Big block intake manifold question
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Pro
Joined: Jul 2004
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From: Waterford CT
Big block intake manifold question
I have a question for the corvette world. I have a BB 454 that I am going to transplant into my very non-original (it's currently on it's third engine) '69 coupe. It's got Edelbrock performer RPM oval port heads and matching intake. All the online research I have been able to do says this manifold will NOT fit under the hood of a corvette. I have a factory big block hood and GM put chevy big blocks under this hood so I now it will fit, if I use the right intake manifold. I am only interested in aluminum intakes so the low profile factory CI intake is out of the question.
So who can give me a lead as to what aluminum intake can be used that will allow the use of a factory type air cleaner under a stock big block hood?
So who can give me a lead as to what aluminum intake can be used that will allow the use of a factory type air cleaner under a stock big block hood?
Race Director
Joined: Jul 2015
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From: SW Florida.
I believe that performer does work with a drop base air filter. You're going to use the engine anyway. put the engine in with a carburetor on it with no air filter stud. Shine a flashlight under and slowly close the hood. once you're sure it's not going to hit the carb, loosely ball up some aluminum foil or get some Playdoh. ball it up, put ball on top of carb and close the hood. it'll squash down to show you the clearance you have between the carburetor and the underside of the hood. You could also try putting air filter base and top on carb with no element in between for clearance check. Use a bolt into carb. NOT a stud sticking up.
Last edited by derekderek; Dec 29, 2019 at 10:45 AM.
Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
It will NOT fit without an L-88 hood. The L-88 had a high rise dual plane from the factory and it required the hood they designed for it.
All single four barrel intakes (Including the LS-6) were of the low rise style. The LS-6 intake is the only aluminum unit GM made for Vette's and it was rec port only as well as giant power reducer. A member here made good power with one (Vortec-Pro), but it would have made a lot more with a real intake on it.
As a side note.....the oval port Tri-Power will fit under the bulged 427/454 hood!
A drop base will give more room.....but not with a 3" filter which is the very minimum thickness filter as to not choke off the base toward the center where it necks down.
Jebby
All single four barrel intakes (Including the LS-6) were of the low rise style. The LS-6 intake is the only aluminum unit GM made for Vette's and it was rec port only as well as giant power reducer. A member here made good power with one (Vortec-Pro), but it would have made a lot more with a real intake on it.
As a side note.....the oval port Tri-Power will fit under the bulged 427/454 hood!
A drop base will give more room.....but not with a 3" filter which is the very minimum thickness filter as to not choke off the base toward the center where it necks down.
Jebby
Race Director
Joined: Apr 2011
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From: North of Toronto - Ontario
For the holley it's pretty much limited to the GM LS6 sqr-port as mentioned above, lots of people have installed them, some not bothering to do anything about the sqr-port to oval heads, others have re-shaped the ports, searching will show the different takes on it.
For q-jet, the GM L36 intake and the old torker II are pretty much all that fits.
Playing with drop-base air cleaners and thinner filters opens it up a little so maybe if someone has a successful combination they might jump in but take that with a grain of salt, there's very little room in there
M
For q-jet, the GM L36 intake and the old torker II are pretty much all that fits.
Playing with drop-base air cleaners and thinner filters opens it up a little so maybe if someone has a successful combination they might jump in but take that with a grain of salt, there's very little room in there
M
Instructor
Joined: Aug 2017
Posts: 198
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From: Murphy, Tx.
Definitely very little room to work with. My combo is a 454 with aluminum heads, RPM air-gap intake, Holley 850,and 3 inch air cleaner with a drop base. With an aftermarket L88 hood, I have less than 1/8 of an inch between the hood and air cleaner lid. I run solid engine mounts so I have very little engine movement.
Safety Car
Joined: May 2008
Posts: 3,751
Likes: 720
From: Lafayette Louisiana
Agree, I had a 68 with a 454 with an Edelbrock performance 2-0 intake, Qjet, regular big block hood and a 1" thick or high air filter, regular motor mounts and the hood would barely shut. Hood underneath had rub mounts with the engine movement.
Went back with the cast iron OEM intake and all fit as it should. Or the other option as mentioned above was to go with a L88 hood which I did not do.
Hope this helps.
