well title says it installed a new engine standard boar 302 mild heads e cam and a gt 40 explorer intake. just getting things set and noticed when i took it for a spin that the brakes are stiff as hell. also a little surging under load. I also noticed my fuel pressure seems high it reads 46 w/ vacuum 48without. it is supercharged with an fmu. any help would be great. looked around here and haven't seen any thing. also checked for vacuum leaks and there seem to be none. also all the pollution stuff has been deleted and plugged. no egr either. hopefully this is enough info to get some thoughts.
new engine gt 40 intake very stiff brakes vacuum seems low
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txstang84
15 Year Member
<ahem> sorry...
Have you checked your idle vacuum? Even with an E cam, it should be somewhere around 12-15 depending on timing. Timing may be retarded some, if it's too low, your idle vacuum will drop. Also, if you don't allow the engine to build vacuum in the booster, the brakes will certainly be stiff. Pretty much every engine build I've been involved with which used an after market cam had this issue during initial start up and run in. But, after a short drive where vacuum was built up in the intake, everything was pretty normal. You may also want to check the check valve (little 90* fitting) on your brake booster...if it's leaking, inop, or the grommet dry rotted, the booster won't hold vacuum and you'll have defacto manual brakes.
If you have the means, consider ditching the FMU and go with bigger injectors and a proper tune. The FMU cranks up the fuel pressure by restricting the fuel return, and when pressure exceeds about 80psi or so, the stock injectors start having issues opening against the pressure...this leads to lowered injector life cycle, and difficulty fine tuning when the pressure goes up since you have to factor in reduced injector response time in with the pulse width.
my timing is set at 10 degrees btc. I have not checked my idle vacuum. however i beleive my boost gauge also shows vacuum. new not installed yet i'll have to look. i will have to check that brake check valve. but i have only driven the car around the block. as for the fuel i plan on going all injector when funds are avail but had to settle for some 24lbers for now with the fmu, and a tune will be in the future once most of the quirks are figured out. thanks try some stuff see what i come up with.
79'293stang
Active Member
Yea, there is something up. With an F cam I pull around 10 for vacuum and my brakes work just fine. How did you check for vacuum leaks?
Finding vacuum leaks
Revised 04-Aug-2011 to add pintle cap, PCV grommet & power brake check valve grommet to checklist.
There is no easy way to find vacuum leaks. It is a time consuming job that requires close inspection of each and every hose and connection.
Small vacuum leaks may not show much change using a vacuum gauge. The range of "good readings" varies so much from engine to engine that it may be difficult to detect small leaks. The engine in my first Mustang pulled about 16.5" of vacuum at 650-725 RPM, which I consider rather low. It was a mass market remanufactured rebuild, so no telling what kind of camshaft it had. Average readings seem to run 16"-18" inches at idle and 18"-21" at 1000 RPM. The only sure comparison is a reading taken when your car was performing at its best through all the RPM ranges and what it is doing now. Use one of the spare ports on the vacuum tree that is mounted on the firewall near the windshield wiper motor.
Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as propane or throttle body cleaner. Fire is an excellent hair removal agent, and no eyebrows is not cool...
The vacuum line plumbing is old and brittle on many of these cars, so replacing the lines with new hose is a good plan. The common 1/8” and ¼” vacuum hose works well and isn’t expensive.
The PCV grommet and the power brake booster check valve grommet are two places that often get overlooked when checking for vacuum leaks. The rubber grommets get hard and lose their ability to seal properly. The PVC grommet is difficult to see if it is correctly seated and fitting snugly.
Fuel injector O rings can get old and hard. When they do, they are prone to leaking once the engine warms up. This can be difficult to troubleshoot, since it is almost impossible to get to the injectors to squirt oil into the fuel injector mounting bosses. If the plastic caps on the fuel injectors (pintle caps) are missing, the O rings will slide off the injectors and fall into the intake manifold.
Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $3-$4 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:
http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/
Most of the links above have store locators for find a store in your area.
Use motor oil on the O rings when you re-assemble them & everything will slide into place. The gasoline will wash away any excess oil that gets in the wrong places and it will burn up in the combustion chamber. Heat the pintle caps in boiling water to soften them to make them easier to install.
