As you know I am putting a blown 540 together. I hope to be in the 1000 horse range and worry about blowing head gaskets with 12 pounds of boost. The hardest part I think on the motor is putting out a lot of boost with no rpm. I will often cruise along at 12 or 1500 rpm locked in 5th overdrive with 308 gearing and push it. The boost climbs quickly but there is no rpm to cushion the motor so cylinder pressure is high. I believe this could be hard on head gaskets.
I did O ring the old block and run stainless wire in the groove and copper gaskets but I hate them, they tend to seep.
I want to run a composite gasket for better sealing of fluids.
This is the shot of cylinder 1 and 3. You will notice the big blocks have 6 studs around the first cylinder and yet the next cylinder, #2 in the picture or #3 in the motor is missing the 12 o clock stud. This can lead to a potential head gasket failure.

I am running brodex heads and they have provision/center drilled for adding extra head bolts but I did find that they are NOT drilled in the right spot. I spent about 5 hours carefully figuring out the correct spot and angle for these 4 new holes. I set up the mill and using it as an extremely accurate drill press drilled and taped 4 holes for 7/16 head bolts. They are drilled on a 10 ½ degree angle. I also found that the spot that Brodex marked was .050 and .025 out from where they should have been.
If I had blindly drilled the holes they wouldn’t fit the block.
This is one of the holes I drilled and taped

You can see the bosses here cast into the block along the lifter gallery for the extra bolts.

I used 7/16 cap screws 2 inches long torqued to 55 foot pounds in the lifter gallery

The last thing is my firewall is modified so a head can be slipped on the studs making it easy to service the motor. With the hydroboost and the modified firewall I have lots of room for the tall valve covers.

I know that there are only a few guys who would do something like this but I thought maybe some others might just like to know the option is out there for building a high power bigblock.

 

Very NICE!! I find it interesting that Brodix missed the correct spot for the extra studs. I've got GM aluminum heads and have the plugs in the intakes. My current block has no provision for the extra studs. On my "to do" list..

Great pictures..

 

Impressive work as usual! Just wondering, what is that pattern on the top of your pistons? Is that to help prevent detonation, or promote flame travel, or something else?

 

The pattern is the CNC milling of the dome. While it is smooth to the touch is still shows the milling cutter pattern. I am running 8-1 compression but the blower and 12 pounds of boost raises that to 14.5 to 1

 

I'm wondering why the #1 & #3 cylinders aren't utilizing the cast in bosses for the extra studs. I would think where the studs are located now is a better spot but those bosses were put there for a reason.

 

I was taking NO chances with Brodix being off so after establishing the correct angle to drill on I first drilled and taped a 1/4 x 20 hole and installed a 1/4 inch cap screw and installed the head. Right away you could see the bolt hole was in the wrong location. I then carefully check all the other holes and found them also off.
I set the head back up in the mill, centered on the existing center drill marks that Brodix put in the head and then moved the hole .050 inboard and .025 towards the back. I used a 5/16 milling cutter for a drill bit. I redrilled over the 1/4 inch hole with the same 5/16 milling cutter.
All holes came out exactly right and all extra head bolts screwed down tight with only finger pressure and were easy to start.
I also found that by drilling and taping on a 10.5 degree angle the head of the cap screw laid flush against the bottom surface of the block boss.
It was scary at first thinking about drilling and taping an expensive set of heads but I went slow, measured again and agiain and even did a few test pieces of aluminum.
If I had to do it again I could do all 4 holes in under 1/2 hour instead of the 5 hours or so I spent.
The heads are on and torqued down to specs. Intake to follow tomorrow and then I will tear the blower down just for routine inspection and new seals.

 

You need to get to the back side of the bosses to get at the bolt heads so you need to be in the lifter gallery. If you tried comming down from the top it would involve a hole in the top of the intake port as well and would also fall under a rocker arm. There is just no other spot except where they put the bosses.
The bosses make it easy. After drilling and installing the bolts I used weld bond on the inside of the ports to smooth out the flow once again. From inside the port it looks smooth once the weld bond dries and is sanded smooth.
This is the hole in the port. After the bolts were installed and torqued down I filled all signs of the hole in with Weld bond and sanded smooth when dry.

These ports are huge

 

that's some nice work there, love the allen heads

 

A blown 540 with a 5 speed

 

Thank you Marck. An allen bolt is the only thing that fits.
You have quit a project with lowering the floor. I cut mine to make extra foot room for my wife's purse

 

I don't beat on it John. I like the expensive toys but just play with it. I am upping the rearend gearing to 355 from 308 to bring the rpm up a little. The cam is 264/270 @ .050 so it might like a little more rpm.
If I was serious I would put a ford 9 inch in. I can do it. That and a pair of large slicks but I like running fast across country.

 

You have just provided about as good a cure for the weakest part of a BB chevy that you can to run a blower. Without this fix your playing with potential failure just waiting to happen. I would still run a stainless or copper O-ring in the heads however.

 

Norval, based on my 620 hp 454 with a 6 speed and a 3.70 rear end, I think that much power would like the 3.08 gear better. If you want a little more rpm, wait a little longer to shift. If that motor makes 1000 hp, and if it don't, it ought to be close, you are not going to need much gear. I can't imagine you not being able to break traction when ever you want up to at least 100 mph with the 3.08 gear.

If you are using Cometic gaskets; they are better than O-rings anyway, and I am a guy who loves 0-rings. I know of guys running 14 to 1 and a bunch of nitrous with Cometics.

If you get bored with that 540 send it down to California and I will see what it will do in a 2000 lbs. drag car.......free of charge!!

 

Are you saying you can use these gaskets instead of 0-ringing the heads?

 

Yes, call them and do a little research. I have never run them but the guys I know who do really like them. I prefer 0-rings because copper head gaskets are re-usable.

 

John I agree the 308 gearing is plenty but I tend to drive alot in high gear, even through town where the rpm is down to 600 or 700. I feel this could have been part of the problem with me wiping my roller cam last year.
I also know that it will be 4th gear before I get any traction with street tires. I was able to take it slowly to the top end of 3rd gear before and punch it just before red line and have the tires disintergrate. It can bet scary. I already bought the 3.55 gears and will run them. I have tried 308, 355, 373, 411 and 456 in the mustang and found the 355 the best for it. I want to try them in my vet.
I did find that the 411's with my old blower motor were all wrong. I couldn't use 1st gear and often took off in 3rd.
If I don't like the 3.55 I can go back to the 308's

 

I hated the O rings. I ran stainless O rings and copper gaskets in the last motor and really didn't like them.
I am running Fel pro composite gaskets in the 540, that is until I have a problem

 

Pardon ME, but I find this amusing.....

I used to start out in 2nd gear with my L48 topped with L98 injection all the time....336 and Muncie....

Norval on the other hand starts out in 3rd, and goes sideways....

uhh....may I suggest a 2.47 rear and a powerslide???

take off the converter and use a clutch to make your feel at home....

 

Uh, what are you talking about?

 

Maybe I have been lucky, but other than a little weeping I have had no issues with the O-rings and I feel good about running them with the amount of nitrous I am spraying. The next motor will have 13.5 to 1 and see a 500 shot. I already have that block O-ringed.