Went back with the cast iron OEM intake and all fit as it should. Or the other option as mentioned above was to go with a L88 hood which I did not do.
Hope this helps.
Safety Car
Joined: Oct 2000
Posts: 4,080
Likes: 565
From: Allen TX
It will NOT fit without an L-88 hood. The L-88 had a high rise dual plane from the factory and it required the hood they designed for it.
All single four barrel intakes (Including the LS-6) were of the low rise style. The LS-6 intake is the only aluminum unit GM made for Vette's and it was rec port only as well as giant power reducer. A member here made good power with one (Vortec-Pro), but it would have made a lot more with a real intake on it.
As a side note.....the oval port Tri-Power will fit under the bulged 427/454 hood!
A drop base will give more room.....but not with a 3" filter which is the very minimum thickness filter as to not choke off the base toward the center where it necks down.
Jebby
All single four barrel intakes (Including the LS-6) were of the low rise style. The LS-6 intake is the only aluminum unit GM made for Vette's and it was rec port only as well as giant power reducer. A member here made good power with one (Vortec-Pro), but it would have made a lot more with a real intake on it.
As a side note.....the oval port Tri-Power will fit under the bulged 427/454 hood!
A drop base will give more room.....but not with a 3" filter which is the very minimum thickness filter as to not choke off the base toward the center where it necks down.
Jebby
My combo is alum rect port heads, LS6 alum low-rise intake, 240/250 dur cam w/ .570"/.570" lift on 110 LSA, Hooker long tube headers. Spins to 5500 effortlessly. 25hp loss on the top-end (over 5000rpm) compared to a high-rise intake that would fit under the L88 hood? More? 25hp is still 5% on an engine like mine (~500hp flywheel), so that isn't negligible, but its also probably all at the upper revs, not the entire power curve.
Last edited by WA 2 FST; Dec 30, 2019 at 01:20 PM.
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Safety Car
Joined: Apr 2006
Posts: 4,057
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From: BC
It will NOT fit without an L-88 hood. The L-88 had a high rise dual plane from the factory and it required the hood they designed for it.
All single four barrel intakes (Including the LS-6) were of the low rise style. The LS-6 intake is the only aluminum unit GM made for Vette's and it was rec port only as well as giant power reducer. A member here made good power with one (Vortec-Pro), but it would have made a lot more with a real intake on it.
As a side note.....the oval port Tri-Power will fit under the bulged 427/454 hood!
A drop base will give more room.....but not with a 3" filter which is the very minimum thickness filter as to not choke off the base toward the center where it necks down.
Jebby
All single four barrel intakes (Including the LS-6) were of the low rise style. The LS-6 intake is the only aluminum unit GM made for Vette's and it was rec port only as well as giant power reducer. A member here made good power with one (Vortec-Pro), but it would have made a lot more with a real intake on it.
As a side note.....the oval port Tri-Power will fit under the bulged 427/454 hood!
A drop base will give more room.....but not with a 3" filter which is the very minimum thickness filter as to not choke off the base toward the center where it necks down.
Jebby
Le Mans Master
Joined: Dec 2003
Posts: 5,381
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From: N J
You might even be able to use the sb hood. I dont know if it offers more room than the stock hood does on my 77, but after swapping
a 454 in there, I was able to close my hood with a edelbrock rpm performer intake,a holley 4150 series choke less carb, drop base air cleaner with a 3" filter and
a flat, non dished air cleaner top with a flat cap bolt so its all flush. No stud or wing nut.
a 454 in there, I was able to close my hood with a edelbrock rpm performer intake,a holley 4150 series choke less carb, drop base air cleaner with a 3" filter and
a flat, non dished air cleaner top with a flat cap bolt so its all flush. No stud or wing nut.
Le Mans Master
Joined: Mar 2001
Posts: 6,240
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From: Watkinsville, GA and Glen Cove, NY
Don't want to hi-jack, but please take a stab at quantifying "giant power reducer" for us street-engine guys. I recognize every engine combo will differ.
My combo is alum rect port heads, LS6 alum low-rise intake, 240/250 dur cam w/ .570"/.570" lift on 110 LSA, Hooker long tube headers. Spins to 5500 effortlessly. 25hp loss on the top-end (over 5000rpm) compared to a high-rise intake that would fit under the L88 hood? More? 25hp is still 5% on an engine like mine (~500hp flywheel), so that isn't negligible, but its also probably all at the upper revs, not the entire power curve.
