Pt 1. Speedway's 461 Double Humps, Making a Drill Jig for 400 Small Block Chevy Steam 🕳 Holes. 

The 10 Deg. angle has to do with making a clean break into the water jacket when drilling the hole so close to the clearance hole for the head bolt, on factory iron heads.

Yes, the TH 375 was available in full size and mid size GM cars from 72 to 76. So they're not very plentiful or sought after for performance use. But, there's nothing wrong with mine, and if it pulled a giant Caprice wagon and camper around, I doubt a small T roadster will break it. 😁Have a Happy and Blessed New Year.

Ed, thanks for the helpful info. And since you brought the point up about checking with the manufacturer. I will. It's always best "to check twice, cut once... Check once, cut twice." That's an old shop motto. As I get things in order here I'll keep things posted. And I'll definitely relay what the supplier of these heads have to say about drilling the intake side holes. Before that I want to post a video of a leak test (valves) on the bench. HAVE A BLESSED AND SAFE CHRISTMAS AND HAPPY NEW YEAR!

@@silverstreak232 Not sure what your name is, I am Ed. The Trick on the 400 engine is to use like a Howard Stewart water pump or Edelbrock. The high performance water pumps boost the static pump pressure not cooling system pressure. Get you a good water pump, if you can. I believe it will help. Typically on competition engines that do not set around idling at 1,500 to 2,000 rpm. The steam pockets do not form with the higher RPM. Your aluminum heads will certainly help the cooling. I am never telling someone what to do. Only trying to help out. 400 Chevys are a good engine full of potential. Also make sure that you have a large enough head gasket bore for your application. That it clears the cylinder bore chamfers. Compromising the fire ring in the gasket is a way for head gasket failure. Unshrouding the chambers is another way to pick up power and reduce heat build up in the head gasket.👍👍 You have a Very Blessed Christmas also. Take care, Ed.

EXCACTLY , the uppers have never been needed , some engineers (and I live in Detroit ) go to work under the influence and that is why we have stupid things not thought out by people ... steam can not accumulate in the pocket on the top side because it is angled up , the lower pocket is angled down .... I've seen experts destroy heads putting the upper holes in ...

Stay tuned, I have to get set up here in my pop's shop. when I get started I'll post detailed videos with the design, layout, and making of the jig. Just be aware if you intend to put aftermarket (or even GM) aluminum heads on a 400 that not all heads are suitable. Edlebrock for example only recommends drilling the 1/4" steam holes on the exhaust side. Check with the manufacturer. See Ed's comment (Edsmachine93). Also, making a jig is very convenient and economical if you plan on using it multiple times. I bought my materials from Travers. I was asked about making the jigs for sale, but the time and material cost would out weigh the demand. Good Luck and Happy New Year.

listen to DV. If there's any advice I would listen to, it would be his.

Good morning. I just rolled out of bed. I'm starting to understand that now. I'm really new at this (if you can't tell already) and it'll take a little time to get used to A holes. I guess I am feeling a little bitter. I had to go through some major life changes this past year that I didn't expect or want. I started making these videos as a new hobby. I also like to share ideas and good life experiences. Anyway, I am getting long-winded. Thanks for the encouraging words and stay tuned.

I wouldn't let it get to me. But i explained how I'm going through some unpleasant stuff to start with. So, maybe I'm just being to touchy. I do enjoy the vast majority of the comments. I just started this video thing. So I'm not used the A holes of the internet. Thanks for the kind words.

suit yourself

If you're so sure of yourself, present your evidence and proof I'd be glad to see it.

Steel? Nobody makes steel heads.

Sure man! Thanks for the feedback!

@@silverstreak232 I should have pictures this Friday of the cleaned up cambers and runners and flow bench # in about 4weeks due to waiting on .100 longer exhaust valves.

Are you using the the Speedway heads? The static compression ratio will be right on 10:1 with the 64 cc chambers and 70 style dished forged pistons. This should be adequate with pump gas and aluminum heads. The cam is an old Weiand Xccelorator #8102 (hydraulic) that was available back in the late 80s to mid 90s. the specs are 288 intake 288 exhaust 112 lobe sep angle. At .050 it's 214 & 214. .444 lift with 1.5 rockers. Not a HOT cam by any stretch. but it's bought and paid for and should perform great on the street. The rest of the short block is a relatively stock 511 casting with two bolt mains. I don't have easy access to a dyno so HP and TQ will only be a guess at best. With that cam I wouldn't expect it to make over 400 or so HP. But I would imagine that the TQ could reach over 450 lb/ft up to the 5500 rpm range (easily). That's only guess work. That'll get a 27 T roadster moving along. As far as the heads go. I'd like see how well they run as is at first. Without a flow bench, big improvements are hit and miss with the newer port designs. They can be easily ruined. It just goes to show how bad some of the old factory stuff was, when a guy could take a grinder to a head and find 20 to 30 HP in an afternoon. I'll talk about that in a separate video. As far as having a shop drill your steam holes, that is a good idea. I'm doing this project to show a method of how it can be done with a tool that will allow the use of a hand drill on a workbench. And it can be done over and over again with no time wasted. It may be a good idea for a professional shop. But, they would know better than me. The 400 SBC has been out of production for over 40 years. They're not as common or as popular as they were. The LS is a better choice (for serious HP) But, you can be the judge. Thanks for the great feedback. I do not have an Instagram account related to this yet. But that may be a possibility in the future.

@@silverstreak232 hey yes I’m using the speedway heads also, originally was going to have the head ported for a Different build but plans changed. So the heads were at the head porters already and we changed direction for the 406. We’re not doing any port work just sanding the walls smooth to improve flow all of the work is going into the combustion chamber. If you look at the area around the valve there are small walls from the valve seat machining this are cfm killers in all heads and is fairly easy to remove even for a novice. I like to support my local guy so I’m letting him do the work cause he’s already got the head there and I’m curious to see what they will flow after it’s done. If I was doing it myself I would also do what you’re doing. But I have a mill so wouldn’t need any guide. However I was just commenting his 45deg angle because he does this for a living and thought you would like to know that information. I can’t find any specifics on that cam so I don’t know what the intake closing point is and you need to be careful with dynamic compression on these big CI sbc a little changes allot. So even at 10:1 you can get knock if your dynamic pressure is wrong. I’m going for 11:1 on my build with a .055 quench unfortunately, I have flat top pistons. So getting a good quench is difficult for me. I’d like to see 0.040 so I’m having him open up the chamber to match my 4.155 bore to try and increase head CC a few to raise it up. But we will see. With 10:1 on a stock 400 you would want 55 ABDC closing point for about 180psi cranking pressure with a light car like that you might get away with a little higher dynamic pressure but 180psi is a good target.

@@silverstreak232 here’s basically all that’s being done to my speedway heads: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-9taMJTlzu6c.htmlsi=Lh96DKw6y92quSpR

Hey @silverstreak232 funny story my head guy got back to me and you were 💯 correct on your angle of the steam holes not 45deg he looked at it I decided your angle was the idea angle 📐