67 Tire Brand and Design

[Joe L.]

Re: 67 Tire Brand and Design

The 3- 2bbl system was analogous to the vacuum secondary 4 bbl. The end carbs have no accelerator pumps and to force them open suddenly with mechanical linkages will simply cause a huge stumble. Unless different end carbs with accelerator pumps were used with the mechanical linkage there would certainly be a performance loss rather than gain. I kept the vacuum linkage on my first Corvette - a junky 67 L-71 coupe in 1971, and I'll keep them on my present 67 L-71 convertible restoration project.

Patrick------


I agree 100%. While I once very foolishly converted a Holley 4 barrel from vacuum to mechanical secondaries, I learned a lesson I never forgot (and this happened 48 years ago!). I would NEVER convert a Holley to mechanical secondaries. That goes for 1X4 Holleys or 3X2 Holleys. Of course, I'd never own a 3X2 set-up so that part is moot.

[Michael J.]

Re: 67 Tire Brand and Design

I have two sets of tires and wheels for all my old cars. One for show and judging, and one for driving. For instance, my '67 has the tank sticker optioned rally wheels and Goodyear Power Cushion bias ply white walls, but I have Torq-Thust Ds and Pirelli P4000s for driving it. There is no comparison for driving, the bias plies are junk and the original wheels are heavy and fragile. So, are you going to have it judged or drive it is the question, if both get two sets.

[Robert M.]

Re: 67 Tire Brand and Design

Patrick------


I agree 100%. While I once very foolishly converted a Holley 4 barrel from vacuum to mechanical secondaries, I learned a lesson I never forgot (and this happened 48 years ago!). I would NEVER convert a Holley to mechanical secondaries. That goes for 1X4 Holleys or 3X2 Holleys. Of course, I'd never own a 3X2 set-up so that part is moot.

Come on guys where is your sense of adventure? HA
I agree with Joe completely 3x2 is nothing but a pain no matter what you do. The L71 motor should have come out just like the L72 with a big 4 barrel!

[Michael J.]

Re: 67 Tire Brand and Design

Come on guys where is your sense of adventure? HA
I agree with Joe completely 3x2 is nothing but a pain no matter what you do. The L71 motor should have come out just like the L72 with a big 4 barrel!

That is one reason I appreciate my '68 and '69 R code Cobra Jet cars, they had the big Holley 9510 735 CFMs with dual metering blocks.

[Duke W.]

Re: 67 Tire Brand and Design

Come on guys where is your sense of adventure? HA
I agree with Joe completely 3x2 is nothing but a pain no matter what you do. The L71 motor should have come out just like the L72 with a big 4 barrel!

Trips was just a marketing gimmick, and the manifold design is compromised. That's why you never see them a real race cars.

Duke

[Michael J.]

Re: 67 Tire Brand and Design

Trips was just a marketing gimmick, and the manifold design is compromised. That's why you never see them a real race cars.

Duke

Absolutely, but they sure do look cool. I never open the hood that people don't oooh and ahhh about those, just like opening the hood of my Cobra with those 4 big Webers on it.

[Robert M.]

Re: 67 Tire Brand and Design

I have two sets of tires and wheels for all my old cars. One for show and judging, and one for driving. For instance, my '67 has the tank sticker optioned rally wheels and Goodyear Power Cushion bias ply white walls, but I have Torq-Thust Ds and Pirelli P4000s for driving it. There is no comparison for driving, the bias plies are junk and the original wheels are heavy and fragile. So, are you going to have it judged or drive it is the question, if both get two sets.

It will not be driven much regardless what wheels are on it. If I judge the car, the point deduction would not be a killer for the repros. Since none of the cars are daily drivers, I am a purist, just me, and have only put radials on one car I have owned. When us old guys were growing up we never complained about the bias ply tires and how bad they were to drive on. That is pretty much how I feel about them today.

[Michael J.]

[Robert M.]

Re: 67 Tire Brand and Design

Michael. you lost me when you mentioned a Cobra, now non DOT tires. I know where there is a set of 4 non DOT tires. $1000 a piece! Yikes

[Michael J.]

Re: 67 Tire Brand and Design

Well, don't tell Don Hooper, but I have to admit I have a Cobra (that was in reference to Duke's comment about the impressiveness of multi-carb setups, which the Cobra has in spades), hate to mention it around here…….. Yes, non-DOT tires are very expensive, and usually in poor shape, but not always. My spare is in pretty good shape, and the judges always like to see it, and you lose no points if it is the correct OEM.

[Michael J.]

[Steve B.]

