Intake Manifold recommendations
Thread Starter
Instructor
Joined: Oct 2008
Posts: 121
Likes: 0
From: Hooksett NH
Intake Manifold recommendations
In planning a top end project on my 75 L48, (heads & cam) should I reuse the stock intake manifold, or upgrade to a Edel. Performer, or any other? I want to keep the Q-jet. Is the stock manifold aluminum or cast, and how does it flow. I'm looking at heads with NO heat crossover. Is that a mistake? There is no emissions for this car in NH. Do I want to delette the EGR, the heat riser, and the choke. I'm only going to drive in the warmer weather. (above 40*)
Burning Brakes
Joined: Aug 2006
Posts: 1,155
Likes: 0
From: San Diego California
I believe your L48 vette has the iron intake manifold. The aluminum was for the L82, and was added to the L48 in 1980. You may want to get the Edelbrock Performer that's aluminum, flows well and fit under your hood. The Endurashine looks
. If your vette will not be smogged, and will be street driven in warm weather, you can do whatever you want- and dont need the EGR. .
. If your vette will not be smogged, and will be street driven in warm weather, you can do whatever you want- and dont need the EGR. .
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
Having done this swap, I must tell you that you probably will notice no difference in performance. The only advantage from using the Edelbrock is the lighter weight of using aluminum over cast iron.
You'd be better off investing that money in some other area on the engine, like headers. It was the last mod. I made a couple of years after I did all the other stuff. (see sig.)
You'd be better off investing that money in some other area on the engine, like headers. It was the last mod. I made a couple of years after I did all the other stuff. (see sig.)
Instructor
Joined: Jan 2009
Posts: 193
Likes: 0
From: NJ
I went with the edelbrock performer manifold and edelbrock performer RPM heads, and I am very happy with my performance gains. Best of luck with you top end rebuild! Remember the last place you wanna cheap out on is the heads!
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
i agree with what everone said. i think it would be good to lose all your egr stuff if you have no need for it . very little in performance gains in the manifolds but a non egr one would certainly tidy things up.
Safety Car
Joined: Apr 2007
Posts: 4,435
Likes: 9
From: Kalamazoo Mi
here is a plate i made for a mustang endurance car (i did a sloppy job with the silicone, but its a 1 event car so
)
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
There was a test in one of the ragazines I glanced at it on the mag rack they tested a performer edelbrock against a cast iron factory manifold it made 9 more hp on the dyno that might end up being 6/7 hp at the ground your not likely to feel that but it would pull probably about 20 pounds off your car you don't have to accelrate, stop or go around corners with. Manifold is not very expensive at around $120.00, but if your in a money crunch $120.00 torwards a set of headers would be a better investment.
Last edited by Little Mouse; Jan 31, 2009 at 12:30 PM.
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Le Mans Master
Joined: Oct 2007
Posts: 7,445
Likes: 970
From: Tennessee/Rhode Island
I had a 350 2 bolt with 73 smog heads that I swapped the OEM cast iron intake manifold for an Edlelbrock Performer a few years back ( not a corvette) and there was definitely a performance improvement. I would consider the switch if your intake is a cast iron one for the L-48 which is basically GM's run of the mill passenger car intake but would not if you had the aluminum L-82 intake since the performance gain is more dubious. I have the original L-82 aluminum intake on my car with an EGR block off plate. 9- 10 more HP and more torque, better throttle response, no EGR, and lighter weight to me is worth the $150 for the manifold.
Race Director
Joined: Jun 2000
Posts: 10,039
Likes: 670
From: FL
Edelbrock RPM Q-Jet part #7104. Probably the best dual plane for the Q-Jet. Flows better than the Performer.
I am using the stock Q-Jet, just made a new fuel line to accomodate the increased height (search for "Lars fuel line" for directions). Replaced the hot air choke with an electric choke. Google "electric choke" Q-Jet for a kit.
Edelbrock will tell you that the 7104 does not fit the Corvette.
I am using a Moroso Low Profile Racing Aircleaner. 14x3" filter. Barely touches HEI. Just had to dimple the base a bit for the accelerator pump arm. 3/4" clearance between aircleaner and stock hood.
