Weight reduction: Running out of ideas.

[BBShark]

Is it the vibration of the box itself that is producing the sound? Maybe some dead soft aluminum strips on the outside "diaphragm" might help

I was working on a project recently where we had to attenuate sound produced by flow through a jet engine component. I was able to identify a large peak frequency with a cell phone app. It's called FrequnSee.

 

[rtj]

You could search something called boom tubes by Dr Gas.

 

[rtj]

You could search something called boom tubes by Dr Gas.

It used to be called spin tech, but it looks like he calls it spin pro muffler. Might work well in you design. He published his theory on how why it works.

 

[greg75vette]

Ok, so I just read through the whole thread. Good read! Your level of dedication is impressive.
My only 'helpful' comment is have you thought of going with a tubular frame? I've heard good things about SRIII's and supposedly they're a lot lighter. They can also be set up to take C4 and C5 suspensions. Since you already have the C4 suspension, that gets you a ahead a bit. Something like that might open you up to a lighter C4 diff, as well. Admittedly, you might be too far invested in your current frame to switch, however.

 

[68/70Vette]

Did you install an alum block bb? I thought you posted photos of one.

Yeah, did that a few years ago. So far it's held together, although I do tend to keep the RPM within reasonable limits to ensure some longevity.

I've been a long time interested viewer of your weight reduction posts. Wonder why you keep rpms down with the aluminum block. I have a Keith Black BB aluminum block in my project 70. I believe it's designed to tolerate large boost supercharge pressures. I don't think it's an optimally light weight BB.

It's just a matter of dollars..if you have an aluminum BB and aluminum heads, you can buy titanium rods and intake valves. Last time I looked, I think the titanium rods were about $700 to $800 each.

If you (or me) were one of those Silicon Valley stock option holders cashing out in the 100's of millions, we could have the C3 body and chassis duplicated in carbon fiber and magnesium. Dream on.

 

[69427]

Is it the vibration of the box itself that is producing the sound? Yep. Maybe some dead soft aluminum strips on the outside "diaphragm" might help.

I was working on a project recently where we had to attenuate sound produced by flow through a jet engine component. I was able to identify a large peak frequency with a cell phone app. It's called FrequnSee.

Larry, I'm not bright enough to completely follow that. Would I be welding in some annealed strips, or something?

ps: The cell phone app sounds neat. Unfortunately I'm still too cheap to get a smart phone.

 

[69427]

Ok, so I just read through the whole thread. Good read! Your level of dedication is impressive.
My only 'helpful' comment is have you thought of going with a tubular frame? I've heard good things about SRIII's and supposedly they're a lot lighter. They can also be set up to take C4 and C5 suspensions. Since you already have the C4 suspension, that gets you a ahead a bit. Something like that might open you up to a lighter C4 diff, as well. Admittedly, you might be too far invested in your current frame to switch, however.

I've asked several guys with the SRIII frames and one guy with one of those 4" tubular Grand Sport replica frames about the weight of those things, and nobody has been able to tell me anything. And to be honest, I think I could weld up an aluminum frame cheaper than what the steel aftermarket frame guys are asking for their stuff. I priced out some aluminum tubing a while back, and I think I could get sufficient material for a complete frame for about $2k. Not cheap, but I would love to build one as an interesting engineering project/exercise.

 

[69427]

Working on a couple items (rear exhaust Y-pipe and batwing replacement) to try to pull a couple more pounds off the car. Here's the current setup (steel tubing Y-pipe and C3 batwing).



I pulled the Y-pipe off to weigh it and make a replacement piece in aluminum tubing. Here's the current piece and the partially tack-welded replacement (I can't weld the two end pieces on until I finish the other welds and grind/smooth the internal weld surfaces first). The welding is going damn slow as it's difficult to weld much of a bead length each time on this thin stuff without burning through the walls.



The new piece is slightly different shape as I cut and shortened the inlet tubes at the mufflers so I could replace that length with extra lengths of aluminum tubing. Should be about a five pound reduction in weight.

Also working on trying to replace the C3 batwing with a C4 D36 piece. The C4 part is 7# lighter than the C3 piece.



The 3/4" adapter plate/ring will add back a couple pounds (after significant final shape trimming), but I should be able to nullify that by being able to eliminate/replace the current adapter brackets for the (C6) toe arms and the rear spring, and also possibly being able to use shorter spring hanger bolts due to the higher spring perch on the C4 cover. So far it looks like I can drill the C4 cover to match six of the C3 cover bolt locations (the same number as I'm currently using with the C3 batwing). The other two bolt locations are going to be harder to accomplish at the moment.
The hardest part of this change will be narrowing/welding the batwing width to match the current narrowed batwing, and also probably needing to revise/replace the batwing frame-tabs to accommodate the slightly different location of the outer mount bushings.
I should be able to get about ten more pounds off the car with these mods, although I do wish that ten pound reduction was from a location up front and higher, but I'll have to take it where I can get it.
I'm still trying to work out the design for an aluminum replacement of the front suspension crossmember to take 5-10 pounds off the front sometime.

