Major engine problems

[BADAZ chevy guy]

I found a 80-85 350 truck engine in the wrecking yard last month. It HAD good compression all around 160-165 on all 8 cylinders. I installed a Summit Racing SUM-1102 camshaft kit and did a 30 minute break in @1800 to 2200 RPM. Intake manifold is an Edelbrock 2101 with a stock Quadrajet from a 1984 to match up with a 700R4.

From the first test drive the engine has no real power from a standing start and just moderate power above 20 MPH. Then loses all the power at anything close to top end.

Then yesterday I busted a heater hose and overheated the engine quite badly. Now I'm doing a new compression test and I'm getting 115-120 on all 8 cylinders.

Questions:
1. What would cause the initial low power? (Checked the cam gear timing marks, Distributor is NEW and dropped in the right spot, Carb is a Reman from Carb from National in Florida and worked fine on the old engine. Lots of power.
2. Why did I drop compression on all 8? I could understand 2 cylinders lost because of a head gasket or cracked head, but ALL 8? Tested with two different gauges.

Any thought? ANYONE!!!

[wildwilly4x4]

camshaft difference could cause the compression readings to be different. That may also be why you have no power. Torque convertor, carb, engine static compression all need to match with the cam for it to work right. Just tossing a big cam into a stock motor without matching a looser convertor, deeper rear end gears, etc. is asking for poor performance. Also some cams seem to work better on the low end buy advancing them a few degrees.

[Shady Rascal]

Back when I was a young mechanic the old guys in the shop would say that badly overheating an engine would cause the rings to lose tension and collapse, leading to heavy oil burning.

I thought it was an old wives tale until I saw it happen repeatedly over the years. The overheating causes the rings to collapse and they don't press against the cylinder walls as well as they did before overheating.

It's okay if you think I've become one of those old mechanics who tell wive's tales. But, it's something to think about.

[BADAZ chevy guy]

Originally Posted by wildwilly4x4

camshaft difference could cause the compression readings to be different. That may also be why you have no power. Torque convertor, carb, engine static compression all need to match with the cam for it to work right. Just tossing a big cam into a stock motor without matching a looser convertor, deeper rear end gears, etc. is asking for poor performance. Also some cams seem to work better on the low end buy advancing them a few degrees.

SUM-1102 is just one step above a stock camshaft. It's the cam Summit Racing recommend if using a stock stall convertor and an Edelbrock 2102 manifold. It has a power curve from 1,500 to 4,000 RPM I don't think the cam choice is the problem.

[wildwilly4x4]

Not too sure then... sounds like you may have some work in for you then. All else working good, it had to have been low on power due to a fuel or timing issue. Good luck with it!

[Desert1957]

This is a quote from summit about your camshaft.

"Camshaft Manufacturers Description: Smooth idle, low -midrange torque, towing in 350 c.i.d. engines. Works with stock converter and lower compression."

I would recheck the timing, cams like this need more initial timing and a quicker curve in the distributor.

I worked on a truck that had this cam with a 2.73 rear ratio, it was a dog until the rear was changed to 3:73's. this cam will lose a lil bit of "offidle" performance.

Desert

[wildwilly4x4]

Just a thought..... Are you positive your valves arent too tight?? If the lifters werent primed all the way when you set your valve lash your valves could be running just a bit open causing the poor performance and overheating you mentioned. Something maybe worth checking..

[Nick_R_23]

Originally Posted by Shady Rascal

Back when I was a young mechanic the old guys in the shop would say that badly overheating an engine would cause the rings to lose tension and collapse, leading to heavy oil burning.

This is likely your issue. Overheating can definitely damage your rings, as well as other parts inside the engine if it got hot enough. Your OP is pretty vague, though, what defines "overheated badly? 220* is hot but likely won't cause any damage, now if you hit something like 280*+, better start yanking the motor.

Also, what are you comparing "no real power" to? It's an 80s smogger engine being installed into a 4-5000lb truck. It won't put you back into the seat. Does it bog through the bottom end and come alive up top? Or lack power all around?

[JrRacer]

I would check your valve lash as wildwilly suggested. May be too tight.

[SkinnyG]

And double check that the cam timing is correct. It could be out a tooth.

['76 Big Block]

Pardon me for asking, but are you sure the engine is a 350 and not a 305---the two are similar in out ward appearance, so if you didn't measure bore, it's someone else saying that (since you stated the engine was '80-'85).
The other possibility is that your valve springs may be too weak for the cam. Years ago, I tried to poor boy a cam swap using a comp cams "Magnum 280" cam----off idle it was a dog, and at about 55 mph, power dropped off to nothing because of valve float. I ended up pulling heads and replacing springs (as was recommended by Comp Cams in the first place---live and leardn!)
Good luck with your truck!

[ryanv70c10]

What was your ignition timing set at?