Problems with 1.7 rockers and cobra intake install (read)

Ian'sGT's · 04-04-2001, 09:38 PM

The car was fine before the mods. It is a stock 95 GT with all the bolt ons. 4.10 gears pullies headers x pipe flowmasters short belt etc. The car ran strong going 13.80's and 90's on pep boys tires. I put on the 1.7's and the upper and lower intake and now the car runs like a bastard until about 5600 rpm and then it starts to break up. I checked the timing wich was a little high and set it to 14 degrees wich is where it was before. I used the stock push rods out of the 95 GT instead of the ones out of the cobra. I was told there is no difference in length. When I back the timimg down it seems like it got a little better but it is still present. The car pulls like a ***** until 5700 and then it slugs off. If I stay in it it seems to come back on until it hits the stock limiter at 6250. Three of us put it together and everyone of us has done this before with no problem.

Anyway, if anyone has any input they can share than let me know as this is starting to piss me off!!! I want to go to the track sunday but I want the car running its best.

thanks,
Ian

------------------
Come see the ponies at:
http://members.tripod.com/elevensGT.page1.html

Oldschoolpony · 04-04-2001, 10:24 PM

Have you tried going back to the 1.6's? I had a similar problem in a different engine and the valve springs were at fault. It is possible that with the extra lift from the 1.7's the springs cant keep up. Also, changing just the rocker arms changes the geometry of the valve train. I'm no expert, but I've tried alot of different things on heads and ended up torching valve guides because of bad geometry( angle of the rocker arm to the tip of the valve )
Also, check for any vac. leaks.

ByrdPE · 04-05-2001, 04:41 PM

Quote:

Originally posted by Oldschoolpony:
I had a similar problem in a different engine and the valve springs were at fault. It is possible that with the extra lift from the 1.7's the springs cant keep up.

Ditto!!Do you still have the stock valve springs??If so,this is probably your problem.
Good Luck!!

------------------
FMS 373,Mac U/D Pullies,B&M shift kit,B&M Trans cooler,
KYB's,FMS 65mm T/B,Moroso cold air kit,75mm Bullet,BBK sub frame connectors,Power-slotted rotors w/performance friction pads
PST performance sway-bar kit,3G alternator,Maximum Motorsports Strut tower brace,Maximum Motorsports G-Load brace
Maximum Motorsports lower control arms,Autometer,oil,H2O,
volt MSD6AL,MSD Blaster coil,'Tiny Avenger'intake pipe

93CobraR · 04-05-2001, 08:01 PM

Theres NOOO way it's because of the springs. Thats too little of a difference to make that big of a problem. I will tell you it's between two things, more then likely the rockers were adjusted wrong, or the intake ports are too big for the head ports causing turbulance.

------------------
87 GT, 4 inch cowl hood,17x9 Cobra R's/255/45's,GT-40 heads,long tubes headers,h-pipe,Flows,BBK cold air, Mass air,70mm MAF, 1.7's, 1" spacer,underdrive pulleys,Pro 5.0, King Cobra, Adj. fuel Reg., Lakewood Lift Bars,50/50's,subframes, 4.10's.
Best time 12.96
Best MPH 103.42
Best 60' 1.695

Visit my site at:
http://www.geocities.com/cobrar93_2000/MyPage.html

[This message has been edited by 93CobraR (edited 04-05-2001).]

Ian'sGT's · 04-05-2001, 09:52 PM

Well I learned some new things today. First off I was told that because I did the intake swap and never unhooked the battery it is possible that something messed up when all the sensors were unplugged and removed.

A freind of mine that helped with the install brought his scanner over today and found a code in the car that said the thermal air sensor was messed up however this code was in there from before. We then took the car out and drove it. He took a snapshot 15 seconds before and after the problem and everything looks good until 5700. The car starts to break and the computer goes into open loop. The timing total advance is at like 41 degrees when in closed loop. At 5700 it goes to open loop and the timing drops to 28 degrees. Now I don't know what is making this happen! What is making the computer go into closed loop and break up like this. I know the rockers were adjusted right and the intake isn't to mutch becasue I had this same setup on my 87GT with mass air, minus the 1.7 rocker arms.

All the input is appreciated.

Thanks,
Ian Muller

exgmguy · 04-06-2001, 03:16 PM

My .02

Revving a stock motor to 5700 just slows you down. Also, at 5700 rpm the added lift from the 1.7's could very well be the valves floating. I would probably bet on it.

If you still have the stock heads and cam reguardless of other bolt ons you should be shifting at 500-5200 rpm.

egiap's 5.0 · 04-07-2001, 07:42 AM

when you bought your rockers they shuold have come with shims. after rocker arm touches push rod and tip of valve I think more than one full turn of wrench you need to put shim under rocker ped. Hope this helps.

------------------
Amsoil dealer, find out about amsoil's preferred customer program, buy at dealer cost.

