305 Build

[305Racer]

Building a GM 305 for a 2500 lb. dirt car we have a open head rule no porting or polishing, must be cast steel, a open cam shaft rule, open compression rule, Open carb, open intake, and bottom end. Must be a standard stroke 305 3.480 crank 5.7 rods. Max 315 cubic inch. Min 51 lbs on crank.
I have a 3.480 forged scat crank 51 lbs, scat 5.7 bushed forged rods stroker clearanced with 7/16 cap screws, Mahle pistons and rings -5cc's. Block has been bored 60 over at 3.796 and line honed.
Will be running a 600 Double pump Holley mech sec. built by Bobby at Competiton Carbs sitting on top of a Air gap Rpm Torquer intake, MSD Dist. with 6AL Box and Coil.
Want to keep the compression around 10-1. I know a lot of the 305 sprint guys use Dart heads but wich ones? Any help on the correct runner size and valve sizes would be greatly appreciated. I am guessing the horse power on this set up to be at around 400. Max RPM to be at 7500.

PLEASE DART GURUS HELP ME.

[want-a-be]

Run the 49 cc heads. 180s might do you ok,... but I'd be running the 200s if it were mine. Why are you wanting to stay around 10-1 on the compression if there are no limits?

What are you doing to do for a cam. Do you have a vacuum rule?

Don

[Awesome Bill]

I agree on the heads, but the rods are overkill for sure, but if that is what you have, run them. I would order the heads with a 1.94/1.50 valve, You may be able to get the 170 s/r head to work better being the bore is so small. The 2.02 is not going to run! We have run these and the big valve is way to close with that bore. I don't think Don Mentioned this. The S/R head is better than you think and does have the proper cc runner and valve size suitable for this. Also get some Tit valves if they will let you. You can pick them up cheap on some sites I have seen. Anything else in the engine should be super light. Get the cam core as big as possible, this helps. There are a ton of things you can do with this and you will amazed how it runs.

[want-a-be]

I would order the heads with a 1.94/1.50 valve, You may be able to get the 170 s/r head to work better being the bore is so small. The 2.02 is not going to run! We have run these and the big valve is way to close with that bore. I don't think Don Mentioned this.


Went through my feable mind while I was typing...but forgot :o to mention he only needed the 1.94/1.50 valves for this build. Thanks Bill.

Don

[305Racer]

Ok reason for 10to 1 compression was to stay away from race Fuel but I can run it. I really have no problem running race fuel so it is no problem going HIgher.

Finding 305 Forged pistons has proven to be a challenge and expensive thus the reason for the Mahle pistons Trying to stay away from a custom built piston. I am only running for a minimal 100 to 200 dollar purse.

No vacum rule,

You say the rods are overkill what do you suggest.

The only parts I have on the shelf right now are the carb intake and block the rest will be ordered this week hopefully if I can get this combination figured out.

Cam I have was actually a Freeby from a friend It is a Sig Erson complete roller Kit including roller lifters, 1.6 ss roller rockers, Springs, Clips, Retainer's, Spring shims, Cam Button. It is a retro fit Hyd.
512 lift
219@50
Adv duration is 288
110 LObe sep
I confirmed the kit with Sig Erson all part numbers match and are in the original unopened packaging.

Question what Timing gear would you suggest for this cam?

Will be running 1/4 to 3/8 mile occasional 1/2 mile once a year dirt tracks.

The sr head you are refering to : do you mean ss or the sr torker from world
As far as the Dart web site says I cannot get the 180 volume head with 1.94 -
Valves or in 49 cc Sorry but I am a newbi at some of this stuff. And no tit allowed so cannnot do that.

[305Racer]

Sorry I allso have the msd set up on shelf
I actually called Dart dont remember the Guy I talked to I was actually dishearted by what he told me something about no they would not build the the heads with the guide plates installed and springs installed I could get bare heads and have a local builder do the g-plates and springs, valves, drilling out the push rod holes for 1.6 rockers and so on but that dart only sold production run stuff is this true.

Sorry but my experience with like 4 local so called engine builders has been like a big hole to throw money into with very poor results. Want this engine built right to last for a while.