Yesterday I got my copy of the latest issue of MuscleCar Enthusiast. Featured in the magazine is a really cool '68 Cutlass Ram Rod 350 W-31. The car is regularly run in the Pure Stock Drags. His best ET is 13.5 (I don't recall the MPH) on original style bias ply redlines. I know the W-31 engine is no slouch and 13.5 on street tires of any kind is pretty impressive especially with a small block. His car has 4.56 gears and a 4-speed. I just love seeing ANY small block car do well.

Here's my dumb question. My best ET (albiet on slicks) with the coupe is 14.9 at 91 MPH running a 3.31 rear. I've always thought it would be really fun to run the car at the Pure Stock Drags and it would be equally cool to do well if I ever do go. The big question is running on the original bias ply tires and getting traction with them, but assuming I could work that out I have to wonder if 4.11 gears in the coupe could net times in the 13's while maintaining the stock nature of the car as required by the Pure Stock Drags. Asking to cut .9 or more off my ET seems like a lot to ask from just a modest gear swap. Perhaps my technique could be improved too but still .9 or more is a huge jump. The more I think about this the more I'm impressed by that Cutlass.

The stock bias ply tires are much taller (nearly 29 inches tall vs. the slicks I used which are just a touch over 26 inches tall) so at the very least I'd need a better gear to make up for the loss of leverage running the taller tire. Amazingly, those tall skinny tires have pretty decent straight-line traction (but once the break loose they are done). There are probably a bunch more little tricks I could employ (super tuning, chassis tweaks, etc.) but it would be hard to come up with nearly a full second in ET I would think.

Dang that Cutlass is impressive but I've no idea if he has some "tricks" inside the engine and his Olds 350 is certainly making more torque than my 327 but still, WOW!

For those who don't know me by now, the car is a '65 SS with a 350hp/327ci and a 4-speed.

Rich,that W31 is an amazing car.
I recently drove automatic 1970 W31 that has 3.90's in the rear..this car,with headers and on regular,raised white letter street tires,runs 13.5-13.6's at around 100 MPH..which is pretty fun on the street.Its about half second slower than my car,but you sure can't "feel" it..that Cutlass runs well.
Anyway,I kinda think the swap to 4.11's might net you mid-low 14's,more if you tune it I would guess
Remember,these guys that run those ET's in the pure Stock Class aren't talking,if you know what I mean.
I follow the results of those races myself..very cool stuff.I even had the chance to watch a few of the pure stock guys and the FAST class cars run at Raceway Park recently..FAST class guys where running at 130 MPH+ at 11.02-11.03 on repro bias plys :eek:

Install some good valvesprings, degree-retard the cam some, blueprint the carb and timing curve, add some 4.56 0r 4.88 gears and I bet that lil 327 will run faster than the Cutlass.

The guy with the Cutlass also broke his bellhousing and driveshaft the first time out to the Pure Stock Drags and later roasted his rear axle. I'm not sure I'd care to tempt fate that much with my own car so maybe those 3.31s and 14.9 time slips are just fine..... :D

Please do not take this wrong, as I do not mean to criticize, but I think your car could benefit from tuning. 91 mph seems awfully low for an L79 car, indicating that there may be hidded horsepower waiting to be unlocked.

As a point of reference, we (my dad) had a '69 Malibu a few years back with a 255hp/350 that was bone stock, except for 2" dual exhaust (stock manifolds). This car was no lightweight, with A/C, PB, PS, bucket seats, etc., and it would trap 90 mph. My '70 Nova SS with a very mild 8.2:1 350 would trap 97-98 mph.

I'll bet that with some tuning (jetting/timing, etc.), you can get that car into the high-90s as-is. Get the mph up, and drive it like you stole it, and I would not be surprised to see high-13s with no major changes. smile.gif

I've run the car down the strip quite a few times and 92mph is the most I've ever been able to coax out of it. Without a serious gear change I don't think the MPH will go up much. I have maxed the timing and I've never seen a reason to mess with the jetting or secondary timing (vacuum) as the plugs always look great and I've never felt a soft spot up top. It continues to pull hard well above the redline of 5800 though ET slips tell me it's still best to shift at 5800-6000. My point is I don't think fuel delivery is an issue at any point in any of the idle to 7000 range.

I get the same MPH with street tires as I do with slicks BTW. Since the engine will NOT be messed with, gears are really my only course of action if I want to lower my ETs and raise my MPH. Heck, headers alone could do wonders but that just won't happen.

