Okay, today we began putting the cam in my 1971 350 for my trans am. Assumed the motor was just a basic low performance 350/270 horse with 8.5:1 compression. Had the valve covers off, decided to compare them with some circa-1980 350 heads I have at my house. The heads on the 71 look like they were ported compared to them and looked liked they flowed pretty darn good. This motor is out of a 1971 full size blazer and came with a 4 barrel quadrajet. Decided for kicks and giggles to run the head numbers. Well, the number is: 3973487. Ran this at Mortec, says they are 1971-72 LT1 heads. If there is an X after them they are normal lo-po heads. There is no X. Motor's Id code is V0210TBG. It is a 4 bolt main. What motor is this? Is it possible they put LT1's in blazers back then? Motor has a quadrajet and a stock cast iron manifold. But apparently they added quadrajets and got rid of the hi-po manifold in 71. Any info you guys can provide me would be appreciated.

 

Hmmn, 'X" on the heads used to mean larger port volumne, not sure in your case.

I don't think GM put LT-1 engines in Blazers...you need to realize that the vehicle is 30+ years old, and could easily have had the engine swapped at anytime.

 

I've built several engines with the 487 (and a couple 487x) heads.

Just your basic 76cc smog heads from the early to mid 1970s. All I've seen were on 4-barrel cars. Decent for a mild engine but nothing great.

I've found the same casting #s on Impalas, Chevelles, and trucks but I have never seen one on a 'Vette.

Of course, I haven't messed with more than a handful of early '70s 'Vettes.

jms

 

only ones that got the old lt1s were Z28s and Corvettes. Almost all old picups got the 4 bolt blocks though. 4 bolt block does NOT mean lt1. Not positive, but if memory serves me right the lt1s had the 462 casting. I think they were only made in late 69 and 70. after that compression was cut and so was the lt1. Boy that was along time ago. I think they ran something like 11.0 compression ratio in the lt1s. Solid lifter cam, 370 HP 380#ft of torque.

 

Whay just struck me as abnormal is that the head numbers were supposed to be LT1's. They continued the LT1 after 1970, it just had the compression dropped and lost a holley carb. It just struck me as strange that the blazer would have LT1 heads. Oh well, even if they aren't LT1's, they look great compared to the late model heads I have. Motor is still going in the trans am though.

 

Well I guess you can call them anything you want. I know when the compression droped from 11.00 to 9.00, they weren't called lt1s anymore. That happened in 1971. The valve lash for the lt1s were I .024 E.025 while the 350 hipo was I.024 E.030 for 1970. For 1969 lash was .030/.030 , same as the z car.