Small Block Cams

[Larry Allen]

I have a stock 59 283cu in with the 245 HP dual carbs. When I rebuilt the engine I put in a Erson Viking-10 high lift grind. It's just too much for the stock exhaust system, I can't use full throttle at all. Does anyone have any knowledge as to what is a good cam for this engine? I have not been able to find any specs for the original cam or any aftermarket specs for the small block with stock exhaust.

Thanks.

[Bill Clupper]

Re: Small Block Cams

Larry, the camshaft for the 245 hp engine in '59 is the same hydraulic lifter camshaft that was used on the single four-barrel 230 hp engine of that era, and in a variety of low performance engines through the late sixties and beyond. The part number (1981 catalogue) was 3896929. the camshaft casting carries the number 3896930. If not available directly from chevrolet, (which it may be), there are copies available from Mellings, TRW, and a number of other suppliers.

[Bill Clupper]

Re: Small Block Cams

Larry, the camshaft for the 245 hp engine in '59 is the same hydraulic lifter camshaft that was used on the single four-barrel 230 hp engine of that era, and in a variety of low performance engines through the late sixties and beyond. The part number (1981 catalogue) was 3896929. the camshaft casting carries the number 3896930. If not available directly from chevrolet, (which it may be), there are copies available from Mellings, TRW, and a number of other suppliers.

[Joe L.]

Re: Small Block Cams

Larry----

Your original camshaft was GM#3733431. I can't give you the exact specs of this camshaft at the moment, but I can give you the specs for GM #3896929 which replaced it. I believe the specs for the 3896929 camshaft are very close, if not identical, to the 3733431. Anyway, these are:

intake duration @ .050" camshaft lift= 195 degrees

exhaust duration @ .050" camshaft lift= 202 degrees

intake valve lift= .390"

exhaust valve lift= .410

Your engine's relatively small valve size and stock exhaust system configuration will not support a very aggressive camshaft profile, but I have no information regarding the Erson camshaft that you're using. With less restrictive mufflers, as used on the higher performance engines of the 57-61 Corvette era, you might be able to use the GM#3863151 327/350hp camshaft. Both of these stock camshafts I mentioned are GM discontinued, but are available in reproduction from Crane. Otherwise, for a camshaft recommendation I'd suggest that you consult the factory techs at Crane Cams, Competition Cams, or Crower Cams. They know well the dangers of "overcamming" an engine and will not steer you wrong.

[Joe L.]

Re: Small Block Cams

Larry----

Your original camshaft was GM#3733431. I can't give you the exact specs of this camshaft at the moment, but I can give you the specs for GM #3896929 which replaced it. I believe the specs for the 3896929 camshaft are very close, if not identical, to the 3733431. Anyway, these are:

intake duration @ .050" camshaft lift= 195 degrees

exhaust duration @ .050" camshaft lift= 202 degrees

intake valve lift= .390"

exhaust valve lift= .410

Your engine's relatively small valve size and stock exhaust system configuration will not support a very aggressive camshaft profile, but I have no information regarding the Erson camshaft that you're using. With less restrictive mufflers, as used on the higher performance engines of the 57-61 Corvette era, you might be able to use the GM#3863151 327/350hp camshaft. Both of these stock camshafts I mentioned are GM discontinued, but are available in reproduction from Crane. Otherwise, for a camshaft recommendation I'd suggest that you consult the factory techs at Crane Cams, Competition Cams, or Crower Cams. They know well the dangers of "overcamming" an engine and will not steer you wrong.

[Loren]

Re: Small Block Cams

Larry:

The specs I have for the #3733431 (casting 3732798) are intake AND exhuast lift are .398 and duration for both intake and exhaust is 300.

[Loren]

Re: Small Block Cams

Larry:

The specs I have for the #3733431 (casting 3732798) are intake AND exhuast lift are .398 and duration for both intake and exhaust is 300.

[G B.]

Okay, I'll bite.

You puzzled me with the comment "It's just too much for the stock exhaust system, I can't use full throttle at all". I don't understand exactly what you mean.

