1999 225 EFI (3.0L) New O rings and Seals needed when changing head?!

[mercman867]

I have a 1999 225 EFI and bought a set of XB heads and ECUs. I intend of changing to and from stock heads & ECUs to the XB heads depending on when I need that extra power I put on XB heads. When I go on long journeys, I put on stock heads and ECUs to have better fuel economy and less stress on Motor. Will i need to change seals and O rings each time I pull off and change the heads?

Thanks.

[rchevelle71]

Dont forget head bolts

[mercman867]

Will those have to be changed too?!

[mrcrsr]

you don't have to change the head bolts, but yes, the orings should be changed.

[Chaz]

Yot sure where that rumor got started. Prob the Merc manual, but hey, aint they the same guys who sell bolts for like 10 bucks each .. ;)
Torque to angle is more than likely a better way to tighten fasteners, but personally I still like the old way better .. :cool:
Perponents of TTA say that under head and thread engagment friction goes up expodentually as load is increased. They feel that 30 ft/lbs is about all you can go before the numbers go haywire. After that , they want 45 60 90 120 degrees of rotation to properly secure the fastener depending on size, thread pitch, OAL etc.
I went thru this a number of years ago with an engineer at Oliver Rods. He gave me a half hr speach on proper fastener ediquet. I listened, I torqued his bolts to 30 ft/lbs then set my wrench to 70 lbs. I put my brand new Snap On torque to angle gauge on the end of my wrench ... yup , then I got to his number , my wrench clicked .. LOL
If someone wants to be real anal about it. The SAE has done the math for you. Just look up the parameters of a new stock Merc bolt and it will give you the acceptable allowed strech of a used one. Even then , I would go another 5% of that number , cuz really who has ever seen a head bolt fail .. :nonod:
I have clipped enough of these 3.0L heads to know that they are "bent" at least .003 to .008 when they are brand new ... the factory should worry more about their hatchet tolerances, than that of their bolt vendors .. :rolleyes:

[HP]

I have found they do break....you may get 2 re-torques from Merc head bolts but that is it period. When mercury says replace the bolts you better listen. They have done the math on these. After you have torqued them to yield take them out and look at the headbolt at the top of the threads....... Stretched. Just my 2 cents with Mercury headbolts.

[Chaz]

Does the factory manual really say that for the 3.0L engine ? What page is it on, or better yet can someone copy and paste it up ?
I have seen the bolts streched at the top thread / shank area. It was from running heads that were clipped to get desired cc's and then just blindly running the bolts down to where the shoulders trenched their way into the deck of the block. Thats why I send out a set of sae washers with every head I mill ... sometimes a little machinist blueing goes a long way .. But then it's just easier to blame the bolts I guess ..:rolleyes:

[tony1204au]

The manual calls for 20ft/lbs plus 90*....... I usually reuse the head bolts and tighten them to 35ft/lbs...
Yesterday for the first time I encountered bolts that wouldnt get to 35... At about 30 they didnt feel like they were getting any tighter..
They were just stretching..... So had to order a new set....

[mrcrsr]

you will feel that the bolt is about to yield when you tork them. it would be nice if there was a published length for a good bolt. just rebuilt my third 'c' cummins this year, in the head gasket kit comes a cardboard template that you put the head bolts in for go/no go of the length of the head bolts, basically you put the bolt in a cutout notch, if the bolt fits in its good.

[tony1204au]

I guess Mercury want to sell us new bolts everytime we take them out, hence not giving us the published length...
I had a torque wrench on them and I only felt it when they started to yield... but not before... In the past Ive gotten them all to 35ft/lbs but this time they started to stretch at about 30... Maybe these were already re used a few times...