My HSR modification
Thread Starter
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
Originally Posted by SloRvette
The water neck is a little bit of a PITA. I made up a custom one. You might want to lay something out before you head to the welders.
If it becomes a problem then I can live without the IAC.
Another issue is the throttle wire. I might have to modify that.
I don't have a throttle body yet. I read somewhere that the HSR uses a LT1 style throttle body. What is the differance between a LT1 style and a TPI style?
Last edited by JoBy; Oct 14, 2005 at 01:52 AM.
Drifting
Joined: Feb 2003
Posts: 1,978
Likes: 2
From: San Antonio Texas
Very interesting mod you're into...a very good idea...I was thinking one might extend the runners with a 1" (25mm) matching piece, and then smooth the entrances as you did. Do you think this would be an obstruction to the throttle-body air flow? How much distance is there from the base top, to the bottom of the lid? Good luck with this, and keep us posted.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
"What is the differance between a LT1 style and a TPI style TB"
Same size / same fitment ,just a different TPS / IAC .The throttle hookup is similar to the late TPI TBs as in the cable runs around a quadrant instead of hooking on to a stud like the early ones..
Same size / same fitment ,just a different TPS / IAC .The throttle hookup is similar to the late TPI TBs as in the cable runs around a quadrant instead of hooking on to a stud like the early ones..
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Thread Starter
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
Originally Posted by Curveit
Very interesting mod you're into...a very good idea...I was thinking one might extend the runners with a 1" (25mm) matching piece, and then smooth the entrances as you did. Do you think this would be an obstruction to the throttle-body air flow? How much distance is there from the base top, to the bottom of the lid? Good luck with this, and keep us posted.
The plenum is lowerd about 1" at the front, less at the rear.
The front runners are close to the TB.
I lowerd the plenum a 1/8 inch more after this picture.
And then I lowerd the front side of the front two runners to get them level with the throttle bores.
Last edited by JoBy; Jan 8, 2006 at 05:15 AM.
Thread Starter
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
Originally Posted by Slalom4me
Any updates?
Originally Posted by yedister
How does all these modification affect the flow of the intake?
yedi
yedi
Most of this lost volume is regaind from removing the cast pipes around the bolts thru the plenum.
The flow should increase some from radiusing the entrance of the runners, but that could be done to any HSR.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Originally Posted by JoBy
I lowered the plenum another 1/8" after this picture.
. 
. What is your opinion about milling the top of the HSR to remove three
of the ribs from the left side for another 8mm clearance? There
are nine ribs in total. For the sake of visual symmetry afterward, the
three on the right side could be milled, too. No impact on runner
length or plenum volume.
Also, do you have an LTx TB? In the present configuration, how is
hood clearance with the TB in place? Is there any room between the
TB and the manifold, thermostat housing, fuel rail cross-over?
If so, what is your opinion about cutting the front face of the plenum
(like a slice off a loaf of bread) then reattaching it at an angle of
several degrees to tip the TB downward?
As this picture of SloRvette's C4/HSR illustrates, the engine and hood
are located on two different planes with an intersection that isn't
favorable to the HSR.
.
Last edited by Slalom4me; Jan 8, 2006 at 11:05 AM.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
For those who know their way around the TB, what is underneath
the plate on top?
Any reason why there can't be modifications to shorten the bosses
for the top bolts to bring the bolt heads closer to the plenum?
How about the plate? I've read about others changing the bolts to
ones with a lower profile head and or countersinking them further.
Why not complete removal? Is it a cover for coolant passage?
.
the plate on top?
Any reason why there can't be modifications to shorten the bosses
for the top bolts to bring the bolt heads closer to the plenum?
How about the plate? I've read about others changing the bolts to
ones with a lower profile head and or countersinking them further.
Why not complete removal? Is it a cover for coolant passage?
.
Thread Starter
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
Originally Posted by Slalom4me
What is your opinion about milling the top of the HSR to remove three
of the ribs from the left side for another 8mm clearance? There
are nine ribs in total. For the sake of visual symmetry afterward, the
three on the right side could be milled, too. No impact on runner
length or plenum volume.
of the ribs from the left side for another 8mm clearance? There
are nine ribs in total. For the sake of visual symmetry afterward, the
three on the right side could be milled, too. No impact on runner
length or plenum volume.
Originally Posted by Slalom4me
Also, do you have an LTx TB? In the present configuration, how is
hood clearance with the TB in place? Is there any room between the
TB and the manifold, thermostat housing, fuel rail cross-over?
hood clearance with the TB in place? Is there any room between the
TB and the manifold, thermostat housing, fuel rail cross-over?
