which block?

I about ready to start working on the motor of my 72 skylark. I have two engines available to me, a numbers matching 72 and 70. I was wondering if there were any reasons for using the 70 block over the 72. I know the compression is higher on the 70 but the 72 is numbers matching..

Any thoughts.

This is not going to be class 1 restoration, just a fun project.

JG

 

if I had the two here, I would save the numbers matching motor and build up the 70 high compression motor. If you ever want to go back to stock, numbers matching car...the motor will be there.

Mike

 

Thats exactly what I did with my 71,Building a race type motor out of a 70 and keeping the original motor in case I kill the other.Wanted that 10.25:1 compression motor.
Pat:laugh:

 

blocks

yea i would go with he 70 block too. what is the compression on a 71?

 

71 motors and 72 motors all have 8.5:1 compression The most hp is the 71 4bbl at 260 hp vs 315 hp in the SP code 70 350 engine.:TU:

 

hrm

well then im confused because when i bought ths car the previous owner said its the origional engine but on the acctual engine it says it need 91 octane or higher. now thats higher then 8.5 and its a 71 skylark 350:af:

 

71 COMPRESSION NUMBERS

These numbers are all that I found for these engines.My sources were the 71 Chassis manual and the Guide to BUICK GRAN SPORTS by Steven Dove.I also thought at 1 time the 71 engines were 9.0:1 but several books convinced me differently.These include the engine code TB,TD 4 BBL MOTORS and theTC,TO 2BBL MOTORS.At least its not a 73 motor,they have 8.3:1 in all the motors even the 455.
PAT
:TU:

 

heh

heh ouch, but since my engine need 91 oct or higher that would mean its higher compression then 8.5 would it not? cause if so then im pissed at the prev owner but happy for the power increase.

 

With the two blocks I have there is only a half point difference in compression. I think I could make that up by using a thinner head gasket.

As for the person who is using the 91 octane. Check the block under the number or around the number 1 spark plug (at least on the 72 block it is) there is a letter code. My code is WC which means its a 72 350 2bbl engine.

JG

man its cold up here today. the temperature dropped 20C in about 8 hours. I woke up this morning it was minus 28C. Spring is coming in a couple of weeks and i can't wait

 

ok

ok thanks. but does n t one know if ita for 70's 71's to because its cold outside and my car is being stored for winter and it would be a big waist if i went out there to find out nothing.thanks:beer

 

Hey Patrick to answer your question about the octain required for your 8.5/1 engine which you do have it's like this. In 1970 GM was told to meet the new standards for emissions and that ment lowering the C.R. for 71 on up models. They of course complied and and compression was dropped to 8.5/1 for both 71 and 72. Gas at the time of this change was redaly available at the pump in the form of 106 to 108 octain leaded fuel and regular for the time was around 100 to 101. Gm new the octain ratings would go down with the unleded fuels to high 80s or low 90s. In 1972 Unleded fuel rated at 91 octain was sold at the pump and this is what Buick put on the sticker under the hood. Over the next decade and well into the 80s the fuel octain rating for unleded gas continued to drop. As refining processes got better 91 to 92 octain became the highest octain needed for production vehicles being manufactured.