I am using the stock Q-Jet, just made a new fuel line to accomodate the increased height (search for "Lars fuel line" for directions). Replaced the hot air choke with an electric choke. Google "electric choke" Q-Jet for a kit.
Edelbrock will tell you that the 7104 does not fit the Corvette.
I am using a Moroso Low Profile Racing Aircleaner. 14x3" filter. Barely touches HEI. Just had to dimple the base a bit for the accelerator pump arm. 3/4" clearance between aircleaner and stock hood.
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
You should be concentrating more on a combination of parts that work in concert to give you the type of performance you want.
If you are going to go with heads and intake, you should add a cam and headers along with a performance exhaust system. Pick heads, an intake and a cam that match up in the rpm range you want your power. You will get more out of your time and money.
If you are going to go with heads and intake, you should add a cam and headers along with a performance exhaust system. Pick heads, an intake and a cam that match up in the rpm range you want your power. You will get more out of your time and money.
Thread Starter
Instructor
Joined: Oct 2008
Posts: 121
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From: Hooksett NH
Here's what I have in mind for a build right now. Any advice is welcome. World Prod. S/R Torquer heads (67cc chambers w/170cc runners, 2.02/1.60 valves). Summit 204/214/112 cam kit. Reworking carb, & distributor. Here's where I'm having trouble and would like help. Figuring head gasket thichness. I found:
dish pistons @18cc
deck @ .025
bore/stroke 4.00x3.48
Looking for static compression to figure out head gasket thicknes and see if I have to up Cam specs. ? .015 steel shim?
dish pistons @18cc
deck @ .025
bore/stroke 4.00x3.48
Looking for static compression to figure out head gasket thicknes and see if I have to up Cam specs. ? .015 steel shim?
Melting Slicks
Joined: May 2006
Posts: 3,438
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From: Raleigh NC
St. Jude Donor '13-'14
Drifting
Joined: Aug 2008
Posts: 1,381
Likes: 11
THe stock L48 intake is good to about 4,800 to 5,000 RPM depending on cam, heads, and exhaust, but generally it can be out performed above this. It will produce low RPM power superior to any after market manifold. If you plan on spending time above 5,000 RPM there are better choices. The little Chevy V8 spins so easily with a good set of heads, a moderate cam, and a good four barrel carb that's it's almost a shame not to run it fast.
Racer
Joined: Oct 2005
Posts: 449
Likes: 0
From: Boulder CO
I'm not familiar with 80s. Do you have currently have an electic choke or is the choke on the manifold? If it's manifold based, you'll have to install an electric choke which is not a big deal.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Here's what I have in mind for a build right now. Any advice is welcome. World Prod. S/R Torquer heads (67cc chambers w/170cc runners, 2.02/1.60 valves). Summit 204/214/112 cam kit. Reworking carb, & distributor. Here's where I'm having trouble and would like help. Figuring head gasket thichness. I found:
dish pistons @18cc
deck @ .025
bore/stroke 4.00x3.48
Looking for static compression to figure out head gasket thicknes and see if I have to up Cam specs. ? .015 steel shim?
dish pistons @18cc
deck @ .025
bore/stroke 4.00x3.48
Looking for static compression to figure out head gasket thicknes and see if I have to up Cam specs. ? .015 steel shim?
SUM-K1103, 214/224 .050 duration.
Bore 4.00
stroke 3.48
head cc 67
head gasket .015
piston dish .018
piston down .025
Compression ratio 8.69
cubic inch 349.85
are you sure the dished piston is 18cc ?
Last edited by Little Mouse; Feb 1, 2009 at 02:22 AM.
Race Director
Joined: Oct 2002
Posts: 12,065
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From: Smalltownville Michigan
Cruise-In 5, 6 & 10 Veteran
St. Jude Donor '09
I found an aluminum factory Qjet manifold from an 81 Z-28 that works really wel with my car. The best part about factory pieces is that clearance issues is a lot less..
Thread Starter
Instructor
Joined: Oct 2008
Posts: 121
Likes: 0
From: Hooksett NH
I'm not sure the stock L48 pistons are .018cc dish, that is what i read somewhere online, and the L82 was .012cc dish. Can someone verify this? This is the missing info. that is going to effect my compression figure.