stock LT1 manifold
Thread Starter
Pro
Joined: Jan 2009
Posts: 686
Likes: 4
From: Austin Texas
stock LT1 manifold
I've seen some opine that its a fine piece. Measure the cross sectional area ("CSA") of the openings. I don't mean the entire opening, but the effective opening where air can actually travel, which excludes about the ower 30% of the port openings where that injector boss is. After the measurement, yes indeed, it is a good piece - FOR STOCK HEADS with a 1.8" sq. CSA.
But if you go to Dart, AFR, LE, or other aftermarket source heads having a CSA greater than 1.8, that stock manifold becomes restrictive.
That's why I punched out the walls on mine to 1.75" X 1.25" to give CSA of 2.18.
It was a good match for the stock heads, which themselves were restrictive. Had to be, since the LT1 is capable of outperforming the LT5, and management could never allow that !!
One man's opinion, take it or leave it.
But if you go to Dart, AFR, LE, or other aftermarket source heads having a CSA greater than 1.8, that stock manifold becomes restrictive.
That's why I punched out the walls on mine to 1.75" X 1.25" to give CSA of 2.18.
It was a good match for the stock heads, which themselves were restrictive. Had to be, since the LT1 is capable of outperforming the LT5, and management could never allow that !!
One man's opinion, take it or leave it.
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Are there any flow bench numbers, compairing stock flow to various porting work anywhere?
I would like to see the numbers for stock LT1 heads and intake. How much can they be improved or not.
Anyone?
I would like to see the numbers for stock LT1 heads and intake. How much can they be improved or not.
Anyone?
Team Owner
Joined: Mar 2001
Posts: 30,847
Likes: 293
From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Tony from AFR can port a miniram to 410.
http://forums.corvetteforum.com/c4-t...m-miniram.html
They make minirams for LTX engines
http://forums.corvetteforum.com/c4-t...m-miniram.html
They make minirams for LTX engines
Last edited by BrianCunningham; Aug 4, 2009 at 11:56 AM. Reason: Miniram not LT1
Le Mans Master
Joined: Sep 2000
Posts: 6,976
Likes: 527
From: Clouds Over California
I've seen some opine that its a fine piece. Measure the cross sectional area ("CSA") of the openings. I don't mean the entire opening, but the effective opening where air can actually travel, which excludes about the ower 30% of the port openings where that injector boss is. After the measurement, yes indeed, it is a good piece - FOR STOCK HEADS with a 1.8" sq. CSA.
But if you go to Dart, AFR, LE, or other aftermarket source heads having a CSA greater than 1.8, that stock manifold becomes restrictive.
That's why I punched out the walls on mine to 1.75" X 1.25" to give CSA of 2.18.
It was a good match for the stock heads, which themselves were restrictive. Had to be, since the LT1 is capable of outperforming the LT5, and management could never allow that !!
One man's opinion, take it or leave it.
But if you go to Dart, AFR, LE, or other aftermarket source heads having a CSA greater than 1.8, that stock manifold becomes restrictive.
That's why I punched out the walls on mine to 1.75" X 1.25" to give CSA of 2.18.
It was a good match for the stock heads, which themselves were restrictive. Had to be, since the LT1 is capable of outperforming the LT5, and management could never allow that !!
One man's opinion, take it or leave it.
http://forums.corvetteforum.com/c4-t...afr-heads.html
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Stock Lt1 head #s are real similar to L98s...lousy 
Ive personally seen 199 to 211 in person. Without pulling the sheet up I think the exh were around 150-160
Intakes around 220 cfm from what I understand.
Cris, what are you matching yours to, 1284?
Almost got one done here, little more necking down on the guides and it goes to the flow bench to see where things stand.
Not going to crazy on this set, going on a mild build. .
The Lt1 heads are screaming for larger valves, especially the exhuast.
Stock seats leave something to be desired.
I dont think stock for stock or ported a LTx will ever keep up with the LT5/LS6. LT5s with porting alone/headers are good for 440+ at the tire, stock cams, bottom end, etc but they can still run good..
Ive personally seen 199 to 211 in person. Without pulling the sheet up I think the exh were around 150-160
Intakes around 220 cfm from what I understand.
Cris, what are you matching yours to, 1284?
Almost got one done here, little more necking down on the guides and it goes to the flow bench to see where things stand.
Not going to crazy on this set, going on a mild build. .
The Lt1 heads are screaming for larger valves, especially the exhuast.
Stock seats leave something to be desired.
I dont think stock for stock or ported a LTx will ever keep up with the LT5/LS6. LT5s with porting alone/headers are good for 440+ at the tire, stock cams, bottom end, etc but they can still run good..
Thread Starter
Pro
Joined: Jan 2009
Posts: 686
Likes: 4
From: Austin Texas
What is 1284 ?
I just opened up the pinch points on my heads so they're about 2.06 sq. in. as far as I can best measure and made the transitions smooth. Then made the manifold ports to have 2.18 sq. in. in the region where the air flows. Also, put the manif. and heads on a block and look into the injector holes to identify opportunity areas for removal of material that injected fuel impinges directly onto. Intake valve face on the 45 is 60 thous wide and seat is 40 thous wide. Chambers perfectly blended to seat's 31 deg cut, bowls blended perfectly with 89% of valve face dia. in throat. Did some removal around the plug area and flattened the chamber roof. Using 028 head gasket will re-coup lost compression and also improve quench height. Chambers very smooth, exposed plug threads smoothed. guide bosses substantially removed / rounded. LT4 springs & retainers, GMPP valves:
http://www.crateenginedepot.com/site...363755-613.htm
http://www.crateenginedepot.com/site...363756-616.htm
I have a spare set of those valves listed over in "for sale" section.
I just opened up the pinch points on my heads so they're about 2.06 sq. in. as far as I can best measure and made the transitions smooth. Then made the manifold ports to have 2.18 sq. in. in the region where the air flows. Also, put the manif. and heads on a block and look into the injector holes to identify opportunity areas for removal of material that injected fuel impinges directly onto. Intake valve face on the 45 is 60 thous wide and seat is 40 thous wide. Chambers perfectly blended to seat's 31 deg cut, bowls blended perfectly with 89% of valve face dia. in throat. Did some removal around the plug area and flattened the chamber roof. Using 028 head gasket will re-coup lost compression and also improve quench height. Chambers very smooth, exposed plug threads smoothed. guide bosses substantially removed / rounded. LT4 springs & retainers, GMPP valves:
http://www.crateenginedepot.com/site...363755-613.htm
http://www.crateenginedepot.com/site...363756-616.htm
I have a spare set of those valves listed over in "for sale" section.
Last edited by ChrisWhewell; Aug 4, 2009 at 01:16 PM.
