GT350 Intake Manifold Install Observations

[El_Centenario]

Very good information that I will use in the near future for when I install my intake. So just to sum it up, the JDM Evap hose kit is needed for a straight up install without issues?

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[ddozier]

Very good information that I will use in the near future for when I install my intake. So just to sum it up, the JDM Evap hose kit is needed for a straight up install without issues?

JDM evap harness not hose for a plug and play install of the evap, or you can cut and extend the two wires in the factory harness. If soldered and heat shrink wrap is used there should be no issue.

Dave

 

[El_Centenario]

JDM evap harness not hose for a plug and play install of the evap, or you can cut and extend the two wires in the factory harness. If soldered and heat shrink wrap is used there should be no issue.

Dave

Thanks! Soldering some extra wire shouldn't be an issue. I'll check back for more tips on the install

 

[wildcatgoal]

I personally did the cut and solder extension on a recent GT350 install. Get some split loom to cover the wire and use 3M Super 33 electrical tape and you will never know you did it.

 

[Gibbo205]

That's how mine has been.

Think this is how mine is too. Do the two different methods effect how the car drives at all?

 

[Terminator2]

For what it's worth looking at pics of the gt350s engine bay they have the aspirator and brake booster hooked up just the same as most are installing them. The booster is hooked directly to the intake manifold on the gt350 the one port on the aspirator is capped and the T remains intact and attached to the intake tube.

 

[Dominant1]

Here is how Jpc hooked mine up:

 

[ddozier]

Here is how Jpc hooked mine up:

They installed the aspirator from the GT along with the GT350 aspirator and used the 2nd port to feed it, thats one way to do it.

For what it's worth looking at pics of the gt350s engine bay they have the aspirator and brake booster hooked up just the same as most are installing them. The booster is hooked directly to the intake manifold on the gt350 the one port on the aspirator is capped and the T remains intact and attached to the intake tube.

One thing you would have to know to compare a GT to a GT350 is why Ford uses a different brake booster for the GT than they did for a GT350. Both boosters show a check valve at the booster so you will likely not see much of a difference by using the 2nd port and connecting the brake booster line directly to it but the stock GT was not setup that way. In theory the aspirator will supply a more consistent vac signal than a connection directly to the manifold as a vac source.

The T connection is not the important part of the vac system, the GT350 cold air intake only has the drivers side port and that is why the two return vac lines are T connected to that single port, the GT has two ports, you can leave them T connected and plug the other port or split them into two connections. It really does not matter just do what you think looks better as the two setups will function the same.

Without knowing what is different I just prefer to see the GT vac system to remain as close to the original way it was designed as possible. Now if someone does some testing and can show that there may be a benefit to using the 2nd port as the brake boost vac source I am willing to make the change. Since my car is a dedicated road course track car brakes are very important to me.

Dave

 

[Bullett]

Hmmm. This is an interesting read. I actually have the 350 manifold, that and stock CAI that I'm about to install.

 

[50Mustang]

Hmmm. This is an interesting read. I actually have the 350 manifold, that and stock CAI that I'm about to install.

I'm with you; have my GT350 IM, stock GT throttle body, and JLT intake I plan on installing this coming weekend.

 

[defector]

After putting some miles on my car I have some updates:

1) The vacuum is spot on with no changes. 20.5" Hg once it warms up. The reduced vacuum was only at high-idle.

2) I bought the wire extension from JDM. Works nifty if a bit long. Would like to buy one half as long for 1/2 price.

3) 09JSW's installation is totally fine for vacuum routing. Dozier, your installation also works but is not the same installation as intended by Ford on the GT350 so I would promote that with a level of caution. It might be great, but not the same as on the GT350. Meaning, the GT350 pulls brake boost from the manifold plenum not the aspirator.

The benefit you might achieve is possibly more consistent brake vacuum, at the expense of possibly some of the vacuum created by the aspirator being "used" by the brakes which could slow your CMCV response time - probably not a big deal, but there is a tradeoff that you are making that Ford did not intend.

 

[ddozier]

3) 09JSW's installation is totally fine for vacuum routing. Dozier, your installation also works but is not the same installation as intended by Ford on the GT350 so I would promote that with a level of caution. It might be great, but not the same as on the GT350. Meaning, the GT350 pulls brake boost from the manifold plenum not the aspirator.

The benefit you might achieve is possibly more consistent brake vacuum, at the expense of possibly some of the vacuum created by the aspirator being "used" by the brakes which could slow your CMCV response time - probably not a big deal, but there is a tradeoff that you are making that Ford did not intend.

Thank you for your comments and it is certainly something I have put a great deal of thought into before I posted my opinion on the subject. The question for me and the reason I chose to use the method I chose is while the GT350 uses the manifold port and not the aspirator port the GT is just the opposite in that it uses the aspirator port for brake boost. So do you follow the GT setup being mindful of the GT vac system and brake hardware or do you follow the GT350 vac system being mindful of the intake manifold change.

I chose to follow the layout in the GT and not the GT350 as the brake components and the rest of the vac system are GT not GT350. The reality is both methods will likely not cause an issue on the street, but until I get the car back on track and test I will not know for sure what method is better on track. I do have an untested theory that for a track vehicle that spends most of its time in a low vac open throttle running condition the aspirator port should yield a more consistent vac signal to the brake booster. I do have all the items needed to make the change at track should I need to do so.

Having said that prior to installing the GT350IM with the stock GT setup I have had times where I have revved past the RPM point for matching the downshift while still being on the brakes and have lost servo assist from the brake booster resulting in a very firm pedal. I am aware of the possibility of this happening and now I have more concern about the vac signal to the brake booster than others may have. As a precaution after this happened more than once on track I replaced the check valve at the booster and still had the issue happen on track.

I believe the biggest issue is the vac system on the Mustang does not have much of a vac reserve and relies on a strong vac signal from the manifold to function properly. The tuners that are modifying cam angles in the pursuit of max power are doing so with an effect on peak vac levels that can be produced. Even in the factory tune the GT is prone to prolonged run on after the throttle pedal input is removed and the car will hold the throttle open briefly in some cases, my guess is Ford is using this to help with emissions or something. This is something that could definitely limit vac signal. I have not looked for it in the tune but I can feel it when it does it and others have commented on it as well. Ultimately the use of a vac canister and a series of check valves may need to be added to resolve the issue for cars that are used the way I am using mine.

Sorry for the thread Hi-Jacking.

Dave

 

[defector]

ddozier - your approach might be better for you considering how you drive your Mustang. It seems like another idea, would be to use both the GT and the GT350 aspirators to create even more vacuum using some extra T's, etc. I had no issues with my brakes, but I drive like a 47 year-old. And admittedly, I don't know what I don't know, so I'll admit there are things about the car that I can't comment on.

My knowledge is fairly good on this as I worked with the Ford engineer who developed this intake manifold - I wanted a GT350 but decided the next best thing was a GT with a GT350 intake manifold.

 

[Asonitez]

Im guessing this is HP gain but what kind of gains does doing this give you?

 

[Terminator2]

Im guessing this is HP gain but what kind of gains does doing this give you?

Extends useable power 1000 RPMs over stock manifold and most see around 25whp gains at peak and up to 60-70 whp out at 7200-7500 over stock manifold.

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