT better than what you've got now. Ideally you'll need to program your own, since no "mail-order" tune is EVER going to be really right; but your existing 305 setup is TOTALLY WRONG for a 350, so just getting the right thing in there is a big step in teh right direction.

For exhaust, you need EVERY SINGLE PIECE, starting at the heads, and ending at the back bumper. Like I said, DON'T bother with long tubes, or "true duals"; both of those things are too much maze but too little cheese. Neither will make a noticeable difference to your TBI engine's power output, but they will make the car FAR worse to deal with for the rest of its life. A better plan would be to get a set of high-quality chassis-specific headers for one of these cars, BUT NOT FOR THE TBI MOTOR; get the ones for a TPI 350. I highly recommend getting them ceramic coated, again, for the benfits of longevity: they don't rust near as bad, and that will keep underhood temps down, so all your wiring, hoses, connectors, sensors, etc. won't tend near as bad to turn into dust from heat. Get a high-flow cat for the same thing, and then your choice of cat-back from a rpeutable mfr; Blowmaster, Borla, Edelbrock, Hooker, Dynomax, etc. etc. etc. Look for one with 3" pipe all the way to the muffler. You DO NOT want ANY piece that will bolt to the L03 exhaust, because in order to do so, it has to neck down to 2¼". Very very very very bad.

Putting in the right injectors & chip, and getting rid of the restricted exhaust, will make an AMAZING difference, regardless of the actual CR.