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Topic: Hood Spacer Mod

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LEAD_NOT_FOLLOW
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Hood Spacer Mod
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I decided I wanted a way to cool under the hood a bit more, and havn't had any luck yet finding a set of vents I like and I could get for cheap. I will go with the cowl hood in the near future once I need the extra few inches of clearance under the hood. But in the meantime I decided to do a spacer mod to raise the back of the hood up a bit. I got the idea from Randy's website and somewhat followed that.

Here is what it looks like stock.



And here is what the hinge looks like stock.



First off I needed to get the materials.

* Aprox 6" of 3/4" square tube
* 4 m8x40mm bolts and washers

I unfortantly didn't have much square tubing laying around, so I had to go to my local metal shop and get some. All I needed as aprox. 6", and I walked out with 4 feet worth. (so if anyone wants to do this, I'll sell 6" sections for cheap!).

I than cut the 3/4" square tube into two 3 1/4" peices.



I than drilled 2 holes in each peice aprox. 2" apart and centered. I decided to shot them with some paint to prevent rusting.



Next it was time to install them. I started at one side and than did the other side. Just a hint if your going to do this, your hood prop you have isn't good enough, you need to get something else as well or the hood WILL fall, and maybe onto your hand (it cought my finger = bloddy mess).

Here is what they look like installed on the hinge. The spacer goes between the hinge and the hood. (yes I know the 2nd bolt isn't all the way down)



Once installed, I aligned the hood again, and shut it to make sure it shut correctly.

Here are the results.





I've got about 1/2" or so all the way along the top of the hood, not sure how well it will help to get the heat out, but I"m sure it's better than nothing.

Overall I'm pritty happy with the mod. It only took me about an hour start to finish, and I did it on "coffee breaks".

If anyone want to do this, I have over 3" left of square tubing that I don't have any use for, I'll sell 6" peices cheap!


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LEAD_NOT_FOLLOW
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Few more pics.









And the money shot from inside.



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01jeepxj
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Look Good Adam.


 


I just sold some vents too :(


 



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90XJkid
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Did you notice any temp change with this mod?

Did the hood still latch and unlatch easily?

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aci4369
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I actually took these from him and put them on mine, and they worked great.  I didn't notice temp decreases in my gauge but I can gaurantee that it was cooler.  You can watch the heat pur out.  I don't know if it was my gauges or if it didn't change the temp that much but I could see the heat pouring out.  

With latching and unlatching, it was just the same as it was before the swap.   

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GrumpysXJ
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that actually does not look too bad-

so thats what Lead's XJ looked like on the road huh? Just jokin' with ya

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90XJkid
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Do you think that this would release more heat at speed compared to hood vents?

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aci4369
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I would bet they would be close, but I don't know.  I think that the vents would work better at slow speeds though which in my experience is when you need it most.  But I think that either would be better than stock.

I like the way that it looks.  Like the way that the hood vents look better though.

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ChevelleSSLS6
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It wouldn't change coolant temp much at all, as that's controlled by the thermostat. It would however reduce underhood temperatures.

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90XJkid wrote:

Do you think that this would release more heat at speed compared to hood vents?


At speed ... there is a downflow of air in front of the windscreen ... Its why the inlet is there for the interior vents ... therefore the vehicle airflow is pushing the hot air back into the engine bay ... whether vents are fitted or the bonnet is raised.


Hot air will rise out the lifted bonnet gap at low speeds .... up to about 25mph ... same as with vents ... Over that speed and the vents start to become scoops .... which is not always the desired effect.

Rearward, centrally mounted vents will be affected moreso than vents fitted towards the rear, outside edge of the bonnet.

To ensure that I dont have any negative effects on the normal nosecone air intake ... I clamp a foam packer around the bonnet release cable at the middle, rear of the bonnet when the bonnet is raised during summer ... As it restricts the download airflow yet still allows hot air to rise / be drawn out  from the bonnet rear corners.


 ChevelleSSLS6 wrote:

 

It wouldn't change coolant temp much at all, as that's controlled by the thermostat. It would however reduce underhood temperatures.

 

X 2

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ChevelleSSLS6
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Comet #2 wrote:


At speed ... there is a downflow of air in front of the windscreen ... Its why the inlet is there for the interior vents ... therefore the vehicle airflow is pushing the hot air back into the engine bay ... whether vents are fitted or the bonnet is raised.

 


This is what makes cowl induction ('z28 style' scoops and old Chevelles in particular had these,among others) work.

 



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Comet #2
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Comet #2 wrote:
At speed ... there is a downflow of air in front of the windscreen ... Its why the inlet is there for the interior vents ... therefore the vehicle airflow is pushing the hot air back into the engine bay ... whether vents are fitted or the bonnet is raised.

ChevelleSSLS6 wrote:
 This is what makes cowl induction ('z28 style' scoops and old Chevelles in particular had these,among others) work.
And dont those old Chevelles and Camaros look good.  smile

I guess they went to cowl bonnets because the earlier cowl systems from the firewall wasted so much space and made working on the engine difficult ???


Whats often forgotten in regard to cowl induction and cowl induction bonnets is that the purpose of those features is to direct air solely to the air filter on top of a carburettor .... In many cases fibreglass cowl bonnets are/were shaped to fit around the airfilter.

Today of course that system can be still be used to direct air to the air filter before it reaches a throttle body.

They are also good for directing air at turbo intercoolers etc.

What cowl induction systems and cowl induction bonnets are not good for ...... is removing hot air build ups in the engine bay of vehicles such as an XJ - under all driving conditions.

To remove the hot air from an engine bay effectively - vents needed to be placed where vehicle air flow will suck it out ... e.g. high on the rear of the fenders or the rear corners of the bonnet .... This will also increase air intake at the radiator somewhat.

 A cowl bonnet which is no more than a high bonnet i.e. has no ducting channels - just lets inducted air waft all over the engine bay with possible repercusssions to radiator intake .... depending on how inneffective the radiator intake / engine bay airflow already is .... and we all know how good the XJ is - in that regard  wink 

Benefits of the cowl bonnet such as the one available for the XJ are that the higher clearance, compared to the stock bonnet means more heat dissipation space above the rocker/valve cover .... and the bonnet will offer a similiar rising heat escape point at crawling speeds - as what a cheap set of vents do.

They do of course look very cool ......

Under hood temps can be measured after fitting the XJ cowl bonnet and one can imagine / pretend / be mislead that the engine bay temps are cooler .... but its really only the temp of the inducted air mixed with the engine bay air. All the issues that cause the high temps in the first place are still there.



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LEAD_NOT_FOLLOW
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GrumpysXJ wrote:
so thats what Lead's XJ looked like on the road huh? Just jokin' with ya
Yeah like 4+ years ago. What is it with everyone bumping old threads with pics of my XJ a llllloooonnngggg time ago? It's kinda embarrassing that my XJ looked like that actually...

 



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aci4369
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Embarrassed about how it looked then or now???

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