427 Catheral port Dyno
Before you spend more $$$ on a cam, go 2in headers/3.5 collectors. You are at the power level where it makes sense to crossover to a bigger/better header. I would certainly, absolutely, try that first before doing anything.else. Congrats, the combo is rocking!
FYI, and don't get offended-please, but I think your heads are crap and it still made amazing power. I can only imagine a Brodix cathedral or a Mast 295 cathedral on this and the power it would make. I have talked with a guy several years ago who made 2hp per cube on a decent 408 with ET cathedral heads. It's totally possible, you just have to get a touch more serious and you are there. We should meet, I am in South Florida, lmk if you ever come to my area.
FYI, and don't get offended-please, but I think your heads are crap and it still made amazing power. I can only imagine a Brodix cathedral or a Mast 295 cathedral on this and the power it would make. I have talked with a guy several years ago who made 2hp per cube on a decent 408 with ET cathedral heads. It's totally possible, you just have to get a touch more serious and you are there. We should meet, I am in South Florida, lmk if you ever come to my area.
Far as the Brodix Cathedral port, I haven't been able to find one person show me a na 427 make more power using them. I'd buy them if someone would. Maybe the BTR canted valve Cathedrals will be the ticket, cause I'm not spending 7k for Mast 295s with everything need to run them.
Probably a wise choice to stick with what you have and would only make financial sense had you started with a Brodix or MAST head. But you NA guys sometimes go to extreme lengths to get every last bit of power you can find.
PRC 247 intake valve - 2.120
Brodix BR1 intake vavle - 2.100
MAST 295 intake valve - 2.165
Any consideration to try a LLSR?
I too would be hard pressed to move backwards in valve size especially on a large bore cylinder unless I could be guaranteed improvement everywhere being a road race car.
It's not apples to apples as the examples below are all turbo cars but for the ones who have doubts about a cathedral port:
https://ls1tech.com/forums/drag-raci...ler-388-a.html
https://ls1tech.com/forums/forced-in...goes-dyno.html
Ironically both of those cars were/are owned by the same fella. The 3rd gen is still running an OEM style rocker with untouched BR1's.
I know Pete Harrell is a big fan of the MAST 295's and example there would be Cleetus/Leroy's engine running them.
I'm also really wanting to see more on these BTR canted valve heads in both ports (cathedral and square).
PRC 247 intake valve - 2.120
Brodix BR1 intake vavle - 2.100
MAST 295 intake valve - 2.165
Any consideration to try a LLSR?
I too would be hard pressed to move backwards in valve size especially on a large bore cylinder unless I could be guaranteed improvement everywhere being a road race car.
It's not apples to apples as the examples below are all turbo cars but for the ones who have doubts about a cathedral port:
https://ls1tech.com/forums/drag-raci...ler-388-a.html
https://ls1tech.com/forums/forced-in...goes-dyno.html
Ironically both of those cars were/are owned by the same fella. The 3rd gen is still running an OEM style rocker with untouched BR1's.
I know Pete Harrell is a big fan of the MAST 295's and example there would be Cleetus/Leroy's engine running them.
I'm also really wanting to see more on these BTR canted valve heads in both ports (cathedral and square).
Well tried alot of different things to make some gains.
So far I've swapped Cams
250/260.5 628 620 112+ 1.5
Added 2 inch headers
Fic 750cc injectors
E85 picked up 7 wheel 2* timing added lost adding more.
10 pound lighter flywheel
SD tune
104mm lid
103mm Tb
Magnum-f trans and fresh clutch
Weather was horrible 116 degree dyno room and alot of humidity
She's down power.
So far I've swapped Cams
250/260.5 628 620 112+ 1.5
Added 2 inch headers
Fic 750cc injectors
E85 picked up 7 wheel 2* timing added lost adding more.
10 pound lighter flywheel
SD tune
104mm lid
103mm Tb
Magnum-f trans and fresh clutch
Weather was horrible 116 degree dyno room and alot of humidity
She's down power.
The weather is only 6 degrees higher than your first run on that dyno though. I feel like you stepped backwards on the cam by lowering the lift, maybe not much, but some.
