blackmount1 said:
I did find the control arms and their bushings moving in and out excessively, I can pry on it, with not much very force, it will move, and stay there. Pry it back, same thing. It moves, and stays there... about a good 1/8" of movement and it translates to alot more then that in Toe at the wheel, and causes the control arm to pivot one way or another making the toe angle change drastically... I'm thinking this is why it gets stuck, and going lock to lock pushes the bushings in a different direction... I've got 75ftlbs on each mounting bolt, being only 3/8ths they wont go much more then that before snapping or stretching.
Yeah, this makes sense to me. I'm not an ME but I would think that if it had been plastically deforming the subframe back and forth that much then the subframe would have fatigued and failed by now.
The subframe itself is all .156 wall according to the builder, I personally don't think its as much as a wet noodle as most here are suggesting, especially once bolted into place with the additional bracing connecting the one section it needs support the most ontop of that- but I've been wrong before, and won't dismiss that idea until I'm 100% sure otherwise..
I've sourced a stock subframe and pair of control arms from a local hoarder for $75. Went ahead and ordered the Lot from Superpro... Poly Bushings for all of it.. I won't really have time to work on it much this week, started an old job with a new company, and they are throwing me right into it, but I also want to give the builder a chance to come up with some resolution until a buyer hands me cash for the subframe, or I finish restoring this OEM one.
The subframe itself is all .156 wall according to the builder, I personally don't think its as much as a wet noodle as most here are suggesting, especially once bolted into place with the additional bracing connecting the one section it needs support the most ontop of that- but I've been wrong before, and won't dismiss that idea until I'm 100% sure otherwise..
Yeah, my opinion changed somewhat when you mentioned the other stuff that bolts to it. I still wouldn't rule it out without at least observing it under hard cornering or doing some before and after measurements. Did you fix the control arm thing yet?
I nor the builder has come up with anything, I think a firmer bushing would be a cheap fix, but haven't been able to track down one of correct dimensions.
blackmount1 said:
I nor the builder has come up with anything, I think a firmer bushing would be a cheap fix, but haven't been able to track down one of correct dimensions.
If you have access to a lathe, making delrin bushings is simple.
Stiffer bushings are a good idea, but can you check bumpsteer?
If it's a strut, you probably want to pull off the spring, disconnect the sway bar on one side and exercise the control arms. Since this problem didn't exist with the old subframe, it's possible the steering rack isn't at the same location (primarily height, although forward/aft will have slight affect), or the rack isn't in the same lateral/side to side location.
blackmount1 said:
I nor the builder has come up with anything, I think a firmer bushing would be a cheap fix, but haven't been able to track down one of correct dimensions.
It sounds like something is shifting, not compressing or bending. Bending or compression would spring back. Do you know what is shifting position?
I've confirmed the issue is bushings. I do not have a way to make my own unfortunately
blackmount1 said:
I've confirmed the issue is bushings. I do not have a way to make my own unfortunately
Can you explain what is happening at the bushings so we can try to puzzle out a solution?
blackmount1 said:
I've confirmed the issue is bushings. I do not have a way to make my own unfortunately
GRM has an article on DIY bushings. Delrin require a lathe (or a set of specs and a machine shop), but urethane ones can be molded and molds are fairly straightforward: https://grassrootsmotorsports.com/articles/how-make-your-own-delrin-and-urethane-bushings/
A paint pen and strategic go-pros would be where I was headed I think. Catch it in the act with marked points of reference to help you clearly see what it's doing. Cool car collection - I understand shiny part syndrome. I do love tubular parts regardless of if they actually help or not....
Streetwiseguy said:
Needs more triangles.
I agree, especially in regards to the engine.
Received the new bushings over a week ago, installed them and paint marked everything... 200 miles later of torture testing, normal driving, and normal spirited driving, nothing moved the slightest bit, and completely cured every issue I was having.
Just wanted to update...
In reply to blackmount1 :
Awesome news!
So I have to think this 2700 lb car is a fwd chassis, yeah?
blackmount1 said:
Received the new bushings over a week ago, installed them and paint marked everything... 200 miles later of torture testing, normal driving, and normal spirited driving, nothing moved the slightest bit, and completely cured every issue I was having.
Just wanted to update...
Awesome! Appreciate the update.
I have nothing to add other than this such a cool idea, 3000GT VR4 with turbo delete! Really the V6 N/A Mitsu 6G series are underrated, the later series 6G with MIVEC was quite potent for the time.
The subframe does look comically similar to the AWD DSM. A lot of drag racers swap to tubular subframes and control arms for weight reduction but the factory pieces are quite strong with the OEM braces in place.
In reply to Lof8 - Andy :
Sure is.
In reply to engiekev :
It's a great engine for revs, and responds well to basic NA modifications.... And yeah those 3.8L's are awesome. They make 300Wheelhp, with a reflash, and there are guys out there making 600hp purely Naturally aspirated. I have one in my garage that did spend some time in the car.
I wouldn't mind revisiting it, but I would really like to see a Rotary in a RWD Layout in the near future... People have been stuffing V8's in these cars since the early 90's when you could still buy them new, but no one has ever done a Rotary... I think something like a PP ITB 20B as an end goal would be simply epic... Otherwise the original goal was a Titanium Rod, Dry Sumped, 4.0L spinning north of 8,500RPM similar to the Dakar Rally Engines, but thats a bit more unrealistic, and the engine itself is still quite heavy.