Re: 67 Tire Brand and Design

Michael. you lost me when you mentioned a Cobra, now non DOT tires. I know where there is a set of 4 non DOT tires. $1000 a piece! Yikes

Robert, if you can get four original non dot blackwall tires for a 1000 a piece, I would grab them if they were spares with full tread and of course no cracks on the sidewalls.
To answer one of your other questions, Firestone Deluxe champion tires had a ribbed sidewall that was changed to a smooth sidewall sometime during late 66 or early 67.

[Duke W.]

Re: 67 Tire Brand and Design

Well, don't tell Don Hooper, but I have to admit I have a Cobra (that was in reference to Duke's comment about the impressiveness of multi-carb setups, which the Cobra has in spades), .

I never said that. In fact the typical 48 IDAs that guys run on small block Fords and Chevies are too small. A four barrel and single plane or even large runner dual plane will make more power. For an individual runner system the throttle bore should be at least as big and preferably a little bigger than the inlet valve.

I went around this with the Cosworth Vega guys for years. They thought Webers, usually 42 DCOEs would make more power than the EFI. I said they would not but might make better peak torque because of the longer overall inlet runner length.

It took a few years of dyno testing, but they finally realized I was right. The CV induction system has two 1.75" throttle bores (straight through, no venturi, choke, etc. just the butterflys and shafts) with a generous plenum and short (4") runners that are larger than the head ports. That's a top end system where each cylinder "sees" the flow area of both throttle bodies compared to one 42 mm throttle bore that is further restricted by a venturi.

The same applies comparison applies to any multicylinder engine. Webers look cool, but most were designed for relatively smaller cylinders than typical American V8s and they aren't the way to get maximum power from a highly tuned engine.

The Grand Sport engine got it right with 58 mm DCOEs, but those are very rare because only a few sets were made for 2.5L four-cylinder F1 engines back in the late fifties, and I don't think they were ever produced again after those few sets.

Duke

[Michael J.]

Re: 67 Tire Brand and Design

I never said that. In fact the typical 48 IDAs that guys run on small block Fords and Chevies are too small. A four barrel and single plane or even large runner dual plane will make more power. For an individual runner system the throttle bore should be at least as big and preferably a little bigger than the inlet valve.

I went around this with the Cosworth Vega guys for years. They thought Webers, usually 42 DCOEs would make more power than the EFI. I said they would not but might make better peak torque because of the longer overall inlet runner length.

It took a few years of dyno testing, but they finally realized I was right. The CV induction system has two 1.75" throttle bores (straight through, no venturi, choke, etc. just the butterflys and shafts) with a generous plenum and short (4") runners that are larger than the head ports. That's a top end system where each cylinder "sees" the flow area of both throttle bodies compared to one 42 mm throttle bore that is further restricted by a venturi.

The same applies comparison applies to any multicylinder engine. Webers look cool, but most were designed for relatively smaller cylinders than typical American V8s and they aren't the way to get maximum power from a highly tuned engine.

The Grand Sport engine got it right with 58 mm DCOEs, but those are very rare because only a few sets were made for 2.5L four-cylinder F1 engines back in the late fifties, and I don't think they were ever produced again after those few sets.

Duke

I would never question your racing and performance knowledge Duke, I was just referring to your comment about the 3X2 setup " Trips was just a marketing (visual impressiveness) gimmick, and the manifold design is compromised. That's why you never see them a real race cars." I agree with that, but still you have to admit those 4X48 IDA Weber setups on Bondurant and MacDonald's cars in the '64 FIA series on those Cobras really worked pretty well…..

[Duke W.]

Re: 67 Tire Brand and Design

It would be interesting to test one of those Cobra FIA engines with both a good aftermarket high rise manifold of the era (both single and dual plane) with a 700-750 CFM carb and the Weber setup, all other things equal. I think like the Cosworth Vega situation Webers might make a bit more peak torque, but no more and maybe even a little less power than the best carburetor/manifold setup, but no doubt the Weber setup was ultra cool looking.

Back in '67 I was at a National SCCA race at Riverside and ran across a one-off C-modifed car that I had read about called "Hussein". It was powered by a Chrysler 426 Hemi with a quartet of 48 IDAs. (I have no idea who cast the manifold.) I remarked to the owner: "Isn't it a bit undercarbureted... wouldn't 58s work better?" He looked at me and with a bit of cynicism replied: "Do you know where I can find any?"

IIRC it was very fast in a straight line, but it never did handle very well with that lump of a Hemi behind the driver. The Hemi probably weighed about 750 pounds compared to about 550 for the all aluminum Chevy big blocks that showed up in Can-Am cars that year, and the intake stack diameter of the Lucas injection systems of those first 427 Chevy Can-Am engines was about 2.25". I think they got bigger in later years as displacement increased (primarily from increased stroke) to 465, then 495, and finally 510 CID with the linerless aluminum blocks cast by Reynolds.

Duke