I would say you would see some good gains having the msd opened up and going to a bit shorter runner in it (Ironmask would be my go to on this).
I would say you would see some good gains having the msd opened up and going to a bit shorter runner in it (Ironmask would be my go to on this).
The weather is only 6 degrees higher than your first run on that dyno though. I feel like you stepped backwards on the cam by lowering the lift, maybe not much, but some.
I would say you would see some good gains having the msd opened up and going to a bit shorter runner in it (Ironmask would be my go to on this).
I would say you would see some good gains having the msd opened up and going to a bit shorter runner in it (Ironmask would be my go to on this).
I ported the Msd and gained over the first dyno trip.
It has crossed my mind to shorten the runner's.
I've got a few ideas on why it lost. But I'm all ears if someone has insite
Well tried alot of different things to make some gains.
So far I've swapped Cams
250/260.5 628 620 112+ 1.5
Added 2 inch headers
Fic 750cc injectors
E85 picked up 7 wheel 2* timing added lost adding more.
10 pound lighter flywheel
SD tune
104mm lid
103mm Tb
Magnum-f trans and fresh clutch
Weather was horrible 116 degree dyno room and alot of humidity
She's down power.
So far I've swapped Cams
250/260.5 628 620 112+ 1.5
Added 2 inch headers
Fic 750cc injectors
E85 picked up 7 wheel 2* timing added lost adding more.
10 pound lighter flywheel
SD tune
104mm lid
103mm Tb
Magnum-f trans and fresh clutch
Weather was horrible 116 degree dyno room and alot of humidity
She's down power.
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he meant Ls7 port heads, only the factory castings have the valve dropping issue, aftermarket Ls7 castings dont have this issue. Also the Ls7 makes way more power and tq and is also not limited when it comes to intakes. Pretty silly to use cathedral ports on a large cubic inch LS.
Well took the time to do some exhaust testing. Picked up 14 wheel. So a 4 inch y pipe and cutout are getting built.
Also after month's of waiting on the BTR canted valve head's with no eta as of last week. I put in some calls and made the choice to buy the 295 MAST cathedral heads. 6 week's build time and we shall see what is to be gained. Ls7 rockers should bring lift to .672 intake and .655 exhaust. Went 62cc chambers and .040 head gasket.
Also after month's of waiting on the BTR canted valve head's with no eta as of last week. I put in some calls and made the choice to buy the 295 MAST cathedral heads. 6 week's build time and we shall see what is to be gained. Ls7 rockers should bring lift to .672 intake and .655 exhaust. Went 62cc chambers and .040 head gasket.
Last edited by raymond mckinney; Mar 20, 2025 at 06:58 AM.
Pulled the heads off and found our missing power.
24 degrees timing 12.4 afr TR6 plugs
63% injector cycle duty FIC injectors Hellcat pump
CRANK has been checked reluctor wheel is in correct place. Bearings are perfect!
Hoping it'll clean up at 4.130
Thinking about -4 cc Flattops or +2.8 dome
62cc .041 headgasket this go around.
Pulled the heads off and found our missing power.
24 degrees timing 12.4 afr TR6 plugs
63% injector cycle duty FIC injectors Hellcat pump
CRANK has been checked reluctor wheel is in correct place. Bearings are perfect!
Hoping it'll clean up at 4.130
Thinking about -4 cc Flattops or +2.8 dome
62cc .041 headgasket this go around.
Dude....Fuhhhhhhhhhk.
Was that on 93 or E85? Seems a bit rich (but not enough to get fuel behind the ringland and break it off) for na. The compression wasn't crazy on this thing.
Was that on 93 or E85? Seems a bit rich (but not enough to get fuel behind the ringland and break it off) for na. The compression wasn't crazy on this thing.
Not really sure what happened. Everyone thought the reluctor moved. E85 tested at E78 at its lowest point. Gonna clean the fuel system and injectors.
Ordered some 4.130 Diamonds with 3.84cc reliefs. Hope to beat the Florida heat to get it back together!
Ordered some 4.130 Diamonds with 3.84cc reliefs. Hope to beat the Florida heat to get it back together!