Firebird 73: pragmativc approach for ride improvement
 

Hi everyone,

I just introduced myself in the introductions section, so this is now my 3rd post in the forum ! :hello:

As I said in the presentation, I still don't have the car with me (coming to Europe from the US, currently going through the customs clearance, hope it's just a matter of days...) :goggles:

The process for the homologation of a classic US car here is quite long and painful. Lots of paperwork and quite restrictive regulations in terms of the nature and amount of modifications allowed (well, in principle, NO modification allowed, there's always some margin to play... but clearly I would not be allowed to fit a supercharged engine, or an entire new custom chassis, etc)


I'd like though to anticipate some things though, since the whole process above can take 2-3 months, and any change made to the vehicle is better to be made before the final technical inspection: after that, the main specs of the care will be "frozen"... i.e. I won't be able to change the size of the tires except for equivalent sizes (+/-3% of the distance per full wheel spin)

For this reason, I'd like to take advantage of the 2-3 months paperwork period, and I'd like to ask for your help/advice.

Some things to consider:

- Important: as I said, I don't have the car, so I didn't drive it yet... my "needs" are hence just based on my own assumptions. According to (1) the previous owner, (2) the shop who did some restorations and upgrades before the previous owner purchased the car, and (3) the independent inspection I ordered, the car rides and handles well without any apparent issue.

- I am not an expert ("competition") driver, I won't do Autocross or Drag racing whatsoever... most of the usage will be cruising with wife and kid, although I enjoy driving a bit hard some times on mountain roads, through corners, etc. I would like to obtain a good compromise btw cruise/comfort and a firm/accurate ride.

- It is the 1st time that I will own and drive an american muscle car, so no previous references.


Short description of the car:
- 1973 Pontiac Firebird
- 400 ci engine with Edelbrock intake and 4BBL carb, MSD ignition
- TH350 with Hurst dual gate shifter
- Ron Davis dual electric radiator
- March serpentine
- Disc brakes in all 4 corners (I think relatively basic stuff, not sure)
- Otherwise, stock suspension
- Bushings, etc replaced
- American Racing 17'' wheels
- Nitto NT450 tires (225/50R17 front, 255/50R17 rear) --> any issue due to having 2 different sizes? would it be better with 255 in all 4 corners? I'm afraid I can't go much bigger than that due to potential homologation issues...

- I have ordered (to be installed here in Europe) a rear sway bar (3/4'' from Hellwig, adjustable in 3 positions). The front sway bar seems to be stock.
No clue about the front coils and rear leafs, nor for the shocks (red at the back, white at the front, that's all I know) but they appear to be relatively standard and maybe quite new.


>>> Based on that information, I was thinking about adding some sub-frame connectors (i.e. from Hotchkis) for extra chassis rigidity.

>>> After reading this forum, I also started to consider other "full package" upgrades, such as:
- Ridetech 4 link
- Hotchkis TVS stage 1 or 2
However these are quite expensive (+ you add the shipping to Europe + customs...) and not sure if really necessary for the kind of driving I will do. Moreover, they may be a "risk" in terms of the homologation process in front of the authorities here, but not sure...

>>> Also I saw advertised in the forum some 2nd hand components like Hotchkis front control arms, front coils and Bilstein shocks. Again, not 100% sure about the choice. Do you think these would be interesting to add?

>>> In case I would stay with a "basic" set-up, would you recommend:
- the sub-frame connectors?
- the lowered coils?
- improved shocks? any particular recommendation?
- improved rear leaf springs?
(for the 3 last elements, any particular advice regarding the rates to be picked?)


>>> Or would you rather push for the "full package" investment? (in case it would be OK vs the authorities, I will check that next week...)

>>> Or...... (also an option...) would you rather NOT DO ANYTHING ?? :D

Basically, I am a bit overloaded with the amount of information and the number of choices available in the market.... :drowninga:

I will try to attach some pictures (not sure how it works...) of the underbody so that you can figure out how the car is right now.

Thanks a lot in advance for your recommendations !!!
See you around ! :cheers:

I vote for the basics since its just a road car.

Hotchkis leafs and coil springs to drop you 2" from current
Hotchkis front hollow sway bar 1 1/8"
Hotchkis Subframe connectors
Hotchkis subframe down bars
Koni classic shock OR Ride tech HQ shocks
Quick ratio steering box, Delphi 600

275mm tires on new 18" x 9" wheels with the correct backspace.

Hi Vince,
Thanks for the advice and sorry for my late reply, quite loaded with work over the past week.

Still trying to figure out what the best route can be.
You're probably right and maybe I shall start just with some basic stuff, like shocks, leafs (in case I want to change the stance), sub-frame connectors maybe? (not sure if their impact vs price is important) and not sure about new sway bars.
I've been recommended also the quick ratio steering box.
Is the Delphi 600 the only model that would fit? or are there other options? from what I saw, this is relatively expensive as well. Good change vs stock? is the stock one too soft ? what ratio would you recommend?

Since apparently, and after all the customs paperwork, the car should be here at home within a week or two, I will probably wait a few days and drive it at least for a week to be familiar with it, then judge about the ride quality and try to define priorities accordingly.