I could be somewhat wrong as my techinque is probably not the best either but while ETs change from run to run, MPH doesn't change much and is more telling of a car's potential or so I've been told (it should be able to ET slightly better with a 91-92 MPH). Besides, it's a show car first, a street cruiser next and a race car last. I'd rather be able to take it to a show with all it's numbers matching components in place! :D I know the car has more potential in it than I'm able (or willing!) to get from it and I'm okay with that.

I really do need to try a few runs on my original style bias ply tires to see if they could be made to return some decent (read not embarrasing) ETs. Also keep in mind, as hot as the L79 appears, it still only delivers 360 lbs/ft of peak torque. Once the car is rolling it's impressive, but getting the car rolling from the start is the trick.

I doubt that gearing would have a significant effect on MPH... ET, yes, but not likely MPH.

I tend to wonder if the secondaries are opening all the way (or at all) on the 585 cfm Holley.

Something just does not seem right, since our 255hp 350 in a heavier '69 came close to the same MPH. The '69 in question was by no means well tuned... it had the stock carb jetting, stock advance curve. The only "tuning" was the initial was set at 8 BTDC deg instead of 4 BTDC. This was with a 2.56 gear and TH350. HP is usually indicative of power / weight ratio, and I would think a '65 L79 should do much better than this car, not just 1-2 mph better.

Maybe I am just nuts?

Regardless, best of luck to you! You have a beautiful car! smile.gif

You know, I think you are right, to raise MPH I'd have to simply make more power.

If the secondaries weren't opening I don't think I'd have the CFM to get to 6000+ rpm's. I should probably verify somehow that the secondaries are in fact opening. I guess I could simply disconnect them and see if it runs poorly at the top end.

Good call novadude. 92 seems low unless your 65 has around 600 of ballast somewhere!! And then badbob's advice is what I would have mimicked but in a more mathematical way...

set your rear gear ratio ( given the large tire size) to hit max rpm across the stripe. I wonder what the math would tell you.

But first, I'd coax some more mph of it.

I'd think you'd have to spend a good penny in hidden stuff to run as good as the best do in Pure Stock. Really like that class though.

Rich

one time i made the mistake of putting the wrong check ball in the 3310-1 vacuum sec carb on my chevelle. the secondaries wouldnt open at all and the car would still pull to 6000rpm. of course it didnt feel that great up there, but it still pulled those kind of rpms with only 2 barrels working.

your car should be able to handle every bit of that 585 cfm. if you are using the stock secondary spring the secondaries probably arent opening fully. i honestly believe that if you installed the purple or tall yellow secondary spring the car would perform better.

Originally posted by RatONaStick:
Rich

one time i made the mistake of putting the wrong check ball in the 3310-1 vacuum sec carb on my chevelle. the secondaries wouldnt open at all and the car would still pull to 6000rpm. of course it didnt feel that great up there, but it still pulled those kind of rpms with only 2 barrels working.

your car should be able to handle every bit of that 585 cfm. if you are using the stock secondary spring the secondaries probably arent opening fully. i honestly believe that if you installed the purple or tall yellow secondary spring the car would perform better. I happen to have a spring kit I plan to use on the wagon project so I could play around a bit if the weather warms up....

On the one hand you'd think that GM & Holley would have installed just the right spring for max performance, but on the other hand they had the distributor curved so that max advance didn't occur until above 5000! They may have purposely detuned things a bit to keep the average guy happy but to allow for some ability to improve on things for those guys who wanted to play around with things a bit. And I suppose detuning it a bit kept some warranty claims from occurring.

I did recurve the distributor so I have a total of 36 degrees all in by 3000. That sure perked the thing up.

I can also say that the only magazine test drive done of an L79 netted a 16.00 at 90mph with a 3.70 rear (and no posi for some reason). I've at least bested these times by a bunch even with street tires. My best street tire run I think was 15.166.

Rich,I would change the spring for sure.Then you know whats in there,and you're getting the best performance.I've had very good luck with 2nd from lightest spring,which is yellow.This is with small blocks and big blocks.The purple spring (3rd lightest) is about as stiff as needed IMHO.
Don't assume the factory put the best spring in there,thats for sure.You might not even really feel any difference,but the timeslip might tell a different story smile.gif

Some of the faster combos of legal Pure Stockers have run low 12's at the Pure Stock Muscle Car Drag Race in Michigan. BUT although meeting the letter of the rules, they aren't like they left the factory. NHRA style "blueprinting" of the engine can be done, as long as factory specs are met, 2 1/2" mandrel bent exhaust systems with aftermarket mufflers are legal, and a lot of suspension tweaking goes on, especially to loosen the front end up. Another popular trick is to soak those bias ply tires in traction compound.

