question about roller rockers and cam

[StangYellow]

I have an 85 306ci with the X-303 cam, gt-40x heads and SVO 1.6" roller rockers. For some reason the car isnt getting the timeslips I think it should be getting (high 13's). I want to know if switching to a 1.7" RR would help me out. The heads have the Ford Racing springs to allow the higher lift of the X-303. Are the 1.6 RR's ok, or should i go bigger? Thanks.

 

[Rick 91GT]

You will not gai anything with the 1.7's IMO...what is the entire combo? How heavy is the car? What is the 60, 330ft, and 1/8 times?

 

[StangYellow]

Here is the whole combo. 306, 5 speed, flat pistons, Holley 650 double pumper, Edelbrock Performer RPM intake, GT-40X heads, FRPP springs, SVO 1.6" RR's, stock crank, stock rods, X-303 cam, MSD ignition/distributor, FRPP wires, Autolite plugs, 3.73 gears, Pony wheels on 235's. The 60 ft times are in the 2.1 range, but the 1/4 mile is in the 13.8-14.0 area @ 101mph. I race at New England Dragway where the altitude is no more that 2,000ft.


*edit* the car has full length headers with an off road H and flowbastard catback.

 

[goldbomb79]

well, for one your 60 ft times are a little high. do you spin alot off the line? how do you shift? what suspension setup do you have? what brand and type of tire are you running at the track?

 

[StreetStang37]

either way hes only trapping 101's. what were other cars trapping? (stockish LS1's, LT1's, 4.6's). theres a couple of tracks in my area and they usually differ about 4mph, sometimes more. the trap seems a little low but that can be the track as well. btw, how much timing are you running? at some normal tracks I would hope for atleast 105-106's.

 

[RIO5.0]

StangYellow...Myself and 2 other guys run at NED.....you go to TT sessions??? Maybe we can hook up some time??? One of the guys comes up from Saugus..

Good luck...I know the feeling of wanting better times...

 

[StangYellow]

I go on wednesday street nights maybe once every month and a 1/2. Im not a regular there, too many homeboys with honda's if you know what i mean. I heard that its not very crowded on friday nights, so Ill try going on those days.

I understand that the 60ft times are poor and yes there is wheelspin on the line, and thats my fault. But The 100MPH is what bothers me. I think it only hit 101mph once..... somehow. My 02 has hit 103mph more than a few times and thats with a few bolt ons, the 306 is a legit built motor. I shift the car around 6,000 and there is a 6500 chip in the ignition. Ive tried shifting higher and lower and there are no changes in MPH. Maybe I should change that 306 number into 347, maybe that is the answer.

Thanks guys.

 

[MUSTHAVE302]

I also don't think lift is your problem.

my guess is there is 3 tenths to be had w/ traction, and 2-3mph in tuning. To be honest, with an 85 that should be kinda light, you should be looking at easy 13.20's. Have you checked your total timing? What about jetting? I would think total advance should be around 34 degrees. It's possible your balancer's outer ring has slipped too if its a stock piece - they are notorious for that.

I buddy had an 86 w/ very similar buildup except he had trick flow TW's instead of gt40x's. Everything else was the same, including cam, gears, carb size, etc. That thing ran 12.60's all day w/ slicks and pulled great up to 6500. He built a nice shortblock that was balanced, and he spent the $400 to put the motor on a dyno and get it tuned too. I forget how much HP (this was about 8 years ago), but i think it was in the 360 range.

 

[StangYellow]

The timing is at 32* and the balancer is an ATI, no more than 2 years old. Fuel pressure is good, oil pressure is good, and there are new filed rings on the pistons. The only noticeable problem is the carb throws a little black smoke in the upper RPMs, like 5K+. The fuel pump is a Walbro 190lph. The engine will rev to 6500 no problem but I think it starts to fall flat up there. Maybe its the carb jetting thats messing me up. Ill have to play around with that a little and see what happens.

 

[GT40XStang9]

FWIW - I've run in the 102 mph range also w/ my X heads, but the same night my bro-in-law's '03 Mach 1 (5 speed) was running in the 98 mph range. I was also getting 2.4 60 ft. times (yah I know). I agree w/ Musthave302 - there's mph to be found in the tune.

 

[StreetStang37]

yeah ive been to the track where ill hit mid 104's while LS1's were in the 99-102 range and my buddies stock 99 cobra running 99 mph. I also been to the track where ill hit 109's and LS1's will be in the 104-108 range.