I just bought a 350 from a friend of the family ( i know that the motor and heads are sound). He had this in a 77-79 (im not sure) GMC work truck with low miles. What i wanted to know was if these heads are garbage or not. Should i waste my time and money getting them magnafluxed and then a valve job? Can they handle mild performance modifications or would i be better off buying the L31 vortechs?
Thanks,
-Bob

 

If you don't know what motor it actually is, just knowing what kind of sheet metal this person last had wrapped around it won't tell you much about what parts it's built out of.

If it's a stock 77-79 truck motor, then the heads are trash; as is every other piece except for the block, crank, and rods. You'd be better off with the Vortec heads (AFAIK Vortech doesn't make heads, only blowers). I would not spend a dime on late 70s truck heads, except that I've had to pay in times past to get somebody to come out and haul them off when too many of them accumulated around me.

Best thing to do would be to get the casting number off of them and post that, it will tell exactly what they are, and then you can make an informed decision.

 

Sorry, my mistake Vortec. So these heads are garbage, ok thank you.
-Bob

 

you might as well check the casting number on the heads, what if they're not original?

 

Yup, get the casting #; especially if you don't know for sure that ithe motor actually came in that vehicle originally (different from "he had it in a ....") or that they haven't been changed somewhere along the line.

 

Write down the casting numbers; you can do it for heads as well as for the engine, and check them at this link:

www.mortec.com/castnum.htm

Hope that helps,

 

Although, that list doesn't always tell you whether a head is "good" or not. It will at least tell you what years and motors it might have come from. There are lots of people here who have spent many years researching the finer points of which heads are good to use for what kind of motor, which ones aren't good for anything at all, etc., and most important, why.

 

If the last three digits are 881 or 882, toss them... they aren't worth their weight in water.

From what I hear, RB has trouble even paying people to take them off his property!

 

OK, so I was searching and found this old thread... I just got my car for free and the engine (he told me it was a 350) has 881 heads I am pretty sure, I think they were 888888881 or something to that nature. He told me the engine has less then 10,000 miles on its rebuild. What is so bad with these heads, should I get new ones??

 

They are thin casting, crack prone, typically have 1.72 and 1.50 valves in a truck, don't flow very well from large ports, also have a huge and compression reducing 76cc chamber.

If it were me I would beg, borrow, buy a set of 601 casting 305 heads (52 cc chambers, 1.84" & 1.50" valves, decent port flow and velocity, smallish ports) , port them, do a 3 angle valve job and bolt them onto that 350. Then I would invest in a good cam kit, such as the comp Xtreme 256 or 262. That would bring the power from like 180 HP/ 270 ft/lbs up to about 300 HP/ 370 ft/lbs with headers and in a good tune. In the process you would bring the compression from a sick 7.8-8:1 up to about 9.5-10:1, which will increase fuel mileage, HP, and TQ. A stock L05 TBI 350 shortblock with these heads and a mellings MTC1 cam made 255 RWHP for me.
I did however have an issue with the 10.3:1 compression in a 5,300 lbs Full Size Van, towing a 3,500 lbs trailer in hot weather. I killed a piston due to detonation(too lean, too much timing, not enough octane, HEAVILY LOADED, constant load, etc). In a lighter F-Body, I don't see this being a problem.