I just swapped on some gt40p heads that had some work done to them and have been converted to stud mounted 1.6 roller rockers and along with a gt40 intake manifold onto my 95 mustang gt. I used hardened stock length push rods as the heads had guide plates. I have the valve lash set to about 1/4 turn after there was no up and down play between the rocker and lifter. I could have gone half turn but the polynut was already pretty tight. Anyways, after buttoning up everything i decided to see if everything is okay and runs. Well it fires up and runs, but the at idle it shakes wayyy to much for having a stock cam. Never like i had before i swapped the heads or intake. Im at a lost. Im not sure if maybe a lower manifold gasket slipped causing a vacuum leak or maybe i have the incorrect valve adjustment? The mid pipe is not hooked up but that shouldn't affect cold start idle (open loop o2 sensors)? I had primed the oil pump before i even set the lash as well just to make sure the lifters were pumped up. The car revs and sounds fine at higher rpms, just at idle the engine is shaking too much. Idle rpm is steady smooth at about 1000 rpm. What do you guys think this could be?
Engine Heads and Intake Swap Problems :/
- Thread starter yyz5oh
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Grab a vacuum gauge, show us what it reads, I would run a compression test to, you may have a valve hanging up. Go back over you work like timing, firing order that kind of stuff.
I hope you did not damage anything. Do the lifter preload adjustment once again. There are plenty of instructions on line letting you know where and how much to turn the engine over to get all the valves correct. I don't know what you mean by the polylock being tight but they all should be very close when adjusted correctly. It sound like a valve or two is hanging open.
I have it set to 1/4 turb preload? I thought between 1/4 to full is considered fine? If anything they would be on the more chattier and lose side instead of tight and hanging a valve open, no?
Yes, a 1/4 turn is ok. I usually set mime at 1/2 turn and consider the threads per inch, condition of the lifters and oil I plan to use if I vary from that. Are you starting at #1 and turning the engine over 90 degrees to do the next one or are you doing more than 2 at a time which you could knowing the CORRECT FIRING ORDER as some manuals state? If the valves are ok you may have a vacuum leak.
I went cylinder 1-8 adjusted a cylinder at a time. The Exhaust opening Intake Opening method. Im leaning towards vacuum leak as well as it sounds fine when i rev it and shake is gone.
Yup made sure of that and made sure to keep 5 and 6 away from each other and 1 and 3
With adjustable rockers you can adjust them with the engine running. Pull a valve cover, start the engine, back a nut off until you hear it clacking, slowly tighten it back up until it just gets quiet, then tighten it 1/4 turn more for the preload. Repeat for the remaining rockers.
It will get a tad rough in idle when you do the final 1/4 turn, but it will quickly smooth itself out when the preload bleeds down to zero lash.
It will get a tad rough in idle when you do the final 1/4 turn, but it will quickly smooth itself out when the preload bleeds down to zero lash.
And hot oil will splash and smoke will burn your eyes and nose, the neighbors will call the fire department and any critters living above where your working will die.
Maybe.
Maybe.
Ok well I did the test where you block the pcv valve and check for any vacuum at the oil filler and didnt have any, so the lower intake gasket should in theory be fine. I do not want to take off the lower intake manifold again if I do not have to. So this probably means my valves are miss adjusted which i had a feeling of because when I crank over the motor it doesnt sound right either. Anyways, I just unbolted the driver side valve cover and roller rockers. Let the lifters sit for couple minutes. If i push down on my pushrods through the guideplates i cannot seem to compress the lifter spring? Is there not supposed to be spring tension on the lifter as i push down on it, hence when setting the preload it goes down? I just tried to adjust them again by turning the engine over by hand until cylinder 5 exhaust valve was opening, i adjusted that cylinders intake valve. Then when intake opened and started to close I adjusted that cylinders exhaust valve. I moved the pushrod up and down till they stopped jiggling/no up down movement and then gave the nut a half turn from that point. I repeated this for cylinders 5-8 and by the time i was done and turned the motor over by hand a few times again all the pushrods I had just adjusted had a bit of slack in them again and were a bit loose? So are my lifters a problem or is this side of the motor safe to say is set or did I do this all wrong again??!!
No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
If you don't get an 11, you have computer or wiring problems.
Please check and repost.
It is time to beg, borrow or buy a vacuum gauge to troubleshoot the problem. Most auto parts stores will rent or load one if you have a credit card.
Vacuum Gauge readings
