chevy 350/290 crate engine

[Jonny B]

Fitted this motor on my 1974 c1500 longbed,mated to a stock th350 and torque converter.
Not sure of rear gearing but feels high 273 or 308 ,31" tires.
Engines run in now,but she has no low end power and needs revs and cam to kick in ,then she goes strong.I cant find cam rpm range specs to pick a new converter with higher stall,been told to choose converter with 500 rpm over bottom rpm range number of cam.If anyone has this motor or can help on which converter i should use then youre advice would be great help

 

[cstew47]

Fitted this motor on my 1974 c1500 longbed,mated to a stock th350 and torque converter.
Not sure of rear gearing but feels high 273 or 308 ,31" tires.
Engines run in now,but she has no low end power and needs revs and cam to kick in ,then she goes strong.I cant find cam rpm range specs to pick a new converter with higher stall,been told to choose converter with 500 rpm over bottom rpm range number of cam.If anyone has this motor or can help on which converter i should use then youre advice would be great help

290hp isn't much, but, you may see better results by lowering the gear ratio. a 2.73 or 3.08 with 31" tires must really be slow accelerating. A 3.73 would make a world of difference. Much lower would probably not be good on the highway with a TH350. An overdrive tranny would be great. When I put 4.56 gears on my K5 with 35" tires, I could really feel the grunt.

 

[BKING33]

I second the gear ratio. Any truck I had with 308 or 273 was a dog off the line. That was always the 1st improvement I would do.
3.42 or 373 are the best ratios for a 31" tire.

 

[75gmck25]

Years ago I bought one of these engines. 222/222 @ .050 cam and about 8.2 compression smog cylinder heads. Not a good combination for a truck.

I found it much better when I swapped to a summit 1101 cam and set base the timing to about 15 degrees BTDC. However, I also have 4.10 gears.

The 1101 cam will drop about 40-50 horsepower off the 290, but at the same time move the torque curve down to an RPM where it’s more useful in a truck with stock torque converter and relatively high gearing

if you want 300+ hp out of you’re 350, the first purchase should be better flowing heads with 64cc chambers. The next purchases would be a moderate lift cam (up to about 218 @ .050 duration), a good dual plane intake, and headers. A high stall torque converter should also be on the list if you want good power off the line.

 

[rich weyand]

Read this thread: Crate Engine help!!!! | GM Square Body - 1973 - 1987 GM Truck Forum

 

[RobertWichert]

My 330 HP "Base 350" Chevy crate motor was terrible with an AVS2 carb and MSD distributor until I switched the vacuum advance from "ported" vacuum to manifold vacuum (driver's side port). BIG difference.

 

[AKguy]

This is from the factory sheet for part number 19172591, 350/290 long block. No mention of effective RPM range:

Camshaft:
The 350/290 HP engine uses an aggressive flat tappet camshaft to achieve the level of performance for its intended usage. Camshaft lift is .450" intake / .460" exhaust. Camshaft duration (@.050") is 222 degrees intake and exhaust. Lobe centerline is 114 degrees. Normal engine manifold vacuum for the 350/290 HP engine is 10-12" Hg at idle (650-750 rpm).

 

[Rusty Nail]

Sounds like a L79 / L82 camshaft.

*a hush falls over the crowd*
Shhhhhh!

they like pushin manifold vacuum here....

hay look! It's @rich weyand ! exactly on cue!

 

[Raider L]

@Jonny B,

TCI makes what they call the "Saturday Night Special". It's 400-500 rpm over stock torque converter, non-lockup. I works out to about 1800-2000 rpm stall 12" converter and I believe you would really like it. It's for mild to moderate performance 350 engines with a TH350 trans.

I had it in my truck and I loved it. It really allowed my performance 350 to get going fast off the line. It's made for quick acceleration.

 

[75gmck25]

GM definitely used one of their old 222/222 @ .050 cams in this engine.

Back to the OP’s question.
The Comp Cams Factory Muscle grind 151H or part number 12-106-3 is a reproduction of this cam.
They list the RPM range as 1000-5800, but I think you would need more compression to get it working at that low rpm.

As a quick fix, try bumping up base timing to about 16 BTDC and using a new advance weights set to get 18-20 degrees more by about 2000 rpm. It won’t be the final cure, but it will help with low end until you are able to get a torque converter or lower gears. It should still be fine on 87 octane gas, since the compression ratio is so low, but listen for pinging.

 

[Jonny B]

Lots of great help,thanks.I will change the converter and reset timing til it runs like i want it.I know it isnt a big powerful motor and heads are poor and cam is bad choice but its all i could afford,not much choice in UK.As it is this truck is a slug and no fun compared to my xj cherokee straight 6,ive had 6 sbc and this spec engine on a big heavy truck with high gears is a poor choice.

 

[75gmck25]

I replaced the 222/222 @ .050 cam with the Summit 1101 cam (194/204 @ .050) and it improved low speed torque quite a bit. I probably could have gone up a little more with duration (maybe the Summit 1102 at 204/214), but decided to stay conservative.