hood scoop/windsheild firewall

[rustyT]

Heres a question I think a few more of us than want to admit need an answer to. At WF last year we were red tagged for not having a firewall between the engine compartment and the windsheild,we asked if we could put just a metal wall in between the winsheild and the hood scoop,they wanted a "dead air space " between the firewall and the engine compartment,so in other words,it needs 2 firewalls between the two, the problem is that our hood and scoop are two pieces,we cant figure a way to have the two firewalls and be able to get the hood and scoop off the car. This I think is a problem everyone needs to adress,because if its a rule for one,its going to to be a rule for EVERYONE!! Any help would be greatly appreciated. Thanks,Phil.
ps.I will try to get some pictures soon,but for the ones that dont know,my car is the #2727 that is pictured in front of Sums fatgmc somewhere on here.it shows how our hood is configured.

[Dynoroom]

Rusty, I'm sure you've read the rule (probally over & over again) and for the others here is what it say's.

3.F "A full firewall to provide a watertight and flame-resistant barrier between the engine and the driver is required in all categories. All non-production firewalls  shall be made of metal with a minimum thickness of .060". A thickness of .095" is recommened. All holes must be sealed."

Many hood scoops are open at the windshield, it my even be the only air inlet for the engine in some cases. Some cars have the injectors or blowers stinking out of the hood so I'm not sure what the problem is. I would ask for a review of your "red tag" as someone thought this was really bad.
Do you have a "open" car?

[Sumner]

Rusty, I'm sure you've read the rule (probably over & over again) and for the others here is what it say's.

3.F "A full firewall to provide a watertight and flame-resistant barrier between the engine and the driver is required in all categories. All non-production firewalls  shall be made of metal with a minimum thickness of .060". A thickness of .095" is recommended. All holes must be sealed."

Many hood scoops are open at the windshield, it my even be the only air inlet for the engine in some cases. Some cars have the injectors or blowers stinking out of the hood so I'm not sure what the problem is. I would ask for a review of your "red tag" as someone thought this was really bad.
Do you have a "open" car?

Mike here is the car...........



You can see that the scoop housing goes back to the windshield and is removable from the hood.



This part is separate and inside the scoop housing and attaches to a plenum on the carb, so the engine compartment is open at the back of the plenum area in the scoop housing to the windshield.  So now the windshield becomes the firewall at the back of the scoop housing.  When they pointed this out we agreed with them and saw their point.  We asked if we could then cover the lexan windshield inside the housing with .060 or .095 metal to turn it into a barrier like the rules request and what a number of cars seem to do in this situation.  They said no.

Then we asked if we could cut the back of the scoop housing short of the windshield so that there was an air space between it and windshield like some cars that have cowl induction.  They said no.

They wanted two fire walls inside the air scoop housing.  One about where the cars real firewall is around the back of the plenum in our case and another by covering the windshield like I mentioned above.

Finally in order to run we said can we just remove the whole scoop housing.  At first they said no and then I pointed out that a lot of cars run with their carbs, injector stacks, etc. sticking out the hood.  They then reluctantly said yes.

Phil just wants to make sure the same issue doesn't come up again and personally I think the two firewall thing is not like what others are having to do.  I think covering the windshield with metal inside and slightly outside the scoop housing is adequate.

Actually I think the real problem that was kind of hinted at was the color of the car bothered them  .

There are pictures of how the scoop/hood was made on my site here.....

http://purplesagetradingpost.com/sumner/temp-pictures/temp-web-nc-1.html

c ya,

Sum

[Dynoroom]

So is the answer to fit the scoop to the engine inlet (but still removable) then finish the hood to seal to the firewall and not the windsheild?
I also don't see why they said you couldn't cut the back of the housing off and have an air gap. I'm not looking at it by this might be why they have said in inspection meetings we (the SCTA) are going to be more user friendly i.e. flexable.

[Sumner]

So is the answer to fit the scoop to the engine inlet (but still removable) then finish the hood to seal to the firewall and not the windsheild?.......

That would be hard to do as the carb body, and he has different ones is right up in that opening.  Also the carbs, spacers, etc. are different heights.  I think if they really want two firewalls with an air gap between them we can get one in ahead of the windshield.  Just not easy as the throttle linkage is also in that area.

Good talking to you yesterday.  Something came up last night and I couldn't finish the FE page on your site.  Maybe tonight,

Sum

[Blue]

Sum, I am not an LSR veteran, but I know something about other sanctioning bodies and their tech/safety rules.  What you have is an airbox and the airbox itself cannot be considered a firewall.  There are good reasons for this, and I have personally seen this scenario in normally aspirated big blocks:

1. Engine sucks an intake valve;
2. Engine backfires through manifold and blows out airbox (even more likely here since you have an inlet sized for very high speed creating restriction against the backfire);
3. The damaged carb or FI now has a pressurized line feeding the fire in what's left of the airbox.  In the setup in the pictures, this would lead to direct fire exposure of the windshield.

Granted, if the scoop is integral to the hood, the hood would suffer damage and possibly blow off at LSR speeds.  The fire would then also hit the windshield.  I think they are looking for some space and no direct path.

JM2c, I have to side with the tech inspectors on this, although I think the proper terminology is not "two firewalls with a dead air space", rather it should be "an airbox cannot serve as a firewall, no engine component can touch the firewall (including the airbox), and a full firewall is required".

[Sumner]

Sum, I am not an LSR veteran, but I know something about other sanctioning bodies and their tech/safety rules.  What you have is an airbox and the airbox itself cannot be considered a firewall.  There are good reasons for this, and I have personally seen this scenario in normally aspirated big blocks:

1. Engine sucks an intake valve;
2. Engine backfires through manifold and blows out airbox (even more likely here since you have an inlet sized for very high speed creating restriction against the backfire);
3. The damaged carb or FI now has a pressurized line feeding the fire in what's left of the airbox.  In the setup in the pictures, this would lead to direct fire exposure of the windshield.

Granted, if the scoop is integral to the hood, the hood would suffer damage and possibly blow off at LSR speeds.  The fire would then also hit the windshield.  I think they are looking for some space and no direct path.

JM2c, I have to side with the tech inspectors on this, although I think the proper terminology is not "two firewalls with a dead air space", rather it should be "an airbox cannot serve as a firewall, no engine component can touch the firewall (including the airbox), and a full firewall is required".

We had no problem with the fact that the windshield is not an adequate firewall.  What we don't agree with is that we were not allowed to plate that area of the windshield with metal of the required thickness as other cars have done.  If that was done then that area would be no different than the area directly behind the motor where there is also a metal firewall.

Oh well, we will see what happens this year,

Sum