What is a 94, Heavy Duty 350 engine ?

I have 94 Chevy pickup, the engine is suppose to be a Heavy Duty 350. All I remember is that the horse power and/or torque was rated lower than the standard 350 engine.

At 275k miles, I now have a loud knock, perhaps spun a rod bearing? I plan on rebuilding the engine but looking at the rebuild kits, there is no sign of a kit for a Heavy Duty version.

How do I identify if the engine is the HD version or not?

What is different?

Are there any issues to address during the rebuild if this is the Heavy Duty version?

Thanks

Check your owners manual and compare it to the 8th digit of your VIN... they stopped giving as much information, but mine's still got it in there. On my '86 the std. engine is VIN L, HD version is M. The compression is about 1/2 a number lower... don't remember exactly what maybe 9:1 for std, 8.5:1 for HD or something like that. The HD also has 4-bolt main bearing caps. I'm pretty sure the torque is higher on the HD. The rebuild kit is probably the same for both, but check with your local parts professional

I didn't think about the VIN showing the version of engine! Thanks for the info. I didn't remember the compression ratio being lower but I do remember the 4 bolt main, now that you reminded me. I think that was the main selling point to me in 94.

Look for 4 bolt mains and heavy duty valves and valve springs and rotor caps and heads.

Rings and bearings may be the same for both in a rebuilt kit.
If you are rebuilding go all of the way down and replace cam bearings to.

I hate to sound stupid, heavy duty rotor caps? Are these part of the rocker arm assembly?

I saw a cam bearing puller/installation tool. Is this a must have, nice to have or just a scam ?

They also sell a oil pump primer tool. Can I just use a screwdriver or drill or is this needed?

Thanks

I hate to sound stupid, heavy duty rotor caps? Are these part of the rocker arm assembly?

I saw a cam bearing puller/installation tool. Is this a must have, nice to have or just a scam ?

They also sell a oil pump primer tool. Can I just use a screwdriver or drill or is this needed?

Thanks

I'm thinking the rotator caps on the exhaust valves, the spring retainers which rotate the valve.

The cam bearing installation tool is no scam; it's an absolute necessity if you plan on replacing the bearings yourself.

The primer tool is also a must, if you value your oil pump driveshaft (a screwdriver shank chucked into a drill can slip, shearing off one of the tangs on the shaft).