Drilling Steam Holes for 400 Small Block Chevys in FloTek 102-505 Heads - Steam Hole Mod.

This is our way of modifying the wonderful FloTek 102-505 aluminum Small Block Chevy head for use on a 400 Small Block which requires steam holes.
I am SURE FloTek can provide this service if you contact them, as I rank their customer service A1+. I spoke with Stephanie and was told of I had ANY questions at all to just call and ask.
I had no problems (thank goodness) doing this mod on my back porch floor, although a drill press would have been the best way.
I have slinder fingers and could feel the "pads" and the support casting that is in between the cylinders and hit every one, adjusting the angle of the drill as needed for each hole. I started with 30* but ended up with what looks like 40* or so. No structural integrity was compromised with this modification if done without hitting the inside support cross casting.
I used a 9/64" bit for all of the holes and enlarged the exhaust side holes to 13/64" and radiused the holes with a 1/2" bit for the specifics on MY modifications. I may enlarge the bottom (exhaust side) holes if I feel it is needed.
I hope this helps others out with their questions and please give a like if you think its worth it!
I marked the spots to drill with a FelPro #8364PT gasket and center punched the holes so the drill wouldn't walk on me. Go SLOW!!!
Thanks to FloTek for the great customer support!!!
Marty Wilson
Wilson Racing and Engine Shop

[@silverstreak232]

I tried calling Flotek's customer service for answers about this since their website says "contact us about 400 sbc". Never heard back from them after numerous attempts. I found out more from your video than I ever could from the people that make and sell these heads. Thanks for posting!

[@timculpepper4939]

My experiences ! I simply drilled them straight down and use the 350 head gasket for a template. I did at six pairs of heads that way with no problems. Great job

[@johnalarcon5006]

Good job man!

[@martywilsonwilsonenginesho7940]

Are they stock heads or aftermarket???

[@mb-fs1yo]

Have ran 305 heads on a 400, did not drill holes. Bigger valves n such but didn’t drill the holes. Ran circle track 1/2 mile 7000 rpm never overheated.

[@jimclarke1108]

:oops:

[@gmcnelly2468]

you really only need the bottom (spark plug side) holes in the 400. The top of the siamese cylinders will rise and flow to/ thru the top of the block/cylinder head coolant holes.

[@timothyroatenberry1274]

I had a 400 Chevy in my 1946 Chevy coupe, it kept running hot & overheating,put a wind high flow water pump, electric fan, bigger fan on water pump, still run hot ! Put built 350 in, no problems ! But it don't have the power or torque the 400 did ! The 400 was a brute !!

[@johnalarcon5006]

I actually had to drill a hole in my friends 350 Chevy block when he used trick flow heads .

[@406MenaceRacecar]

Hi, I have a 400 and it looks like the holes were drilled straight in, not angled. Is this a problem? I pulled the motor apart because it got hot breaking it in, it ran hot immediately upon driving (225 going up n up n up) and oil pressure was garbage! So I pulled it apart and sure enough the mains are wiped

[@jesseleblanc1199]

Just curious what size holes did ypu drill

[@sportsmansparadice42]

Do all SBC 400ci motors need those steam holes drilled?

[@barryacromp6775]

Use brake fluid for cutting lubrication

[@Cjdanks448]

This gives me anxiety

[@mikeeagle2653]

If your going to. Make a video people need to be able to hear you. Fix the sound