LS4 / F40 swap - fieroguru (Page 76/216)
fieroguru APR 17, 06:28 PM
Now for the invisible hood vent that didn't quite work as planned...

I am trying to keep the exterior of this car bone stock with the exception of the wheels/brakes and the head lights were popping up somewhere north of 80 mph.

Over the years there has been quite a bit of discussion around venting the radiator compartment via the head light area. Most of those discussions focus on drilling a large hole to the wall the headlights mount on and vent the air into the wheel well. Upon quick review, there isn't a single wall to pass through and in fact that area is open to the spare tire compartment. Here are a couple pics of that area:



As you can see in the 2nd picture the wheel well is seperate from the front firewall and has a gap all they way down to where they are welded together. So any hole in this firewall panel will vent to the spare tire area. If I wanted to do that, I would just cut the holes in the wall right behind the radiator.

So I started looking for other places to vent the air and settled on the outer side of the head light pocket. It is light gauge sheet metal and easily accessed for drilling. You will notice that there is already a hole there for the turn marker light wires to pass through.


Here is how much space is between the panel and the fender:


So I decided to drill two 3" holes in the side panel as shown:


On the Driver's side, the headlight module was in the way, so I relocated it down to make clearance for the holes:



To vent the air from the pocket between the panel and fender, I drilled three 3" holes in the wheel well liner.


Once the wheels/tires are put back on the holes are difficult to see just walking by the car. You have to get down and look up into the wheel well to see them:


Initial testing shows some minor improvement, but the light covers still popped open, but it took about 10mph more to do it. I suspect the headlight assembly is making it too turbulent/difficult for the vents to remove enough air pressure to keep the headlight doors closed. I still need to find/install the air dam for the fascia and I might try different torsion springs for the head lights... they might just be weak.
dobey APR 17, 10:05 PM
Does your 2.5 car have all the insulation in the engine bay still? Removing all that from the firewall and replacing it with a solid piece of metal probably doesn't help the engine noise in the cabin.
CTFieroGT87 APR 18, 12:17 PM
To dobey's point, I think while the interior is out, a nice layer of Dynamat would help greatly. The cars I've driven with it installed have been extremely quiet.
fieroguru APR 18, 06:51 PM
Yes, the 2.5 has the factory firewall insulation, the LS4/F40 car does not have any insulation in the engine bay (but I may add some between the rear firewall and the smooth one). I had already put some sound deading material on the inside of the firewall, the floor boards under the seats, and the center console area. I need a nice warm day to remove the roof panel and swap to a hardtop one. That will eliminate the vibrating sunroof, lessen the wind noise and avoid any potential sunroof leaks.

A month or 3 back I posted about my laptop going blank and baking the motherboard in the oven to fix it. Well it did it again early this week and the baking trick didn't work this time. So I ordered 2 new motherboards (one for a spare, figured if I had a spare in stock I would never need it, which is a good thing in my book) and will try to get the laptop back up and running this evening.
dobey APR 18, 09:16 PM
You could spray the back side of the smooth firewall with Herculiner or Lizrad Skin (which actually is a sound dampener), to reduce sound making it into the cabin and provide some insulation, too. The Lizard Skin goes on pretty thin, but works as well as, if not better than, the much thicker/heavier Dynamat and similar roll-on products.

Just a suggestion. I'm probably going to get some Lizard Skin sprayed on in various places, in both my Fiero and my Avalanche.
KissMySSFiero APR 18, 09:43 PM
how are you liking the transmission? How does it shift? You already mentioned the clutch characteristics.

Are you still thinking of producing the flywheel and starter mount?

I couldn't agree more on the sunroof, I'll never own a sunroof car again.

------------------
SSFiero@Aol.com 87 Gt-5spd-62k miles.

fieroguru APR 19, 10:15 PM

quote
Originally posted by KissMySSFiero:

how are you liking the transmission? How does it shift? You already mentioned the clutch characteristics.

Are you still thinking of producing the flywheel and starter mount?




Overall the transmission is OK to Decent. Some thinks I love about it, some things are marginal/tolerable and others I don't much care for.
I love the 6th gear for the quieter cabin noise, the lower cruise RPM and what should be better fuel efficiency. 3rd gear is also quite nice with the power band/RPM range of this engine... I can hit 100mph at 6800 rpm in 3rd with 24.6" tires.

