wanna help me pic a cam?

[Greasy Harley]

Im building a 350 for my '68 C10. Nothing crazy, shootin' for good dependable motor.
Engine specs:
Bore________4.06" (0.060" over)
Stroke_______3.48" (stock)
Quench _____.037" (±.003)
Compression__9.25:1 (±)
Speed Pro flat top pistons with 4 valve reliefs (-6cc)
Heads are 76cc "493" castings with 1.94" valves that have been moderately ported ( I probably made them slower  )
transmission will be Th400, not sure which torque converter it will have, but it will be mild.
I will build a Quadra-Jet M4M for it and mount it on a factory high-rise cast iron manifold. I'm keeping the points ignition.
The truck weighs 4100lbs, with me in it.
I want to focus on dependability and drivability, but I defiantly want it to pull as strong as possible.
Any Cam gurus here wanna help me out?
Thanks,
-Russ
_________

[Cliff Ruggles]

What will be the use of the vehicle?

You want the tightest possible converter in a heavy truck with a small CID engine in it.  A "loose" converter never works well there.

What rear end gears?.....

[old cars]

Sounds like a street build.
 If the block has not been bored yet you should consider having the cylinder bores Sonic tested first. 350 blocks can vary a lot in both in evenness and overall wall thickness. Unless you anticipate an output less than or about 350hp. Which is where you might be.
The 493 head being considered a smog head should be avoided. Using these open chamber heads can cost up to 30 ft-lbs torque and similar hp on a relatively mild street build. The Vortec head is probably the best iron cylinder head Chevrolet has ever produced for a small block. Better than fuelie heads. 350 hp is easily attainable.
Expect about 10.4:1 comp ratio with the info you provided (64cc head)
Camshafts. this can be controversial but 217@.050 duration is a very liveable flat tappet street cam

[Cliff Ruggles]

Going from memory here and I could be wrong (bad cases of CRS these days and even worse cases of DGS) but I remember 493 castings to be identical to 993's except maybe they were used on 400 SBC's?

If so they will have excellent ports and capable of great power, but as mentioned a large more "open" style combustion chamber so don't make much compression on a 350 build with flat top pistons in it.  The more open chambers are a double edge sword, they kill compression but unshroud the valves a bit for good air flow.

Assuming the 493's are the same as 993's (441's, 136's, and 487's will also have the larger ports) they are nice heads and at one time highly sought after by some Class racers who were required to run 76cc heads.  441's, for example are sought after by some engine "builders" who specialize in circle track engines requiring the larger combustion chamber castings.

I'm still in favor of 041's or 186's instead.  The later Vortec heads are also excellent as mentioned, but they require a special intake manifold and do not have exhaust crossovers so not heat for the intake.  Not typically a problem unless you want a working divorced or hot-air choke, or plan on using the vehicle to plow snow when it's 10 degrees outside!........Cliff

[Greasy Harley]

What will be the use of the vehicle?

You want the tightest possible converter in a heavy truck with a small CID engine in it.  A "loose" converter never works well there.

What rear end gears?.....

Usually just driving around town, short jaunts on the freeway 20-30 miles, haul broken down motorcycles or loads to the dump on occasion. I might go play at the autocross track and run it down the strip a couple times , but just screwing around, nothing serious. I am certainly not building it to race, I will do that stuff just cuz it's fun.

I was going to match the converter to the application, just haven't gotten that far yet, open to suggestions on that also.

It has 3.73:1 gears but I might regear to 3.42 with a TrueTrac in the future. Running 235/75R16 tires (29" tall)

Sounds like a street build.
 If the block has not been bored yet you should consider having the cylinder bores Sonic tested first. 350 blocks can vary a lot in both in evenness and overall wall thickness. Unless you anticipate an output less than or about 350hp. Which is where you might be.
The 493 head being considered a smog head should be avoided. Using these open chamber heads can cost up to 30 ft-lbs torque and similar hp on a relatively mild street build. The Vortec head is probably the best iron cylinder head Chevrolet has ever produced for a small block. Better than fuelie heads. 350 hp is easily attainable.
Expect about 10.4:1 comp ratio with the info you provided (64cc head)
Camshafts. this can be controversial but 217@.050 duration is a very liveable flat tappet street cam

I anticipate an output less than 350hp. 280-300 would be more than adequate. I'm not running vortec heads, consider me more of a "purest". I'll be using old technology on my 53 year old pickup. That being said, you are 100% right, I could definitely make more power with a set of vortec heads and a roller cam, just not into it.


I'm looking for as much power as I can get running mid grade, 10% ethanol, on a hot day and not have to retard the timing. I'm at 2500-3000 ft elevation (if that matters).

Thanks for all the help, I love this forum.
-Russ

[Cliff Ruggles]

A completely stock 350/300hp engine did it with a 194/204 camshaft on a 112 LSA.

