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Author Topic:   305 heads
#23
Member
posted April 09, 2002 12:33 AM
I am looking for anyone that runs a sbc 305 4bbl head on their 355. I run them on a cast flat top pistoned 355 and the thing is a dog!! I run a 1/2 mile track in a bomber class car(cast in cast out) rochester 4bbl
and single exhaust with spec muffler. Turbo 350 trans in second gear with 3.23 in the rear. I turn 3200rpm in the corners and only muster 4000 at the end of the straight. What I hope to fined out is if the heads are killing the engine or I'm I looking at the possibly a bad cam choice? The rules state stock engines so the cam is only an RV type cam. Any help would be great!!

thanks
#23


EVANSRACING24E
Member
posted April 09, 2002 12:57 AM
i ran 305 heads for three yrs and not had a problem but i also had a lot taller gear for a 1/4 mile track. you might try a little taller gear to get the rpms up and you might notice a big difference.


smayo964
Member
posted April 09, 2002 08:19 AM
Evensracing24e is right #23. I also have been running 305 heads for a couple years on a .3 mile track. I also run the t-350 trans in first, but with .273 rear gears and will maintain a strong 6,700rpm average. I was running an approx. 274/268 cam in my setup. I assume you are running a 268 duration cam, or close. I had a sb400 with the same 305 heads, using a 268 cam and still would turn it the same rpm range, but with a **** load more torque out of the corners. I also ran the stock exhaust manifolds for a season with good results. You only need about 15" of 2" pipe off the manifolds. You carb might be the problem. Need to look at your metering rod combinations, mixture screws, and spring tension on the secondary vacuum butterfly. We ran this setup on my bro-n-laws street stock on year and it took a bit to get the combination right where the carb would flow good. Hope this helps. If you have any further questions, drop me a message or e-mail me.


powerglides
Member
posted April 09, 2002 08:41 AM
smayo964 What size of tires do you run to get that rpm. My track size and gearing are exactly the same and I turn 5500rpm


smayo964
Member
posted April 09, 2002 02:56 PM
We were required to run DOT rubber on 8" rims. My main setup that ran the best was running 245/60-15's. I tried running 255's, but didn't like the way they fit the rim and rolled in the corners, etc. Depending on where I drew for my heat race, I would sometimes drop down to either 235's or 225's (extreme) to help get a jump out of the corner passing, etc. and increase my overall ratio at wheels. I had about 84" rollout on the 245's down to about 80" rollout on the 225's. My overall ratio (trans/rearend) was .688 The only problem you had to be careful with is during the hot months where the track stayed dry slick, was spinning the tires running the smaller rubber. Hope that helps.


ryan
Member
posted April 10, 2002 12:49 AM
I run a 688 final also your track must be a big .3 and mine must be a small .3 track because I run 255/70/15 I dont know what the tire roll is I never measured.

[This message has been edited by ryan (edited April 10, 2002).]

o5racer
Member
posted April 10, 2002 12:58 AM
any motors going to be a dog if its only tuning 4000 at the end of the strait. before you mess with anything id check with other drivers at the same track and see what they are running for gears.


smayo964
Member
posted April 10, 2002 06:34 AM
Hey Ryan. One question I have before you make any changes, is how are you running in relation to the balance of the field and what width rim are you running. For starters your tire size is "HUGE" compared to my setup. Your rollout just between the series size (60 to 70) is equal to several inches, let alone you are running a size greater in width, which will also increase your sidewall height. I used to work in a garage, Goodyear, and per the Goodyear rep, he explained the percentages of sidewall vs tire width (size). For ex- I ran on my left front a 215/65-15 since I could not get another 235/60-15 in time, but the circumferences were within a 1/4". You can go out to any tire web page and get tire specs (based on that brand) to get a feeling of what size in a particular series will match another size in another series. If your rules allow it, just dropping to the 60 series in a 255 will increase your rear gear due to the tire being a couple inches smaller in height and smaller in rollout. This will also tighten up your setup and minimize tire roll. Food for thought, you never really want to get your sidewalls "bubbled out" to far greater than the rim width. Also, if you are on a tight .3 track, you might want to try dropping down to the 235/60 range for a starting medium.


ryan
Member
posted April 10, 2002 01:08 PM
I am running the same RPM as a bunch of the front runners some of the guys however do turn their cars over 6,000 but they don't have any advantage over anyone else. I was just curious on the 1,200 rpm difference


smayo964
Member
posted April 11, 2002 08:50 AM
Ryan. As one last thought. If you are running comparible to the rest of the field, I would take a good look at your cam specs to see what the power band is rated for your cam. If you are running a cam that is rated 2,500-6,000 (for ex.), and your engine is running in the mid to low end of the range, you might want to intentionally raise the rmp to see if the combination works better. I know that's hard to swallow on race night, doing R-n-D, but unless you get the track by yourself to test, that's probably your only out. Just food for thought. By the way, I didn't mention earlier, I'm running the small 1.9/1.5 valves in my 305 heads. Good luck at the track.


Flatlander
Member
posted April 11, 2002 01:30 PM
My track is a high to medium banked clay track. Minimum weight is 3500.


Flatlander
Member
posted April 11, 2002 04:41 PM
I have never ran a 305 head but when I use to run a 1/2 mile track I ran a 538 final gear and turned about 58 hundred rpm with a flat top motor. Some of the guys I ran against run 543 and some run 529 and they cranked anywhere from 58-68 hundred rpms.


Flatlander
Member
posted April 11, 2002 10:04 PM
thers a lot that goes into that eqaution lighter parts in the engine lighter rotating mass in trannie these can also raise RPMs driving stlye can also to some degree


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