Removing front core support

[LamboZ]

Im looking to remove the front core support.

Not just the top where the hood prop is, but the lower one also that is connected to the frame rails.

 

Heres a picture of what im looking to remove.

NOT MY CAR.

 

Im looking to remove the one thats wrapped in the picture and the lower one also.

 

I would add some bar stock with bracing (with adjustabilty) to replace the lower one but i want the top one gone all together.

the lower one is in the way of some parts and i just need to make a lower profile type cross bar.

The top one is 100% in the way.

 

The Car has a front strut bar, and is getting a 8 point roll cage for the wondering.

 

Is this a bad or good idea?

Ive always read that nothing in FRONT of the strut wells are structual.

correct?

 

Thank you very much.

[JMortensen]

All I can tell you is that I've torn up a couple radiators in my car, and that happened from chassis flex. The chassis flex comes from the struts with maybe a little more from the sway bar. It should be possible to brace the strut towers enough to stop that flexing from happening, but until that is actually accomplished, the core support is definitely structural.

 

You've got the upper and lower frame rails to deal with on a Z, and they're very long, so any flexing going on is magnified out at the end there. I think what you're looking at doing CAN be done right, but it's going to require one hell of a strut tower brace, and I'd strongly suggest some kind of lower bar to tie the bottom together.

[LamboZ]

Jon, thanks for jumping in.

 

i found this picture just a sec ago in another thread.

 

 

now he still had the top one but he did remove and make his own bottom one.

now i would do the same, but alittle less profile.

I dont have much space up front with my engine setup.

 

I could very well make pretty much a strut bar but place it alittle more foward where the top core support bar is now.

 

Ill never track this car around a track like you do with yours, its just a fast street car.

 

Strut bar that the car has now is almost like the PDK front bar, so it does have extra bracing.

[blueovalz]

I wished I could remember the string, but there was a good one quite a while back dealing with this issue (owner wanted a IC in place of the upper core support.

 

What Jon said is correct, and this problem can be resolved. The 8-point cage is important only in how the towers or front frame rails are connected to it. Any twisting forward of the firewall will need to be reduced to near zero flexing. This can be accomplished through very thorough bracing of the towers, but this then leaves the effects of the swaybar which is slightly forward of the towers. My approach was to triangulate the towers, firewall, and the engine block (which along with the tranny, is solidly mounted with front and rear engine plates). It makes for a very rigid chassis (along with the cage). Lastly, I used a firm rubber foam to isolate the radiator from the fabricated core support, and during the 17 years I've had this set-up, I've never had a radiator failure.

 

[Pop N Wood]

There was a recent thread where someone cut out their top bar.

 

Do a search.

 

The last 3/4 of the thread is him trying to correct the mistake.

 

I think Jon was being kind in how he phrased his answer. Z’s already flex a lot in that area. Ideally you want some type of X arrangement to keep the left and right halves from scissoring up and down. The farther out on the frame rails, the more leverage you will have. I consider both cross pieces structural. If they weren’t then Datsun wouldn't have double lapped the pieces as heavily as they did.

 

The only way I can see to get an X arrangement at the strut towers would be to solid mount the engine making it structural. Even that would be less than ideal. If you look at a picture of a Zed with the front quarters removed, you will see a box structure going along the top of the fenders. Sort of looks like a truss to me. The box structure is tapered and curves towards the front of the car where it attaches to the radiator cross member. That tells me the part was designed to accept loads at the end and not necessarily the middle.

 

One option is to replace the frame rails with heavier steel. This could undoubtedly be make strong enough to prevent the scissors motion, but it will weight more than a structure that uses geometry rather than shear mass for strength.

[Pop N Wood]

Looks like my post crossed blueovalz.

[Michael]

Without quantitative analysis it would be difficult to reliably infer from the shape of the upper frame rails the structural importance of the upper radiator support. Most likely the upper radiator support also plays a significant role in crash protection, in rigid mounting of relatively heavy and delicate components (the radiator), and in overall vibration reduction.

 

If would venture to think that triangulating the front strut towers would allow the removal of the upper radiator support - especially if you replace the lower radiator support with a stronger piece. Crash protection will be compromised, but this is probably not your main concern anyway.

[heavy85]

Ive always read that nothing in FRONT of the strut wells are structual.

correct?

 

Not exactly but sort of. All the loads are imparted into the chassis originate in the strut towers and crossmember (well except the swaybar but assume that is probably relatively little) so the most efficient way to strengthen the chassis is from the strut towers back. In stock form there are no strut bars so the upper radiator support is probably providing a lot of side to side strength. So if you were to make a beefy strut tower brace in addition to beefy lower support then the upper support should be able to be removed with little drama - especially for a street car where you are not really trying to optimize things. Just very softly mount the radiator and I would think you should be fine. This is all of course without regard to impact protection which I can't really comment on. Basically I agree with what Michael said. Devil is in the details so I think it's really all in how it's implemented and if done properly should be fine.

 

Cameron

[LamboZ]

Well I figured ive changed everything else on this ride, might as well go ahead and cut them out.

 

im fooling around with ideas now for a new lower support bar, im trying to make it so I can mount my front bell pan on it also.

[AK-Z]

Brace brace brace. Since you are going to be cutting out a vital structural memeber, there is no such thing as bracing overkill in this case.

[johnc]

Think of the engine compartment as a rectangular box with the firewall and core support as the small ends of the box. The loads coming into this box are on the long sides. Removing one end of the box turns the engine compartment into a tray. The loads are still coming into the long sides of this tray. What's going to keep this tray from bending?

 

Think about it that way, make yourself a carboard tray, and experiment.

[LamboZ]

Well I cut them out, the lower bar ill be making looks very much like the one in the picture above.

except ill be adding 4 support bars on it that will connect to the frame rails also.

The top bar is gone, nothing will replace that except something like a strut bar (oval tubing) but more forward then where the bar use to be stock.

Ill mount my zues fastners for the hood on that bar too.