Building a 350 sbc

[SXlover]

I'm completely new to 350 sbc. Never had one open or anything. Closest I've come to it is a 2 stroke sled engine.

With that said I've been tossing around the idea of getting involved in racing IMCA Hobby Stocks at my local dirt track. I also know engine builders don't share much for secrets.

As some of you may know you can run a GM 602 crate engine with a GM 2bbl Rochester carb limited to 6,200rpm or you can run a claim motor. (If you aren't sure what that is, it means somebody can pay $550 fo claim the engine minus flywheel, clutch, pressure plate, bellhousing, breathers, carb, starter, motor mounts, oil/temp sending units, fan and pulleys, clutch ball, clutch arm, throw out bearing, water pump, fuel pump, rod and plate, distributor, plug wires, water outlet and restrictor, exhaust mani and pipes)

Claim motor specs have to be as follows. No 400 or larger cubic inch parts. Max 361 cubic inches. Max 9:1 comp ratio. Flat top or dish pistons. OEM or OEM appearing replacement steel crank. OEM or OEM appearing replacement steel rods. GM 5.7 inch, 6 inch or GM Vortec rod #10108688. Conventional flat tappet cam and lifters. Wet sump oiling. Can't alter firing order (1-8-4-3-6-5-7-2). Steel, unaltered approved OEM and minimum 76cc combustion chamber heads. Max valve size are 2.02in intake and 1.60in exhaust. No porting or polishing. Steel roller tip rocker arms allowed. GM 1.250in (+or-.015 tolerance) maximum O.D. valve spring. Unaltered approved OEM cast iron, low-rise, 2 bbl intake. Unaltered OEM type harmonic balancer. OEM type steel or aluminum water pumps. Can use MSD #8728 rev-control with an rpm chip. No ignition boxes. OEM HEI distributor only. OEM cast iron exhaust manifolds, with max of 2.5 in OD exhaust pipes.

Basically can a claim motor be built cheap enough to run with a crate? What are some good build specs for a claim motor? Just looking for ideas, have a little discussion about building 350s. This is all pretty much new to me. I know a lot of racing is driver and car setup, not motor.

Any good books/articles you recommend for this kind of stuff? Willing and eager to learn this kind of thing.

 

[Devilin AblueDress!]

Keeping in mind I am many states way from you BUT Crate doesnt = high performance....Just a reman motor that arrives in a crate. Around here ANY motor can be "claimed" (basically short block, as you described WITH OUT heads) For your engine to be claimed you have to win the feature, as in you can win every heat you enter and take 2nd place in every feature and no worrys about having your engine "claimed". EVERYONE and I mean EVERYONE that seriously races starts with a 400 sbc. With just a little bit of machine work they will with stand AMAZING amounts of overheating.

 

[SXlover]

Keeping in mind I am many states way from you BUT Crate doesnt = high performance....Just a reman motor that arrives in a crate. Around here ANY motor can be "claimed" (basically short block, as you described WITH OUT heads) For your engine to be claimed you have to win the feature, as in you can win every heat you enter and take 2nd place in every feature and no worrys about having your engine "claimed". EVERYONE and I mean EVERYONE that seriously races starts with a 400 sbc. With just a little bit of machine work they will with stand AMAZING amounts of overheating.

I understand crate doesn't mean high performance and claim has many different meanings. Using crate engine in this setting means ONLY this, unaltered, and sealed with GM parts (special bolts, etc.). http://www.summitracing.com/parts/nal-88958602 or http://www.summitracing.com/parts/nal-19258602

If you start out running a crate, that motor cannot be claimed even if you do win. If you run a claim engine and switch to a crate during the year, then that crate can be claimed. In this setting to be claimed you just have to be in the top four, and those elgible fifth on back in feature can claim unless they are running a crate. That's the basics of it. I do understand though that different classes through out the US have different rules. IMCA Hobby Stock rules state you cannot use ANY 400 or larger cubic inch parts. I want to be legal even though to win in racing you have to cheat. I'm kind of curious if it is better off to just buy the crate or build a claim motor...Crates are limited to 6200rpms.

 

[Devilin AblueDress!]

