turbofire327

Finally made it to a test night at Bandimere Raceway in Denver, CO. I'm running a 310 with the following specs:
.525 lift solid roller
roller tip rockers
ported heads with 1.94 intakes
ported stock Q-jet iron manifold
modified Q-jet to work with camshaft and altitude(I live at 7220 ft.)
balanced bottom end, dished pistons, 9:1 compression
headers, with dual 2 inch exhaust, thrush mufflers, cut outs
running this engine in my chevelle with a four speed saginaw and 3.36 gear with stock skinny wheels and tires

Anyway started the night in the high 16's, by the end of the night I got down to 16.05 at 89mph by adusting the carb and uncorking the cutouts
I know the exhaust is restrictive because I picked up 3 tenths by uncorking it. That will change shortly with a larger exhaust.
I know the et is lousy since I had to leave at idle or loose traction, however I shifted at 6000 rpm and went through the traps at 6000 in third gear.
The time corrected for sea level would be 15.10 and 94mph which sounds reasonable.

Really I am looking for other 305 owners to chime in here with info on their own times for some perspective. Also I welcome suggestions on how to make this thing quicker. I know it needs slicks so I am building a new diff this winter, any other suggestions?
Thanks
BTW I know my car is off topic but there are a lot of 305 owners here, so thanks.

sofakingdom

iTrader: (1)

L69 5-speed cars did real close to 15 flat off the showroom floor. Some of the best of the 305 TPIs (not the auto ones) were in that same range.

86LG4Bird

iTrader: (1)

What's the weight of the Chevelle with you in it?
I'm disregarding the ET because of the trans/gearing/tires detrimental effects on it. But even from the corrected mph, that performance from a solid roller motor with headers and uncorked exhaust sounds a little disappointing, doesn't it? It's really hard to judge, not knowing if the "ported" heads are any better than stock.
What are the cam specs? Since its a SR, I'm assuming they're pretty healthy, so it looks like a bad match with that low CR, compounded with the altitude you're running at. Too bad you don't have flattops in there
Does the engine feel sluggish until you reach ~3000 rpm or so?

FWIW, the stock internal LG4 305 in this 3475 lb (with driver) car traps about 90 mph: https://www.thirdgen.org/forums/carb...ds-hanger.html

So assuming your Chevelle at 3800 lb with you in it trapping 94 mph corrected, you're making 50 hp more than that, or about 255 hp at the crank.
Tell us more (cam & heads specifics, etc), and we can better tell if the performance is on par for the parts you have, or measures to improve it.

RAS

Well with that low of compression you'd be safe running a turbo or supercharger. Would help alot at your altitude.

turbofire327

Car weighed 3480 with me in it, it has been severely lightened in the front end.
Cam specs, duration 224 @ .05, lift .525.
This engine has merely been an experiment, the engine started out as a stock rebuild, I drove it for a couple years. When it was stock it ran 17.98 at 78 mph at the same track a few years ago. Prior to that was the stock somewhat worn out 327.
The current combination is much faster than the two prior but still seems slow to me, I drive it on the street it is not sluggish, even launching from idle it has slight wheelspin. Even with the big cam, car idles fairly smooth at 800 rpm. The reason I like this 305 is the mileage, it gets 18mpg on the highway.
Head work was basic, smoothing the bowls, matching the intake ports to the manifold, nothing exotic to screw them up.

Anyway thanks for input, keep it coming.

I'm really wondering if I need to spin it harder with that camshaft but I'm somewhat relunctant with a stock bottom end.

sofakingdom

iTrader: (1)

That's not much cam.

Never heard of anybody making a SR that little, but hey, there's lots of stuff I haven't heard of, so .... yeah. What cam is it?

3480 is about 150 - 200 lbs more than a L69 5-spd car weighed. So .... yeah. Sounds like something's a little off somewhere. You're just barely faster than a showroom-stock car with a weenie stock hydraulic cam and a Q-Jet that got 22 mpg went, in 1983.

Maybe some tuning?

That would depend to some extent on how hard you're already spinning it? Maybe less hard? Where are you shifting and trapping now?

turbofire327

I agree it's a small SR but it's much larger than any of the stock cams. Also you have to remember that any camshaft seems bigger when you live at 7200 ft. elevation since the air is thinner, cylinder pressure is also much less. As I posted above, I'm shifting at 6 grand and going through the traps at the same rpm. I know the car is not as aerodynamic as a third gen camaro, but can it make that much difference? I would go back and make some changes but winter is setting in and the tracks are closed until spring here in Wyoming and Colorado.

sofakingdom

iTrader: (1)

I missed the RPMs somehow... sorry...

Might not be a bad idea to run it on a chassis dyno and see what RPMs it makes the best power at, and adjust driving technique and/or gearing if necessary.

I agree, building a motor for high altitude is quite different from lower elevations; you tend to need more compression (probably the thing hurting your combo the most), and of course tuning is WAY different.

I doubt aerodynamics are all that big of a deal... a tenth or a mph, but not much more than that.