Originally Posted by Slalom4me
If so, what is your opinion about cutting the front face of the plenum
(like a slice off a loaf of bread) then reattaching it at an angle of
several degrees to tip the TB downward?
(like a slice off a loaf of bread) then reattaching it at an angle of
several degrees to tip the TB downward?
I automatically get the TB at a better angle compared to the unmodified HSR.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Originally Posted by JoBy
That can also be done. I think it would have to be quite thick if you are
going to bolt it to the plenum and have the TB bolts in another angle
without interferance.
I automatically get the TB at a better angle compared to the unmodified HSR.
going to bolt it to the plenum and have the TB bolts in another angle
without interferance.
I automatically get the TB at a better angle compared to the unmodified HSR.
Envision making a vertical slice about 12mm wide to take off the face
of the plenum, laying the top forward several degrees and then reattaching it.
Think there is sufficient clearance for the TB (IAC & TPS), thermostat
housing and rail cross-over to all co-exist there?
.
Thread Starter
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
Originally Posted by Slalom4me
Look closely at the manifold below on the right to see what I mean.
Envision making a vertical slice about 12mm wide to take off the face
of the plenum, laying the top forward several degrees and then reattaching it.
Think there is sufficient clearance for the TB (IAC & TPS), thermostat
housing and rail cross-over to all co-exist there?
.
Envision making a vertical slice about 12mm wide to take off the face
of the plenum, laying the top forward several degrees and then reattaching it.
Think there is sufficient clearance for the TB (IAC & TPS), thermostat
housing and rail cross-over to all co-exist there?
.
You did some serious photoshopping in that picture. You moved the lathe in the background too. =)
You could probably cut the front of and weld it back at an angle, but I don't think you would gain that much. On mine the whole plenum is tilted down and I don't think the TB will hit the hood.
I will find out about clearance under the TB when I one on there.
Drifting
Joined: Mar 2005
Posts: 1,923
Likes: 0
From: GA
Originally Posted by Slalom4me
For those who know their way around the TB, what is underneath
the plate on top?
Any reason why there can't be modifications to shorten the bosses
for the top bolts to bring the bolt heads closer to the plenum?
How about the plate? I've read about others changing the bolts to
ones with a lower profile head and or countersinking them further.
Why not complete removal? Is it a cover for coolant passage?
the plate on top?
Any reason why there can't be modifications to shorten the bosses
for the top bolts to bring the bolt heads closer to the plenum?
How about the plate? I've read about others changing the bolts to
ones with a lower profile head and or countersinking them further.
Why not complete removal? Is it a cover for coolant passage?
Drifting
Joined: Mar 2005
Posts: 1,923
Likes: 0
From: GA
Joby,
here's some measurements from an old LT1 TB I have laying around.
From the bottom of the TB (which dhould line up with the bottom of the plenum) to the lowest part of the IAC housing is 1.983". the IAC itself doesn't go lower than that point and that low point is 1.100" to the left of center (looking at the front of the TB) In the center the lowest point of the housng is 1.357".
The upper bolt boss's upper wall thickness is .195" and they stick above the top plate approx. .050". You could make a thinner top plate (say .100") then grind the bosses down flat to around .100".
Hope this helps with figuring your clearances.
here's some measurements from an old LT1 TB I have laying around.
From the bottom of the TB (which dhould line up with the bottom of the plenum) to the lowest part of the IAC housing is 1.983". the IAC itself doesn't go lower than that point and that low point is 1.100" to the left of center (looking at the front of the TB) In the center the lowest point of the housng is 1.357".
The upper bolt boss's upper wall thickness is .195" and they stick above the top plate approx. .050". You could make a thinner top plate (say .100") then grind the bosses down flat to around .100".
Hope this helps with figuring your clearances.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Some fittings attach to the back of the plenum and space back there
gets a bit tight when everything is assembled.
Is it possible to install the distributor while the plenum is on the
manifold? Can the cap be removed once everything is in place?
.
gets a bit tight when everything is assembled.
Is it possible to install the distributor while the plenum is on the
manifold? Can the cap be removed once everything is in place?
.
Thread Starter
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
Originally Posted by Slalom4me
Some fittings attach to the back of the plenum and space back there
gets a bit tight when everything is assembled.
Is it possible to install the distributor while the plenum is on the
manifold? Can the cap be removed once everything is in place?
.
gets a bit tight when everything is assembled.
Is it possible to install the distributor while the plenum is on the
manifold? Can the cap be removed once everything is in place?
.
