Ok, I figure I have some high 13s as i sit now after i figure out how to get some traction. I have decided not to mod anything else untill what i have now is running how it can/should. Even so I look down the line and there is much I can still do to this LB9. as of now my heads and cam a stock. I dont plan on wasting alot of money on this 305 so I want to do as much as I can with as little as possible. The next step must be heads and a cam along with further modification to my TPI. I am leaning towards porting my heads like in Sitting Bull's thread. Porting and install 1.94"/1.60" Valves in the stock head (I hear mixed opinions about larger valves in 305 heads and I want to hear more) I also figure this should be the time to do other machine work to the heads. I know the push rod holes need to be elongated, Many people say that screw instuds should be installed? In general At what amount of lift does this become reasonably necessary? Of course a valve job is a given and I was also tossing around the idea of milling the heads to raise the compression to 10:1 - 10.5:1 range from the stock 9.5:1 . Then finally comes my cam delima and how big is too big for my moderatly modified TPI 305? Keep in mind the heads will be worked over and my modified tpi flows conciderably better than stock. There are two comp cams I was looking at : XE256 and XE262. I am tempted to try the 262 but it kinda scares me a little for a 305. Anyways, how much more do you guys think is in this lil brigs and straton 305? How much more is to be gained from a good porting of the heads and a more agressive cam? Computer tunning should not be an issue as I am moving towards prom burning at the present time.

 

2 questions for you, how has your 305 tpi car been as a daily driver? is it a 5 speed or auto?


The 262 cam is a bit big for a 305, especially if you're only revving it to 5k or so. But if you dont some internal work or have a built motor assuming your intake is matched for it it will work. We put a similar cam in a friends truck with a 305. At first it was absolutely horrible because we couldn't rev the thing past 4500 due to a bad transmission and intake restrictions. Once we got that mess cleared up and we were revving to 6500 it seemed to be a good cam with a lot of power at 4500+

 

Its a 5 speed car. It is a garage queen, not daily driven only 58k on the clock. Well, at the track I shift at about 5500 rpm (doesnt fall on its face at 4500), I have ported plenum SLP runners. I have a stock base that I opened up to fit TPIS bigmouth gaskets. The base will be opened up even more once the heads are opened up. I just need to start data loging to see whats going on.

 

Hey smmurfin I have a set of mildly ported sr torquer 305 heads that I'm selling. Let me know if you're interested.

 

first of all i would like to say i love what you have done with the car and the fact that your car is an identical of mine lol. but smurf im gonna say first just go through check everything out. plugs, wires, and check the timing. make sure everything is to perfect spec. the mph is about right for the time you have. but you need to get that 60 down. before you go digging anymore into that motor just get a good set of hoosier QTP or something similar. dont go too big on the slicks either only like a 26-9.0 or along those lines. and go back to the track. once you get those 60's down near a 1.9 or a 2.0 i would say you would be a very high 13 or a real low low 14. i say do that then if you can reach that and want to be faster dig back into the motor. as for cams the xe262 would be fine. its totaly streetable for the tpi 305. those xe cams work great in tpi motor because of the large lobe separation angle. i myself have the xe252 in mine and its a great cam. but if your gonna add the cam get a set of the 981 valve springs as well to match it. for heads. yes a small amount of milling would be fine. if your engine is stock bore though do not use 1.94 intakes. they serve no purpose from what i have read. i know that might turn into a debate but for a stock bore 305 it just doesnt need that big of a valve. look at mw66novas motor he ran stock 1.84 valve to a 13.0 in the 1/4. other than that keep that 305 in there. no 350 swaps now.

 

Well all this im my post is down the line. I dont intend on trying to make more power if I cant even put the power I have to the ground. I doubt I will use Full slicks as I dont wana frag my drive train. Center Force Clutch + Slicks = Broken stuff

I will definatly mount a Fresh Drag Radial tho. That and some practice is all I probably need.

