BBC head gasket issue?

Well, after fighting this problem for a long time I am going to ask for some different opinions. What we have going on is every third pass or so we are pushing the head gasket on the #2 cylinder. It normally just pushes the gasket and doesn't damage the block or the head but has burned the head on a few occasions. it is a 10.2 deck iron block that is dead flat and o ringed in the block with good ARP 7/16 studs. The heads are solid brodix bb2x that are also dead flat and have reciever grooves. Has .060 copper gaskets. The static compression is 10.5 and it has a Littlefield manifold with a SSI 60* b rotor at 45% over. and a supermag 4 set at 28* the fuel pump is a hilborn175-2 and flows 13 gal. when tested by Gerardot. it has port and hat nozzles I do not have the exact nozzle and main #'s with me but if needed I can post them. The odd thing is, is that for 2 or 3 passes the plugs will read that it is fat and then on the next pass boom head gasket or sometimes burned piston. We have tried everything from going way rich in that cylinder to retarding the timing back to the 28* we are currently at had been up to 40* before that. To taking compression out first of the entire motor then to just that cylinder by changeing the chamber in the head. Have tried a colder plug in that cylinder also. Motor is apart now getting ready to order new pistons so now is the time if we need some major renovations. this is also in a pulling application. What the hell is going on here?????

Thanks in advance for any advice you can give.

 

BBC's weakest are #2 and #7 as these are missing head bolts. Do you use the inside head bolts/studs?
Also, the deck surface finishes for copper need to be smooth, unlike the surface finish for paper gaskets.
Is this an 8-71 or 14?
Are there an high speeds?
Does the plug ever have signs of oil on it?

 

What's your ignition system? Do you have the #2 and #7 wires routed well apart? How is the rotor phasing at the extremes of your timing limits? How is the condition of the rotor and cap? Do you run a large diameter cap or a small diameter cap? Maybe you've got a spark taking the path of least resistance at an inopportune time (ie: spark 7 liking cylinder 2 better than cylinder 7...)? I had the exact same problem once upon a time with a street gas BBC under boost with a small 90mm diameter distributor cap.

 

you may want to check that the o rings are lining up properly with the reciever grooves i usualy just spray a little fog coat of spray can primer on the deck surface and then bolt the head on just snug, and then wack the head with a rubber hammer where the valve cover bolts to and when you pull the head back off you should see a tell tale mark of where the o ring is positioned.
also make sure that your fuel inlet hose has a spring inside so it wont collaps and make the motor go lean.
also make sure the intake is sealing good around that one port.

good luck
Scott Hohensee

 

when you say the piston is burned, how is the center melted? or like at the corner at the intake valve? I agree to look at ( Do you have the #2 and #7 wires routed well apart? How is the rotor phasing at the extremes of your timing limits? How is the condition of the rotor and cap? Do you run a large diameter cap or a small diameter cap? Maybe you've got a spark taking the path of least resistance at an inopportune time ) is the timing pined ? do you use any timing controls? and not burning the fuel can cause a problem, when we ran something close we used 1/2" studs and o-ringed the heads with a reciver grooves in the block

 

Head Gasket

Have you had to repair the area where the locator pin is in the block or the hole for it in the head? If the pin has been repaired, it might not be aligned perfect and it may be keeping the head from seating properly. Good Luck.

 

Ok. No sign of oil on the plug. It is a 4-7 swap camshaft so 2-7 do not fire next to one another. o ring and reciever line up properly. It has the extra head studs. It is a 14-71 blower. timing is fixed in the super mag 4 and there are no timing devices. No lean outs in the fuel system. Tried all different torque sequences and pressures on the heads. We have run different heads, intakes, blowers (8-71 60*littlefield same over drive) with the same result. Thanks for all the input so far. We have already tried all of these things. What are we missing???

It is pushing the gasket out the front at between about 4 o clock if you were looking at the cylinder from above on the right side.

Lets hear some more ideas. Thanks!

 

Forgot. No repairs to the dowl pin area of the block or head.

Thanks.

