Intake Manifold Replacement, 1995 350, TBI

[CrystalLaker]

I need to replace the intake manifold on my 1995 Response that has a Pre Vortex 350 Chevy with throttle body fuel injection.  It currently has a cast iron manifold. At this point the only new cast iron pre-vortex manifold that I have found has a kinda universal and cheap look to it so I am looking for another alternative. I was wondering if anyone has any experience with a similar replacement/swap 

Edelbrock makes two intakes that I thing my/will work but both are aluminum, 2104 and 2506.  The 2104 is not a dedicated marine manifold and I would need to stay away from even brackish water with this one which is not a real issue. Per Edelbrock it has an operating range from idle to 5500 rpm. This manifold has a rear water crossover. My current manifold does not have this crossover.   The 2506 is a marine intake with brass lined water jackets and OK for salt water.  The operating range on it is 1500-6500 rpm.  The rear water crossover is blocked with brass plugs.

I am leaning towards the 2506 because if seems to more closely match the original. However, I'm wondering if I should be concerned with the higher rpm range since I assume lower rpm torque is more desirable.  

Am I reading too much into this operating range thing?  Any help is appreciated.

THANKS!!  

Edited February 5 by CrystalLaker
typo

[Woodski]

Go with the 2506, that actually replicates the original GM marine manifold configuration.  The Edelbrock Performer RPM is a copy of the GM manifold.

[justgary]

Is brackish water a problem where you boat?  If so, you could add a heat exchanger and switch to closed cooling.  Brackish water is hard on the block and other parts as well, so it is worth keeping it out.

[CrystalLaker]

9 hours ago, Woodski said:

Go with the 2506, that actually replicates the original GM marine manifold configuration.  The Edelbrock Performer RPM is a copy of the GM manifold.

Thanks Woodski, As I research this further I have found the Performer RPM (2506) referred to as a "high rise" manifold.  Edelbrock specs show it's 0.70" taller than the 2104.  I don't think that 3/4" will make a difference but will be checking before placing the order.   Thanks Again 

[CrystalLaker]

7 hours ago, justgary said:

Is brackish water a problem where you boat?  If so, you could add a heat exchanger and switch to closed cooling.  Brackish water is hard on the block and other parts as well, so it is worth keeping it out.

Thanks Justgary..  No, staying away brackish water isn't a problem, 2x in 28 years.     

[justgary]

2 hours ago, CrystalLaker said:

Thanks Justgary..  No, staying away brackish water isn't a problem, 2x in 28 years.     

I was on my phone when I asked that.  I can see now from your profile where you are.  I assume your brackish adventures were on the St. Johns River.  Converting to closed cooling is useful even in fresh water, but it does cost money.  I enjoyed the process of fitting everything under the hood and fabricating mounts.

My son lives near Williston.  We have done several canoe trails down there, but not much lake boating.

[justgary]

On second thought, if you are replacing your intake manifold because it rotted out, perhaps closed cooling will help save your block from rotting out the rest of the way also.

Have you also changed your exhaust manifolds?  If you see a rust ring around the joint between the manifold and riser, it is probably time.

[CrystalLaker]

12 hours ago, justgary said:

I was on my phone when I asked that.  I can see now from your profile where you are.  I assume your brackish adventures were on the St. Johns River.  Converting to closed cooling is useful even in fresh water, but it does cost money.  I enjoyed the process of fitting everything under the hood and fabricating mounts.

My son lives near Williston.  We have done several canoe trails down there, but not much lake boating.

Correct on the adventures on the St. Johns. Actually Black Creek which feeds into the St. Johns. Afternoon ski followed by dinner at a waterfront restaurant. Fun times as long as it was in my buddies boat

I'm installing a new base engine with dry joint exhaust.  The intake looks suspect and the last thing I want it for to fail soon after install. If I get another 28 years out of this engine it will be someone else's problem by then.  I'm gonna stick with the raw water cooling. My hats off to you finding room for the closed system,  I'm having a hard time just finding enough room to add a raw water filter.

I talked to a tech at Edelbrock today and he gave me a different option.  He suggested the 2604. I'd still have to stick to fresh water with this one but it has the blocked rear water crossover and its operating range is idle to 5500.  This is an air gap manifold but it's pad height is still lower than the 2506 I was considering.  He thought that going with the lower operating range manifold (idle to 5500 vs 1500 to 6500) would better suit the purpose of a ski boat.  This makes sense to me also plus the air gap is suppose to keep the fuel cooler with a potential for increased power.  I'm gonna look into the 2604 further.   

Thanks again for the suggestions

[CrystalLaker]

On 2/4/2024 at 9:32 PM, Woodski said:

Go with the 2506, that actually replicates the original GM marine manifold configuration.  The Edelbrock Performer RPM is a copy of the GM manifold.

Woodski, Edelbrock is telling me the 2506 will not work with the TBI, even if I use the adapter that I have on my original manifold.  They said the 2506 will only work with a Q jet marine carb (???).  I know Mercruiser used my manifold (their 17620) with several different carbs and of course the TBI. I'm not sure what's different about the 2506.

Do you have any experience using the 2506 with TBI or know of anyone that has?  

Thanks 

[Woodski]

I don’t know, I don’t have personal experience with it, I went with a standard aluminum one and added zinc anodes.

[CrystalLaker]

10 hours ago, Woodski said:

I don’t know, I don’t have personal experience with it, I went with a standard aluminum one and added zinc anodes.

Thanks, are you running the 350 magnum EFI?  if so, can you tell which manifold you went with?

[justgary]

12 hours ago, CrystalLaker said:

Woodski, Edelbrock is telling me the 2506 will not work with the TBI, even if I use the adapter that I have on my original manifold.  They said the 2506 will only work with a Q jet marine carb (???).  I know Mercruiser used my manifold (their 17620) with several different carbs and of course the TBI. I'm not sure what's different about the 2506.

Do you have any experience using the 2506 with TBI or know of anyone that has?  

Thanks 

Did they tell you why it won't work?  The only thing I can think of is the holes are the wrong size, and maybe the studs are in the wrong place, but an adapter should fix that.  Can you post a few photos of your manifold and adapter plate?

[Steve B.]

Q jet is the old quadrajet style spread-bore intake. Sounds like they don't want any kind of adapter there.

[Woodski]

@CrystalLaker - Intake Manifold = Edelbrock EDL-7104.  I bought it prior to the air gap version which I don't think is a big deal on a 140 or 160 degree thermostat.  I have a Weber carb, there is a spacer (wedge plate) between the carb and intake manifold to keep the carb level.  The specific manifold criteria will be which cylinder head bolt pattern you have and what bolt pattern for the wedge plate (if you have one) or throttle body unit.  It should be either spread bore or square bore.

[CrystalLaker]

21 hours ago, Steve B. said:

Q jet is the old quadrajet style spread-bore intake. Sounds like they don't want any kind of adapter there.

thanks, yes both the Edelbrocks and my original Mercruiser accept both Q jet (spread bore) and square bore (usually with an adapter). 

[CrystalLaker]

23 hours ago, justgary said:

Did they tell you why it won't work?  The only thing I can think of is the holes are the wrong size, and maybe the studs are in the wrong place, but an adapter should fix that.  Can you post a few photos of your manifold and adapter plate?

they did not tell me the why.  I thinking it may be flow thing vs holes in the wrong place. the hole on all these look similar and are made for spread or square bore carbs.  I'mm out of town at the moment this shows it better than a pic