*Engine won't run right since head install, please help!!!

[mattsclean90]

I just bought a 90 lx with a fresh 306 in it. The car was running perfect and had the following upgrades already done to the engine:

Trick flow intake
Trick flow stage 1 cam (499,510 lift)
1.6 fms roller rockers
stock heads

So after driving it like this for a few weeks I decided to put a set of edelbrock performer rpm heads on it. They are the ones with the small 1.90 intake valve. I tore the engine down myself and put felpro 1011-2 head gaskets on. Put felpro 1250 intake gaskets on and made sure everything was in perfect shape. I added the heads with a set of comp cams pro magnum 1.6 ratio roller rockers and stock length pushrods. Well I adjusted the valves the same way I always do by bumping the engine over and adjusting the intake valve when the exhaust starts to open and adjusting the exhaust when the intake valve starts to close. Well it was time to fire it up and it fired right up but the rockers sounded way too loose. They were clacking and the engine didn't want to rev up at all. Studdering and not much vacuum unless you revved it up around 5,000 or so. So I readjusted them again and the same thing happened.

So I ended up changing the roller rockers to harland sharp 1.6's today and readjusted them the same way again. This time they seemed too tight and the engine would do nothing below 5,000rpms again. So I went back and loosened them all 1/2 turn and now the engine will rev from around 2,500rpms and up perfect. But below that and it won't run at all basically. Missing and studdering real bad. But as soon as the rpms hit around 2,500 then the engine revs up perfect and nice and quick like it should. So I loosened them up again and now they are too loose and the engine still only runs at around 2,500 and up. I'm completely stumped as to what is wrong unless I have the wrong length pushrods. I ordered a set of FMS stock length hardened pushrods because that's what I was told to use. Where did I go wrong guys? I have went over the whole engine and everything is fine. The distributor is on the right tooth. The timing is set at 10* initial. No leaks of any sort. No loose vacuum connections. 35psi oil pressure at around idle and 42lbs of fuel pressure at idle. The engine is beyond sluggish and doesn't want to rev until around 2,500rpms......Please help!!!

 

[mob]

you put the dizzy back in the right way?

 

[mattsclean90]

If the distributor is one tooth off would it do this? The engine is missing and stuttering until around 3,000rpms and up when it revs normal. I am really confused as to what is going wrong here. I thought at first maybe my pushrods were the wrong length but I've read where stock length should have been fine.

 

[mattsclean90]

If I have the improper length pushrod will my engine act this way and stutter and miss at low rpms and then rev fast and nice once I rev it hard in the rpms? The car acts like the valves aren't opening and closing like they should and it has no vacuum hardly down low and won't run unless you are really revving it high. Once I get it past 3,000rpms or so it will clear out and will rev fast. But as soon as you let off the gas the engine dies instantly. You have to keep giving it lots of pedal to keep the engine running and if you just slam it hard then it stutters and misses until it all of a sudden revs quick up high. The tach would hit 7,000 in an instant from about 3,500 just fine and smooth. I really need some help guys. Throw some ideas out there and let me know what you think.......

 

[OonDeanisS]

my brother had the same problem, he forgot to put the correct shims on the roller rockers when installing them since he got performer rpms its different so call edelbrock and ask them which ones to use

 

[jrichker]

If the distributor is one tooth off would it do this? The engine is missing and stuttering until around 3,000rpms and up when it revs normal. I am really confused as to what is going wrong here. I thought at first maybe my pushrods were the wrong length but I've read where stock length should have been fine.

There is no such thing a one tooth off as long as you can make the timing marks line up using a timing light. Paint the balancer mark you want to use, like 10 -14 degrees advance. Then pull the SPOUT, connect the timing light and shoot the mark. If you can get it to line up, you are good to go. Do not attempt to set the timing without a timing light, it will never be correct. Be sure to put the SPOUT back in when you are finished.

Dump the codes and see what the computer says is wrong… You may have knocked something loose or damaged a sensor while you were working on things. Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[irish]

I think regardless of what you read or heard, you should borrow/buy a pushrod length checker and use it....between that and pulling codes you should be able to get a concrete answer...

 

[2002BLGT]

well I hope you checked the part number of the spark plug you used , because a regular stock ford head and edelbrocks use a completely different plug , I would hate to think you had did all this swapping for nothing though

 

[7-UP BILL]

well I hope you checked the part number of the spark plug you used , because a regular stock ford head and edelbrocks use a completely different plug , I would hate to think you had did all this swapping for nothing though

Good Call The stock plugs are short and don't extend into the firing chamber of the Edelbrock heads. The threaded part of an Edelbrock specific plug is quite long. Autolite 3924 is the stock heat range for Edel heads.

 

[2002BLGT]

Good Call The stock plugs are short and don't extend into the firing chamber of the Edelbrock heads. The threaded part of an Edelbrock specific plug is quite long. Autolite 3924 is the stock heat range for Edel heads.

yea my car just got done laying down a [email protected] with edelbrock performer RPM 2.02 valve heads on a 306 with a Xcam and custom Sniper tune , previous best was a 7.99 at 85mph , fastest mph tonight was a [email protected] , so the edelbrock heads are definitely no slouches , good heads if you get the rest of the combo to work with it .....

 

[mattsclean90]

I am running the autolite 3924 plugs in it. I readjusted the valves today to 1/4 turn past zero lash and the engine ran perfect for about 10 minutes and then all of a sudden the same thing started happening. Started stuttering and dying below 4,000 rpms and acted like a valve was hanging open or like a major lean issue down low. I ended up getting my old mechanic from years ago to come pick up the car and I'm just going to let him fix it. My patience has run out after 3 days of this car driving me nuts. Oh well, I hope it's something cheap that I've overlooked......

 

[jrichker]

Something cheap would have been to dump the codes. A problem that changes suddenly after a few minutes of operation may be a change into the inputs of the computer.

Good troubleshooting eliminates the things that are good and leaves you with the possiblities of things that are bad. Chasing rabbits or getting tunnel vision while persuing a problem will lead you down a trail to failure.