Robert_5_liter · 04-11-2001, 03:41 AM

My 95 Gt dumps the timing out at 5000 Rpm down to 28 degrees but has 44 degrees at 1800 rpm total adv

04-11-2001, 05:21 AM

The stock springs are weak from the factory.If it was ME,I would first change out the stock springs.Second thing I would do,is,not shift the car at such high rpm.The best way to find the optinum shift point,is goto a track and run the car and record your shift points and your ET times,you'll find the best rpm range to be shifting at on your lowest ET's..

Also the cobra intake,which uses the same lower intake as the GT-40, levels off at around 5500RPM,so there's no point in running it up to the rev limiter @ 6250 cause your not gonna be making any power then.

------------------
Paxton Blown 87GT
ICQ#112698436

04-11-2001, 05:26 AM

IAN

Ask Jeff how he likes the Southside traction bars that I sold him

I'm thinking the same Jeff you know,is the same guy I sold them to,awhile back...

------------------
Paxton Blown 87GT
ICQ#112698436

spinemup · 04-11-2001, 08:04 AM

sn95 computer suck... they pull timing at a certain rpm in order to save the weak t-5 trannys. i doubt its valve adjustment. i bet if you put an FMS rpm extender and replace the valve springs you'll be runnin like a champ.... even though i see no reason why you would wanna rev a stock motor to 5700 but what ever floats your valves.... umm i mean "boat"

LX XLR8R · 04-11-2001, 09:09 AM

my old car stock and speed denisity pulled upward of 5,800..usually when i see cutting ouit like that at higher rpms it usually mean one of 2 things..spark or fuel..is the fuel pump on its way???did you burn a wire or is a plug bad???check these simple things first..do you have a FP gauge??

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

Ian'sGT's · 04-11-2001, 08:22 PM

I have been told that we should never take a near stock mustang above 5500 rpm. My only problem is this. I have been bracket racing that car for two years and the car runs the fastest times shifting it at around 5900 rpm. Maybe I have the only near stock mustang in the country that likes high r's, but I know it does. I bet I have at least 100 pass's on that car and I know where it runs best.

I will also tell you that my brother in laws near stock 91 LX dosn't like anything over 5600 rpm. My 87 GT used to be shifted at around 5600 also. But this car likes the rpm's. I don't know why but it does.

I am going to be trying a few things in the next couple of days to try an remedy the problem. I will keep you posted, and I will keep shifting that pig on the rev limiter!!!!!!! :~)

Later,
Ian

------------------
Come see the ponies at:
http://members.tripod.com/elevensGT.page1.html

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04-04-2001, 09:38 PM	#1
Ian'sGT's Registered Member Join Date: Apr 2001 Posts: 3	Problems with 1.7 rockers and cobra intake install (read) The car was fine before the mods. It is a stock 95 GT with all the bolt ons. 4.10 gears pullies headers x pipe flowmasters short belt etc. The car ran strong going 13.80's and 90's on pep boys tires. I put on the 1.7's and the upper and lower intake and now the car runs like a bastard until about 5600 rpm and then it starts to break up. I checked the timing wich was a little high and set it to 14 degrees wich is where it was before. I used the stock push rods out of the 95 GT instead of the ones out of the cobra. I was told there is no difference in length. When I back the timimg down it seems like it got a little better but it is still present. The car pulls like a ***** until 5700 and then it slugs off. If I stay in it it seems to come back on until it hits the stock limiter at 6250. Three of us put it together and everyone of us has done this before with no problem. Anyway, if anyone has any input they can share than let me know as this is starting to piss me off!!! I want to go to the track sunday but I want the car running its best. thanks, Ian ------------------ Come see the ponies at: http://members.tripod.com/elevensGT.page1.html

04-04-2001, 10:24 PM	#2
Oldschoolpony Registered Member Join Date: Mar 2001 Location: Gainsville,Fl Posts: 229	Have you tried going back to the 1.6's? I had a similar problem in a different engine and the valve springs were at fault. It is possible that with the extra lift from the 1.7's the springs cant keep up. Also, changing just the rocker arms changes the geometry of the valve train. I'm no expert, but I've tried alot of different things on heads and ended up torching valve guides because of bad geometry( angle of the rocker arm to the tip of the valve ) Also, check for any vac. leaks.

04-05-2001, 08:01 PM	#4
93CobraR Registered Member Join Date: Oct 1999 Location: Cincinnati, Ohio Posts: 1,575	Theres NOOO way it's because of the springs. Thats too little of a difference to make that big of a problem. I will tell you it's between two things, more then likely the rockers were adjusted wrong, or the intake ports are too big for the head ports causing turbulance. ------------------ 87 GT, 4 inch cowl hood,17x9 Cobra R's/255/45's,GT-40 heads,long tubes headers,h-pipe,Flows,BBK cold air, Mass air,70mm MAF, 1.7's, 1" spacer,underdrive pulleys,Pro 5.0, King Cobra, Adj. fuel Reg., Lakewood Lift Bars,50/50's,subframes, 4.10's. Best time 12.96 Best MPH 103.42 Best 60' 1.695 Visit my site at: http://www.geocities.com/cobrar93_2000/MyPage.html [This message has been edited by 93CobraR (edited 04-05-2001).]