My combo is alum rect port heads, LS6 alum low-rise intake, 240/250 dur cam w/ .570"/.570" lift on 110 LSA, Hooker long tube headers. Spins to 5500 effortlessly. 25hp loss on the top-end (over 5000rpm) compared to a high-rise intake that would fit under the L88 hood? More? 25hp is still 5% on an engine like mine (~500hp flywheel), so that isn't negligible, but its also probably all at the upper revs, not the entire power curve.
Safety Car
Joined: Oct 2000
Posts: 4,080
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From: Allen TX
No doubt, it would look fantastic. I put one on my '69 ragtop when I installed AFR heads, new cam and a Performer Air Gap intake.
My thinking is that if I spend the money on an L88 hood, paint, and a hi-rise intake, I may as well go with some better heads and a different cam. Get 75-80hp gain, instead of just 30-35. I don't know... the current combo runs great, so it is hard to just consider doing hood/paint and body work just to install a better intake manifold.
My thinking is that if I spend the money on an L88 hood, paint, and a hi-rise intake, I may as well go with some better heads and a different cam. Get 75-80hp gain, instead of just 30-35. I don't know... the current combo runs great, so it is hard to just consider doing hood/paint and body work just to install a better intake manifold.
Le Mans Master
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From: League City Tx
Thread Starter
Pro
Joined: Jul 2004
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From: Waterford CT
A big thank you to all for your input. I have found it helpful. I have decided to go with the LS6 intake and just ordered a new repro intake. As some have said, it will likely only hurt in the upper rev range and I am primarily interested in low and mid range torque.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Don't want to hi-jack, but please take a stab at quantifying "giant power reducer" for us street-engine guys. I recognize every engine combo will differ.
My combo is alum rect port heads, LS6 alum low-rise intake, 240/250 dur cam w/ .570"/.570" lift on 110 LSA, Hooker long tube headers. Spins to 5500 effortlessly. 25hp loss on the top-end (over 5000rpm) compared to a high-rise intake that would fit under the L88 hood? More? 25hp is still 5% on an engine like mine (~500hp flywheel), so that isn't negligible, but its also probably all at the upper revs, not the entire power curve.
My combo is alum rect port heads, LS6 alum low-rise intake, 240/250 dur cam w/ .570"/.570" lift on 110 LSA, Hooker long tube headers. Spins to 5500 effortlessly. 25hp loss on the top-end (over 5000rpm) compared to a high-rise intake that would fit under the L88 hood? More? 25hp is still 5% on an engine like mine (~500hp flywheel), so that isn't negligible, but its also probably all at the upper revs, not the entire power curve.
You can just put the two manifolds next to each other and it becomes very apparent when you see it....
The cracked up part about the LS-6 for the Vette was those huge 310cc rec ports and then they bolt a manifold that makes about a 110 degree turn and another 30 or so degree turn to get to the port.....I am positive the unit in the Chevelle was worth another 50+ and many statements prove that.
If GM would have been smart....they would have used an oval port on the Vette LS-6 or cast some aluminum oval port heads....it would have ran better everywhere.....
Jebby
Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
Jebby
Safety Car
Joined: Oct 2000
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From: Allen TX
It will be down after 3500 or so and above that....on that combo I would say as much as 60 horsepower after 5500.....think about it...your combo is close to a factory L-88....a real bone stock L-88 made about 560-570 through headers.....and revved to about 6800...
You can just put the two manifolds next to each other and it becomes very apparent when you see it....
The cracked up part about the LS-6 for the Vette was those huge 310cc rec ports and then they bolt a manifold that makes about a 110 degree turn and another 30 or so degree turn to get to the port.....I am positive the unit in the Chevelle was worth another 50+ and many statements prove that.
If GM would have been smart....they would have used an oval port on the Vette LS-6 or cast some aluminum oval port heads....it would have ran better everywhere.....
Jebby
You can just put the two manifolds next to each other and it becomes very apparent when you see it....
The cracked up part about the LS-6 for the Vette was those huge 310cc rec ports and then they bolt a manifold that makes about a 110 degree turn and another 30 or so degree turn to get to the port.....I am positive the unit in the Chevelle was worth another 50+ and many statements prove that.