Check what you have on the car you may have a decent steering box on it now. I do recommend the pinion geared Delphi 670 boxes in 12:1. They feel incredible.

im not sure what restrictions you have as far as what you can install on your car but the Hotchis subframe connectors work pretty good. Im a fan of the DSE version.


maybe this will change your mind about the drop

Wow!
Vince, thanks a lot for the photoshop session... It does indeed change a bit my mind... Mucho lower than what I thought. Do you think it's representative of, let's say a hotchkis or similar suspension kit? (i.e. 1,5-2'' drop?)

Otherwise, any suggestion on where to find the Delphi? (any place or dealer in Europe it would be great, if not I'll have to go as usual with the shipping costs and cuatoms, I'm kinda getting used to it.......)

I'll have a look at the subframe connectors as well. Juat out of curiosity, while other components have more design and engineering into them, the connectors seem to be at least at first sight quite aimple provided that you get the geometry and dimensions roght. Anyone has experience in bulding them DIY? Or not a good idea?

I like the Hotchkis TVS kit. But since you ordered the Hellwig rear bar, you should perhaps get their front bar to match it. Hellwig tends to size their bars a little stiffer than other brands and you don't want to have a stiffer rear bar than front. On their first gen Camaro front bar, the Hellwig hollow bar uses .188" wall tube. The Hotchkis front hollow bar is .156" wall tube. This makes a big difference in rate. I don't know if the Hellwig second gen front bar is heavier wall but it might be.

If you were happy with the present ride height, you could change just the sway bars and shocks and have a nice riding car to cruise & see if you are happy with it that way. Lowering the car requires stiffer springs and the Hotchkis springs put the car at a good height, you can't go lower without troubles. The Ride Tech system will improve the ride quality over the Hotchkis due to the multi-link rear suspension.

David,
Thanks a lot for your advice, very interesting.
I would really vale your opinion on the following:

- I bought the rear sway bar because the car originally didb't come with it, only with the front SB (stock)

- I went for Hellwig not due to a particular preference but rather because amongst the options I saw back then, this one was including the arms to attach it to the subframe, so I thought it would be more of a no-brainer for installing it; as you can see I'm not really an expert.

- said that, per your comments, not sure that a stock front bar with the Hellwig at the rear makes a good combo in terms of stiffness front vs rear. Should I understand that it's better to have a stiff one at the front and a less stiff one at the rear?

- or would it be a better solution to forget (sunk cost) about the rear hellwig and go for Hotchkis front+rear? Or rather stock front and another option at the rear? Or... a full TVS system front/rear (I would tend to say "stage 1" since for the usage I intend to do, not sure that the front control arms really make sense, I read that the 2nd gen stock ones are not that bad for a "civilized" usage...)

- regarding a potential shock upgrade, would you be so kind to suggest some recommendations on brand/model? (Always considering the kind of cruising usage I mostly intend to do). It is my 1st american muscle car so I lack experience, and being based in Europe i am notvery familiar with the brands and alternatives most of them from the US

- on the srpings (front coils and rear leafs) I am not decided yet, I will test the car first for some days. Do you think it's worth? Same on the sub-frame connectors, I don't know if thehandling improvement would be noticeable. As I said I would do cruising most of the time but we have quite a lot of mountain roads here

I will probably need to forget about the 4 link due to restrictions in the homologation here.....

- finally (hope you're not bored !), two "bonus questions":
A) quick ratio steering: interesting? Or would it penalize driving in the highway? (Too over-reactive)
B) the current tire size of the car (225/50R17 front / 255/50R17 rear) is very hard to find in Europe, don't know why, so probably I will change all four. I was told I'd better go with a profile of at least 50, if not 55, because otherwise the ride would be too harsh and many vibrations. Do you think a 245/45R17 would be good? Or is it maybe too large, specially at the front? (The car is not adapted or minitubed in any way)


Sorry for that many questions !! As you can see I'm starting and the disadvantage here is that access to testing different components is much more difficult than in the US so I guess I'd like to be as good as possible from the beginning...


Thanks David and everyone for your recommendations, I really apreciate them and enjoy reading you, it' s very instructive!

I would order a matching front bar from Hellwig and install the front bar before adding the rear bar, this will keep the rear from having oversteer which is dangerous. Drive the car for a while and see how you like the handling. If you decide to lower the car, then look at getting just the Hotchkis front and rear springs & their Bilstein shocks.

You can fit a 245 tire front and rear easily BUT the wheels have to have the correct back spacing. We have run up to a 275 X 17 on the front and rear but back spacing has to be exactly right. A 245 would be easier to fit but again, you need the right back space on the wheels.

What is the rim width and back space you have now?

As Vince said, adding a good Delphi 600 steering box is a great improvement. The 12.7:1 constant ratio improves response, but the stiffer feel keeps the car from feeling over assisted. You would need a new rag joint to fit the smaller shaft, and hose adapters to adapt the O ring seal ports to 45 degree SAE flare threads to fit your hoses.

The car would drive & corner better with more positive caster, but that requires at least the tubular upper A arms. I think you can get by without them but they would be mandatory for autocrossing. The steering box will improve feel a lot. I would align the car to my specs on my web page.