Thinking out loud here...Both those links state "high rise dual plane intake"...is that a 2 barrel? First link state engine is "externally balanced" as far as I know ONLY sbc chevy externally balanced was a 400. Max displacement 461 ci, thats a 350 bored .60+? In my oppinion yes a "claim" motor could be put together for much less than those prices on links and SPANK on those links but then you run the risk of being "claimed". ALOT can be done to warm up those 2 barrels as well! Sounds like they are trying to keep it a level playing feild. To make car setup and driver ability more of a factor than motor winning the race.

 

[SXlover]

Thinking out loud here...Both those links state "high rise dual plane intake"...is that a 2 barrel? First link state engine is "externally balanced" as far as I know ONLY sbc chevy externally balanced was a 400. Max displacement 461 ci, thats a 350 bored .60+? In my oppinion yes a "claim" motor could be put together for much less than those prices on links and SPANK on those links but then you run the risk of being "claimed". ALOT can be done to warm up those 2 barrels as well! Sounds like they are trying to keep it a level playing feild. To make car setup and driver ability more of a factor than motor winning the race.

You have to use an unaltered GM 2bbl Rochester carb and Speedway Motors carb adapter #135-3502G on those crate motors. And I can't tell you about the externally balanced part. These are Chevrolet Performance motors if that matters at all.

Assuming you meant max displacement 361 and not the 461 as you typed...yes that would be a 350 bored .60 over.

On the claim motors you must use unaltered OEM 2bbl carb for that engine, but you can machine the booster ID to 0.25in, venture ID machined to 1.375in and throttle bore ID machined to 1.6875in on the Rochester carb. 0.625in booster height and must remove carb choke plate. All this is coming right from the 2013 IMCA Hobby Stock which is what I'm interested in getting involved in.

I want to race. Just trying to learn the engine side of it since this is all new to me. I will more than likely purchase a turn key car with a motor already, just kind of curious incase I want to build a motor and open one up that I get.

 

[alswagg]

GM Vortec engines are all externally ballanced. We run a ZZ4 in our ole Vette and a 377 MPI in our Cj7. The 377 runs a WOT of 6,500 and the ZZ4 runs 6,200. A ZZ4 has around 375 hp, the 377 has 405 hp. both with 650 cfm throttle body's.
Do you have to run a antiquated carb, or can you also run EFI?? Rochester made some huge TBI's rated at 650 cfm, these are two barrel two injector throttle body's. Al

 

[SXlover]

It just says on the claim motors you must use unaltered OEM 2 barrel carburetor for that engine, but you can machine the booster ID to 0.25in and venture ID machined to 1.375in. Throttle bore ID machined to 1.6875in on the Rochester carb, 0.625in booster height and must remove carb choke plate.

12 volt ignition system and OEM HEI distributor only. No billet distributor or crank triggers. Ignition rotor, cap, coil, and module must remain OEM-appearing. May use MSD #8728 rev-control with any rpm chip. No ignition boxes.

 

[Sxr700Bandit]

I see that they dont have to many specifics on the cam shaft. So does that mean that you can run a longer duration cam to move the power around? I realize that a cam wont work to well without some help like headers to help the exhaust flow...

 

[SXlover]

Yes you can run basically any cam you want. Don't see too much about cam, valve lift, duration, etc. You can't run headers. Must be OEM cast iron exhaust manifolds, with no center dump type manifolds.

I've been doing some of my own research on it lately and that basically means the Ram Horns from Corvettes are out. The best info I seem to have found is to run the LT1 manifolds.

About all you can really do to these motors I've figured out is a cam. And even then it has to be a Conventional flat tappet cam and lifters. You can also do crank, rods, and pistons...but pistons must be flat top or dish.

Max valve size is 2.02 intake and 1.60 exhaust. With max OD valve spring at 1.250 with a +or- .015 tolerance.

With so many cams out there, I don't even know where to start. I did read about staying around 220 to 236 duration @.050 and .450-.480 lift. But I don't even know if that's close. Another part I read was about maybe using 108 degree lobe seperation instead of 106 degree. I've learned quite a bit about cams the last couple of days. Lots of it is still foreign to me though lol.