423 SBC combo help

[enigma57]

Gary, the distributor is subject to dynamic (not static) forces in the running engine not only side to side, but due to the spinning meshed gears on the drive end and constantly changing engine speeds and loading, I believe it would be subject to forces oscillating upward and downward as well.

Now I may be all wet on this, but I find it hard to see how the plastic material at the rear of such an intake would not flex at least somewhat under those forces. I recall a while after those intakes were introduced, AFR developed a retrofit metal piece to brace that area. And it was said to help.

So I had assumed the metal reinforcement had solved the issue and haven't given it another thought until it was brought up here in this thread.

Best regards,

Harry

[GARY C]

Gary, the distributor is subject to dynamic (not static) forces in the running engine not only side to side, but due to the spinning meshed gears on the drive end and constantly changing engine speeds and loading, I believe it would be subject to forces oscillating upward and downward as well.

Now I may be all wet on this, but I find it hard to see how the plastic material at the rear of such an intake would not flex at least somewhat under those forces. I recall a while after those intakes were introduced, AFR developed a retrofit metal piece to brace that area. And it was said to help.

So I had assumed the metal reinforcement had solved the issue and haven't given it another thought until it was brought up here in this thread.

Best regards,

Harry

That was due to China Wall Sealing issues and I think they offered replacement intakes to all their customers with the new metal inserts but I have not seen any other issues raised since that.

https://www.chevelles.com/threads/afr-t ... es.389107/

[RW TECH]

1.75 hooker super comp headers for a G-body
flowmaster super 40 mufflers

Maybe the cam isn't ideal but it's not miles out of the ballpark so forget about that for now. Same with converter stall, etc. Maybe all of it could be better, but the headers and mufflers are where I would pay attention. 3000 lbs with that displacement and those parts should be running at least 10-teens even if the converter and cam aren't real swift & other things are a ways out of tune. I would actually expect it to run 9.6x @ 136-ish on a decent day.

A long time ago a local buddy had some 1-3/4" street hooker headers on an iron 292 "turbo" headed 364-ish CID small block with a not so insane flat tappet cam in it. The car regularly ran 11.6x ET. He is a semi-regular on this forum so if he sees this maybe he can chime in & add more details.

After switching to 2" race headers (Stahl pattern / subflanges) with bigger collectors the car ran closer to 11.2x. No other changes, just headers. This is what I would address first. 1-78" minimum with 3.5" collector, something more along those llnes.

[RW TECH]

1.75 hooker super comp headers for a G-body
flowmaster super 40 mufflers

Maybe the cam isn't ideal but it's not miles out of the ballpark so forget about that for now. Same with converter stall, etc. Maybe all of it could be better, but the headers and mufflers are where I would pay attention. 3000 lbs with that displacement and those parts should be running at least 10-teens even if the converter and cam aren't real swift & other things are a ways out of tune. I would actually expect it to run 9.6x @ 136-ish on a decent day.

A long time ago a local buddy had some 1-3/4" street hooker headers on an iron 292 "turbo" headed 364-ish CID small block with a not so insane flat tappet cam in it. The car regularly ran 11.6x ET. He is a semi-regular on this forum so if he sees this maybe he can chime in & add more details.

After switching to 2" race headers (Stahl pattern / subflanges) with bigger collectors the car ran closer to 11.2x. No other changes, just headers. This is what I would address first. 1-78" minimum with 3.5" collector, something more along those llnes.

[steve cowan]

1.75 hooker super comp headers for a G-body
flowmaster super 40 mufflers

Maybe the cam isn't ideal but it's not miles out of the ballpark so forget about that for now. Same with converter stall, etc. Maybe all of it could be better, but the headers and mufflers are where I would pay attention. 3000 lbs with that displacement and those parts should be running at least 10-teens even if the converter and cam aren't real swift & other things are a ways out of tune. I would actually expect it to run 9.6x @ 136-ish on a decent day.

A long time ago a local buddy had some 1-3/4" street hooker headers on an iron 292 "turbo" headed 364-ish CID small block with a not so insane flat tappet cam in it. The car regularly ran 11.6x ET. He is a semi-regular on this forum so if he sees this maybe he can chime in & add more details.

After switching to 2" race headers (Stahl pattern / subflanges) with bigger collectors the car ran closer to 11.2x. No other changes, just headers. This is what I would address first. 1-78" minimum with 3.5" collector, something more along those llnes.

in your opinion with the bigger header-
poor exhaust flow due to early casting design compared to later castings
header complemented lift and duration used at the time
rpm used on that combo
not really questions but interesting theories on why the bigger header helped.
i think the exhaust side is very interesting and extremely complex and very few understand including myself.

[prairiehotrodder]

My personal experience with headers is that primary tube size isn't as big of a deal as many think. However low quality restrictive mufflers can make a huge problem.

On my 540 BBC everyone told me the 2" tubes were a big problem and i would gain alot from going bigger. I bought some really high end lemons headers with 2.25" primaries and gained nothing. However on the 423 SBC we allready have a set of 1 7/8 headers in the works to try along with a couple other things. It won't be a super scientific test because we have to do a couple things at once not one at a time like we should. Hopefully they help. I'm sure they won't slow it down.
Thanks to everyone for their input on this thread.

