Small Block? or Big Block? ???

[JUSBLAZ]

I have seen threads with people asking what the difference would be between having a SB vs BB , but that's not my question.

My question is what changes or modification do I have to do to install a BB. My concern is that my truck is already at the body shop, and don't want to screw things up once I get it back.

Any thoughts?

[1969k10stepside]

Some have problems with the distributor hitting the firewall,others have problems with the valve covers hitting the firewal.Some modify the firewall slightly to allow clearance,others move all the drivetrain related crossmembers(Motor crossmember and t case crossmember) forward between 1"-3" to allow room.Others install a body lift to get off easy,and then there is some that dont have any probelms mounting a bbc in their vehicle.*This is assuming your Blazer/Jimmy is a 4x4,if its a 2 wheel drive,you wont have to do what I stated above to allow clearance as there should be no issues.

[JUSBLAZ]

So there is no way of knowing prior to installing the motor?

[1969k10stepside]

Not really,you wont know till you test fit it.I guess if you know what causes the problems and you have parts that wont effect clearance there wont be any problems.Some have trouble with the valve covers,well..if you have the low valve covers you might not have clearance issues.The best thing to do would be to test fit it first

[Yukon Jack]

I did lots of research and thought I would be fine with a 2" body lift and stupidly sent my K20 to the body shop without test fitting the bbc I was putting in it. I ended up having major firewall issues that required cutting out pockets for head clearance. I had no distributor clearance issues but I'm using a small cap MSD distributor.

The problem with moving the motor forward is you end up getting close to the radiator and you lose some driveshaft angle.

Burt4x4 used a 73-up engine crossmember and had minor firewall clearance issues. Now he is using a custom engine crossmember.

I read a post on another board where the person used some 1" spacers to drop the engine down. Sounds like a good approach to keep in mind.

You can check out my sig to see my problems with my bbc swap in my 69 K20. Once I get my K5 running I'm going to work on the K20 to get rid of most of the body lift. I think I will probably drop the engine 1" and cross my fingers that that will allow me to reduce my body lift to 2".

[JUSBLAZ]

Thanks for the insight!

That bums me out I had my eye on GM's 502 crate

[Yukon Jack]

Don't give up the idea, just know it might not just slide in. If I were to do it over, I would have test fit the motor and probably moved it forward a bit to get it to fit. Just couldn't do that easily while it was at the body shop and all torn up.