Ok, have a 350 block that came from a 77 monte carlo. I want to bore it to 355 and put it in place of the 305 in my 91. Is it possible to do this and stay street legal (sniffer test) and use all my original emissions equipment and knock sensor. I'm aware of ecm issues and plan on getting a custom prom burnt.

 

Emissions: Yes
Knock Sensor: No, has to be for a 350
ESC/EST Module: See knock sensor

Search a little, youll find the answers

 

what tranny are you using?

the old 77's use a 2 peice rear main seal and the 86 and up use a 1 peice

 

stock tranny, 700r4, it'll bolt up fine, that's already been researched.

the reason i asked about the knock sensor is because the block is out of a 77 that didn't have a knock sensor at all.

 

The point is the '91 flexplate won't bolt to the '77 crank. You need a 153-tooth flexplate for 2-piece rear main seal such as used in '82-'85 3rd gen V8's.

With proper PROM tuning (I wouldn't recommend a "custom" chip - it may be close, but probably not), it should run fine and pass sniffer.

The LO3 exhaust will choke a 350. It chokes an LO3, for that matter.

Don't forget the dipstick on the '77 will be on the driver's side. Getting it to clear the exhaust manifold will be a chore. But, if you get headers to unchoke the exhaust, the dipstick tube will clear them, too.

 

You need to do more research.

Every Gen I small block Chevy starting in 1955 had the coolant jacket drain hole into which the knock sensor mounts.

 

I'm aware of the flexplate issues as well but didn't know the specifics you just gave so thx for that, I already have a set of new headers still in packaging so that dipstick issue should be ok too, and yes, custom prom tuning is what I meant. Thx for all your help everyone.

 

I was just looking thru summit's online catalog and they show 168 tooth flexplates for 2pc rear main seal. Can I use that, or do you think I should stick with getting the 153-tooth?

 

You'll need a different starter. It will be moved farther out from the engine center, which can cause problems with headers.