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Author Topic:   305
Dirt Maniac

Total posts: 149
posted January 16, 2005 02:58 AM  
hey guys running a new class and we have to run 305 stuff, stock rods, cranks, and basically stock piston, however the rules say if the piston cost over 200 a set its illegal(maybe a cheap hypo?), running with a quad carb, and stock intakes, with i believe 425 max lift cam, can you guys give me some pointers?

Dirt Freak

Total posts: 257
posted January 16, 2005 09:27 AM  
I run a class that is a 305 chev or 302 ford ONLY class. Rules specify "stock dished pistons only" or "stock replacement CAST dished pistons."

Some guys use the replacement pistons from NAPA becuase they have a shallow dish and are really cheep. The crate motor pistons or the vortec pistons are the "hot ticket" but are spendy. You would spend over $200 for these easily, and I gaurentee they would be legal. They are STOCK.

The 305 GM crate motor was discontinued this last year, and are impossible to find, so dont waste your time trying to find a new one.

I use the 70 era "ashtray" pistons as recomended by my engine builder, for a couple reasons. Most stock replacemtnt pistons have a recessed head, lowering it in the bore enough that the older ashtray pistons are still higher in the bore then them, even with the deep dish. He also likes the longer skirts for stability because we are not allowed to bore over, and most of the 305's you will find are not in the greatest of shape. The holes just arent round like they would be if they didnt have 100,000+ miles on them.

It comes down to having your heads done right and choosing a good cam. My engine builder is like 70 years old, and has been doing this for a LONG LONG time and swears that I have a great engine. He is right, as it keeps up with all the big dollar guys and even won me a track championship of sorts this year.

Compair your rules to mine here and if you need any tips or pointees I would tell ya what I can. Unless you are gonna race against me, then I wont....LOL j/k

Dirt Maniac

Total posts: 149
posted January 18, 2005 11:48 PM  
i dont know if your familiar with the cam coupees, they run a 305, ill see if i can post the engine rules,

Only 305 cubic inch Chevrolet (GM) engines are permitted. Maximum overbore is

.060 meaning a 315.07 cu. in. maximum is allowed. No one piece rear main seal

blocks are allowed. Only blocks using the two piece rear main seal are allowed. Block casting numbers are (78-79) 460776, 460777, 460778, 361979, (80-84) 14010201. 14010202,14010203, 14016381.

2. Valve springs must be stock GM chevrolet or equivalent. They cannot exceed

120 lbs. on the seat when tested on the engine. Valve spring diameter must be stock

for 305 engine, with a maximum of 1.250" diameter.

3. No vacuum leaks between the intake valve and the top of the carburetor.

4. Intake Manifolds must be stock GM quadrajet spread pattern, cast iron or aluminum.

No angle cut, milling, grinding, acid dipping, coating, welding, port modification, or

hole relocation beyond basic stock street car rebuild allowed. No modifications

allowed except blockage of heat riser and EGR holes. No bow tie high performance

or after-market manifolds allowed. Quadrajet carburetor attaching bolt pattern is a

rectangle with dimensions of 4 1/4" x 5 5/8".

5. Cylinder heads must be GM stock 305 cubic inch heads. No special after-market

cylinder heads permitted. Only 2 valves per cylinder, intake valve maximum of 1.84"

permitted. Exhaust valve is a maximum of 1.50". No special valves or valve sizes

permitted. Swirl stainless type valves allowed but no polished valves allowed.

Cylinder heads limited to a minimum of 53 cc combustion chamber. No interior

deburring or polishing permitted. Studs may be pinned or screw-in studs (no guide

plate permitted). Poly locks okay. No angle cut heads or excessive grinding, milling,

acid dipping, coating, welding, port modification, or hole relocation beyond the basic

stock street car rebuild. three angle valve job is permitted. Casting numbers must

remain in head, if they are missing, the head is illegal. No vortec heads of any kind.

6. Crankshaft must be stock 3.48" cast iron. No racing cranks allowed. No polishing of

crank counterwights allowed. No knife-edging of crank allowed. No one peice rear

main seal crankshafts allowed. All crankshafts must use the older style two piece

rear main seal. Engine must have stock 305 OEM harmonic balancer. No after-

market fluid dampers or any other after-market harmonic balancer allowed.

7. Rods must be stock 5.7" GM rods. Aluminum rods prohibited. No steel racing rods

allowed. No polishing of rod I-beams allowed. No 6" rods allowed.

