big bore dart big M 4.625 in blown alcohol

I've got a Dart big M that is bored to 4.625 diameter, I would like to use it in a blown alcohol application. It is a 10.2 with a 4.00 billet crank, 6.800 brooks rods, 1.4 CH venolia pistons 12:1, Dart Big Chief 11 deg, indy intake, MSD promag 20, SSI 14-71 f rotor @ 30 over, 2800 lb door car with a powerglide. We want to run 6.80-7.00 ets. My question is this, does the big bore take away too much material between the cylinders for good head gasket retention? I will use o-ring, receiver grooves, the 4 extra bolts and a .060 to .080 gasket. It leaves about .215 whereas the 4.5 deal is .340. Should I sell the block & pistons and go to 4.500 bore?

 

11 degrees with that much blower. Huh? NEver heard of that. Does it work well?
And about the o-rings, you are going to have to run a "Figure 8" style where there is only one wire between the cylinders. No room for two side by side. Or run an ICS from SCE if your heads hit the whole 4.630 round.

 

Big m

I didn't realize there might be a problem with the 11 deg / blower combo? We previously ran Glen Self ported 18deg Big Dukes with same blower. I saw that Scott Filkins uses 12deg heads and went 5.98, obviously thats a different animal but.... I figured we'd have to do the figure 8 style oring. thanks for the input, JJ

 

Please explain this more

 

The ICS titan gaskets are the self sealing O ring gasket that don't require o rings in the block and heads. They do pretty darn well if you are not pushing giganourmous amounts of boost. But the gasket is perfectly round around the bore.
When we as a racing world went to the 14, 12 and 11 degree heads, we did that for naturally aspirated pro stock style deals. And lots of them have the exhaust side and sometimes the intake side of the chamber flared out greater than the standard numerical mind would consider figuring the bore. (Unshrouding those valves to the outside is one of the ways to increase the flow numbers, and subsequent performance.) So there will be part of the perfect circular O ring in the gasket that may not hit a flat deck surface of the head. It will slightly hang over into the chamber area. And if that happens, then there is very little sealing going on at all, and those gaskets are useless. We see it alot in the trick small block heads, and it is not uncommon in the big block world as well.
Many people will set the gasket on the block and go; "Cool! Perfect!" then assemble without laying it on the head. Then are asounded when the engine does not run, and are shown that the head chamber was way bigger then the gasket or the block bore.
Does that help at all, or did I get eveyone more confused?

 

Had a 4.565 bore Merlin block. Ran the ICS gaskets and they were fine up to 16lbs. of boost (6-8 passes). When we went to 28lbs they made it two passes and gave it up. The gaskets both looked like cookie dough that had been rolled out, bolt holes oblonged etc. Went to o-ring and receiver groove, problem fixed, although we needed to add some material to the coners of the combustion chamber for a better platform,sealing area. Talked with ICS about the failure, they wouldn't do sh*t not even a discount on a regular set of copper gaskets.

 

Thanks, totally understand

 

john barnes, I think that the head bolt positions on a BB/C wont allow the figure 8 style O ringing. The grooves get too close to the either the bolt holes in the block or its the clearance in the head bolt holes that wont take the reciever grooves.

 

That bore size on a 4.840 bore space block is a mistake, if you plan on making any real boost or power. I would stay 4.560 or smaller. Unless you have more than one of those blocks to junk. At least thats been our experience.

 

John we used to run figure 8's on our blown BBC. If I were you I'd run the wire in the head and the reciever in the block. I'm talking 7/16 head studs.

In my experience 4.625 is pushing the limits, but that doesn't mean you won't get away with it. There are plenty people in this area with 1800 HP nitrous motors running 4.600 (Dart Big M) and put many many runs on them. You are going to be making more than that but I thought you would like the comparison.
Remember your detonation control is key, keep control over it or it will wreck any combination. timing and fuel
Janke Engines was succesfully building 4.560 bored BBC's with good for the day 14's at a higher overdrive than that in the early/mid 90's.
The other thing you could do is flow those heads on 4.625, 4.600, 4.560 and 4.500 and see how much they are effected.

 

I have ran that block @ 4.630 on a 1700 hp nos engine, no comparison here. Nos does not and will not put the cylinder psi that the blower will. I know TURBO guys running them big as well, but on a roots deal they just wont live. And the TURBO guys also are seeing this on that bore now. It just depends on your wants, but no way in hell would I try it again. Cheaper to buy the right block now, and not wish you had when it blows the cylinder out between the bores and hydraulics the engine. But at a low overdrive you might, but then again, you might not get an STD with a hooker either...

 

I agree with this, if its all together and healthy right now its going to be easy to sell and then you can get yourself something with a small bore where the jugs will stay round and the decks healthy.

Once you find out its not a doable idea you are going to be stuck mid season with a pile of hurt parts in wishing you had done it over the winter.

 

You can set the o-ring OD at 4.800 with a .041 wire and leave it out .012 to .014. Put a reciever groove to match with a .048 width and .010 depth. That will seal as good are better than anything else on a flat deck and 7/16 studs. Set the static at 11.5 and pulleys for 25#. Set the timing at 28*. That should be more than enough power to run 6.90's at 2800#. Depending on the valve size and dowel location, them heads might not fit a 4.500 bore.