I have a 91 RS that i thought had a 305 TBI (LO3). Only had it for a few months and when I finally got to doing some serious work I realized its not the original engine. A friend checked it out and told me that it is a GM 350 truck motor, with all the original 305 accessories, even the TBI unit and harmonic Balancer and timing cover.

I have no idea where to begin, but I want to figure out what engine I have and hopefully what year it is. I would also like to get an idea what the hp and torque output of this engine should be. Can anybody help me?

 

check the top of the block behind the driver side cylinder head. it will show the size of the engine in liters and will have a block number on it, get the block number and cross reference it with this website:

http://www.mortec.com/castnum.htm


how did your friend find out that its a 350 motor out of a truck? i can't tell the difference between a 305 and 350 without the block numbers or removing the cylinder head.

 

I'll check that out first thing tommorrow. Is there a way to figure out what year truck it came out of. Mortec just gives hte year ranges. I'm curious how old it is.

My friend got under it and found the casting number I think. Long story, but I wasn't there. I dorpped my car off with an accquaintance realy to let him troubleshoot some electrical issues. He was real busy and he called somebody to check on the numbers. They told him it was a 350 truck motor but he didn't get me anmore details and he didn't write the numbers down. Said he had to get under it and look at them with an inspection mirror. Took his phone down there with him.

And now that we sorted out some timing issues among other things the car actually feels like it has a 350 in it.

This was all just yesterday after work, and I have just started looking into it, but as my friend explained, the engine in my car has an incorrect timing cover on it, I presume from the 305. The timing marks are in a different position, so when I hadn't been able to get teh car to run to its potential previously. It is much stronger now.

 

Get the suffix number code off the block. It's stamped into a pad in front of the passenger side head. That will tell you a lot more than a casting number. Casting numbers are only good if you need to know if it might be a 305 or 350 block because they use different sized bores.

 

I gave a quick glance in front of the passenger side head. haven't looked real hard yet but didn't see it. Should I be looking on the horizontal surface or the vertical surface? I guess it might help if I cleaned that area some. All the accessories don't help visibility either.

thanks

 

if im not mistaken, i don't think you can see the code with all the accessories bolted up. but if you can, its in front of the passenger side head parallel with the head mating surface, just above where the water pump bolts too.

 

check the harmonic balancer, the 350 has a rubber part, seperating the inner from the outer, 305 balancer dont have that

 

oh yes they do.... there is no difference between a 305 harmonic balancer and a 350s

 

ok...I keep getting conflicting answers from people on and off this board about whether the balancers are the same. One guy told me that its extrememly important that I get a 250 balancer on it immediately before the engine is damaged by vibration. And in fact my car does have a lot of vibration despite running fairly quietly. When I am in park or in gear with my foot on the brake tanding still I get a hum that kind of vibrates through the whole car. maybe it is the balancer.

 

i dont see a need to have different balancers from 350 or 305, its the same crank, only difference is the size of piston. 4" = 350 3.75"(i think) = 305

 

I know the 350 crank is much heavier than the 305 crank but everything else is the same

 

iv all ways known the 305 and 350 to be the exact same motor with exception of the piston size and water jacket

 

the 305 and 350 crank are the same only weight diff may be do to balancing there for the balancers are THE SAME ... anyone says different is driving a ford!

 

I believe that I have read that the only different harmonic balancer for SBC is on the 400. The others are the same.