04-05-2001, 09:52 PM	#5
Ian'sGT's Registered Member Join Date: Apr 2001 Posts: 3	Well I learned some new things today. First off I was told that because I did the intake swap and never unhooked the battery it is possible that something messed up when all the sensors were unplugged and removed. A freind of mine that helped with the install brought his scanner over today and found a code in the car that said the thermal air sensor was messed up however this code was in there from before. We then took the car out and drove it. He took a snapshot 15 seconds before and after the problem and everything looks good until 5700. The car starts to break and the computer goes into open loop. The timing total advance is at like 41 degrees when in closed loop. At 5700 it goes to open loop and the timing drops to 28 degrees. Now I don't know what is making this happen! What is making the computer go into closed loop and break up like this. I know the rockers were adjusted right and the intake isn't to mutch becasue I had this same setup on my 87GT with mass air, minus the 1.7 rocker arms. All the input is appreciated. Thanks, Ian Muller

04-06-2001, 03:16 PM	#6
exgmguy Registered Member Join Date: Feb 1999 Location: Utica, Michigan Posts: 2,631	My .02 Revving a stock motor to 5700 just slows you down. Also, at 5700 rpm the added lift from the 1.7's could very well be the valves floating. I would probably bet on it. If you still have the stock heads and cam reguardless of other bolt ons you should be shifting at 500-5200 rpm.

04-07-2001, 07:42 AM	#7
egiap's 5.0 Registered Member Join Date: Apr 2001 Location: Mansfield, OH. Posts: 113	when you bought your rockers they shuold have come with shims. after rocker arm touches push rod and tip of valve I think more than one full turn of wrench you need to put shim under rocker ped. Hope this helps. ------------------ Amsoil dealer, find out about amsoil's preferred customer program, buy at dealer cost.

04-11-2001, 03:41 AM	#8
Robert_5_liter Registered Member Join Date: Mar 2001 Location: Ohio, lorain usa Posts: 32	My 95 Gt dumps the timing out at 5000 Rpm down to 28 degrees but has 44 degrees at 1800 rpm total adv

04-11-2001, 05:21 AM	#9
Mustanguy Guest Posts: n/a	The stock springs are weak from the factory.If it was ME,I would first change out the stock springs.Second thing I would do,is,not shift the car at such high rpm.The best way to find the optinum shift point,is goto a track and run the car and record your shift points and your ET times,you'll find the best rpm range to be shifting at on your lowest ET's.. Also the cobra intake,which uses the same lower intake as the GT-40, levels off at around 5500RPM,so there's no point in running it up to the rev limiter @ 6250 cause your not gonna be making any power then. ------------------ Paxton Blown 87GT ICQ#112698436

04-11-2001, 05:26 AM	#10
Mustanguy Guest Posts: n/a	IAN Ask Jeff how he likes the Southside traction bars that I sold him I'm thinking the same Jeff you know,is the same guy I sold them to,awhile back... ------------------ Paxton Blown 87GT ICQ#112698436

04-11-2001, 08:04 AM	#11
spinemup Registered Member Join Date: May 2000 Location: middleboro,ma, usa Posts: 734	sn95 computer suck... they pull timing at a certain rpm in order to save the weak t-5 trannys. i doubt its valve adjustment. i bet if you put an FMS rpm extender and replace the valve springs you'll be runnin like a champ.... even though i see no reason why you would wanna rev a stock motor to 5700 but what ever floats your valves.... umm i mean "boat"

04-11-2001, 09:09 AM	#12
LX XLR8R Dirk Diggler Join Date: Feb 1999 Location: SLOATSBURG, NY Posts: 1,931	my old car stock and speed denisity pulled upward of 5,800..usually when i see cutting ouit like that at higher rpms it usually mean one of 2 things..spark or fuel..is the fuel pump on its way???did you burn a wire or is a plug bad???check these simple things first..do you have a FP gauge?? ------------------ 1987 black notch(ex 4 banger) DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one.. AIM=onesillynotch

04-11-2001, 08:22 PM	#13
Ian'sGT's Registered Member Join Date: Apr 2001 Posts: 3	I have been told that we should never take a near stock mustang above 5500 rpm. My only problem is this. I have been bracket racing that car for two years and the car runs the fastest times shifting it at around 5900 rpm. Maybe I have the only near stock mustang in the country that likes high r's, but I know it does. I bet I have at least 100 pass's on that car and I know where it runs best. I will also tell you that my brother in laws near stock 91 LX dosn't like anything over 5600 rpm. My 87 GT used to be shifted at around 5600 also. But this car likes the rpm's. I don't know why but it does. I am going to be trying a few things in the next couple of days to try an remedy the problem. I will keep you posted, and I will keep shifting that pig on the rev limiter!!!!!!! :~) Later, Ian ------------------ Come see the ponies at: http://members.tripod.com/elevensGT.page1.html