Engine I give up

rockyracoon

10 Year Member
Nov 23, 2005
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margate NJ
Have tried to seal lower intake 5 or 6 times in the last two months. Its always the same, engine running lean. So after replacing the gt-40 lower with another gt-40 am getting the same result. If I hook the lower intake gaskets into the tab on the head gasket there is only like 1/8 " (or less) of gasket material going above the top of the intake ports on the heads. If I adhere the gaskets higher without using the tabs on the head gaskets then there is not much gasket material below the bottom of the ports on the intake. I never had this issue with the dart heads but with these pro comp heads it is a problem. Im using the fel pro 1250s but I have used the stock gaskets for a gt-40 (explorer) with the same result. today my vac reading was 6 - 7" hg and the exhaust exiting the tailpipe was super hot and was getting lean codes.

Im starting to wonder if its the angle of the heads at the runners. I may try to loosen up the head studs and try to install the intake. I assume the headers would have to be unbolted and am wondering if (since the motor only ran for 20 minutes) after new head gaskets were installed, could I still use them after loosening and re torque. Also do they make a thicker lower intake gasket our motors ?
 
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08GT500

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Jul 12, 2018
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Have tried to seal lower intake 5 or 6 times in the last two months. Its always the same, engine running lean. So after replacing the gt-40 lower with another gt-40 am getting the same result. If I hook the lower intake gaskets into the tab on the head gasket there is only like 1/8 " (or less) of gasket material going above the top of the intake ports on the heads. If I adhere the gaskets higher without using the tabs on the head gaskets then there is not much gasket material below the intake ports on the intake. I never had this issue with the dart heads but with these pro comp heads it is a problem. Im using the fel pro 1250s but I have used the stock gaskets for a gt-40 (explorer) with the same result. today my vac reading was 6 - 7" hg and the exhaust exiting the tailpipe was super hot and was getting lean codes.

Im starting to wonder if its the angle of the heads at the runners. I may try to loosen up the head studs and try to install the intake. I assume the headers would have to be unbolted and am wondering if (since the motor only ran for 20 minutes) after new head gaskets were installed, could I still use them after loosening and re torque. Also do they make a thicker gasket for our motors ?
Hi,
Can certainly assist you with this, yes indeed, the pins used the the OE Head’s allow heads to shift when torquing down. I usually run hollow but solid pins (not split pins) and install the intake with gaskets and tighten down just enough to keep the heads aligned, once I get through the first head torque of 3 steps, I’ll back off on the intake bolts as the heads will no longer shift.
Additionally, I use “Hi Tack”- if uncertain about it, it’s an adhesive for doing just that- holding intake gaskets in place. You want to stick them to the head, only need a little to do this, usually I use two 1” long spots on the top of the intake gasket, one 1” long spot on the base. Cut out the 1250’s cross resirictor in the coolant passage, and a razor blade to get the ports lined up correctly.
You’ll note the GT40 lower have much smaller ports than the heads, and is the real airflow restriction, place a gasket on the intake surface & you will note this. Port matching will help, and #2 & #5 Intake ports are the worst restriction, and any help you can give them by porting that lower will free up considerable flow, and turbulent airflow= Power, and allow breathing to higher RPM’s
Note, GT40/40P head’s both don’t respond much (if any) to lift over 0.500, unless ported.
If you fully torqued the gaskets, you should install new gaskets. They’re designed to crush once, if anything, you can use the old gaskets to mock up for Valvetrain geometry purposes, if the same thickness as what you’re replacing with.
Headers shouldn’t require removal, bolts loosened- yes...but heads will remain straight if using the intake to align them there.
Ok, Best!
-John
 
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mikestang63

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Aug 27, 2012
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if you have replaced the heads, where they milled? are all of the surfaces clean and straight? If the heads have been milled you may have to also mill the intake so ports line up.Put the intake on the block with no gaskets or RTV and see how it lines up to the heads, block and how large the gaps are. Take a straight edge to the intake side of the heads and to the head sides of the lower intake. If they milled the heads or intake too much, that will cause problems too. You should not be able to slide a 3 thousands feeler gauge under the straight edge.

Also if your block deck is warped out of spec. that will cause issues as well. same thing. Did anyone check the deck RA? with an MLS head gasket you dont have as much room for error It should be nearly perfect straight and true. with 9333PT1 or 8482 head gaskets not able to get a 2 thousand with alum heads or 4 thousand feeler gauge for iron heads under it and the straight edge

If the block, heads or intake were prepped wrong with an aggressive disk that could cause sealing problems.