8. Pistons may be either flat top or stock GM pistons. Cast type pistons allowed. Flat

top pistons must have four valve reliefs in each piston. Cast in piston at time of

manufacture. Any type piston rings allowed. Must have minimum of two

compression rings and one oil ring. Floating wrist pins are allowed. No coating of

pistons allowed. Engine block permitted a minimum of .0 deck clearance. Piston

must not hit straight edge held over cylinder while engine is cranked with starter.

9. Camshafts must be hydraulic only. Cam may be indexed. A .450" lift camshaft may

be used with 1.5" ratio rocker arms and is legal. If 1.6" rocker arms are used, you

must not have more than .450" lift at the valve or its is illegal, meaning you must

have a camshaft with less lift. If lift is checked at valve, a .005 tolerance will be

allowed. Hydaulic lifters only.

10. Rocker arms must be stock stamped, steel configuration and only 1.5" or 1.6"

allowed. No aluminum or other roller rocker arms. Valve lift cannot exceed

.450" with either 1.5" or 1.6" rocker arms when measured at the valve.

11. Engine displacement formula for determining cubic inches is: Bore x bore x .7854 x

stroke x number of cylinders = cubic displacement. Any engine exceeding

maximum allowable cubic inch displacement limit will cause disqualification. Only

305 cubic inch Chevrolet (GM) engines permitted with a maximum over bore of

.060", which results in 315.07 cubic inches.

Dirt Freak

Total posts: 257
posted January 19, 2005 08:47 AM  
Them are some weird rules. First they lean towards staying "strictly stock' then they put a few racing twists in it.

All I can suggest is, get a good set of 416 or 601 heads bore it over and find some GOOD 4 valve relief flat tops. Have the heads done by someone you know is good, buy a .425 rule cam of your choice (there is alot of them available) and give 'em **** .

Dirt Full Roller

Total posts: 70
posted January 19, 2005 09:07 AM  
I run a hobby stock class that has a piston rule close to yours. I run the Speed-Pro hyper pistons with 4 valve reliefs. They have the anti-friction coating on the skirts. Nice pistons and you can get them for under $200.

Dirt Maniac

Total posts: 193
posted January 19, 2005 10:24 AM  
who are these people that make engine rules?

No One Piece Seal Blocks? a 305 is a 305 even if the crank seals better.

I would bore it to the maximum .060 over... take advantage of that.

You are also allowed to zero deck the engine... Do it. Compression makes power.

get Flattop pistons.. They came stock in Camaros & Firebirds in the mid 80's... just order a set .060 over.

Try to find head # 081.. thats the last 3 numbers of the casting number... we flowed several different heads & those are the best 305 head you can get. Next would be the 416s, then 450s, then 601s. The 601s have a small chamber so they are good if you were limited to dish pistons.

Your cam will need to match your RPM range you plan to run... What size track & what rearend gears will play a big part of the cam choice.

Use a GM Aluminum intake to take advantage of the less weight. They came stock on lots of GM cars in the 80s & are very plentiful still & very cheap.

hope that helps some.

what type of car will you be using & can you run headers or is it stock manifolds?

Dirt Freak

Total posts: 385
posted January 19, 2005 04:24 PM  
Compression is the best thing you can do - use the steel shim head gasket - like .019" compressed instead of a .042 or so for the composite - about 1/2 point of compression there. Call the cam MFGR's they have cams ground specificly for the .450 lift rules and have worked to get the most HP on a restricted class. If you're going to get the crank polished have them offset grind it .010 to get .020 more stroke - won't cost any more but every tiny bit helps (plus they probably won't measure stroke that accurately if they tech...) Use the aluminum intake since it's allowed and it'll save weight off the front end...

Wonder if any of the 305's on IROC's or Camaro's came with aluminum heads from the factory??? didn't see iron only?? Anyhow mill them to the minimum 53cc and get the machinist to "bowl hog" when cutting the valveseats...

Dirt Maniac

Total posts: 149
posted January 19, 2005 11:19 PM  
they are basically a limited mod, we have to run a complete metric chassis, and has to weigh atleast 2400, and we get to run mod headers, will mostly be running on a 1/4 mile track thats got good banking and drys out in the summer, as for the heads we have to use certain casting numbers so no aluminum,

Dirt Maniac

Total posts: 149
posted January 27, 2005 08:21 PM  
ok guys i heard a crank from a 350 and a 305 was the same, can some one elaborate???? thanx

Dirt Maniac

Total posts: 138
posted January 28, 2005 01:35 PM  
Same stroke, but balanced differently if I'm not mistaken, to account for different pistons etc. in the motor.

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