As of now the 305 will be in there for a while it has low miles and I really dont drive it much (less than 1000 miles this year) I am also tryn' to see what kind of numbers I can squeeze out of it with out spending a boat load of money.

Anybody else have opinions on larger valves in a 305? F-Bird'88 seemed to think they are a good idea.

 

I say get a set of LS1 valves, retainers, and keepers for about $40 - $50
If you're high mileage you probably need guides installed anyway, so it's no more money to get 8mm guides.
You'll probably also need fresh springs for a new camshaft as well, so swapping to the Comp conical 918 spring wouldn't be much trouble.

Keep in mind that installing larger valves without opening the seat area up to match does actually hurt flow by shrouding. Open the seats up to around 90% the diameter of the valve and you'll gain much flow.

Theres' a few pics of the swap on my site.

 

Where would one go about getting the LS1 stuff at that price? Replacing stock stuff in the valve train at the time of head work and a cam swap is a given even with my low mileage, babied motor. What size are the LS1 valves anyways?

 

2.0" and 1.55"
8mm stem diameter

Go to the classified section of LS1tech.com

If you can't find anything in a reasonable amount of time, then contact this guy:
SMC Performance
Email: valvegod@aol.com

He charges a little more than a private party would, but they are garanteed to be perfect quality parts.

 

If you are looking for more info you can see specs on my cam and heads along with ETs in my sig.

 

I guess they aren't much bigger than the 1.94" valves I was concidering, but isnt 2.0" pushing it on even a heavily ported 305 head? i just dont wont it to be over kill.

 

I've been out of the loop for a while, I'm trying to get back up to speed but 2.0 seems very big. My buddy and I built a 350 for his truck in high school and it was 1.94. That was pretty good on his 350.

 

1.94 valves are plenty large for a 305, much bigger is just overkill in my opinion. I have no actual data to back that up though. Much bigger and valve shrouding will become a problem due to the small bore on a 305.

 

I guess as of now i am leaning towards just getting a set of the budget manley 1.94" (~50$) intake valves and sticking with the stock exhaust valves. I like the idea of the comp 981 springs due to the fact that I wont need as much machining and i can reuse my stock retainers and such. Looking at the comp cams catalog it seems that 981 springs are recomended upto .500 lift. I guess I will just call them up and see what they think. With the 1.6 rockers I have, the XE262 will make max lift in the .49x range. Maybe pushing it for the 981 springs? Keep in mind this motor is and is staying TPI and will probably never see 6000 rpms.

 

anybody have concrete evidence that larger valves in a stock 305 head are worthless? I know you need to do some porting to take advantage of them. How about the exhaust valves? I am tending to believe that if 1.5" is ok for 350s it will be just fine for my tobe cammed 305. Why throw away another 50 bucks for valves and more for machining for 1.6" if they wont do anything?

 

I'm trying to get ahold of my buddy with the motor we did in HS. As I mentioned earlier he had 1.94 valves on a 350 I dont remember the exhaust valves...Seems like they were 1.5 or 1.6 but I can't remember...either way his drunk has some grunt, some real grunt.

 

no other comments? Anybody? How well do 305s respond to more compression? I wana hear people that have actually upped their compression and how much it helped.

 

My wife suggested the Comp 918 springs that use factory LS1 retainers & keepers, and not the 981 springs you are talking about. The swap to factory LS1 hardware and the 918 springs will increase lift capacity, RPM limit, add a lot of port flow, and reduce valvetrain weight, so there are many advantages. A skilled head worker would have no trouble getting them to work on your 305 heads.
The only issue that comes up is if the valve contacts the cylinder bore, but there are ways around that a good head worker will know.

No the larger valves are not a waste of time unless you neglect to modify the port throat and seat area to match the valves. I don't think you'd gain much by running the 1.6" exhaust over the 1.55" LS1 exhaust valve though.
Dan