91' and 70' model blocks the same??

I have a 70' model sbc block.....will my accessory brackets off of the 91' fit on the older one (without drilling and tapping new bolt holes)?

yes, but your oil dipstick will be on the other side of the block...and your acc. bolt mainly into the heads not the block.

You will have to use a 2 piece rear seal flexplate/flywheel.

So I will have to drill and tap the head then?

how many accessory bracket bolts are there?

Will the 91' H2O pump work?

Only differences I know of are the rear seal design and the 91' would be a roller cam block.

if the heads don't have the accessory holes, you need new heads. I don't think most of those heads had enough material to safely drill the accessory holes.

As long as you're taking head differences into account, remember that the 87+ heads had the different bolt angle on the center 4 manifold bolts. The 87+ blocks also used roller cams, except in the trucks, but I think those blocks were still cast the same as the roller motors.

Originally posted by stockLT1
So I will have to drill and tap the head then?

how many accessory bracket bolts are there?

Will the 91' H2O pump work?

can you just use your heads from your 91, they will match your intake and everything else....also from mid 68 to current gen1 sbc the heads are machined with the correct bolt holes, but the exhaust manifolds from newer heads will not fit older heads :( I think they moved the first bolt hole out a little on the exhaust manifold. Headers are different story.


And the answer to your question...three bolt holes on the front of the heads

Cool, thanks for the info. I think I am going to use some double humps, but I'm not sure yet.

I have access to a milling machine, so the headers won't be a problem. I have a set of ceramic coated hooker shorty's for it.

Don't waste your time on double humps. Grab a set of new Votec heads. They cost a little over $400 and flow way better than double humps ever did.

Too bad that you also need to cough up another $400 for a new intake manifold.

New intake manifold?? for what?

I have a Weiand accelerator...I am going to run a set of 885 heads on it.

Accessories will fit, heads should have bolt holes or you have a weird stupid set of heads you shouldnt be using anyway, everything is interchangable except the lifters, crank and flex plate, if you use the 91 heads you need to use the 87&up intake, or modify the holes on the 86&down intake.

Cool....I have a set of 885 400 sbc heads for it.

I dont know if all the issues have been adressed here. First of all you are going from a roller block to a non roller block. With this exchange you will need to either purchase retro fit roller lifters for your roller cam or go solid,hydraulic flat tappet along with a new cam. If you go solid,hydraulic flat tappet you wil need to purchase new pushrods. Because the roller pushrods are shorter than non-roller. Also if you heads contain guide plates you will need chrome molly push rods. I wouldnt really worry about the manifold bolts as stated earlier because you can modify those middle bolts to fit the diffeerent angled head screws. Just drill them out and they wiil fit. I just went through this exchange with my camaro. And it can get costly but i think going from a two bolt main to a four bolt main is woth it. I dont really see alot of power loss from going roller to non roller as long as you have roller rockers. Good luck with the exchange.

Yeah, I knew that. Thanks for the input......I am going to run the flat tappet lifters and cam on it, I will also run 70' model heads and intake etc. Motor combo won't be an issue, only the accessory brackets.