Brian

[steve cowan]

My personal experience with headers is that primary tube size isn't as big of a deal as many think. However low quality restrictive mufflers can make a huge problem.

On my 540 BBC everyone told me the 2" tubes were a big problem and i would gain alot from going bigger. I bought some really high end lemons headers with 2.25" primaries and gained nothing. However on the 423 SBC we allready have a set of 1 7/8 headers in the works to try along with a couple other things. It won't be a super scientific test because we have to do a couple things at once not one at a time like we should. Hopefully they help. I'm sure they won't slow it down.
Thanks to everyone for their input on this thread.

Brian

i agree,i think any exhaust and muffler set up will hurt performance on the track
look at the length of any type of exhaust-it cant help with any sort of exhaust pulse tuning in my opinion,if car runs faster with an exhaust and muffler setup some thing else must be going on.

[RW TECH]

in your opinion with the bigger header-°
poor exhaust flow due to early casting design compared to later castings
header complemented lift and duration used at the time
rpm used on that combo
not really questions but interesting theories on why the bigger header helped.
i think the exhaust side is very interesting and extremely complex and very few understand including myself.

The heads were ported by a Detroit area "guru" back-back when, but I do not recall anymore than that. Cam was something like 248°/256° flat tappet or thereabouts, then eventually it was changed to a bigger roller. Peak RPM was about 7200-7500 when I drove the car a couple times down the track.

[RW TECH]

in your opinion with the bigger header-
poor exhaust flow due to early casting design compared to later castings
header complemented lift and duration used at the time
rpm used on that combo
not really questions but interesting theories on why the bigger header helped.
i think the exhaust side is very interesting and extremely complex and very few understand including myself.

Steve, I did some digging and found a post he made on the header swap results. I was off on the cam but realize I'm digging from memories dating back to the mid-1980's.

Anyhow, here it is from the horse's mouth and I was around & saw all of this transpire:

"I had a reversion problem with a 364 c.i. 3 9/16 stroker that I raced in the mid 80's. This motor by no means was a serious effort by todays standards. I did'nt even know the flow numbers on the heads and it was never dyno'ed. It had about 9.5 comp. and a small solid lifter cam. Ported 292 Turbo's w/a older style Victor Jr out of the box topped off w/a Holley 750 vac sec. The cam was a old General Kinetics grind that was @ .050 260/270,535/555 w/a 107 lc. I started out with a Hooker Super Comp header that was a 1 3/4 tube size. I raced this motor for 2 years with the small street headers and I did noticed it had a bad reversion problem in the intake. It always looked wet with a dark brown stain in the bottom of the plenum. At the end of the run the motor would come down poping & banging. I chased the jetting,timing,different lash settings and collector extension. It cleared up a little,but the problem was still their and I was not happy with that. While all this was happening the car ran around 11.70's @ 117 m.p.h. I talked to alot of other racers about this problem and know one had a real good solution. So just for the hell of it, I changed to a Hooker race header. I was saving the headers for a roller cam that I was going too run. The tube size was 1 7/8 i.d. that used the adapter port plate. Guess what ??? The reversion problem was gone and it pissed off the motor. The car never pulled the wheels off the ground with the street headers. The motor sounded very strong and pulled better through the gears. At the end of the run the motor would come down clean with no poping/banging. I had guys ask me if I put a big block in the car. The e.t. and the m.p.h. picked up a bunch too. The car ran 11.30's @ 124 m.p.h. with a best e.t. of 11 teens. So I would think that their could be big gains for you with the right header size".

[steve cowan]

RW -
thank you for finding that information very interesting
upon first reading i immediately thought to much cam for the compression but rpm i dont know but i suspect no more than 7000 - 7500rpm at a guess.
thats a huge gain.very impressive.
the intrigue on the exhaust side lives on

[novafornow]

Sometimes too much attention is paid to the tube size, whereas, how soon and how sharp they bend may be just as important or maybe even more.

[ClassAct]

in your opinion with the bigger header-
poor exhaust flow due to early casting design compared to later castings
header complemented lift and duration used at the time
rpm used on that combo
not really questions but interesting theories on why the bigger header helped.
i think the exhaust side is very interesting and extremely complex and very few understand including myself.

Steve, I did some digging and found a post he made on the header swap results. I was off on the cam but realize I'm digging from memories dating back to the mid-1980's.