How are you setting and torquing down the intake? For the intake gaskets- use a small amount of gaska cinch or RTV to hold them in place, make sure the ports line up with the heads. Put a nice fat bead of Right Stuff on front and back china walls and slightly up the intake gasket. Let it set up for a few minutes. Use some threaded rod on each head to guide the intake straight down. Loosely install the intake bolts and snug them up by hand. Walk away for an hour and let the RTV cure and set. Come back and finger tighten all the bolts again in the proper torque sequence. Take a ratchet and snug them down in torque sequence, then torque them down to 10 ft lb with a torque wrench in proper sequence. You will go around the intake several times, each time you want each bolt to click. When each bolt clicks the torque wrench at 10, go to 18 and do it all again. This will take some time but make sure you go around the intake several times until each bolt clicks the torque wrench off at 18. Do not overtorque the bolts . Walk away. Come back a few hours later or next day and torque them all again at 18 ft lbs. You will see they loosened up. Put it all together. After you run the motor and it heats up to normal temperature let it cool. Take off the upper intake and retorque the intake again. You will see some bolts loosened up again. If you are reusing the stock intake bolts that are 30 years old they are most likely stretched and wont hold torque- get a new set of ARP intake bolts and use antisieze. Yes some say this may be overkill but I have been doing this for 40 years and never an intake leak.

Also, make sure your heads are properly torqued down .You often need to retorque them after a few heat cycles.

I didnt cover everything but the jist of this is you cant just throw parts together without checking tolerances.
 
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rockyracoon

10 Year Member
Nov 23, 2005
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margate NJ
The heads are practically new. The deck was checked by the machine shop. The head bolts are studs and nuts.but you are right I did reuse the intake bolts. I used 3m adhesive to secure the gaskets. Did use right stuff on the rails. But the good news is that this morning I re torqued the lower (they were loose) dont know why they got so loose as they were torqued to 20 foot pounds. Anyway after re torquing the engine seems to be running pretty good. There was evidence of oil in the coolant from yesterday but that seems to be resolved. The radiator is now building up pressure when hot and the exhaust exiting the tail pipes is not super hot like it was yesterday.keep in mind that I only have water (temporarily) in the cooling system. My only issue now is an exhaust leak at the head. I did a complete rebuild on this motor in the last month. The engine is surging slightly but with the cam I know it will need a tune however there is no stalling whatsoever just a nice lope. Now I have to wait until the dmv re opens to get my classic registration and tags but here in PA that could be july or august. Our governor thinks he is a king.
 
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08GT500

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Jul 12, 2018
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Hi,
Think all Representatives think they are along,?think they should bed ripped in a pit with weaponsv& well...OTSS!lol.
feel the same!lol.
You want to get that coolant out as fast as possible to preserve your engine bearings, if you haven’t already.. I always wait a day to retorque, absolutely normal as the intakesvgoing into a wedge shape, takes a little time is all,!intake moves slowly when initially torqued. Always needs a retorque.
Providing you don’t overtorque using higher torque wrench settings you won’t peel a head up. Happens, but you sound clear.
What’s your engine vaccuum now?
Engine with an exhaust leak generally causes a rich condition, as all gases don’t reach your 03 sensors.
Do you smell a sweet smell exiting your exhaust? That’s the odor of Antifreeze (Glycol).,?and oil within coolant you’ll want to eradicate.
Milling head’s 0.010 (which most don’t need beyond that will not affect the angles of the intake mating surfaces on the heads to the degree you had explained, head’s shifting when torquing does. Did you replace head gaskets, too?
Tolerance of head’s is 0.007/FT with cylinder heads.
Your surge sounds like idle hunting, certainly want to get it as close as possible prior to tuning.
What Cam safe you running here? A TF-1 or an E-303?are both common Cams for strong street performance, both can be tweaked to run well with mechanical tuning,
Coolant full & system burped?
Set your TPS? Set it at 0.90-0.95V at idle.
Any Coded pulled?
Clean your MAF w/CRC MAF cleaner.
Make certain all grounds are solid, landed on a clean surface with conductivity grease.
Good luck!-John
 

96pushrod

Mustang Master
May 15, 2018
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The heads are practically new. The deck was checked by the machine shop. The head bolts are studs and nuts.but you are right I did reuse the intake bolts. I used 3m adhesive to secure the gaskets. Did use right stuff on the rails. But the good news is that this morning I re torqued the lower (they were loose) dont know why they got so loose as they were torqued to 20 foot pounds. Anyway after re torquing the engine seems to be running pretty good. There was evidence of oil in the coolant from yesterday but that seems to be resolved. The radiator is now building up pressure when hot and the exhaust exiting the tail pipes is not super hot like it was yesterday.keep in mind that I only have water (temporarily) in the cooling system. My only issue now is an exhaust leak at the head. I did a complete rebuild on this motor in the last month. The engine is surging slightly but with the cam I know it will need a tune however there is no stalling whatsoever just a nice lope. Now I have to wait until the dmv re opens to get my classic registration and tags but here in PA that could be july or august. Our governor thinks he is a king.
They were probably loose while you were torquing before the engine was ever ran. I’ve had to run through the final torque sequence a half dozen times before to seat the lower. Keep going until every fastener will no longer budge when you apply torque.
 
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08GT500

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Jul 12, 2018
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Precisely.As mentioned a few times, It takes time for the intake to drop slowly under torque to crush gaskets completely over a timeline. This is absolutely normal to go in for a retorque or two over several hour to a day, or two.
What is your vacuum now with the post where you remarked there was an improvement? You should be sitting at 20+ on a stock motor, Cam overlap can drop cylinder pressure with an E303 Cam, 16-17 lbs. at least- for reference.
Take care Buddy!
-John