400 S/B steam ports

[Grease]

 

I need to replace my heads . I want to know how to drill the steam ports . I am thinking about using a set of mid 90s heads from TBI engine for the smaller combustion chamber size .

I have tired internet searching and didnt find much . One article said 1/8 holes ,one straight in and one at 45 degree angle . It did say which side was which . Another article said the angled hole was drilled at 30 degree angle .

Can ya'll direct me to some good info ?

 

thanks

[monte70car]

Not sure Mike I'm on the hunt for a s/b intake

[Winston Wolf]

Steam holes are recommended for all 400 block applications. Use a 400

gasket as a template and drill the three holes nearest the spark plug side of the head straight down, the other three which are very near the head bolt holes should be drilled at a 30 degree angle away from the bolt hole. The center hole will intersect water about 1" down and the two outboard holes to a depth of 2 1/4". Use a 1/8 drill.

 

 

I would recommend you take it to a cylinder head repair shop or a machine shop. They charge between 40 and 100 bucks to do it. You will need to use a drill press and jig them up somehow if you don't take it in. A couple of those holes are pretty deep and it you break off a drill bit, you'r f'd. Cast iron drills pretty tough by hand, not sure if thats what you have or aluminium?

[Grease]

thank you for the information Winston . It will be cast iron heads . Looking at the head casting onfo I can find I'd gain the most compression by using a set of 305 heads though it would cut back the intake size just a bit . I think I would rather have the compression raised . PO has put dish tops in this 400

I was able to turn up a bad 400 head core to look at as well. again Thanks

[Mike 57]

I think that the compression increase with the 305 heads will be offset by the really bad ports. Port work may help but that costs bucks and never flow like a vortec. There is also a large combustion chamber mismatch that shrouds he valves so larger valves are not much of a help. The 305 heads will give you a big jump in compression maybe too much, there is probably a 18 cc difference. Are they the stock dish pistons?

[Winston Wolf]

I was going to mention the same thing. If they are a stock type flat top, say 5cc dish with a 58cc chamber, .040 gasket and the pistons are .020 down, that's 11.75:1+ right there with a crap head to begin with. Will probably have no power and ping like a bicycle with a pop can hitting the spokes.

 

If your on a tight budget, maybe trade the 305 heads for some bigger ones at the junk yard or find some old used 400 ones...

[Mike 57]

That is the ping I was thinking about but did not want to say

[Grease]

Thanks for the thoughts guys . Winston ,I did build a fixture to hold the heads and have completed the drilling now . So i have plenty to keep busy with now . Hoping to have it running in time for the NMCOA meet in Old Town FL (Nov 6) Now back to your regular programming .