Exhaust and Intake Advice for 5.0 V8

[DanielB23]

I'll be starting to reassemble my 302 in the coming weeks and I'm once again seeking some advice as this is my first engine rebuild. I've got a 5.0L V8 from my 97 explorer and ultimately I'm just looking to make some extra power and learn about engines. Nothing crazy, keeping my first build naturally aspirated. Anyways I have the torque monster headers and a mild camshaft but that's about it as far as power upgrades. I'm wondering if I should also upgrade the exhaust system as well? I'm worried that the TMHs won't be effective with the stock exhaust but I also just want to get my explorer back up and running. Maybe wait to upgrade the exhaust at a later date? Secondly, I want to upgrade the intake because I feel like having TMHs with a restrictive stock intake makes them useless. Outside of a carburetor, what can I do to open up the engine some more? Just a larger throttle body? Cold air or high flow intake? I'm actively researching all of these things but there's so much experience in this forum, I figured why not ask around too. Thanks for your time!

 

[CDW6212R]

The exhaust manifolds are the biggest restriction, they are horrible. But the Explorer/GT40 intake is not bad at all for a mild 302 with near stock rpm limits. The stock programming has them shifting right about 5000rpm, which is a good bit higher than all 302 HO's which came in all Fox chassis cars. Those HO engines had restrictive intake and heads, those were the biggest issues that kept those shifting lower than the Explorer 302's.

The camshaft is not that bad either, but almost any aftermarket cam should make more power at the higher rpm ranges. People push the GT40 intakes(Cobra and Explorer are the same flow), and the GT40 heads, to 5500+ on NA 302's. I'd suggest concentrating on the core engine parts and all supporting items just outside.

Changing the camshaft may create an issue you didn't plan for if it's a big enough cam. The PCM is programmed to handle the OEM cams and many milder cams if they aren't too wild. Unless you've chosen something aimed more at racing or much higher rpm, the PCM program should control it just fine.

The TB isn't really much too small, but the intake elbow is a big restriction, that's the biggest deal besides the exhaust manifolds. If you choose to grow the intake manifold choice, then the heads will need the same amount of upgrade in airflow. Those two are a fairly good match in potential flow. The four cats are OEM restrictive, the rear aren't needed, then the single exhaust of the muffler back is a weak link.

The stock air cleaner is already a "Cold Air Intake", it pulls cold air from behind the right headlight. it flows fine unless you can add a lot of engine airflow, such as say 20% or more flow. Parts that can support 6000rpm efficiently would be 20% more. There aren't any available aftermarket air cleaners anymore for the 2nd gens, the Volant was the best but it went away some 15+ years ago. If you get that far, you might do as others have, build your own enclosed air cleaner box with a larger air filter inside, plus larger inlet piping.

 

[Turdle]

You might consider cast manifolds used 99 up, they have a bit more porting meat. But you'll laugh at the number 3 and 4 ports on your current manifolds. Your header question will be answered with that view.

Does your engine have an EGR pipe on passenger side exhaust manifold?

 

[410Fortune]

He has tmh

The factory
Manifolds are so restrictive that just by bolting torque monsters into a bone stock explorer he gained 20hp

torquemonsterheaders.com | Main Page - Introduction to Torque Monster Headers

Cdw has you covered

 

[DanielB23]

The exhaust manifolds are the biggest restriction, they are horrible. But the Explorer/GT40 intake is not bad at all for a mild 302 with near stock rpm limits. The stock programming has them shifting right about 5000rpm, which is a good bit higher than all 302 HO's which came in all Fox chassis cars. Those HO engines had restrictive intake and heads, those were the biggest issues that kept those shifting lower than the Explorer 302's.

The camshaft is not that bad either, but almost any aftermarket cam should make more power at the higher rpm ranges. People push the GT40 intakes(Cobra and Explorer are the same flow), and the GT40 heads, to 5500+ on NA 302's. I'd suggest concentrating on the core engine parts and all supporting items just outside.

Changing the camshaft may create an issue you didn't plan for if it's a big enough cam. The PCM is programmed to handle the OEM cams and many milder cams if they aren't too wild. Unless you've chosen something aimed more at racing or much higher rpm, the PCM program should control it just fine.

The TB isn't really much too small, but the intake elbow is a big restriction, that's the biggest deal besides the exhaust manifolds. If you choose to grow the intake manifold choice, then the heads will need the same amount of upgrade in airflow. Those two are a fairly good match in potential flow. The four cats are OEM restrictive, the rear aren't needed, then the single exhaust of the muffler back is a weak link.