 

[JPhil]

Maybe you should change your forum handle to "Anorexic427"

 

[69427]

Maybe you should change your forum handle to "Anorexic427"

Well, that might possibly be appropriate (and it's certainly nicer than some of the names I've been called in my life :amused.

 

[69427]

Got the new Y pipe welded and buffed for painting.



Coated it with high temp flat black BBQ paint and installed it on the car. Pretty much looks like the old steel piece but 5.8 pounds lighter.

 

[vette427sbc]

Thats a nice couple'a lbs!
Any worries with cracking from heat cycling?

Has someone mentioned aluminum wiper linkage? not much weight to lose, but could be easy to fab

 

[phantomjock]

No wipers or motor - use RainEx on the outside and window heating element on the inside? Maybe 1/2 the weight - or less?

http://www.frostfighter.com/index.htm

I've "heard this works" in rain - but no practical experience . But if you don't often drive in the wet - might be a weight saving answer.

Cheers - Jim

 

[mrvette]

Wiper door?? alumium but could be made from plastic with a bit creative work......that grate/vent in front of the door?? same thing, bolt on plastic....

as for the operational stuff.....not saving any weight either way IF it retains being functional.....all that stuff is aluminum....:crutches:

 

[69427]

Thats a nice couple'a lbs!
Any worries with cracking from heat cycling? Don't know yet. The pipes are pretty far downstream and subject to a lot of wind cooling so I'm hoping they don't experience a lot of thermal growth during use. I'll find out regardless, I suppose. In the mean time I've learned to keep the old stuff in the trailer and take it along with me to the track days so I can swap out any new parts that fail.

Has someone mentioned aluminum wiper linkage? not much weight to lose, but could be easy to fab

I've taken a couple quick glances at the linkage but haven't got much further than that. You're right that it's not much weight, but it is above the c/g of the vehicle, which makes that weight removal inviting. So far it seems like 90% of the weight I've been moving off this car has been under the c/g.

 

[phantomjock]

I was going through a bunch of files from my tear-down and body off. Came across this pic of the sound insulation in the back of my 78. Don't know if you've any joy like this in your 69 - but that's a good chunk of "fat," if you can.



Cheers - Jim

 

[Bad Bird]

How wide a rear tire can you run with the C4 rear suspension and stock '69 bodywork?

Cheers,
Matt

 

[69427]

How wide a rear tire can you run with the C4 rear suspension and stock '69 bodywork?

Cheers,
Matt

Presently I'm running some C5Z wheels (10.5" width) with 285/18 tires on the rear. I could have fit some 295/18 tires there, but the incremental price difference was too damn high for just 10 mm of additional tread.

I have some 315/16 tires on my C4 that I've been meaning to try on the 69 when I get a free moment from other more "important" projects.

 

[69427]

I was going through a bunch of files from my tear-down and body off. Came across this pic of the sound insulation in the back of my 78. Don't know if you've any joy like this in your 69 - but that's a good chunk of "fat," if you can.



Cheers - Jim

Damn, it's hard to turn down a weight number like that, but until I can figure out how to get the exhaust termination box vibrations toned down a bit more I can't afford to get rid of any sound insulation quite yet.
I would like to find some high temp insulation sheeting that I could just stick to the top surface of the box.

 

[Bad Bird]

How wide a rear tire can you run with the C4 rear suspension and stock '69 bodywork?

Cheers,
Matt

Presently I'm running some C5Z wheels (10.5" width) with 285/18 tires on the rear. I could have fit some 295/18 tires there, but the incremental price difference was too damn high for just 10 mm of additional tread.

I have some 315/16 tires on my C4 that I've been meaning to try on the 69 when I get a free moment from other more "important" projects.

Wow, I'm surprised. That's quite wide considering. Did you notch the frame at all the gain that tire width, or does the C4 knuckle and links give you more room?

Regards,
Matt

 

[69427]

How wide a rear tire can you run with the C4 rear suspension and stock '69 bodywork?

Cheers,
Matt

Presently I'm running some C5Z wheels (10.5" width) with 285/18 tires on the rear. I could have fit some 295/18 tires there, but the incremental price difference was too damn high for just 10 mm of additional tread.

I have some 315/16 tires on my C4 that I've been meaning to try on the 69 when I get a free moment from other more "important" projects.

Wow, I'm surprised. That's quite wide considering. Did you notch the frame at all the gain that tire width, or does the C4 knuckle and links give you more room?

Regards,
Matt

I didn't notch the frame as the inner wheelwell bodywork is basically on the same vertical plane as the frame rail, and I would have had to also cut and modify the bodywork. My intention at the start of the suspension conversion was to leave the bodywork unmodified.
The two trailing links are set inward substantially compared to the original C3 trailing arm, allowing the wheel/tire to pretty much set inward pretty close to the frame rail and inner bodywork.

 

[Bad Bird]

Thanks for the feedback.

