I have an 84 z28 with a 305. my dad and i were talkin about rebuilding his small block 400 and putting that in. I was wondering what all i could use off my 305 to use on the 400. also would i have to do anything in the engine compartment to make it fit? the 400 is out of a 70 impala. would it have all the holes to put the emissions sh*t on? thanks in advance.

 

Yes it has all the holes.

You can use all your accessories, including alt, power steering, AC, etc. You'll need to get the right flex plate; odds are, your car has the 12.8" one, but the 70 has a 14" one. You'll need a 12.8" with the 400 "unbalance".

I'd strongly suggest a set of chassis-specific headers, such as SLP or Edlebrock TES; BUT NOT FOR LG4, if that's what your car is. If your car is a LG4 car, it needs the whole exhaust from the heads to the street anyway, and there's no point whatsoever in spending money to get LG4 stuff which will merely preserve the bottleneck. Instead, get a whole system - headers, high-flow cat, and cat-back - for the L69 version.

You can re-use your 305 intake, carb, distributor, etc., as long as you're reasonable with the cam you put in the 400. Neither the 305 heads nor the 400 heads are suitable. You'll definitely want some others than those; unless you get really deep dish pistons and port the 305 ones and put bigger valves in them. The stock 305 intake isn't a great choice though; I'd suggest a ZZ4 take-off one.

 

There are a few issues to address.

The basics of the 305 will be the same as the 400. The carb and intake will do fine on the 400. Depending upon whether it's an LG4 or L69, the air cleaner would be one concern.

Figure on changing out all the exhaust. Headers and everything on back for '86-'90 TPI single cat application should be considered, especially if your 305 is an LG4.

400 heads stink. Don't even consider using them. Get some good factory 350 heads or aftermarket heads. Chamber size will need to be matched with piston type (flat top or dished) for proper compression ratio.

The 400 is externally balanced. You'll need to use the damper that came with it, no problem. But the flexplate is 168 tooth, and the starter typically gets in the way of 3rd gen headers. A ministarter is typically the work-around for that.

Otherwise, everything will mount up. It's a good swap.

 

(Should have figured RB would beat me to the punch...)

 

i have headmen shorty headers and headman y pipe that clear the 168 tooth starter if that what your looking for.just to get it running all you need is the 400 flexplate balancer,and starter.but like they said stock exhaust will choke the 400 up

 

Stock heads will choke up a 400 worse.

 

If you use a set of non 400 heads make sure you drill the six steam holes in each head. Very simple process, but important on a street engine.

Martin

 

in short
you can't use it.
sell it to me for $100