I remember the bad side effects of a radical cam in a 283 this way: no low end torque and a rough idle. I can also imagine how an extremely restrictive exhaust would limit high rpm power. But I don't think ram's horn manifolds and stock mufflers are going to cause excessive backpressure to a 283 below 6,000 rpm.

Please tell me the specs of the cam that you used. I ran the GM "30-30" cam in a 283 using stock exhaust without noticeable full throttle problems. I'm curious about the details of the trouble you're having.

[G B.]

Okay, I'll bite.

You puzzled me with the comment "It's just too much for the stock exhaust system, I can't use full throttle at all". I don't understand exactly what you mean.

I remember the bad side effects of a radical cam in a 283 this way: no low end torque and a rough idle. I can also imagine how an extremely restrictive exhaust would limit high rpm power. But I don't think ram's horn manifolds and stock mufflers are going to cause excessive backpressure to a 283 below 6,000 rpm.

Please tell me the specs of the cam that you used. I ran the GM "30-30" cam in a 283 using stock exhaust without noticeable full throttle problems. I'm curious about the details of the trouble you're having.

[Mike Adams]

Re: Small Block Cams

You might want to get a desktop dyno program from Mr Gasket or Engine Analizer from Performance Trends. These are very helpful when changing engine componets. You can build the motor and dyno it with any changes to see how it will behave. The libraries have tons of specs and stock systems for numerous engines. I have done two small blocks with combinations tested on these programs and can't complain about the results. Just a thought...

[Mike Adams]

Re: Small Block Cams

You might want to get a desktop dyno program from Mr Gasket or Engine Analizer from Performance Trends. These are very helpful when changing engine componets. You can build the motor and dyno it with any changes to see how it will behave. The libraries have tons of specs and stock systems for numerous engines. I have done two small blocks with combinations tested on these programs and can't complain about the results. Just a thought...

[Larry Allen]

Re: Okay, I'll bite.

Thanks for your response. The cam I put in is a Erson Viking 100H 1.5, it has .447 lift at intake and exhaust with 290 degrees of duration. Gross lift is .298 and duration of 224 degrees.

I can get about 4000rpm if I ease into the throttle and bring it up real slow. But if I try to use enough throttle to open the front 4 barrels it just "shoots ducks". It's not a real back fire but it breaks up badly. I have tried several things, plugs, wires, timing, etc. When I disconected the front carb it gets a little better but still breaks up. Could it be the dual-point distributor, I'm not sure what to do next really. It does idle very rough but I expected that, it really doesn't have any power at any rpm.

I don't have that much experience with car engines but I did build this one. I did build race engines for motorcycles (big 4 stroke, 4-cyl.) so I'm sure the engine is put together right. What do you think?

[Larry Allen]

Re: Okay, I'll bite.

Thanks for your response. The cam I put in is a Erson Viking 100H 1.5, it has .447 lift at intake and exhaust with 290 degrees of duration. Gross lift is .298 and duration of 224 degrees.

I can get about 4000rpm if I ease into the throttle and bring it up real slow. But if I try to use enough throttle to open the front 4 barrels it just "shoots ducks". It's not a real back fire but it breaks up badly. I have tried several things, plugs, wires, timing, etc. When I disconected the front carb it gets a little better but still breaks up. Could it be the dual-point distributor, I'm not sure what to do next really. It does idle very rough but I expected that, it really doesn't have any power at any rpm.

I don't have that much experience with car engines but I did build this one. I did build race engines for motorcycles (big 4 stroke, 4-cyl.) so I'm sure the engine is put together right. What do you think?

[Joe L.]

Re: Okay, I'll bite.

Larry----

Your cam specs are not that radical, at all. Your stock cylinder heads and exhaust system should easily be able to support that camshaft configuration. I think that you have some other problem, possibly fuel or ignition related.

[Joe L.]

Re: Okay, I'll bite.

Larry----

Your cam specs are not that radical, at all. Your stock cylinder heads and exhaust system should easily be able to support that camshaft configuration. I think that you have some other problem, possibly fuel or ignition related.