i run with out the check balls in my holley carbs and even with my bbc it has ran the best with the tall yellow spring once the carb jetting is dialed in. i have done several back to back runs with changing springs and the stock spring verses the tall yellow spring has netted me almost two mph differences in the 1/4 mile and about .2 tenths drop in e.t. this is with a 750 3310-2 carb.

to verify the secondarys are opening there is an easy trick i use to check. take a paper clip and slide it up on the secondary rod on the carb. take it out and run to the rpm shift point and check the paper clip location. you will find if the carb is opening it will slide the paper clip down on the rod. you then can wire the carb open and flip open the secondary's by hand up to the stopping point of the paper clip on the rod. this with a flash light will show how far the secondary's open. the farther the paper clip is slide down the farther the secondary's has open of course.

when tunning for most mph out of a certian combo the rpm shift point that provides the best overall mph should dictate the final gear ratio and tire size. if your shift point like mine on my bbc is 6500 rpms then you should be crossing the finish line at that rpm or close to it to get max. amount of pull thru the 1/4.

i decided to build a nice street car with some mild gears (2.41) for low rpm highway driving. but during my test and tune to get the most out of my project i decided to change to a 2.73 gear because with 2.41 gears i was crossing the line at 5000 rpms in second gear which was way below my shift point of 6500 rpms. with a change to 2.73 gears this allowed me to cross the finish line at 6100 rpms. this made a big improvement.

with my certian combo to maximize the runs i would need like at 2.90 gear ratio in the rear but since none is made i will have to live with the 2.73 gears or if i wanted to i could get a smaller dia. tire to help. but im not.

since mph is the sign of hp being put to the ground gearing alone just wont add hp. but it should help if your gearing is allowing low rpm's thru the finish line. if it was off like mine (being 1500 rpms away from my shift point) then you will see a gain in mph like i did. even tho i didnt add hp per say to the motor i gained a few mile per hour from gear change because it allowed the car to pull more thru the lights.

tunning the carb with jetting and spring changes along with shift point changes and timming total tweaking. i was able to raise my mph from 102 to the now best of 107.19 mph in my car. thats pretty good for super tunning a combo i think. but it took about 5 trips to test and tune and about 55 passes to find it. and i think theres is still more just in the carb tunning. i really believe i can squeeze 109 mph out of this combo. but it will have to wait til next racing season.

i found out everytime something small was changed i had to go back to timming or shift point to maximize that once again. not by a lot but the engine now seams to respond to the slightest change but if i leave the combo alone at any given stage now it will run back to back numbers everytime. its very consistent.

ddeennis,any gains from removing the checkball? I used to do this years ago just for "seat of the pants" to feel the secondaries open but this was before I ever started to go to the track.My current 3310 still has the ball in place.

Originally posted by mr 4 speed:
ddeennis,any gains from removing the checkball? I used to do this years ago just for "seat of the pants" to feel the secondaries open but this was before I ever started to go to the track.My current 3310 still has the ball in place. this is my thoughts on the checkball ordeal.....yes holley put them in there for a reason....but for me i see it a restriction to vacuum response. since the diaphram works on vacuum signal from the venturi.air is being sucked from the chamber of the diaphram ,so the ball gets sucked down restricting the signal some....i would imagine to slow the opening rate to some degree..... and in case of some serious back fire the ball is forced up to block incoming air from blowing out the diaphram....in the case of about any of my engines they are fined tune to some degree and im looking for the most response i can get from each area of the engine.

is there gain from removing the check ball....i kinda think so as far as response time to the secondary's opening up. does it give me more power to run the 1/4 mile not sure never did a back to back run with just a check ball change.

but i think it helps with response time to the opening rate of the secondary's.


if im wrong with my thinking then i guess im wrong but the end result for me is its not giving me any troubles not running one.

my chevelle doesnt like the checkball removed during regular street driving. it runs great at wot from a dead stop, but i cant short shift any gear under wot, or floor it while cruising in 4th gear. it will bog everytime in those situations.

it feels like the secondaries just flop open way too fast without the checkball. since there isnt an accelerator pump in the secondary side this causes a bog until the boosters can catch up with the airflow.

i would imagine this wouldnt be much of a problem with an automatic, especially one with a functioning kickdown mechanism.

but as far as im concerned removing the checkball basically accomplishes the same thing the old screw in the linkage trick does, nothing but problems.