 

bbc

Obviously you've done some work on this thing. I don't know anything about pulling except it's brutal. We ran a similiar combo years ago with a production block full of concrete. It never made it to 30 psi before it broke the deck around either #1 or #2.We rebuilt with another production block and switched to a weak 1471 hi helix and it picked up 13mph and never had another issue. Made about 1800 hp at 8000 rpm 468 inch 28psi.
We started running aluminum blocks after that. You probably know they have the o-ring in the head and groove in the block..plus the sleeves stick out .004 to crush everything.
We didn't have your tuneup knowledge back then...I would think it should work.
Just remembered another thing about that old setup...It would blow burst panels on startup or after a burnout sometimes. Turned out to be leaking between 2 cylinders and crossfiring. I started gluing the gaskets with red rtv and fixed it. Everything was nice and flat so I assume the sealing is marginal on that o ring setup.
I've been told before...if you can make that Chevy fast you'll be one helluva mechanic!
Good luck.

 

I had the same issue with my SM4. I used it for three years (approx. 60 passes per year). The screws that hold the plate in the mag base were loose.(just alittle) Spud Miller found the problem and fixed it....fine now. I would suggest a rebuild or borrow a known good mag. Another set of wires wouldn't hurt either. It sounds like you have covered all the other possible mechanical causes.
Steve

 

I run Chevys in pulling also, I don't have these problems and I run more compression, more timing and maybe more blower (how much cid and how much boost do you run?)

This is a little out there but,,, when is the last time your mag guy checked the timing per cylinder? You could put a timing light on #2 cyl and mark your degree wheel accordingly. Zig told me it takes a while for them to get all the cyls timing right on and by simply taking the mag nut off you can throw it off again.

When does it seem to let go? early or late in the run? high or low rpm? etc

 

It was 533 CI with the SSI 14-71 straight. Boost numbers are from 22 to 35 depending how how hard the motor loads. The mag was checked at the Mallory trailer at BG two years ago and given a clean bill of health (haven't run it enough for anything to go bad!!). It hasn't had new plug wires for a while, though--so maybe!!??. I have had guys (Gerardot, Arnold, Creech, Krider and a host of others) scratching their heads on this issue for a while. Doesn't seem to matter what we do--new parts, used parts, same parts, different torques, sequences, timing, nozzles, intakes, heads, gasket thickness, etc. Although, some of you all's answers are pointing us to a couple of things. Thanks for all the advice--helps to confirm that we do do some things the right way. JW

 

If your running braided hose from the tank to pump make sure to run a spring inside so the pump doesn't suck it closed. i raced with a guy years back that killed 3 motors before finding that.

it was pretty much same issue but it was usualy #4 cylinder that would blow out he also ran the motor pretty fat trying to resolve the problem. i think if he ran the tuneup right on he would have burned many more when the hose closed up.

just something else to rule out. i hope you can get this resolved soon.

Scott Hohensee

 

head gaskets

hello buzz,had the same problems on a 540 and 509 chevy,tried everything,smaller head stud holes,bigger wire,smaller wire,glue,silicone you name it we tried it. Finally we gave in and tried cometics.Go ahead an laugh.put 4.630 on a 4.500 bore. took receiver groove out of the head,left the groove in the block open,(since it was exposed anyway) didn't spray,coat,or paint the cometics. So far they are not sticking out. Have made 32lbs boost,14-71 @ 8800 rpm using a msd 10 plus.yes we run quarter and eighth mile in a dragster for the last two years.don't know if they will work for you, but my copper days are over. sincerely overthehill

 

Wow!! Thats the first I've heard.It's usually the other way around.

 

BAE recommend that you tighten the studs from the outside to the middle vice middle to the outside. It is something to try.

 

Try oring head and block. We had a dart big m block and put and extra oring to the front of # 2 kinda in a half moon shape. helped alot made about 35 pounds of boost.

 

Gasket

My head is spinning from all this, i am not going back a search it all again, so i am not sure if the following was mentioned or done.
Is the gasket always pushed out in the same place, where?
The head studs, is there a chance they have been over stretched at some time so they have lost their clamping force?
some of the sealants act like lubricant. just put it in the front and back edges that go to the out side, use right stuff if you are not currently using it.
put the O ring in the head, receiver in the block, I have them both ways, the wire in the head is far superior, you have to PRY the gasket out of the grooves in the block, those sharp edges in steel or iron really clamp.
OR just double O ring it as mentioned above one in head and one in block, I have not done it, Mr Clark mentioned it at Clark Gaskets one time, i think he said one ring should be a little bigger than the other so they pinch the gasket between the two.

Be sure to let use know what you find out!