74 Heads on 70 Block

Are 74 heads plug and play on a 70 block?

Thanks

 

No! leaks coolant. 70 block doesn't have the correct support to seal scallops in the 74 heads

 

Is there a work around?

 

Drill and tap holes and plug them . then they may need to be ground flat depending on surface clearance to block.

 

I'm having a hard time finding pictures of the bottom of 74 heads.

Can someone do me a favor and post a pic if possible?

Thanks

 

Ok...found some...I think. So are these the holes that need to be plugged??

 

Yes those are the holes that the 70 block can not seal.

 

Thanks....what about performance wise. The pair I'm considering purchasing have larger valves...but I'm concerned about compression.

 

Won't change compression. All are 58 cc. No advantage to getting different year heads.

 

Or in my case...disadvantage. I'm replacing a cracked head. Thanks for the info...I'm more at ease now!

 

All the years heads are supposed to be the same 58 cc chamber size... This does vary 2-3 cc though.

I have sets of 68,72,73, and 74, and 76 heads and I am going to flow test them all to determine which years flow the best. Until then we have no proof of which years are better for performance however I think we will find that the 68-70 heads flow the best. I will post the results once I get them.

 

Great info! Thanks.