On Wed, 5 Jun 1996, David M. Hall wrote:
> G.J. wrote:
> > 2. I installed a Piper "fast road cam" (valve lift .400", duration: 272
> > intake,270 exhaust) and higher-than-stock compression pistons in my 72
> > MGB engine during its rebuild. I'm not getting nearly as much performance
> > as I expected to get with these modifications. I beleive my HIF carbs are
> > performing well(although I'm rebuilding HS4's so I can use them for the
> > vacuum advance)...note: emmissions have been totally removed...I was
> > using a direct line from the VA to the intake manifold, but was told that
> > it will advance my timing at incorrect times (I still don't understand
> > why and when you want vacuum advance). It appears the distributer I have
> > is from a 64-67 (#40897). Could this be the problem? Could the
> > mechanical advance weights be incorrect for my application?
> >
>
> I have some sort of fast road cam in my 72 GT, and I think that when you have
> a fast road cam, that you need to adjust the valves to have different
>clearences
> than stock. Is this true? What do you have your valves adjusted for? I
>also have
Yes this is true, however, this shouldn't affect performance too much.
mine says intake:.012" and exhaust: 0.014"
The difference is because of higher exhaust temperatures.
> a direct line from the intake manifold to the vaccuume advance. My car seems
>to
> run fine, but I've never been in a stock one to compare. I also have a tuned
>exhaust
This is because you have the proper VA. Mine is from an earlier car.
As Greg Grohoski mentioned to me, The VA connected to the intake manifold
retard the timing, and the VA connected to HS4 carbs advance the timing.
> header. I do have one problem, and that is that when I'm cruising at freeway
>speeds,
> sometimes it seems to surge like it's not getting enough gas. I think that I
>need
> different needles than stock dual SU's have. Any tuning help out there on
>the net,
> or that you find would be appreciated. (btw, I've been told that about the
>only
> way to pick the right needles is on a rolling dyno, but I haven't found a
>local
I'm looking to do this in the future ($)
________ ___
/ ______/ | | Greg A.M.Johnson '72 & '66 MGB
/ \ ___ | | Biology Dept.
\ \_\ \ /\ __| | Dalhousie University
\______ / \________| Halifax, N.S., Canada
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