why is back pressure good?

Here's one, I'll look for a couple more.. Everything is almost new exept the body and interior..

Post edited by: vach, at: 2007/05/22 00:52

pumps wrote:

vach wrote:

The little motor is in a 66 Impala, a pretty heavy car.

I remember we used to call them "Lead Sleds" because of the weight but we still loved them. Got any pics of your little 66? My dad had a sweet little 62.My buddy "Slink" had a cool 66 Caprice SS/327 with bucket seats etc.<br><br>Post edited by: pumps, at: 2007/05/22 00:42

id give my left lugnut for a clean 62 impala(regular top;) )

some bondo.

wheels

Motor

Grill

Duck and Steel are right on, the temp of the ex gas also can play into the speed of the pulse, thus some pipes get a heat wrap on them to help pull the ex out of the cyl and get a cleaner burn cycle.
as far as open header and not being able to lite up the tires try putting on a cross over pipe about six inches from the clooector on the header, bump the timing up to 32 degrees at 3000 rpm, see what happens.
the 283 motor needs rpm it has such a short stroke

From what I understand about exhaust back pressure.

When your exhaust valve opens and your exhaust is pushed out, you have a "column" of spent exhaust gasses traveling through your pipe towards the muffler. This "column" has velocity and its momentum creates a vacuume behind it to help scavenge the spent gasses on the next exhaust cycle. With the proper back pressure, the momentum of the "column" will continue towards the muffler until it is assisted uninterupted with the next exhaust cycle.
With out any back pressure, this "column" of spent gases travels too fast/ far and its momentum can be stopped by the vacuume that it has created behind it and the column's momentum can be stopped and reversed back into the vacuume that it created behind it (that should have helped scavenge the next exhaust cycle) when leaving the exhaust port. This causes the exhaust to be piled up in this area. Usually this happens at the lower RPMs.

Fish

Thanks, I'll give it a go and see what happens..


BSKZ650 wrote:

Duck and Steel are right on, the temp of the ex gas also can play into the speed of the pulse, thus some pipes get a heat wrap on them to help pull the ex out of the cyl and get a cleaner burn cycle.
as far as open header and not being able to lite up the tires try putting on a cross over pipe about six inches from the clooector on the header, bump the timing up to 32 degrees at 3000 rpm, see what happens.
the 283 motor needs rpm it has such a short stroke

Ok, sounds good to me.. But why did I bend 2 valves after cruising happily at about 90mph when I was decelerating only through the throttle.. Just curious in my stupidity..

The Fish wrote:

From what I understand about exhaust back pressure.

When your exhaust valve opens and your exhaust is pushed out, you have a "column" of spent exhaust gasses traveling through your pipe towards the muffler. This "column" has velocity and its momentum creates a vacuume behind it to help scavenge the spent gasses on the next exhaust cycle. With the proper back pressure, the momentum of the "column" will continue towards the muffler until it is assisted uninterupted with the next exhaust cycle.
With out any back pressure, this "column" of spent gases travels too fast/ far and its momentum can be stopped by the vacuume that it has created behind it and the column's momentum can be stopped and reversed back into the vacuume that it created behind it (that should have helped scavenge the next exhaust cycle) when leaving the exhaust port. This causes the exhaust to be piled up in this area. Usually this happens at the lower RPMs.

Fish

valve float, lucky you only got two