Anyhow, here it is from the horse's mouth and I was around & saw all of this transpire:

"I had a reversion problem with a 364 c.i. 3 9/16 stroker that I raced in the mid 80's. This motor by no means was a serious effort by todays standards. I did'nt even know the flow numbers on the heads and it was never dyno'ed. It had about 9.5 comp. and a small solid lifter cam. Ported 292 Turbo's w/a older style Victor Jr out of the box topped off w/a Holley 750 vac sec. The cam was a old General Kinetics grind that was @ .050 260/270,535/555 w/a 107 lc. I started out with a Hooker Super Comp header that was a 1 3/4 tube size. I raced this motor for 2 years with the small street headers and I did noticed it had a bad reversion problem in the intake. It always looked wet with a dark brown stain in the bottom of the plenum. At the end of the run the motor would come down poping & banging. I chased the jetting,timing,different lash settings and collector extension. It cleared up a little,but the problem was still their and I was not happy with that. While all this was happening the car ran around 11.70's @ 117 m.p.h. I talked to alot of other racers about this problem and know one had a real good solution. So just for the hell of it, I changed to a Hooker race header. I was saving the headers for a roller cam that I was going too run. The tube size was 1 7/8 i.d. that used the adapter port plate. Guess what ??? The reversion problem was gone and it pissed off the motor. The car never pulled the wheels off the ground with the street headers. The motor sounded very strong and pulled better through the gears. At the end of the run the motor would come down clean with no poping/banging. I had guys ask me if I put a big block in the car. The e.t. and the m.p.h. picked up a bunch too. The car ran 11.30's @ 124 m.p.h. with a best e.t. of 11 teens. So I would think that their could be big gains for you with the right header size".

This is interesting because it mirrors all my testing at the track. I have since come to believe (and I could off my rocker) that when the LSA gets wider from optimum the engine will be literally insensitive to exhaust changes. As the LSA is closer to optimum the engine will respond to exhaust changes when it wouldn’t otherwise. I now call it dumbing down the exhaust.

That’s the only thing I can come up with that would make any sense. I’d love to hear Larry Meaux’s thinking on this if he’d be willing to share.

[steve cowan]

in your opinion with the bigger header-
poor exhaust flow due to early casting design compared to later castings
header complemented lift and duration used at the time
rpm used on that combo
not really questions but interesting theories on why the bigger header helped.
i think the exhaust side is very interesting and extremely complex and very few understand including myself.

Steve, I did some digging and found a post he made on the header swap results. I was off on the cam but realize I'm digging from memories dating back to the mid-1980's.

Anyhow, here it is from the horse's mouth and I was around & saw all of this transpire:

"I had a reversion problem with a 364 c.i. 3 9/16 stroker that I raced in the mid 80's. This motor by no means was a serious effort by todays standards. I did'nt even know the flow numbers on the heads and it was never dyno'ed. It had about 9.5 comp. and a small solid lifter cam. Ported 292 Turbo's w/a older style Victor Jr out of the box topped off w/a Holley 750 vac sec. The cam was a old General Kinetics grind that was @ .050 260/270,535/555 w/a 107 lc. I started out with a Hooker Super Comp header that was a 1 3/4 tube size. I raced this motor for 2 years with the small street headers and I did noticed it had a bad reversion problem in the intake. It always looked wet with a dark brown stain in the bottom of the plenum. At the end of the run the motor would come down poping & banging. I chased the jetting,timing,different lash settings and collector extension. It cleared up a little,but the problem was still their and I was not happy with that. While all this was happening the car ran around 11.70's @ 117 m.p.h. I talked to alot of other racers about this problem and know one had a real good solution. So just for the hell of it, I changed to a Hooker race header. I was saving the headers for a roller cam that I was going too run. The tube size was 1 7/8 i.d. that used the adapter port plate. Guess what ??? The reversion problem was gone and it pissed off the motor. The car never pulled the wheels off the ground with the street headers. The motor sounded very strong and pulled better through the gears. At the end of the run the motor would come down clean with no poping/banging. I had guys ask me if I put a big block in the car. The e.t. and the m.p.h. picked up a bunch too. The car ran 11.30's @ 124 m.p.h. with a best e.t. of 11 teens. So I would think that their could be big gains for you with the right header size".

This is interesting because it mirrors all my testing at the track. I have since come to believe (and I could off my rocker) that when the LSA gets wider from optimum the engine will be literally insensitive to exhaust changes. As the LSA is closer to optimum the engine will respond to exhaust changes when it wouldn’t otherwise. I now call it dumbing down the exhaust.

That’s the only thing I can come up with that would make any sense. I’d love to hear Larry Meaux’s thinking on this if he’d be willing to share.

with the older design heads duration was required to make em run back in the day.
With the bigger header fitted and picked up a ton of power and helped with reversion
would it be the weaker pulse coming back up the header that helped?
with that duration there would be a lot of overlap and the lower compression as well that
may of contributed to a lot of reversion.
good conversation.

[steve cowan]

i am reading larry's threads on header tube and collector sizes
its answered my curiosity -
less compression bigger pipes'
low VE bigger pipes
high EGT bigger pipes
more duration bigger pipes
as heads get more efficient exhaust valve gets smaller and intake valve gets bigger
engines with higher VE have smaller headers
so in the engine RW was describing -
low comp,older design cylinder head needing duration and bigger pipes to work better.
i have read all this from past years,unfortunately my brain has become volumetrically inefficient.

[prairiehotrodder]

This motor is getting some AFR 245 heads along with 1 7/8 headers and a holley strip dominator intake. Hopefully get to the track Aug 20.
Brian