That is actually an EXCELLENT cam for a 350 SBC engine build with right around 9 to 1 compression headed for a pick-up truck.  Even better topped with a set of 1.6 ratio rocker arms.

I used one in a 406 with 993 heads on it quite a few years ago in a K5 Blazer.  Best running SBC engine I've ever had in a heavy 4 x 4 application......

[Greasy Harley]

A completely stock 350/300hp engine did it with a 194/204 camshaft on a 112 LSA.

That is actually an EXCELLENT cam for a 350 SBC engine build with right around 9 to 1 compression headed for a pick-up truck.  Even better topped with a set of 1.6 ratio rocker arms.

I used one in a 406 with 993 heads on it quite a few years ago in a K5 Blazer.  Best running SBC engine I've ever had in a heavy 4 x 4 application......

Does it make a difference that my truck is 2wd? I was looking at cams with slightly longer intake durations @.050, 204-206ish. Am I gonna hate life if I go with a slightly longer duration? The chart I was looking at https://www.crankshaftcoalition.com/wiki/Cam_and_compression_ratio_compatibility points me towards the intake at .050 in the 204-208 range for 9.25:1.

I'm defiantly not an expert and have only a basic understanding of how and why lift/duration/LSA matter. That's why I ask questions.
What kind of lift should I be looking at?

[old cars]

Does it make a difference that my truck is 2wd? I was looking at cams with slightly longer intake durations @.050, 204-206ish. Am I gonna hate life if I go with a slightly longer duration? The chart I was looking at https://www.crankshaftcoalition.com/wiki/Cam_and_compression_ratio_compatibility points me towards the intake at .050 in the 204-208 range for 9.25:1.

I'm defiantly not an expert and have only a basic understanding of how and why lift/duration/LSA matter. That's why I ask questions.
What kind of lift should I be looking at?

Then your right on track. 204-206ish would be considered a True Street cam. look here https://www.competitionproducts.com/Elgin-Chev-SB-Hydraulic-Flat-Tappet-Kits/products/2119/

[Cliff Ruggles]

The link to compression ratio vs cam duration is OK but has one MAJOR flaw in it.  You have to take CID into consideration as well.

The requirements for a 350 build at 9 to 1 compression are different from a 454 build at 9 to 1.

A 204/214 cam in the big 454 would be pretty tiny and lower power range than the little 350 engine.

Nice to see some single pattern offerings in the other link from Elgin.  With the early SBC heads single pattern camshafts work fine.  We used to use the Crane Blazer 288H cam in 350 truck builds back in the old days.  It was a home-run if you were smart enough to use the .020" thick factory head gaskets to keep the quench tight and better flowing heads. 

I learned about 882 heads the hard way as I obtained a set for the 350 that was powering my 1970 GM 3/4 ton truck.  Like an idiot I traded my 441's for them when they valve guides got worn enough the County was trying to hire me to kill mosquitos in the summer months!

I installed those heads with no other changes and turned my strong running 350 into a complete TURD!  I yanked them off so fast and got my 441's back and had them rebuilt, re-installed and power was restored.

My first good lesson in head castings and after that deal I really started looking at port flow, combustion chambers, etc and not just the size of the valves.  Way back then about all anyone knew was "2.02's", "1.94's" or "double hump" when identifying cylinder heads for SBC engine builds........

[Mudsport96]

I would look at one of these if i was doing a truck build. I left the first one in there since it would work with tpi i would think it would be ok for a carb build.

[Mudsport96]

Hopefully i can post the specs, its right at the kb limit

[Cliff Ruggles]

Most likely you are only comparing 2 cams.

Since I first got into this hobby cam companies "juggle" specs slightly to make a "generic" cam look like something they grind themselves.  Part of the marketing strategy with cam companies and for sure it saves them a LOT of money by simply being able to re-box cams they purchase directly from CMC.

The Comp 12-388-4 is probably the same as the Summit 1102.  Even though Comp shows quite a bit less advertised duration they simply rate it at a different open point.

Same thing with the last two cams, so close they are likely the same cam.

Decades ago every cam we purchased no matter who it came from would have different colored paint on each end just before the first journal.  I always wondered why and one day asked my part supplier about it.  He told me that he had been to the plant where they were ground and the paint on each end was so folks on the assembly line would not have to look at part numbers when boxing them up, they used the color coding instead.  I suppose things are more sophisticated these days as the paint markings are no longer used.

Anyhow, the first two are often dubbed the "RV" cam for the SBC engine, 204/214/112LSA.  This is and always has been a very popular camshaft. 

I would use the smaller cam for the build in question here and stick with a stock converter.  Smoother idle and more power right off idle and below 3000rpm's or so works very well in a truck application.  Make sure to open up the pushrod slots in the heads so you can add 1.6 ratio rocker arms.  If you want to put the smaller cam on steroids at some point it keeps that option open.......Cliff