After searching the message board, I found a company that makes port plates (which reduces the port sizes) for the 351C 4V heads. So I figure that a closed chamber 4V heads combined with the port plates may make a nice combo for the 400 short block. What I'm wondering is if the headers that I have for the 400 will bolt up to the 351C 4V heads. If not, what other choices do I have?
you mean the thin platest - not the thick kind where you cut off the whole exhaust side of the head, right?
the headers will bolt up, but the header tubes will be smaller than the ports if you get headers made for 2v heads. i have the 4v heads, exhaust plates, and 1-7/8" headers. the plates match the heads pretty closely, and of course they close off the bottom part of the exh port in the head. but the header tubes are just barely big enough to match the plates on the tops & sides. looks like they could use some work with a dremel to match better. there WILL be a "step" at the edge of the plates, on the bottom of the runner. in other words, the plates do NOT make the 4v ports into 2v ports. the port shape and exit location are still different, even though they may be close to the same size.
has anybody dyno tested these plates on a 400 or larger motor?
Well on the motor I ran last year I had a set of 1969 Boss 302 Heads with the really big valves in them 2.250 int. 1.820 Exh. That motor ran really good an put out 658 H.P.
Now this Year I built my new Motor with a set of Boss 351C heads with the Exhaust port plates put on them with lots of porting done to them. These plates are the ones where they mill the heads and attach the plates that raise the ports 1" and really help them to breath.
As for what kinda headers do I use on ShaZam I built my own 2" Primary 37" equal lenght 3" collector wheelwell exit headers.
I started with a weld up kit from Stahl headers for the Big Block Chevy and they sent the flange plates for the 351C 4V Heads.Welded 2" stubs onto the flange plates and then started to hand fit the rest of the pieces together.
2v headers on 4v heads are going to give you reversion problems with the exhaust flow. Also 4v "quench" heads are (I believe) going to give you too much compression for street gas. Depends on what you want to do with it and how much modification you want to do.
You also need a four barrel intake (adapter plates) or you will get even worse problems on the intake side. Like maybe the intake wont even cover the head ports.
[updated:LAST EDITED ON 06-Feb-02 AT 06:44 PM (EST)]Yeah, if you use the 400 2bbl intake on a 400 motor with 4v heads, you need to weld extra metal around the runners and have the intake mating surfaces milled flat afterwards.