Diagram courtesy of Tmoss & Stang&2birds
Vacuum leak due to slipped lower intake manifold gasket...
Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.
Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif
Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif
Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg
HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif
TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif
Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif
Revised 04-Aug-2011 to add pintle cap, PCV grommet & power brake check valve grommet to checklist.
There is no easy way to find vacuum leaks. It is a time consuming job that requires close inspection of each and every hose and connection.
Small vacuum leaks may not show much change using a vacuum gauge. The range of "good readings" varies so much from engine to engine that it may be difficult to detect small leaks. The engine in my first Mustang pulled about 16.5" of vacuum at 650-725 RPM, which I consider rather low. It was a mass market remanufactured rebuild, so no telling what kind of camshaft it had. Average readings seem to run 16"-18" inches at idle and 18"-21" at 1000 RPM. The only sure comparison is a reading taken when your car was performing at its best through all the RPM ranges and what it is doing now. Use one of the spare ports on the vacuum tree that is mounted on the firewall near the windshield wiper motor.
Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as propane or throttle body cleaner. Fire is an excellent hair removal agent, and no eyebrows is not cool...
The vacuum line plumbing is old and brittle on many of these cars, so replacing the lines with new hose is a good plan. The common 1/8” and ¼” vacuum hose works well and isn’t expensive.
The PCV grommet and the power brake booster check valve grommet are two places that often get overlooked when checking for vacuum leaks. The rubber grommets get hard and lose their ability to seal properly. The PVC grommet is difficult to see if it is correctly seated and fitting snugly.
Fuel injector O rings can get old and hard. When they do, they are prone to leaking once the engine warms up. This can be difficult to troubleshoot, since it is almost impossible to get to the injectors to squirt oil into the fuel injector mounting bosses. If the plastic caps on the fuel injectors (pintle caps) are missing, the O rings will slide off the injectors and fall into the intake manifold.
Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $3-$4 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:
http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/
Most of the links above have store locators for find a store in your area.
Use motor oil on the O rings when you re-assemble them & everything will slide into place. The gasoline will wash away any excess oil that gets in the wrong places and it will burn up in the combustion chamber. Heat the pintle caps in boiling water to soften them to make them easier to install.
Diagram courtesy of Tmoss & Stang&2birds
Vacuum leak due to slipped lower intake manifold gasket...
Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.
Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif
Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif
Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg
HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif
TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif
Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif
ok i took the car for a ride definitely going to pick up a vacuum tester gauge. when i give the car gas it has like no response. the slowly surges forward. in line with that when i first apply the brakes they feel fine. then i let off and reapply them and stiff as a board. i think my problems are related to each other some how
txstang84
15 Year Member
There's no need to fill that EGR porting under the intake as long as it's blocked off by a gasket or your EGR delete plate...I don't know what kind of intake gaskets you used, but I bought ones in the past that blocked off the EGR ports so the heat wasn't running up into the intake. There's not enough pressure coming through there to blow out the gasket or a chunk of Aluminum. That being said, if you have vacuum leaks, they are certainly related to a lack of power. If you have something like what was mentioned above, then your engine is pulling in unmetered air and therefore running lean-that will cause poor power and crappy response. It will also be the root cause of your lack of stored brake booster vacuum.
alright all figured out. apparently 2 of my rockers were overtightened and bent the push rods and valves giving me zero compression on two cylinders. what a bunch of crap this is the second time on this new engine trying to get stuff set and this happens. I am getting rid of these aluminum stud mount heads and getting some simple gt40 heads for my combo. adjustable stud mount rockers like a chevy and see what happens nothing but problems. so at least i figured the issue out. so anyone have a set of gt 40 heads for sale let me know in the market as of now
txstang84
15 Year Member
Don't get rid of the heads...FWIW, adjustable rockers used to be on SBFs... Get the heads fixed, and press on...but take a little more time during assembly...devil's in the details.
yup firgured it out. the heads listing when i bought them never said anything about having to notch the pistons for clearance. they are basically set up like the older twisted wedge heads. so fyi they are aluminum heads sold on ebay supposed to be pro comp castings beware before you buy them.
