New Cam, coil, wires, plugs, traction. Why no 1/8 improvement?

Since my last 1/8 run at the track, I have added (from stock) 245/60-15 tires for traction, a Super Stock Accel coil, 8mm Accel wires, new plugs, and a moderate cam (SUM-3600 from Summitt). The car runs much smoother, cannot smell gas at exhaust, so I am getting good burn in all cylinders (not arcing at #2&3 cylinders on the shock tower, as before), seems to accelerate better, sounds louder and more aggressive. But my 1/8 track times have not improved.

I am currently running stock block and pistons, Edelbrock Performer 289 intake, Edel 600 cfm carb, the cam is comparable to the Edel Performer Package cam, stock heads and exhaust manifold, dualled out with side pipes.

I know I need new heads and headers, and something other than 2.79 rearend, but shouldn't I see some improvement with these upgrades?

 

need a lot more data. turning same rpm? what are the times incl 60 ft? shift points? timing? carb & settings? did you put in a new timing chain & gears? was cam degreed in? how was cam installed? cam specs? that rear gear is a killer. height of old tires vs new tires? torque convereter type & stall? stick or auto?

not unusual to change a combe & have car go the same or slower initially. sometimes tuning the combo is needed for better performance. sometimes the parts chosen just dont work well together. i asked about the timing gears because if you put in a new set & you picked a set for newer than 1972, you retarded the camshaft. not helpful. with that gear, the car will be really sensitive to changes that hurt performance more than changes that help performance.

later

 

Headers make a pretty good difference, and will make a little more of a difference on your engine now than when stock, but the camshaft just opens valves longer for less dynamic compression and the exhaust is still being restricted by the factory manifolds regardless of how much better a camshaft it is over stock.
That is why I said headers first in your original post about cam choice. Been there, done that, made that mistake.

Odds are he's right above, 74 did have 4* retard, but I don't know if it was cam or timing gear differences. If it was the gear, it would hurt that new camshaft quite a bit on a low compression engine.

 

Check the tire diameter on the 245/60 15's vs the "stockers" you had. YOu might have gained traction by getting more footprint but effectively lost gear ratio if the new tires are significantly bigger.

Cleaver

 

I guess the next project would be gears. What is a good combo? The car is primarily a highway driver with 3-4 trips to the track yearly. I am thinking of getting taller rear tires, maybe going to 255/60 or 255/75 if I can get them to fit. That will be in a year or two (I still have lots of tread to burn out). Would I be better off with 3.50-ish or closer to 4.11? I know the 2.79 is killing me, and I guess with the larger tires on the new combo, I lost in performance what I gained in power. I might buy a second rear to put the "racing" gear into, and keep the other gear for "highway" use, since it only takes an hour to swap them out.

By the way, I raced a 2004 mustang, stock, and he only beat me by .900 seconds on 1/8 track. He has 260 HP. Any idea what that suggests my HP is. I actually beat him off the line, then stayed even for most of the run, then he shifted up and went past me.

Currently, I rev to 1800 (no stall converter), lay on it full blast when the last yellow lights up, shift to second at 4500 RPM, then stay in 2nd until right at, or just before the finish line. Right at 68 mph. I am at 4000 RPM at the line when I shift to 3rd. On my stock tires, I was breaking them loose and had to hold throttle at 3/4 or less to keep traction. I don't think I am breaking them loose too much, since my RPMs stay low and slowly build up. Before, they would shoot from 1800 to 3000-4000 as soon as I let off the brake, and I would have to wait a second and then accelerate slowly to keep traction. I think I peel out for just a couple seconds and the grab for the rest of the run with the larger tires.

Am I to the point where I need to open up the air flow with heads and headers? That is what I am thinking. I have the engine over-cammed, and it is limited by the other hardware.

