Ok im new to the forum, but i need some help. My old man (dad) has a 83 transam with a 305 dual crossfire fuel injection system. Threw out the cam bearings! oops. Well i am putting in new bearings a new crank cam and lifters, oil pump and flywheel and of course all new gaskets. Need to knowwhat size cam to put in it. Wanna keep it close to stock. whats the biggest cam i can put in it ( the biggest) that will help with performance but wont have to cause for more modification. Thanks for the help!!

 

Just any cam you put in will help performance. The CFI cam was just about totally round, lol

Anyway... I'd say a Comp Cams XE268H for it. Not too wild, but will give a health HP boost.

 

http://www.compcams.com/catalog/082_083.html look about halfway down the page, the 252AH-12, grind # 12-388-4

 

i just threw in a comp cams 270 kit it said its one of the biggest cams youcan use w/ your stock convertor but you need new valve springs

 

I think the XE268 would be a little too much for him... If it's a manual he'd be better off with a 262 (and still it might be a tad too much), and with an auto a 256. Remember this is with stock heads... if they were aftermarket or ported it would be different, he could run a larger cam, but there's no need for a bigger cam if the heads can't flow more air.

 

thanks for all the info guys. had a thought i have the motor all the way down should i have the heads shaved ifd so how much?? and would that change what can i should get?? Thinkin about doin the comp cam lifter and roller rocker kit??

 

I'm not sure of the CR on the crossfire 305, but if it's close to 9.5:1 I would leave it. Shaving heads would be a last resort to gain compression, I would get pistons instead. Besides the decks of stock heads aren't very thick so there isn't much material that you can take off. With more compression you could go with a slightly larger cam, but I wouldn't. I'd stick with what I suggested.

 

We decided to go all out. we arent gonna replace the pistons they look ok. the back two cylindes were burnen oil BAD. We probally have 5 BURNT valves. We are getting the block hot tanked along with all the bolts. Getting a valve job ha all new ones. Got my cam and roller rockers with new pushrods today!! Also got my fly wheel. Goin to the machine shop today to drop her off so we will se what happens i might need some help gettin her back togeather we will see thanks for your help!

 

Dont forget to paint the block Chevy Red when you get it back

 

chevy red in a pontiac?? isnt it supposed to be blue??

 

No, not blue, that might be mistaken for a Ford color!

 

Well got the motor and the heads back from the machince shop! Its Beautiful!! But unfortunatly my dad (hes gettin old) to the piston caps off and mixed them up. And we all know thats not good so now also added to my proiject list is new forged pistons and the piston rods are getting redone . Oh yeah my dad also broke one of the pistons~!

 

I have vagly heard of this. the machine shop calle dus back our originally quote og 215 was now 300 and change?? They said that my 305 has 350 rod with 9:1 were there alot of these made?? What all does this High Output motor have differently??

 

All 305's had 5.7" rods in them which are the same size stock rods used in a 350. The 305 and 350 also share the same 3.48" stroke crank. Sounds like you might want to find another machine shop if you ask me.... They shouldn't change a quote unless they run into something big that needs extra machine work.

 

well they quoted us on stock 305 pistons.. They said along with a couple other people that not all of the 305's have this (350 pistons) but u say that they all have that?? I thought it was an experimental thing??

 

305s typically had lighter rods than 350s. I've heard some of the early 3rd gen "high performance" 305s got the beefier 350 rods.

It does not have 350 pistons, though. That don't work. Perhaps what they said/meant was flat-top pistons, like L98 350s had. But, L69s and '85-later LG4s also had flat-top pistons, as did LU5s. So, get flat-top pistons (they will have 4 valve reliefs, but they're still called "flat" tops, vs. dished pistons in lower compression engines).

Back to cams: The Crane Compucams are very nice pieces. A 2030 should do the ol' crossfire well.

 

we got flat top pistons with the four valve relifes in them. so what exactly does this mean for my motor ?? i mena is it better what was gm trying to achive??

 

Means they're the right ones.

 

I read or heard that the rods are not interchangeable from a 305 to a 350 because the 305 has a smaller bore, so the rods are thinner... the crank is the same stroke, but not the same exact crank. Any truth to this?

 

The rods and crank can be swapped between the two. It is true that the 305 rods from the factory were not as beefy as the 350 rods, but either can be used. As far as the crank goes it is the exact same.

 

I don't think the cranks are the same... The cranks in a good 350 were forged, but all 305 cranks were cast. Forged is better.

 

I don't think chevy put forged cranks in them. Maybe you're confused with ford? Please correct me if I'm wrong.

 

both wrong, but your closer...
ford had forged pistons in the 5.0... thats why they can miracioulsly hold more boost and run a bigger shot stock... they got the strength. they stopped in 93 i belive with that.