Porting 455 70 Iron Heads

Is it worth porting and polishing heads and intake on a Buick 455 with a small cam? It's mainly a street car, I need to rebuild the engine and I figured while it was out for machine work why not.

This is for a 70 Electra

 

A new cam with with more exhaust lift/duration that intake would probably net you more power for the effort involved. Are you looking for more bottom end, say the TA-112? Are you using the stock converter?

You could smooth down any casting lines and open the valve throat a touch pretty easily. A good 3-angle valve job, shaving the heads .010-.020" and decking the block if you don't bore it to raise the compression will help. Even a 70 with 10:1CR was more like 9.25:1CR in reality.

 

If you’re rebuilding the heads then.
1) you should go with new valves.

2) if you go with new valves and since the heads are going to need a valve job done anyway then you might as well step up to bigger valves.

Then some easy porting work will pay off a lot, not that porting work with stock valve sizes will not help, it will.
It’s not the throat that is the restriction in the stock heads, it’s the massive valve guide .

enlarging the throat correctly is difficult to do on the intake side without the aid of a flow bench.

3) bigger valves will also increase the compression, where as a valve job done with stock valves will sink then and drop your compression unless you mill the heads at least .015”.

If you need guide work and new valves then you might as well go down from the stock 3/8” stem size to 11/32” stems and pick up a few CFM just from that besides easing the load on the valve springs due to less weight.

a proper 3 angle valve job a long with bigger valves and bowl work provides a large flow gain up to .450” lift, flow gains for a motor like your above .500” or higher are useless in a motor like yours.

If you will port the heads then PM me and I can guide you.

here’s the stock intake flow numbers for a 1237661 head casting and in the second column the flow for a bowl port job.
Third column is the flow gain .

If running a can of .450” lift this flow gain should produce a 3 to 4 hp gain per cylinder.

.050”———30.4—— 31.7 + 1.3

.100”——-60.8——62.7. +1.8

.200”——-123.6——128.7. +6.1

.300”——-177.6——181. +3.4

.400”——-209.3——-212.7. +3.4


.450”——-216.2——221.9. +5.7

.500”——-218.5——- same

.550”——-219.6——-224.9. + 5.3

 

Thanks all, Yeah I planned to do a Stage 1 conversion with bigger valves and running a TA 284-88H cam. It also has a Edelbrock Performer intake and I plan on running a Holley sniper and hyper spark system. I do plan on having a professional do it and have them do the oiling mods as well.

I want to do all the planning, bench racing and parts sourcing before I take it to the rebuilder.

 

Besides the larger valves, make sure the conversion includes machining the chambers to unshroud the larger valves. Not machining the chambers nullifies any advantage the big valves may have had.



Devon

 

I can't find the oil mods guide that used to be on here.

Anyone know where it's at?

 

https://www.v8buick.com/index.php?t...id-prep-and-oiling-mods-with-pictures.352231/

https://www.v8buick.com/index.php?threads/400-430-455-block-id-prep-and-oiling-mods.214613/

Pinned near the top of the Street/Strip 400/430/455 forum.

Devon

 

I cleaned up and port matched the heads to the manifolds a million years ago, at home using a couple of weeks of evenings, before the kids were born. Time consuming work. Did not touch the chambers because I decided didn't want to reduce the compression, even a little. The downside to not polishing chambers is that I'll get detonation prone hot spots on really hot days. I countered that problem by installing an MSD timing controller so I can reduce advance from the driver's seat.