Can you assist me in geting better ¼ mile performance while keeping my Comet a streetable car?

Stroker Mav,

Great to hear from a local Maverick racer. I used to run at 42 and Thompson. Since 42 was closed I started at Quaker City. It has been my experience that you sit on your butt too much at Summit.

 

Tell us about your Maverick!!!!! Looks like it is lifting the left front. Your profile says your building a 418W. From the looks of those beautiful headers, you must have the shock towers removed on your ride.

 

Tell us about your Maverick!!!!! Looks like it is lifting the left front.

What stall converter are you running in your 351 Maverick?

 

Hotrock,I like the look of your comet,it has for great street/strip attitude. The stall speed is going to be 5500 with the 418w.In the picture it had a 347,that was at Norwalk it ran 10.73@123. The shock towers were moved out about 1'' on each side but the headers were custom fit for stock suspension. It's great to hear from someone so close maybe we can get together and compare notes and BS about are cars. It's only 30 miles right down 77.

 

Stroker Mav

What stall converter and diff gear ratio do you have behind the 347?

An Essex Terraplane is a big automobile. What condition is it in?

 

It was a 5000 stall speed when it was a 347 but I sold that engine so I could finish the 418.It had 5.38 gears with 14x32 slicks.I plan to change to 4.86 with new engine. The Essex is the same size as a ford or chevy , this is a street rod with a 4.6 dohc cobra engine in it with auto and 9''ford rear. It got put on the back burner 5 years ago when I built a 408 87 ranger pickup for my daughter,then built the maverick for me. She moved to Florida and races at Orlando now it runs 10.30's in the 1/4 mi.

 

I'm impressed. You are out of my league! My only Cobra 4.6L is in its original resting place a `97 Mustang Cobra with 25K miles.

 

I honestly couldn't tell you. It came in the car and is an old one. It looks nothing like the other converters I have saw

 

Soumds like a realy nice low mileage cobra you have. Nothing to be impressed about,I just keep working on one project at a time and trying to get something done. WARNING,WARNING If you bought a DART SHP 9.5 deck block make sure you pressure check it first before you do any machine work .Three guy's reported on YELLOW BULLIT that there blocks had pin holes in the lifter bores and leaked water in the oil. One engine was on the dyno the other was already in the car.Trust me it's way harder to pressure check an engine once it's together.My 418 is in the long block stage and I spent the last two days checking mine and it's OK.Iam glad I found out now instead when it was already running.

 

Stroker Mav, glad to hear your block is tight. I know you were worried about that. Can't wait to see what that beast will do. Should be a great time!

 

with that large a jet in a 650.. bolted onto a smallish 302 Cid motor...i would bet cash that your timing curve is way off from optimum. The gears are good enough to run better shorts even with that converter. You just need to nix that existing setup and go towards more adjustable components. Look at the MSD programmable stuff as it also has map capability to give the best of all world's with simple laptop interface.

Also..once you up that stall speed and/or gear to compensate for this little motors lack of low end torque?.. the dual plane should go away In favor of a higher rev range to match. Good luck with it all.

 

Thanks for the info. Looks like I have three items on which to concentrate. Based on the input of you and others....stall speed, rear gears and timing curve. I'm thinking in that order?

 

No. Get your tune dialed in closer ASAP and then move forward from there. The tune will change some as you swap parts around.. but you'll likely be much much happier until that time. Plus, if you get it closer to optimum tune now.. you cna fine tune later without having as much work to do to dial it all back in to the new components. Think of it as throttle response and torque just waiting to be unleashed. What is the timing curve specifically set at right now?

Tuning procedure usually goes like this.

Adjust initial timing lead to give best idle vacuum(make sure idle speed tuning matches "in gear" idle speed.. not the neutral speeds).. minor carb adjustments(idle speed and mixture).. recheck initial ignition lead to see if more vacuum can be found again or to smooth out any lean pops by reducing it a bit. Do NOT rev the engine under load at this point as you're only dialing in the initial portion of the curve and over-revving with too much lead higher up the rev range can cause damage over prolonged power runs(especially with cast pistons). Usually we shorten the advance stroke within the disty to compensate for the extra lead we gave it down low and to avoid too much total number. This is where the adjustable box mentioned above make your life easier and tuning much less time consuming and challenging. You can even set delays and retard features for various gear changes and overrev protection. I really like the high speed retard features for top end charges. Safer AND faster is never a bad thing.