The gates on the shifter are really close and it takes a little getting used to, but they are OK. Even though the first few gears have triple syncros, they seem to take much longer to sync than I would like and it slows the whole shifting process down (this is probably why no F40 car has posted impressive 1/4 mile ET's). I am running the GM fluid at the revised level, but will be looking into some type of additive to help speed up the synco function.
The worst part about the transmission is the noise from it. When idling it sounds like some gears are rocking back and forth and sounds like a rod knock. I can push on the clutch and it goes away and if I slowly release the clutch it will be quiet for a while. If I quickly let out the clutch in neutral, it will slap back and forth. Also, at low RPM's (1200-1600) in 4th or higher when you start applying throttle it sounds like the internals of the transmission are vibrating (probably the same issue as the knocking at idle, just at a higher frequency. It settles down as the RPM's pick up, but when you have an engine that will pull that low, it would be nice if the transmission didn't complain about it.

There is a good chance I will be offering the LS4/F40 flywheel and starter bracket later this year (Oct/Nov/Dec time frame). I want to put some miles on the setup and ensure everything works like it should before starting to offer them.
dobey APR 20, 08:40 AM

quote
Originally posted by fieroguru:
The gates on the shifter are really close and it takes a little getting used to, but they are OK. Even though the first few gears have triple syncros, they seem to take much longer to sync than I would like and it slows the whole shifting process down (this is probably why no F40 car has posted impressive 1/4 mile ET's). I am running the GM fluid at the revised level, but will be looking into some type of additive to help speed up the synco function.
The worst part about the transmission is the noise from it. When idling it sounds like some gears are rocking back and forth and sounds like a rod knock. I can push on the clutch and it goes away and if I slowly release the clutch it will be quiet for a while. If I quickly let out the clutch in neutral, it will slap back and forth. Also, at low RPM's (1200-1600) in 4th or higher when you start applying throttle it sounds like the internals of the transmission are vibrating (probably the same issue as the knocking at idle, just at a higher frequency. It settles down as the RPM's pick up, but when you have an engine that will pull that low, it would be nice if the transmission didn't complain about it.



Is the shift gate issue a result of using a modified Fiero shifter? I haven't run any F40 swapped Fieros through the gears, but I haven't noticed any issues driving the modern GM FWD 6 speed cars (F40 or M32).

The noise in the trans when idle is a common complaint with the F40 in the G6. I think it was fixed in the newer version of the F40, but not entirely sure as it's a rarity in the G6, and I don't know if it's as much a problem, or a problem at all, in the 4 cylinder cars with the F40. The dual mass flywheel helps with this, as it dampens the vibration coming from the engine. The problem is exacerbated by using a solid flywheel as we have to do here. It's too bad there aren't any dual mass flywheels that have the smaller ring gear, are thick enough for the LS4+F40, and mount to the LS crank flange. It would probably help a fair bit, though would also be much heavier (which may not be a bad thing, given Joseph Upson's experience with damaged internals on his one F40).
Raydar APR 20, 12:03 PM

quote
Originally posted by dobey:

... (which may not be a bad thing, given Joseph Upson's experience with damaged internals on his one F40).



Paul, when you started talking about transmission rattles - especially under load - this crossed my mind as well.
fieroguru APR 20, 03:08 PM

quote
Originally posted by dobey:
Is the shift gate issue a result of using a modified Fiero shifter?


Most likely. Instead of just 3 gates, you have 4 in approximately the same space (you do increase the side to side travel some), but I think the issue is the mechanical advantage built into the fiero shifter. It will self center in the 3/4 gate and 5/6 are along a fixed stop. 1/2 are a little more challenging as the reverse lockout isn't the strongest (easy to go past it). I need to get a longer bolt and shim the lockout tab down further so it will be more of a positive stop.


quote
Originally posted by dobey:
The noise in the trans when idle is a common complaint with the F40 in the G6.



Yup, knew going in about the noise and that the lighter single mass flywheel and lopey camshaft would all make it worse. Just going to have to get used to it.