firebird305

I'm seriously thinking of going from a 305 to a 350. The H.O. 305 in my firebird has 30,000 miles on it and is in real good condition,I was going to use the heads,carb,intake,headers,fuel and oil pump,and some other parts.Is this a good idea,And even thou the heads on my car have been worked (fully ported,shaved,3 angle valve job,roller rockers,e.t.c.)What are the drawbacks of useing them on a 350?

Sitting Bull

Your heads, fuel pump, carb, intake and headers will all work great on a 350. Forget the rest of it.

TBI305Camaro

if the motor is in real good condition why change it?? just so you will have a 350 instead of a 305? Youll gain some power but you need to ask yourself if its worth all the trouble for a ~30hp increase.

Oh yeah and those flowtech headers are 1.5'' primaries...I wouldnt put that on a 350 if it was me,

firebird305

Like i said,It's just something I'm considering.Boy,I can't win with this,Some people treat me like a jerry's kid (no offense to anyone)when i tell them everything i've done to my 305,While others wonder why i'm going to a 350 since i have so much work into my 305,It's crazy Actually I'm beginning to think that just getting a nitrous kit for some more power would be more cost effective anyway,But you make a good point.

Morley

Much higher compression (they are a 58cc head) and possible detonation problems from that and other places on the heads.

F-BIRD'88

I don't think you need our advice on this at all.
You seem to have a good handle on everthing.
I say do'er........ Good Luck

How fast is your 305 in the quarter mile now?
Curious

cp87GTA

I personally like 350s and larger, but shooting the juice in your case would be much cheaper. Not to mention a lot cleaner. It'd take some real good mods to a 350 to get 125 more poneys than your 305, with the juice.

Rob116

I hear what you guys are saying about the juice, but, if it was me, I probably wouldn't hit the 305 with a 125 shot and expect it to last for a long time unless the pistons were forged... I know that those hypers are good, but, one "mistake" and... KABLOOM! That's just my opinion, I could very well be off base. I just don't like what I've heard about the hypertecteutic pistons. (And yes, I am aware that there are some people out there using a 125 shot with cast iron, but, through a long, painful period of "trial and error" (lots of error) I've managed to figure out that if you do it right, you should only have to do it once, otherwise )

Basically, all that I'm saying is that if I was in your place, I'd replace those pistons (which I'm sure you payed some good coin for) with a set of forged. It might be cheaper in the long run. 10:1 is a little high for nitrous anyways, isn't it?

firebird305

...I've seen nitrous set-ups on engines with compression higher then 10 to 1. Hey f-bird 88,I've been able to run a 15.2 (tires spinning) with the 305,I know it has more,I just have'nt been able to get it out.

F-BIRD'88

What was the MPH at the end of the quarter mile run?
How much porting is done to your ported 305 heads?
what size valves? stock or bigger?

firebird305

Speed was 91.39m.p.h.,I didn't want the ports super enlarged,So the port job is mild,and the valves are stock but have a 3-angle valve job

F-BIRD'88

I see, cool... might want to go to the 1.94" valve and do some more extensive porting. especially areound the guide boss and
roof of the port.
The flow/ hp is there, but the 1.84" valve is a real restriction.
real big ports are not nessessary (and won't help) but there are key areas that need to be worked.

F-BIRD'88

Hey that clevite cam isn't the L-82 copy is it?
224/224 .450/.460 114 lsa??

what is the stall speed on your converter?

firebird305

I believe it is a L-82 copy,I know the salemen suggested i might want to go to a bigger T.Q. to reap the full benefits of the cam,But i never did,The T.Q. is stock.

F-BIRD'88

Not a very good cam for a 350, let alone a 305.
No wonder you want to build a bigger motor.

Ya have a big cam but were afraid you'd make the heads too big.
Doesn't work that way. Without the head flow the motor can't breath. The motor will not make power on a cam.
The cam supports the head, but the head makes the power.
I would rip the heads off and re-port them with the bigger valves.
Don't be shy, you cannot make these ports too big on these
heads. Pick up a book by Linkenfelter or David Vizard on porting
chevy heads. You'll see just what to do to get the flow.
Then If you can't get a high stall converter I'd go way smaller in cam. like 206/212 @.050" .440" lift. get the heads to flow, let them make the horsepower. Cam the motor for the torque range you need. 2000 to 5500. With a stock converter, smaller is better. You should be able to get 100 mph out of it and low 14 second ets. Of course when ya put the torque back in the motor you'll need some sticky tires too.

Don't worry, all the stuff will still work great in a 350 down the road. So none of it will be wasted.
The L-82 cam was designed in the 60's for the L-46 350/350hp corvette motor which had 11:1 compression. And needed to kill torque. Not a good cam at all for a 305. It has to go.

After you go this route with a good breathing head and small(er) camshaft, the motor/ car will be much better to drive and better on gas.

Dan88IrocZ

15.2?

Get that thing pinned down to the road and I can see you running much better times. I have about half the work you have into yours and I'm running faster...

Damn man, glue her to the road and give me some slips!!

firebird305

Well,A friend of mine has found a 70 malibu with a well worn 350 in it,He says he'll sell me the complete motor for $200.00 I was thinking,How do you think this 350 would run with the heads and the cam from the 305? Hey dan,If i still have the 305 when the tracks open up again in a few months,I promise to make a all-out effort to run some good times! I have some DR's mounted on "15" inch T/A rims sitting in my garage,Next time i go to the track i intend to use them!

Dan88IrocZ

I'd like to see what you'd run...you sound like to have a mid/low 14 sec 305 if you could plant'em.

TBI305Camaro

Only a 15.2?? I figured you were faster than that. If you would get one of the low compression GM motors with like 8.5:1 the 58cc would put you pretty close to 10 which is what you want unless your gonna run n2o. I say spray the 305. If you plan on switching a 350 eventually i guess you dont care to beat the crap outta the 305 now.

firebird305

Actually,I don't want to "Beat the crap" out of anything right now,I'm just trying to look at what options are availble to me.As far as my times go,I KNOW the car is MUCH faster then that,I just haven't had a chance to find outHow much faster.And as far as spraying the 305,I'm still looking at that option.

firebird305

I think I'm going to stick with my 305,I think it still has potential to run faster times and i'd be cheating myself if i didn't find out,Especially since I've put so much time,effort,And $$$$ into it. Thanks everyone for all the replies,And f-bird 88,Lighten up man.It's christmas.