Quick and dirty test is to just hook up a vacuum gauge and see where you're at right now. Make note of initial settings and then twist the disty as far as it will allow you to go to improve idle vacuum. It might start to break up and lean pop on you, so mixture adjustments will be mandatory to get there. This is your response and off-idle torque until the mechanical advance starts coming in. If you can find significant vacuum increases?.. jab the throttle in gear for some quick low rev bunny hops to get an idea of the fun you're about to have when you pull total lead back. With those heads.. I'd be looking at around 16-20 initial(well, I'd go for more but just to be conservative here).. another 16 or so in the mechanical sweep.. for a total around 36-38 degrees.

Then add vac advance to the FULL manifold vacuum port to supplement light cruise/low load throttle angles. That vac advance pot will be useful for lean burn(mileage) and off-idle/tip in throttle response. Get an adjustable vac pot so you'll end up around 8 - 10 degrees of supplemental when manifold vacuum is the highest(part throttle/light cruise). The engine will seem much fatter across the power band and I've even seen stall converters give another 50-100 rpm of stall speed due to the greater low speed torque multiplication. At the very least.. it'll flash quicker which never hurts anything other than maybe tripping an early light if you're not careful. lol

Good luck.

 

groberts 101,

Thank you for the super detailed reply. I've already read it twice and will read it again and again to totally understand.

Based on your previous post, are you suggesting a laptop programmable ignition system for a carbureted vehicle with no sensor inputs? Is that what you are running in your Comet? If so, I didn't know they designed such a thing! Can you provide me some part numbers so I can do some research? That way I can better understand what you are suggesting. In the meantime I will peruse the Summit Racing website.

Thanks again for the super detailed reply!!!!

 

There's lots of ways to skin that same cat and I was more or less generalizing with the above process. MSD's programmable 6al-2 is what you want to ease much of your growing pains here. A drawn out video on youtube gives greater detail on interface and programming. MSD's tech forum also has dedicated support and helpful suggestions.



Basically, you lock just your distributor out by disassembling the disty guts, pushing the roll pin out/pulling the cam gear, to allow spinning the shaft to another location which allows you to lock it in place and eliminate the advance mechanism. Then you set the timing to maximum needed at any given point in the rev range(mine is set to 54 degrees initial!) and the box then PULLS timing up to 25 degrees from that locked out number. So, in essence the box is a retard only device.

Map sensor capability is easily gained by simply hooking up a standard 5v/3 pin map sensor which can be connected to any full manifold vacuum source with a hose(no need to mount it on the manifold like the factory does). I use the GM unit which avoids the need to buy the overly priced MSD unit with correct pin placement for their harness when you can just re-pin the OEM unit to match MSD's "proprietary" pin layout.. or splice up a factory MAP harness connector to cross the pins back towards MSD's non- standard pin layout. You can also delicately disassemble the MSD map connector and re-clock the pin out order leading to the ignition box as well.

All that 10 minutes of effort will give you the ability to load base tune(just like the EFI stuff) the timing map for maximum power across the FULL rev range. Conventional distributors won't even come close to this same range of adjustability as they are always going to cause you to compromise someplace in the power band. Usually right off idle and leading up to the point at which the mechanical sweep starts working. Also has built in start retard because starters don;t really like very heavy initial lead. This is where you will gain the most throttle response and engine vacuum. The best part is that you gain much torque at idle and tip-in response is much improved as well. Average manifold vacuum for my Comp Cams XE282 is usually around 12-13 inches. After the install of this box.. I now get close to 16. On any highly tuned vehicle.. that's huge! Needless to say... my tip-in throttle response is awesome. Plus.. with 54 degrees of ignition lead.. I can cruise down the road with barely a cracked throttle and get close to 20 MPG with 500 horses. Good stuff and I'll never go back to a conventional design on anything I buy the parts for.