If GM would have been smart....they would have used an oval port on the Vette LS-6 or cast some aluminum oval port heads....it would have ran better everywhere.....
Jebby
And you're right about the manifold design... and I've seen them up close. On a '69 454 I had, I pulled the LS6 manifold and went with an RPM Airgap and it was very noticeable, even by a non-engineer type like me.
Thx for the input.
Paul... thx for letting me piggy-back on this thread. We got some great input from long-time owners/builders on this one.
Le Mans Master
Joined: Mar 2001
Posts: 6,240
Likes: 1,013
From: Watkinsville, GA and Glen Cove, NY
If you end up going with the L88 hood then definitely consider the Holley 300-5 Strip Dominator. I am running it on my engine. It is a smaller single plane and has the stock type slope back to front to sit level on our engines. It fits perfectly with the L88 hood and airbox. I had mine ported and engine builder thinks it is still a good option despite having been around so long. The RPM air gap is good too, but with these big blocks, in my experience there is plenty of low end, even with the single plane, and they hang on better up top. I even saw a build on Speedtalk where a guy made 700hp with the stock 163 gm manifold, although ported, without the divider milled out. I think with your combo, the L88 hood is a good call, only way to get a decent intake in there. Your car looks great without it but will look even better with it. It’s easy to spend other people’s money lol!
Last edited by 69ttop502; Dec 31, 2019 at 01:38 PM.
Safety Car
Joined: Oct 2000
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From: Allen TX
LOL. Yes, keep spending my $$$. 
I will look into that intake as well. My bottom end is not built to be a high-rpm screamer. it is a 2-bolt block, prepped iron crank, forged rods and pistons... but I am not sure I am confident with it living a long life shifting at 6500rpm.
I need to get my car on a dyno. I think while it pulls hard to 5300-5500, it seems to flat-line there to a degree. Still making power, but not continuing to climb. The cam, and valvetrain components that were matched to it, says 2500-6250rpm. Unless the tach is off (another good reason to get it on a dyno), I don't see this thing pulling to 6200... even with heads, cam and exhaust to support that. So that leaves the intake and maybe the carb (750 DP) as the airflow limiting factors in my mind.
However, given this is a street-only car that is 90% cruiser, I'm not sure it is worth the $$ to gain some top-end HP that I will use 1% of the time. On the other hand, my hot-rodding nature does not like leaving power on the table.
I appreciate the candid input.
I will look into that intake as well. My bottom end is not built to be a high-rpm screamer. it is a 2-bolt block, prepped iron crank, forged rods and pistons... but I am not sure I am confident with it living a long life shifting at 6500rpm.
I need to get my car on a dyno. I think while it pulls hard to 5300-5500, it seems to flat-line there to a degree. Still making power, but not continuing to climb. The cam, and valvetrain components that were matched to it, says 2500-6250rpm. Unless the tach is off (another good reason to get it on a dyno), I don't see this thing pulling to 6200... even with heads, cam and exhaust to support that. So that leaves the intake and maybe the carb (750 DP) as the airflow limiting factors in my mind.
However, given this is a street-only car that is 90% cruiser, I'm not sure it is worth the $$ to gain some top-end HP that I will use 1% of the time.
On the other hand, my hot-rodding nature does not like leaving power on the table. I appreciate the candid input.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
If you end up going with the L88 hood then definitely consider the Holley 300-5 Strip Dominator. I am running it on my engine. It is a smaller single plane and has the stock type slope back to front to sit level on our engines. It fits perfectly with the L88 hood and airbox. I had mine ported and engine builder thinks it is still a good option despite having been around so long. The RPM air gap is good too, but with these big blocks, in my experience there is plenty of low end, even with the single plane, and they hang on better up top. I even saw a build on Speedtalk where a guy made 700hp with the stock 163 gm manifold, although ported, without the divider milled out. I think with your combo, the L88 hood is a good call, only way to get a decent intake in there. Your car looks great without it but will look even better with it. It’s easy to spend other people’s money lol!
The 300-5 has smallish runners that flow well but the carb to port transition needs to be radiused a bit......it sure looks the part though and it makes a statement with the hood up.
Jebby