Despite my rantings, I am still having lotsa fun!
Scott

 

everything in performance is a compromise. you have to decide what you want to do. if most of your driving is at hiway speeds, a 4.10 gear for a few trips to the track might not be a good choice. one thing you might want to consider is getting an AOD trans (overdrive unit) which would let you put in a higher rear gear and give you a little better first gear ratio. the two center-sections with gears is not a bad idea, but requires a certain amount of work & you would probably require some type of posi unit or mini-spool. with the AOD you could go to a 3.50 to 4.10 gear, but keep your cruising rpms low.

i am going to put the tallest tire i can get under my son's car for off track useage. that looks to be a 235x75-15 tire, about 27.3 tall. the drag radials i use are 26 inches. i'm running a 4.10 gear, but i dont do much hiway driving.

have you ever tried shifting a little higher? you didnt give specs on the cam, but unless its very small, i would expect it to go closer to 5,000 rpm. the intake should go that high & even an edelbrock 600 should be good to 5k. you might be giving away something there. you could also play with the distributor curve and total advance. more total advance up to the point of detonation usually picks up bottom end torque. try to bring all the advance in byt 3000 rpm. yes, headers & a dual exhaust system would make a difference, too.

 

Is the stock piston/rod/crank assembly safe for RPMs up to 5000? I consider my redline to be 4500, and usually shift at 4000. It really sounds like it is going to blow around 4500. The engine now has around 55k on it, and the first 50k were litterally a little old lady driving to church and to see her daughter on a weekly basis. My wife says her great-grandmother never went above 55, and seldom that fast, so the engine has relatively little wear.

The cam is the Summitt equivalent to the Edelbrock Performer Plus cam for the 289-302. According to Edelbrock, it is supposed to be good from idle to 5500, but summit says idle to 4000.

As far as advanced timing, I currently have the vacuum line running to the port on the carb that has vacuum all the time, so I set the timing to 12 degrees at idle without the hose, then put the hose and and it jumps up to 20-ish, at idle. Around 40 or so at 3000. I can go forward until my vacuum diaphram hits the radiator hose, which is about another 10 degrees, and it never pings or knocks, even on Reg Unleaded. I have the stock pistons for 1974, which have an inverse dome cut into them, and my compression is around 8:1. At the track, I went from 12 degrees at idle to 15 and there was no difference in my 1/8 time.

I guess my next step is heads and headers to allow the equipment I currently have do what they are supposed to do. The cam seems to want more air in and out, the carb is trying to get more air in, the exhaust manifolds are restricting air flow, I am just choking the engine when it wants to breathe and exhale much more than it can.

Does that sound about right?

 

Scooper,


Give us a little more info...specifically your info from your time slips from the track. All of the splits and mph's, EVERYTHING. We can tell a LOT more about your specific problems if we can see this information. Give the info before the changes, and after the changes.

While "it felt a lot better than before" may be true, actual results tell you a lot more. I don't care if you won or lost by 10 seconds against another car...this is not the way to baseline your performance. Compare apples to apples with your car and your setup, and we can help you.

BTW...you definitely don't want to go with a taller tire...this will worsen your 2.79 gear. Car will MPH big time on a 5 mile stretch, but won't get out of it's own way in 60'.

Not ranting...just wanting solid info.

Later,

 

i just looked in summit. thats a small cam, but still try higher shifts when you get a chance. just try 4500 shifts & see if things get better. the info from cam companies is often just a guideline. my son was shifting at 5000, the shift crane suggested. when he took it to 5500 it went .10 quicker consistently. the stock bottom end is good for at least 5500 with good oil pressure & no detonation. my sons car does it every weekend at the track, so im not dreaming. at the track, take the vacuum off the dist and plug the port on the carb. set timing 10-12 adv at idle (low idle, not stepped up). should give around 36-38 total adv. vac adv usually helps economy, but hurts power performance.

yes, other timeslip info would help; maybe one old one & one new one? along with weather data?

 

My cousin's Fairlane with a 289 and that cam shifted at 5800 with everything else stock, 2bbl, manifolds and dual exhaust.

Playing around with Engine Analyzer, you should hit peak hp around 5000, peak torque at 3500. I'd start shifting about 5500 and find the best shift point by feel, or by ET if you have enough time at the track.

