Exhaust Leak

Hi Everyone,


I have been reading your post for a long time but have never
submitted one until now. I hope that somebody out there can help me.
I have a 68 ford Bronco, Brand new 302cid, 351 windsor heads (bigger
valves), Holley Truck avenger carb, and a brand new bronco c4. The
reason I have posted this message is because I have a problem I just
cant beat. I have exhaust fumes coming into the cab. This may sound
easy to correct at first, but I have already done all of the obvious.
I have replaced both of the mufflers, the pipes only have about 3000
miles on them, and for good mesure I have checked them anyway. I did
the donughts off of the manifolds which (did seem to help a little),
and I have put exhaust tips on just to make sure it is clearing the
back of the truck.
The exhaust system is 2" and it is straight back without a cross over
of any kind. And finally the manifolds are stock but not cracked or
broken in anyway, and have brand new gaskets and I have checked the
torque several times.
However the only time that I have any problem is when the window
is down. I have heard tidbits about a vortex being created by having
the window down, that sucks into the cab. I'm not sure this is true
but any help will be greatly appreciated. Anyone who has ever ridden
in an old Bronco knows that in the summer there is no way to not open
the window or take off the top in the summer. I am truely desperate
here. I am a competative athlete and cannot take the fumes. I'm
afraid that if I cant solve this problem I will have to get rid of my
old bronc, and thats too bad because with this engine set up she
screeams!

Thank you in advance for any help, I throw myself on the wisdom
of the group.

(Ltine) wrote in message om>...
> Hi Everyone,
>
>
> I have been reading your post for a long time but have never
> submitted one until now. I hope that somebody out there can help me.
> I have a 68 ford Bronco, Brand new 302cid, 351 windsor heads (bigger
> valves), Holley Truck avenger carb, and a brand new bronco c4. The
> reason I have posted this message is because I have a problem I just
> cant beat. I have exhaust fumes coming into the cab. This may sound
> easy to correct at first, but I have already done all of the obvious.
> I have replaced both of the mufflers, the pipes only have about 3000
> miles on them, and for good mesure I have checked them anyway. I did
> the donughts off of the manifolds which (did seem to help a little),
> and I have put exhaust tips on just to make sure it is clearing the
> back of the truck.
> The exhaust system is 2" and it is straight back without a cross over
> of any kind. And finally the manifolds are stock but not cracked or
> broken in anyway, and have brand new gaskets and I have checked the
> torque several times.
> However the only time that I have any problem is when the window
> is down. I have heard tidbits about a vortex being created by having
> the window down, that sucks into the cab. I'm not sure this is true
> but any help will be greatly appreciated. Anyone who has ever ridden
> in an old Bronco knows that in the summer there is no way to not open
> the window or take off the top in the summer. I am truely desperate
> here. I am a competative athlete and cannot take the fumes. I'm
> afraid that if I cant solve this problem I will have to get rid of my
> old bronc, and thats too bad because with this engine set up she
> screeams!
>
> Thank you in advance for any help, I throw myself on the wisdom
> of the group.

Hey Mike and Steve, thank you both for your ideas. I did
recently adjust that mix, I had been running rich throughout the
winter. That did help a little. What is the major difference between
the exaust porting out the side of the truck rather than the straight
out the rear? And I think your both right about the seams and rubber
on the truck letting in fumes. I have a few rust spots, and a couple
on the tail gate, close to where the exhaust pipes come off of the
bronc.

Thanks again

if the exhaust exits out the side, it will scavenge away while driving down
the road. if it exits out the back or down underneath with turndown off the
mufflers, it will vortex up the tailgate and be sucked in by the vacuumed
that is created inside while driving.
"Ltine" > wrote in message
om...
> (Ltine) wrote in message
om>...
> > Hi Everyone,
> >
> >
> > I have been reading your post for a long time but have never
> > submitted one until now. I hope that somebody out there can help me.
> > I have a 68 ford Bronco, Brand new 302cid, 351 windsor heads (bigger
> > valves), Holley Truck avenger carb, and a brand new bronco c4. The
> > reason I have posted this message is because I have a problem I just
> > cant beat. I have exhaust fumes coming into the cab. This may sound
> > easy to correct at first, but I have already done all of the obvious.
> > I have replaced both of the mufflers, the pipes only have about 3000
> > miles on them, and for good mesure I have checked them anyway. I did
> > the donughts off of the manifolds which (did seem to help a little),
> > and I have put exhaust tips on just to make sure it is clearing the
> > back of the truck.
> > The exhaust system is 2" and it is straight back without a cross over
> > of any kind. And finally the manifolds are stock but not cracked or
> > broken in anyway, and have brand new gaskets and I have checked the
> > torque several times.
> > However the only time that I have any problem is when the window
> > is down. I have heard tidbits about a vortex being created by having
> > the window down, that sucks into the cab. I'm not sure this is true
> > but any help will be greatly appreciated. Anyone who has ever ridden
> > in an old Bronco knows that in the summer there is no way to not open
> > the window or take off the top in the summer. I am truely desperate
> > here. I am a competative athlete and cannot take the fumes. I'm
> > afraid that if I cant solve this problem I will have to get rid of my
> > old bronc, and thats too bad because with this engine set up she
> > screeams!
> >
> > Thank you in advance for any help, I throw myself on the wisdom
> > of the group.
>
> Hey Mike and Steve, thank you both for your ideas. I did
> recently adjust that mix, I had been running rich throughout the
> winter. That did help a little. What is the major difference between
> the exaust porting out the side of the truck rather than the straight
> out the rear? And I think your both right about the seams and rubber
> on the truck letting in fumes. I have a few rust spots, and a couple
> on the tail gate, close to where the exhaust pipes come off of the
> bronc.
>
> Thanks again