I'm fairly new to SBC being originally from the UK where gas is wayyy to expensive, so please bear with me.

I'm not new to engines, just V8's!

Ive been given a late model (1989) SBC in good working order.
Plan is to rebuild it as a replacement for my leaky SBC thats sat in my 84 Blazer.

After the teardown the short engine is in perfect order but one of the heads is cracked.

Do I have to hunt down late model heads or can I use ones from an earlier SBC?

I know 'something' changed in 1987 as regards the SBC but I struggle to find a definative answer, even on the Net.

Suggestions on reliable mods during the rebuild would also be most appreciated.

Thanks in advance.

Two major things happened in 87 for the SBC heads. The heads were redesigned to take different valve covers, and the center two intake bolts on each side were drilled at a different angle. This makes intakes from earlier engines hard to use unless they can be modified. Many early intakes are just slotted and used with an angled washer to bolt on later heads.

The other modification was the one piece rear main seal on the block. This requires a different flywheel and block related parts. Many blocks were also cast and partially machined for roller cam setups. These cam and roller lifter blocks became more common in the ninties.

So if I use early heads I can use early intakes and with the earlier valve covers?

I had a set of 400 SBC heads given to me and wondered if they would be suitable.

I know one difference is the steam holes but thought maybe they would need some machining as presumably they have bigger combustion chambers due to the larger displacement.

Would it be a better bet to buy a 383 stroker crank for the 400 heads or stick with the 350 displacement and buy/find some better heads?

I'm hoping to use TPI btw.

The 400 heads would be preferred over the TBI style heads. You more than likely have 193 castings on your 89 model 350. These heads are very crack prone on the center two exhaust seats, cracking into the heat risers. The 89 model heads are 64 CC combustion chambers, but have very restrictive swirl intake ports, making them a poor performance choice.

On a budget, I would work the 400 heads over, treating them to a pocket port, a flat mill and deck the block to gain a little compression. You could put a small knuckle on the piston to try and achieve around 9.5:1 compression.

Common 400 head casting numbers can be found at www.mortec.com, 493s were common. The early 400 heads are good, heavy duty castings, and offer large ports, and can be made to flow some decent numbers. Just use the 350 gaslet to block the steam holes.

A good alternative would be opting for the World S/R 67 CC heads or Dart Iron Eagle SS head.