I've been tossing around the idea of putting a different Olds engine in my 83 H/O. I think I've seen this question before but can't find it in the forum. I'm thinking a 350 or a 403 will be a easy drop in due to the same outside measurements. What other sizes will work with little to no interference problems. Thinking the 425 or 455 will be to tall. Just checking to see what the possibilities are. Would have to be more horsepower that the 180 horse thats in it to justify the project. Thanks Larry

 

IMO, the 403 is the first choice, the the 350 Olds then the 330 Olds.
Simple install.
A set of shorty headers, alum intake, mild cam, you have a very impressive ride.

Gene

 

If you want a big block olds, just google "big block olds g body swap".

 

Either engine will fit in the Gbody. Granted with the BBO and choice of intake, its harder to keep everything under a flat hood.

 

On or off the computer? That is the 1st question you need to ask yourself.

 

If you can find a good running 403 with stock style pistons, add early heads, mild cam and headers as said. That combo will work on the computer but the cam duration needs to stay around 215 max and a 112 lsa. I had good luck with Sanderson shorty headers but Hedman shorties also fit and have 1 3/4" tubes vs 1 5/8". Just get a custom y pipe bent in decent diameter and replace or eliminate the cat or go true dual. That is how the exhaust should have been done from the factory, Olds had that exhaust on the 1985 FE3X prototype and it was worth 30 horse power with a functioning hood scoop. The factory crossover is just awful but no doubt kept the GM bean counters happy. I would also add something like the big Trans Go shift kit in your 2004R along with a filter service. Also add a girdle cover and maybe new spiders in your 7.5" rear.

 

All the computer stuff has already been removed by a previous owner. It is already set up with true duals hooked up to the stock manifolds. Beings the value has already been messed with by the removal of the computer and I'm also having trouble getting it tuned right this might be the best option by installing a non computer older engine and give it some more go power. If I go with the right engine might also bring the value up some. This is a very nice no rust 57,000 mile 83 H/O

 

The 307 lead the 5L V8's for power in 83 but this is 2015. Run mid 9's compression and a cam to match in a 403 and it will be night and day.