On Wed, Jan 29, 2003 at 06:55:30AM -0700, Larry Hoy wrote:
> > 2) What about drilling the block and head to use larger studs. I
> > believe that the current studs are 3/8", would going to 7/16" help?
>
> Not necessary.
I've heard from some who went through this with his GT2 Tiger that the
bigger studs/higher torque just deform the block and cause problems.
>
> > 3) The machining marks are still quite visible in the head. Is there a
> > way to smooth it out without removing the motor and taking it to a
> > machine shop?
>
> This one confuses me. You don't need to remove the engine to take the
> head to a machine shop. I do recommend you take the head to a machine
> shop and have it pressure tested. That only cost $20 around here.
No, but I need to remove the block to take the block to the machine
shop. I've heard from both Hans Pedersen and Steve Sanchez to make
the surfaces as flat and smooth as possible. I just talked to my
machinist and he said that he had sand the block on jaguars to get
them smooth enough to seal. He's never seen the problem with MGBs, but
he's never seen a supercharged MG before.
I'm going to _CAREFULLY_ sand the machining marks out of the block,
and have my machinist clean up the head. Does anyone have the
wherewithal to count and measure the size of the passages in the block this
afternoon on the off chance I can find some appropriately sized plugs
to go in there. Otherwise, I guess I'll just stuff some rags down the
holes.
>
> > 4a) There were two things that gave me pause when I retorqued the
> > head. First of all, sometimes I could not get the nut tight enough
> > for the torque wrench to click "in the middle" of a swing and I
> > would stop, ratchet the wrench back and it would click
> > immediately. Is this a case of static versus dynamic friction and
> > I may have accidentally torqued that stud to a lower value?
>
> Don't use a click type torque wrench, use the flex type.
I haven't had the torque wrench calibrated in a while, but it is a
snap-on, so it's fairly reputable. If the problem is static/dynamic
friction though, I wouldn't expect beam or click to make a
difference.
How would I tell a quality beam torque wrench from a schlock one?
>
> > 4b) When I retorqued the head, I did not back off all of the tappet
> > adjusters. The theory being that with 10 other studs torqued all
> > of the way down, the added stress from the valvesprings would be
> > negligable.
>
> Shouldn't make a difference.
>
> > 5) Another place where I may have gone wrong was in torquing the head
> > to 55 ft-lbs roather than 50. I had had a head gasket seep on a
> > previous motor, until I retorqued it a bit higher.
>
> I don't know if this will make a difference.
I've had one reply saying go to 60 lb-ft. I haven't heard back from
ARP.
>
> > 6) Has anyone else had chronic problems with blowing head gaskets?
> > What was the root cause?
>
> No, and I run 14:1 compression ratio. However a friend of mine did, he
> was using a click style torque wrench that was not calibrated recently.
> When is the last time yours was calibrated?
Not recently in time, but it doesn't get lots of use either?
>
> Does the head gasket always leak in the same area? If so, where.
It always seems to leak on the spark plug side of the head. I did have
one or two blow between the cylinders, but I don't know if this one
did. Considering that cyl 3 is 4 pounds down from 1 and 4, it may have
blown between cyl 2 & 3.
For what it's worth, several years ago, after building my last
naturally aspirated motor, I problems with it losing power after
sustained high power driving. I had followed the ARP directions and
only torqued the head to about 40 ft-lbs with assembly lube. I
noticed water seepage, retorqued the head to 50 or 55lbs and the
problem was solved. I believe that it was with this head and block,
but they have both been surfaced since then.
Another friend thinks that I'm getting predetonation. The fact that
the electrode for plug #4 was half eaten away certainly implies that
something is going wrong.
When I first put this block on, as I said, it was predetonating pretty
badly under hard acceleration. It was the classic arhythmic sound of
"bbs in a can". Once I backed off the timing, that sound went
away. There was a slight, rhythmic note that I'd hear under heavy
acceleration, but it honestly sounded more like resonance in the
exhuast system, and didn't sound at all like the pinging I'd hear when
things were bad.
Also, when we heard pinging on the dyno back in December, we'd see the
NOx reading go up to 4000, 5,000 or higher PPM and the highest we saw
this week was about 1500PPM. We were also carefully listening for
pinging (the mechanic races, so he has some experience in this) and
none of us heard any signs of pinging, even with the engine advanced
beyond maximum power.
Does anyone have experience with cylinder #4 being more prone to
predetonation and/or running lean on either naturally aspirated or
blown motors?
I'll keep you all posted with what I learn. The most important thing
seems to be finding out what "high performance tricks" make things
better, and which ones make things worse.
Larry
--
I've found something worse than oldies station that play the music I used to
listen to. Oldies stations that play the "new" music I used to complain about.
lrc@red4est.com http://www.red4est.com/lrc
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