 

Old timeslip
.8581 reaction
2.4573 60 ft
6.8990 330 ft
10.5908 1/8 ET
66.69 mph

New timeslip
.6739 reaction and .6390 with advanced to 15 degrees
2.5338 60 ft and 2.4574
6.9928 330 ft and 6.9028
10.6449 1/8 ET and 10.5815
67.80 mph and 67.27

Does that help at all?

 

With those tires and gears, you are running about a 2.50:1 ratio.

 

how tall were the old rear tires & how tall are the new ones? you also said you were leaving about 1800 rpm with a stock convereter? sounds a tad high for a stock converter, but not sure. i had an 11 inch perf converter that stalled about 1900 rpm. i wonder if you could have some trans slippage issues?


anyways, you probably need to get some gears in that car. 3.50 would be a good all-around gear & you could get short track tires & tall street tire for it. or even 3.80 s for it if you can.

my sons car had old shelby hi-rise intake, 600 vs holley, crane 218/228 at .050 cam, 3.00 gears, 11" converter (1900 stall), stock bottom end, 26" radial street slicks, headers w/ full 2.25 exhaust. went 14.90 s at 500 ft altitude track. added 4.10 s with a mini spool; went 14.75. broke the converter turbine hub. went to a 10" 3100 stall converter. went 14.50 s & 14.30 s at the bracket finals at a sea level track. he runs street which requires plates, exhaust & street legal tires. timing 38 deg total with no vac advance. street gas.

shift higher, no vac advance, try shorter tires again, maybe some traction bars? maybe some gears & wider short tires? play with it & try different things. good luck & keep us posted.

 

My stock converter flashed to 2000rpms. May have been looser in 74.

 

Scooper,

Were the runs from the old and the new timeslips made during similar weather? If so, by your first time slip, your slower 60' and higher mph seems to indicate that the car was spinning. On your second new time slip though, it seems that you are pretty consistent with the old setup...Do you have someone reliable who can watch the car and could tell if it were spinning or not?

Hmmmm...does anyone have the stock cam specs for this year 302? The factory cam may not be that far off from the numbers on the cam that you installed. If this is the case, the taller tires that you had put on may have effectively "cancelled out" any performance gains that you may have gotten with the cam swap by numerically lowering your final gear ratio even further than stock. With the improvements that you made, you would definitely be able to tell the difference in the way that the car ran and felt. Changing the plug wires should have made a big difference if some were arcing on the shock tower.

The next time that you go to the track, strive to do everything, and I mean EVERYTHING the same. If you do a burnout, do it the same everytime. When you stage, just ease into the pre-stage beams and then just barely bump into the stage light. Keep a close eye on the tach and attempt to get the car at the same stall speed on several runs. Try to have the engine temp the same. Make sure that the tire pressures are the same. Shift at the same RPM's. If you can do this, it should be close on most runs. If it's spinning, it should spin relatively close to the same on most of those runs, all other things being equal. Do this until your runs are all pretty consistent. Once you do this and get your runs pretty much the same, THEN begin changing the way you do things. Change one thing at a time, like your launch rpm, or the rpm that you shift at. I would work on my starting line technique first, and then, once I had that down, I would work on my shift rpm's. You may even think about letting the auto shift itself for awhile. If you are confident that you are doing things the same way each time, then you can feel confident in whether the changes you are performing are having a positive or a negative effect.

When you change too many things at once, you can never be sure what caused which performance gain or loss, and believe me, you can spend a lot of time and money chasing shadows.

Personally, I would put headers on it before I did anything else and see what that does. You may be shocked. It will probably make the biggest improvement on the car, and should help to really enhance the other changes that you have already made. If the car is spinning though, this will probably only make it worse!

I checked out your site, and am glad that you are keeping the car and doing what you are with it. Have FUN with the car, and enjoy it. The car has a lot of family history behind it, and has led quite an interesting life.

Keep your timeslips from future visits to the track, and try to keep a detailed report of the conditions. This will help you keep track of things in the future. You use to be able to download log-book sheets for free from Jeg's and Summit. Don't know if you still can or not, but they help out a lot.

Good Luck, and keep us posted.

Later,