The stock air cleaner is already a "Cold Air Intake", it pulls cold air from behind the right headlight. it flows fine unless you can add a lot of engine airflow, such as say 20% or more flow. Parts that can support 6000rpm efficiently would be 20% more. There aren't any available aftermarket air cleaners anymore for the 2nd gens, the Volant was the best but it went away some 15+ years ago. If you get that far, you might do as others have, build your own enclosed air cleaner box with a larger air filter inside, plus larger inlet piping.

Man this is some great info for me, thank you. What can I do about the intake elbow? I've got GT40P heads and read somewhere that if you were going to port them then you might as well buy AFRs instead. Just gonna roll with the P heads and probably keeping the stock intake manifold for now.

What would the process of removing the cats look like? Would that require any welding? I've seen true dual exhausts, H-pipes, X-pipes, cat backs...just don't know which direction to go really. I'll likely finish up the engine build before messing with the exhaust, since it doesn't seem like the main restriction point. Unless I'd just be making things more inconvenient for me down the road?

 

[DanielB23]

You might consider cast manifolds used 99 up, they have a bit more porting meat. But you'll laugh at the number 3 and 4 ports on your current manifolds. Your header question will be answered with that view.

Does your engine have an EGR pipe on passenger side exhaust manifold?

Yes it's got an EGR pipe on passenger side manifold. It's getting replaced with a specialized EGR pipe from Torque Monster Headers, I guess so it won't throw a code?

 

[CDW6212R]

The intake elbow is a very tight and narrow bend, there's no real option other than replacing it with something you create. I have one that I paid $55 to have ported, but it isn't really big enough still. One or two people have remade theirs with a larger pipe 90* bend which they welded to flanges to replace the OEM directly. The TB is I think 65mm, which is larger than the elbow, and virtually fine for most moderate 302's. A bigger TB like 70-75mm won't gain enough to be worth the cost, the elbow should be dealt with first.

Any exhaust shop could remove the rear cats, but remember that some won't due to local emissions laws. You can have the fronts replaced similarly, but again it may require lawful replacement code labeled type, or a universal type in other places. That will not effect your current engine project, so worry about that later. Those and the back half will gain some power, but check around, it is all expensive to do.

The options to upgrade the heads become tricky given the "P" headers. You can buy lesser aftermarket heads that may be near $1000 or so, but remember any of them(AFR too) will be made for non "P" plug locations. The plug wires become too close when you use heads with the different plug locations, burning wires is normal then. So the headers you have will be made for the "P" heads, changing will likely require the other type made for the 1996 and early 97 normal GT40 heads(almost all other SBF Windsor heads have the normal port and plug locations). You might as well keep going with the GT40P heads until you decide whether a better head is worth it.

The GT40 lower intake is worth porting to gains a little power, it's common to send it off to get ported, Tom Moss and his son's shop is the most popular porter for those. I'd figure on $200 or so and shipping for that, I haven't read of the cost lately.

 

[DanielB23]

The intake elbow is a very tight and narrow bend, there's no real option other than replacing it with something you create. I have one that I paid $55 to have ported, but it isn't really big enough still. One or two people have remade theirs with a larger pipe 90* bend which they welded to flanges to replace the OEM directly. The TB is I think 65mm, which is larger than the elbow, and virtually fine for most moderate 302's. A bigger TB like 70-75mm won't gain enough to be worth the cost, the elbow should be dealt with first.

Any exhaust shop could remove the rear cats, but remember that some won't due to local emissions laws. You can have the fronts replaced similarly, but again it may require lawful replacement code labeled type, or a universal type in other places. That will not effect your current engine project, so worry about that later. Those and the back half will gain some power, but check around, it is all expensive to do.

The options to upgrade the heads become tricky given the "P" headers. You can buy lesser aftermarket heads that may be near $1000 or so, but remember any of them(AFR too) will be made for non "P" plug locations. The plug wires become too close when you use heads with the different plug locations, burning wires is normal then. So the headers you have will be made for the "P" heads, changing will likely require the other type made for the 1996 and early 97 normal GT40 heads(almost all other SBF Windsor heads have the normal port and plug locations). You might as well keep going with the GT40P heads until you decide whether a better head is worth it.

The GT40 lower intake is worth porting to gains a little power, it's common to send it off to get ported, Tom Moss and his son's shop is the most popular porter for those. I'd figure on $200 or so and shipping for that, I haven't read of the cost lately.

Hmm ok very interesting. Definitely going to figure something out for that intake elbow. All of this is just what I needed to hear, can't thank you enough.

 

[Blk2kXLT]

I have a 50 state (Including CA smog) approved MAC cold air intake for the 5.0L V8 that I need to list for sale.

I would put in the Torque Monster headers as part of the assembly. Took me 10+ hours so if you are already replacing the motor it would be a big time savings now.

Another piece you might consider is a 0.5" upper intake manifold spacer.