66 Nova SS Project

[byndbad914]

unfortunately Penske forgot to send the shock so they are going to next day one on Monday (hopefully). Interestingly enough, this is what happened when I ordered my last set for the Porsche. Anyway, a lot was hinging on getting that shock in for progress this weekend.

That said, I went to the track yesterday to watch Porsche Club and got to check out a couple Cup cars and sho' nuf they run spring rates in the 1500 lbs/in range as base setup as I had heard. The springs are marked in N/mm so I had to calc that out and it came in at 1485 lbs/in, so I am of the mindset to stay heavy on the springs like I learned on the 914. Considering those cup cars are 5 seconds/lap faster than the 914 was, I suspect there is nothing wrong with that

New rad is in, had to cut out the old rad mounting as even tho' they are the same size radiators, they aren't quite the same actual size. Added in the oil cooler and basically the nose is full of cooling devices. I am hoping I do not have to run the second oil cooler like I did on the 914 as this will have way better air flow than the placement on the 914 did.

Also mounted a ball valve for the fuel line so I can easily disconnect the engine. Lastly I made an upper cage that is tied together to mount the rear rocker arms to and tacked it in. Overkill for sure but safe. I can mount the fire bottle and/or battery in the recess.

[Vince@Meanstreets]

looking good Tim,

On the spring rates do you know what ratio they are running on the cantilevers?

[byndbad914]

Vince - I think you are asking me what the motion ratios are? If so, the fronts are struts so the motion ratio is essentially 1:1. On the rear, I do not know exactly what the ratio is but I believe it to be in the 0.8:1 (spring:wheel) range. I know they have to run stiffer front wheel rate than rear in an attempt to balance the oversteer and one guy in particular was having understeer issues with his Cup car but was more in the "enough money to track a Porsche Cup" category and less in the "know how to tune a track car" category Were it mine I would have swapped out springs between sessions and solved the problem.

The Nova has two different mounting holes where I can set the ratio at either 1:1 or 0.8:1. So essentially I should be able to get similar motion ratios and the Nova will be a bit heavier - those Porsches are in the 2600 lb range with full fluids IIRC. I know they list as around 2500 lbs from Porsche but believe that may be dry weight. This implies I may need higher rates yet to achieve best results.


I can say that every single time I went up in spring rate in my old track car the car went faster. I was set to increase it again and then decided to sell and do a Nova project instead. I was at wheel rates higher than many people run in spring rate. There are two basic schools of thought (and this is a rather serious simplification but at the fundamentals accurate) = use the spring to control the car and the shock to control the spring, or use the shock to add control for the car along with a lower spring rate.

The difference is really the individual's ability to tune. I do not have a team from Penske follow me to the track like Pro teams do to revalve shocks based on track data but I can swap a spring in about 15 minutes per corner so as long as I don't move too far in spring rate and overcome the rebound control that is valved in it, I will have a similarly good car. In the end, I will never be as fast as having a team of engineers following me around, but I will be as fast as I can be if I focus more on springs and less on shocks. Basically the engineer at Penske told me he would set me up at near zero compression and let the spring do the work which is exactly what I did on the Porsche with them previously. Having the ability to tune in 0 to around 150 lbs/in equivalent compression is nice to have to predict if I expect to go faster with the next stiffer spring.

To make the discussion more interesting we would get into the characteristics that springs have a linear stiffness that starts at 0 lbs and increasing with translation whereas shocks have a stiffness that is far more dynamic and based on velocity of wheel motion v. total travel. That is where the engineers can come in and balance the overall setup and even tho' I am a degreed mechanic turned degreed mechanical engineer, that stuff is way out of my realm/expertise.

[Al Moreno]

Holly Mother of God! Loving your build Tim!

[SBDave]

Awesome stuff here!

[byndbad914]

thanks guys! Shock showed up yesterday and I did a test fit, there is some interference but fortunately it doesn't appear to be too bad so I hope to machine some clearance in this weekend and verify I am good to go. One thing I didn't recall is that the monoballs are narrow in these shocks - narrower than a typical monoball from Aurora/FK/etc - so my high angle spacers are too wide. I need to call them and see if they can swap them out for a more typical monoball with the correct width for my spacers. The rockers are already machined based on the "typical" width so I can't just narrow up the spacers.

The joys of doing custom stuff.

edit - well, dammit, turns out I am too used to using heavy duty rod ends and spherical balls. There is a bunch of bearings that are 1/2" wide, not 5/8" wide. The problem is I can find some "wide" bearings but the housing also gets wider so they can't swap in. Will have to custom turn the spacers down and then make what is essentially washers to fill in the gap to make up the 1/8". Irritating but solvable.

[tubbed69]

Tim you sure are doing a super fine job on this build,love these novas

[byndbad914]

thanks! now, that said...

MAKEUP!

Anybody remember the Daffy Duck cartoon where he kept getting his face blown off and would walk "off set" and scream MAKEUP?

Well, I am a little bit there. The 18" shock was just going to bind at full extension and that was not going to be a huge issue as it was just a little clearance grinding to solve. However tonight I got in there and got the base of it held into place and started to run the shock through motion into compression... well... I knew I lost 1" of compression asking for an extended eyelet at the one end which indeed minimized the binding as I had hoped. However, what I didn't realize is that I was going to lose another 1.5" with the extended spring cup - the shock body bottoms out on it! It all makes perfect sense since they have to be the same size to fit the spring, but not something that crossed my mind and was apparently a non-issue on the Porsche as I had the exact same setup on it.

I took a shock with 6.2" of motion down to a measured 3.8" and it bottoms out at about 1/2" of bump

So I will need to knock the mount tabs off and flip them over to move the rockers over the support, not under. Not a big deal really, just one of those things. What it does mean is the tubing I have cut and tapped for drop links to the suspension and could be used for the sway bars now all need to get longer as I have to fit a shock at least 3" longer to get full travel back.

Hopefully that is all I need to do; I need to really look at it again tomorrow and think it through some more and try to make sure I am not missing anything else

[rustomatic]

This is definitely the most awesome thread I've looked through on here in some time. I'll look forward to seeing your swaybar mounts. We should re-name this thread Steel Porn--you are definitely a producer!

[byndbad914]

thanks, that is a great compliment! The sway bar stuff will be pretty straight forward using Speedway Engineering bars and arms.