Looking for more from crate motor?
Melting Slicks
Joined: Nov 2010
Posts: 2,216
Likes: 112
From: Michigan
Try some collector inserts, they make some that are ventura shaped, they also make some cone inserts but I think the ventura style would help you more.
w/o knowing more detail of what the car does it's kinda hard to give too much advise but those headers are deff a top end race size and I'm betting the sidepipes are large.
edit: Just saw you said 4" while I was posting so yah deff too big.
Last edited by BOOT77; Dec 29, 2015 at 11:13 PM.
Race Director
Joined: Jan 2000
Posts: 13,011
Likes: 2,250
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Again...I'd do some tuning. Are you sure secondaries are opening? Getting ful throttle- C-3's have a steady problem with this as pedal arm bends.
I'd stick with the dual plane intake unless it's a really small one. Got any pics?
Outside diameter of sidepipes is 4"...but what is the inside diameter of the baffle and how long is it? Most sidepipe headers have way too long primaries...but that's what we've got so we'll work with it.
Cam is exactly that...a good "warranty" cam to not give any issues.
JIM
I'd stick with the dual plane intake unless it's a really small one. Got any pics?
Outside diameter of sidepipes is 4"...but what is the inside diameter of the baffle and how long is it? Most sidepipe headers have way too long primaries...but that's what we've got so we'll work with it.
Cam is exactly that...a good "warranty" cam to not give any issues.
JIM
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
Again...I'd do some tuning. Are you sure secondaries are opening? Getting ful throttle- C-3's have a steady problem with this as pedal arm bends.
I'd stick with the dual plane intake unless it's a really small one. Got any pics?
Outside diameter of sidepipes is 4"...but what is the inside diameter of the baffle and how long is it? Most sidepipe headers have way too long primaries...but that's what we've got so we'll work with it.
Cam is exactly that...a good "warranty" cam to not give any issues.
JIM
I'd stick with the dual plane intake unless it's a really small one. Got any pics?
Outside diameter of sidepipes is 4"...but what is the inside diameter of the baffle and how long is it? Most sidepipe headers have way too long primaries...but that's what we've got so we'll work with it.
Cam is exactly that...a good "warranty" cam to not give any issues.
JIM
Race Director
Joined: Jan 2000
Posts: 13,011
Likes: 2,250
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Putting it on a chassis dyno with someone good at tuning sounds like a better option as we go forward. Need to make sure you're getting what you paid for before we start changing things.
Fuel/ignition systems and tuning to make it all work are vital.
JIM
Fuel/ignition systems and tuning to make it all work are vital.
JIM
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Make sure the secondaries are opening 100%. I have a brand new Holley 750 vac secondary that the secondaries only open about 30-40%... This was on a 440 hp 396".. I tried all kind of stuff to help the secondaries open and they would still only open to a certain points
Put a zip tie on the shaft to the diaphragm and go hammer on it... Come back and measure how much the zip tie has been pushed down the shaft, that will tell you how much they are opening.
I ended up building a 65' Holley 780 vac sec that has the pitot tube in the primary to pull a better vacuum on the secondaries, they open considerably better, but still not 100%. Maybe like 75%, but way better then the new 750 vac sec I tried first.
All of this BS is why I love double pumpers... They always open and hit hard when they do.
I'm betting your secondaries are lazy, hence why it feels soft down low.
After that, the 200r4 and 3500 converter should wake it up nicely.
Put a zip tie on the shaft to the diaphragm and go hammer on it... Come back and measure how much the zip tie has been pushed down the shaft, that will tell you how much they are opening.
I ended up building a 65' Holley 780 vac sec that has the pitot tube in the primary to pull a better vacuum on the secondaries, they open considerably better, but still not 100%. Maybe like 75%, but way better then the new 750 vac sec I tried first.
All of this BS is why I love double pumpers... They always open and hit hard when they do.
I'm betting your secondaries are lazy, hence why it feels soft down low.
After that, the 200r4 and 3500 converter should wake it up nicely.
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Burning Brakes
Joined: Dec 2003
Posts: 1,004
Likes: 7
From: Adelaide South Australia
Getting the timing and carb tuned specifically for your engine combo will make a world of difference.
My first dyno tune on a 383 crate engine put down 311 rwhp.
Disappointing for a 475 hp build.
4 years later I had it tuned by another workshop.
After 5 hours on the dyno, 60 additional rear wheel horses were found.
Still running strong after 4 years. All I have done is replace plugs.
Get the tune sorted out and your 396 should really put a smile on your face.
My first dyno tune on a 383 crate engine put down 311 rwhp.
Disappointing for a 475 hp build.
4 years later I had it tuned by another workshop.
After 5 hours on the dyno, 60 additional rear wheel horses were found.
Still running strong after 4 years. All I have done is replace plugs.
Get the tune sorted out and your 396 should really put a smile on your face.
Last edited by OzzyTom; Dec 31, 2015 at 07:31 AM.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
Why I asked thim this below. Wondering if he has an ideal distributor curve. That motor should smoke the tires all day. 200r with a bigger converter should wake it up
Bigger motors can use more of everythign and get away with it.
The suggestiosn of getting an 02 bung welded in and spending some time monitoring things was a good one.
Sure you want low end and not more power period?]
The suggestiosn of getting an 02 bung welded in and spending some time monitoring things was a good one.
Last edited by cv67; Dec 31, 2015 at 09:29 AM.