Discussion in 'Mopar Racers Forum' started by 63TOAD, Jun 30, 2018.
Sorry, I couldn't resist when I saw the title
Best answers are brief and to the point without a ton of explanation and mathematics which normally confuse and confound people. Not to mention answers that actually address the issue.
Like post #15... Edit: and #26!
Your car was born to do better than14s You have a 13 second street engine with a hesitant driver, and total lack of traction, possibly a really bad tune, but more than anything, your engine is sick. Start with a compression test. At 4000rpm your engine should be capable of making 400 ftpounds, or 305 hp so you're getting an MPH, not even commensurate for that. and your traction issues are reflected in your 60ft, and your ET. Say you tracked at 3100 pounds, and that engine was up to 305hp. That would be a P/W of 10.16, and should go 107mph, and the ET for that with a street chassis would be no less than 13.4 But your 80mph indicates your P/W is actually 23.2, or 129 hp, and your ET is right in alignment with that. My guess is there is a lot more going on here than just the tune. For Shifting at 4000: Non-working secondaries might be 10 hp . Really Bad timing might be another 10. A two barrel cam instead of say a 262 cam might be another 20hp. No headers is not gonna add up to much but let's give it 10. A restrictive exhaust another 10 at 4000. What's all that come to? A total loss of perhaps 50hp. Adding those 50 to the Trap-Speed indicated 129hp, comes to 179 hp...... see what I mean? There is something really ugly going on here. Where you towing another car,lol? Even with two plug wires off and the leftover 6 making 129hp,that comes to 22 hp per hole, and if you put the missing wires back on, you might have 176 so it's still ugly. Even if you reversed two wires, you still can't get to 305 hp. My guess is your engine is just not processing air. And the principle processors are the carb, and very importantly, the exhaust system; plus the cam lobes, their timing, and their install. Don't overlook the carb being jammed up too close to the hood, or the choke not staying open Start with a compression test. And you'll probably need to do a LeakDown as well,to see if you even have an engine left. Then pull the valve covers off and see if your valves are opening. Meh, maybe do this first. With so much missing power, I want to say it's the cam, but even the smallest cam ever installed in a SBM made more power than 129hp,lol. IIRC my stock 1971 Demon 318/904/2.94 went about the same speed and ET............. so there's that. Hang on, you got tirespin in second? You had to be towing something. Or is the track all uphill? Oh waitaminute! You weren't in top gear were you? with a 2.45 hiway gear,lol.
Good, I'll get my laundry list out, gonna need more than that pimply faced kid at the parts counters help with some of this....I do got that right handed thread thing down, pretty good anyway....oh, who's AJ??? ( and I thought I had thought that one through pretty good too...) Second answer: "Yeah, just hit the gas, it works or it don't, and remember the beer this trip!"
1st & second to last paragraph were good. Everything else inbetween & after. useless babble and not helpful. If not just simply patting yourself on the back. Your getting better AJ.
Are you sure the throttle is fully opening, is the transmission slipping. I'm having a hard time with the 80 mph. Are you sure they put the compression rings on. I'm serious, the combo is running in /6 territory.
Deal with the engine first, it’s not making power down track. You current combo can get you where you want. Check total timing, then check fuel pressure through a run. I’m assuming that it runs and idles fine, no smoke out of the exhaust. No abnormal noises.
Wait a minute, so the exhaust manifold has the small 273 port size and the head is a 360 port size. So the exhaust stream is hitting a 90 deg step as it enters the exh manifold. There you go. 273-318 Small-port cylinder heads, with the port diameter 1.09w x 1.55h, 360 has 1.30X1.70. That is a LARGE right angle speed bump.
It sounds like a few mismatched components. I didn’t see where you said what exhaust you have. You mentioned stock 273 manifolds but never mentioned if the stock single exhaust was still in the car? What rear gear are you using? 80 mph trap speed is low. Are you still on the gas or did you lift early? You mentioned you are spinning at launch. There must be some torque there. Do you have a limited slip rear axle? Are you doing a burn out? I have launched a peg leg 1967 Dodge Dart with a 340 into the 13.8 on 215 70 r14 tires and 3.23 gears. A lot of rubber on the track and 2 burnouts. (One for each wheel). What altitude is your track at? If you are in high altitude your car won’t make as much power. I used to run at 2 tracks. One close to sea level. The other at 3000 feet. I picked up .5 just from going to the lower altitude.
Sorry been under the weather I am planning on getting some M&H tires to help with traction. Running 3.55 gears with sure grip
I wouldn't overly worry about the 273 manifolds. They are costing you power but theres not that much hp difference between small block manifolds 5 or so hp at best. Unless going headers I wouldn't be overly concerned. Even then your probably only looking at 25 hp at best. I'd fine tune what you got before looking at swapping parts, something seems wrong, should be faster as is.
IMO most bang for your buck at this stage is: 1. Open headers 2. Different rear tires 3. Tuning the motor 4. Experiment with shift point. You're not racing yet, just testing, so no need to worry about consistency yet.
And not in that order.
Agreed, do #3 1st, tune it the best you can with what you have!
As a CME customer (318 w roller cam 347hp/353tq) and long time gearhead I will offer some "things to consider". 1. Expectations- The 365 HP is probably real on their engine dyno. But understand, you have a smaller carb and very restrictive exhaust. At the wheels you may be 80-100hp lower. That being said - you should still be capable of 14 or better on the qtr. 2. Driver control - Your 330 time could be improved some with throttle control and stickier tires, but were NOT terrible. The engine seems to be pulling ok at the low end. 3. Shift points - I know that CME provides info sheets with their builds. Mine specified power range from idle to 5500. I suspect yours is similar, but probably not under 5000. My a500 trans also has a shift kit and 2500 converter but the governors where not changed so it also has a WOT auto shift point at around 4000. If your hp/tq curve is anywhere near those that I have seen from their Mopar crates (including my custom build) a 4000 rpm shift point is putting you down about another 100hp. That alone is a large part of the falloff in the last half of the qtr. NOTE: didn't see any info about the shifter. If stock without a neutral/reverse lockout, be VERY careful about manual shifting. 4.CME also specifies timing curves for their engines. Mine was spec'd on a mechanical curve of 14* @700, 32*@3000, 36* total over 4000. Their spec is usually a little conservative but on a new engine I would stay close to their recommendations until you have everything else sorted out. 5. Don't get discouraged. For those of us who don't go to the strip every week, it takes time to work through all the possibilities. Little stuff like throttle cable adjustments, colder plugs, tire pressure and all the other stuff that the FABO guys have mentioned make a difference, but work on the common sense (ie. no or low $) items first.
Update I picked up a set of used drag radials and am changing out rear springs and shocks. I am hoping to get more traction next time
What rpm is it turning at the stripe? Is possible that it is not shifting into 3rd gear?
I do not know for sure. It is shifting onyo 3rd gear.
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