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Posted by: Cracker Oct 13 2016, 08:04 PM

Silver lining - starting from scratch is ALWAYS better!

A month ago, I ran into my first real problem, at Barber - I blew an outer CV less than 2 laps into the weekend. The root cause was I had a lowered the drivetrain to avoid a section of existing rear structure (lazy is never a good excuse!) - this caused tthe angles of the CV to be too extreme. In addition, I had also lowered the chassis beyond what was practical with my stock suspension set up. One caveat: The car liked it and felt great on the track but the angles were not sustainable!

In speaking with Chris Foley (thanks a million for answering my calls!!!) - he likes the hub center to pivot shaft centerlines to be within .250" of an inch to each other. My pivot shaft was 1.5" lower and coupled with the lowered drivetrain (which lowers the drive flange on the transaxle) - my CV went kaBOOM. My pivot shaft to hub delta is now only .5" - more inline with what Chris would like to see.

I share all of this (my stupidity) to hopefully help someone else avoid the same pitfalls. I weighed the options and there really wasn't any choice - to make the car safe at high speeds and to KNOW the changes would allow the CV's to last, I had to cut out the rear structure out, raise the trans to the proper level, fabricate the new exhaust, and rebuild everything around what was left.

I also had an issue with my wing strut at high speed, staying stable - deflecting rearward. The wing was a variable pitch...but it wasn't supposed to be! All of this re-work provided a great opportunity to fix this along with everything else. Another bonus, in picking Mr. Foley's brain was integrating his suggestion to implement structure that helps keep the longs from twisting - in relation to each other. It is still not exactly complete nor what I'd like in total structure but if I add too much more - people might call it a race car - not a hot-rod!

My exhaust was a little loud - not too bothersome to me but it didn't meet the 103 dB requirement at many tracks - even ours out East. I "invested" in the Burns Stainless 2-stage system for LS engines. They have a removable baffle which creates an more open system. It is supposed to knock the sound down to about 97/98 (I was at 106!). The cans were too big locate below the floor - so topside they are! I like it anyway (even if it raises my CG)!

Here are a few pictures of the completed project - just in time for tomorrow's departure for Road Atlanta. If any of you local/regional folks want to come on out - I'd enjoy meeting you - come on by. No cost to get in - you'd be my guest. Now if more than 3 people looked at the "paddock" - someone might actually show up.

If you have suggestions and ideas - please share them.

Tony

Posted by: stownsen914 Oct 16 2016, 04:41 AM

Nice work on the car!

What kind of power are you putting down, and which CVs are you using?

Scott

Posted by: Cracker Oct 16 2016, 08:00 PM

Thank you. The engine makes 530 (ish) to the wheels - late model Carrera that have been race prepped.

T

QUOTE(stownsen914 @ Oct 16 2016, 06:41 AM)

Posted by: Randal Oct 17 2016, 10:46 PM

QUOTE(Cracker @ Oct 13 2016, 07:04 PM)

Silver lining - starting from scratch is ALWAYS better!

A month ago, I ran into my first real problem, at Barber - I blew an outer CV less than 2 laps into the weekend. The root cause was I had a lowered the drivetrain to avoid a section of existing rear structure (lazy is never a good excuse!) - this caused tthe angles of the CV to be too extreme. In addition, I had also lowered the chassis beyond what was practical with my stock suspension set up. One caveat: The car liked it and felt great on the track but the angles were not sustainable!

In speaking with Chris Foley (thanks a million for answering my calls!!!) - he likes the hub center to pivot shaft centerlines to be within .250" of an inch to each other. My pivot shaft was 1.5" lower and coupled with the lowered drivetrain (which lowers the drive flange on the transaxle) - my CV went kaBOOM. My pivot shaft to hub delta is now only .5" - more inline with what Chris would like to see.

I share all of this (my stupidity) to hopefully help someone else avoid the same pitfalls. I weighed the options and there really wasn't any choice - to make the car safe at high speeds and to KNOW the changes would allow the CV's to last, I had to cut out the rear structure out, raise the trans to the proper level, fabricate the new exhaust, and rebuild everything around what was left.

I also had an issue with my wing strut at high speed, staying stable - deflecting rearward. The wing was a variable pitch...but it wasn't supposed to be! All of this re-work provided a great opportunity to fix this along with everything else. Another bonus, in picking Mr. Foley's brain was integrating his suggestion to implement structure that helps keep the longs from twisting - in relation to each other. It is still not exactly complete nor what I'd like in total structure but if I add too much more - people might call it a race car - not a hot-rod!

My exhaust was a little loud - not too bothersome to me but it didn't meet the 103 dB requirement at many tracks - even ours out East. I "invested" in the Burns Stainless 2-stage system for LS engines. They have a removable baffle which creates an more open system. It is supposed to knock the sound down to about 97/98 (I was at 106!). The cans were too big locate below the floor - so topside they are! I like it anyway (even if it raises my CG)!

Here are a few pictures of the completed project - just in time for tomorrow's departure for Road Atlanta. If any of you local/regional folks want to come on out - I'd enjoy meeting you - come on by. No cost to get in - you'd be my guest. Now if more than 3 people looked at the "paddock" - someone might actually show up.

If you have suggestions and ideas - please share them.

Tony

Posted by: mgp4591 Oct 18 2016, 12:03 AM

It looks different from the last time I saw it and I like the changes! The layout makes more sense to me with the exhaust run this way and I like the bracing in the rear. Along with the strut supports to the wing I think you'll be steady at speed - great job!

Posted by: Cracker Oct 19 2016, 05:36 PM

Randal - Kind words...thank you. Enjoy the DSR restoration - all of it! You can do it - some things just take time! I'm sending an engine off to George Dean next week for a build and new wiring harness. I'm "planning" on restoring my car over the Winter months.

Mike - Thank you too. Its usually better when YOU design and build around the necessary features. BTW: Rich says thanks for the B-day wishes!

Tony

Posted by: naro914 Nov 29 2016, 08:03 PM

No...no race car here...what are you talking about? How could ANYONE ever mistake that for a racecar... looks almost stock...

Look away...nothing to see here (except a race...um..uh..ehem..cough...hot rod car...)

Posted by: jdahl Dec 1 2016, 07:52 PM

With the exhaust in the trunk, there should be plenty of space for a diffuser... Non-race cars have diffusers.

Awesome looking car!

Posted by: Cracker Dec 1 2016, 08:26 PM

It IS a Hot-Rod Bob...umbradge my friend, I take UMBRADGE!

QUOTE(jdahl @ Dec 1 2016, 08:52 PM)

Posted by: carr914 Dec 1 2016, 08:47 PM

QUOTE(jdahl @ Dec 1 2016, 08:52 PM)

Posted by: Cracker Dec 1 2016, 08:54 PM

TC - I believe that definitely qualifies as a "race car" diffuser...

T

Posted by: stownsen914 Dec 5 2016, 11:41 AM

A diffuser can be done on a 914 - it just ain't easy! Pic below of the one I did on my car a few years ago (pic isn't the best due to the shadows - I outlined the rear of the diffuser in red on the picture to highlight it). The biggest challenge, aside from making the diffuser itself, was getting the exhaust and shift linkage out of the way. I also raised the engine and trans slightly so they don't sit lower than the floor pan of the car, so I could make a true flat bottom front to back.

In case you're wondering, the thing sitting on top of the car is the engine lid, which was off for this pic.


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Posted by: sixnotfour Dec 11 2016, 04:41 AM