I completely understand the desire to leave the bodywork alone of a '69. Not much looks as good. They can get a little tire challenged though with the stock bodywork.

 

[69427]

Thanks for the feedback.

I completely understand the desire to leave the bodywork alone of a '69. Not much looks as good. They can get a little tire challenged though with the stock bodywork.

You're certainly correct there. That's half the reason why I've been trying to take weight out of the car (the other half obviously is acceleration and braking). A bunch of years ago I took a few driving schools that used Formula Ford cars. IIRC the tires on those cars were about 195 or 205 mm width. I thought at the time that that sure was a skinny tire for what is supposed to be an actual competition vehicle, but after driving the car the first time I got a quick appreciation of the advantages of low vehicle weight (IIRC, FF cars were about 900 pounds). Those cars will brake hard and corner damn well. (My car is about three times as heavy as a FF, but only has about about 40% more tire. )

 

[mrvette]

Thanks for the feedback.

I completely understand the desire to leave the bodywork alone of a '69. Not much looks as good. They can get a little tire challenged though with the stock bodywork.

You're certainly correct there. That's half the reason why I've been trying to take weight out of the car (the other half obviously is acceleration and braking). A bunch of years ago I took a few driving schools that used Formula Ford cars. IIRC the tires on those cars were about 195 or 205 mm width. I thought at the time that that sure was a skinny tire for what is supposed to be an actual competition vehicle, but after driving the car the first time I got a quick appreciation of the advantages of low vehicle weight (IIRC, FF cars were about 900 pounds). Those cars will brake hard and corner damn well. (My car is about three times as heavy as a FF, but only has about about 40% more tire. )

My '72 had the later shark flares spliced on to the body by previous owners I did not notice it until parking next to a stone stock '72 and take a tape to the fenders they measure like a '78+ so that enables my 9.5" '89 vette wheels/tires are 50 series....

 

[redvetracr]

Thanks for the feedback.

I completely understand the desire to leave the bodywork alone of a '69. Not much looks as good. They can get a little tire challenged though with the stock bodywork.

thats why GM developed the L-88 fender flare and what looks better than a lowered 69 with L-88 fender flares?....maybe one with L-88 flares and FIA headlights?

 

[mrvette]

I would love to lower my car almost 2" worth, but these dip **** roads around here I"d be dragging pipes, if not more....it's as if they WANT to make the roads ******, and so I even got pissed enough to call the County roads dept, seems all the NOT NECESSARY road resurfacing is done by some stupid committee and none of them come out to actually LOOK and drive the roads....:bonkers: typical dumb assed .gov :flash:

 

[vette427sbc]

So Ive got my C4 D44 separated from the rest of the suspension... The diff and batwing are light as a feather compared to the C3 iron diff (I guess no real surprise here) I really need to get a scale in my shop to start weighing things like this. I can easily pick it up and my gym equipment has a considerable amount of dust on it :crap:
Point is, its more than just a few lbs and you wont have to mess around with the C4 batwing to C3 diff plate.

 

[69427]

So Ive got my C4 D44 separated from the rest of the suspension... The diff and batwing are light as a feather compared to the C3 iron diff (I guess no real surprise here) I really need to get a scale in my shop to start weighing things like this. I can easily pick it up and my gym equipment has a considerable amount of dust on it :crap:
Point is, its more than just a few lbs and you wont have to mess around with the C4 batwing to C3 diff plate.

IIRC, one of the reasons I didn't go with a C4 D44 was the physical size/shape of that unit (the other reasons were price, and the supply of various ratio C3 differentials I had laying around). It looked to me like the C4 unit might not fit the back of the tunnel without some cutting and glassing. I didn't mind cutting up the spare '69 frame I had, but I didn't want to cut up any bodywork for this suspension conversion. (And at this point, I'd be on the hook for another set of custom width halfshafts ($$) if I changed to a different differential.)

Make sure you start a build thread when you start installing that setup. :thumbs:

 

[rtj]

I know it won't help you 69427, but thought this belonged in this thread.

Duntov motors, not cheap:

Aluminum Diff Cover

Although heavy, the iron differential cover is low and almost all the way back . That makes the differential cover about the last part of your racing Corvette to replace with a lighter piece. However, this part was available from the factory for Corvette racers back in 1963, Part # 0228635. If you want to be both trick and period correct, get one of these. We sand cast these covers in 356-T6 aluminum using an original GM wooden plug. It comes with a gasket. This cover accommodates the 1963-1977 2.25 inch rear leaf spring. If you are running a later model 2.5 inch rear spring, this cover won't work.

Free Freight

 

[69427]

Front crossmember

Started cutting and drilling some material for a new front crossmember in aluminum. Planning on a couple geometry tweaks while I'm at it. IIRC, the present steel crossmember is about 35# (I need to weigh it again). I'm taking it out at the moment, and I'll make a small jig with it to make sure I get everything lined up okay before I weld up the new one. Looking for 5-10 pounds less weight off the front end.