intake bolts lose again

[T77911S]

i checked the intake bolts yesterday and all were a half turn lose, and that was bringing them back up to around 16-17lbs. i really think there needs to be a better gasket for the intake. if the gaskets were the size of the intake ports, the blocks would not leak over the gasket in the center AND the blocks would not crack. i can see small cracks developing on the old blocks starting at the port opening. i also put in a set of plugs i had, NGK BP8ES just to make sure the ones in there were not fouled. it ran better. quieter. topped it out the other day, again. it peters out at 150. (this was before tightening the intake). i also have a very small air cleaner on right now to make it easy to change fuel pressures. that could also restrict air flow. one other thing, i think i am over geared. at 150 i am turning about 5500 RPM. at 100mph i am at 3800. i have 18inch wheels on there which dont help. it makes the speedo accurate and drops the RPM for hiway driving which i like. i think 6k at 150 would pull better.

[T77911S]

checked mixture again.

WCP is 3.5bar, should be 3.6 but the numbers are up in the 16's at 3.6. still drives fine except not good throttle response.
13.1 at 900 idle
14.9 at 2500 and 15.7 at 4k in second
15.4 at 2500 in 3rd.

it does drive much better, no more miss or bucking at steady speed. gas mileage really sucks, around 14mpg.

sprayed water in engine bay and no change.
after tightening intake yesterday the engine sounded like it should, today it has that sound like it did when it had the big air leak leak, except not as bad. (i now know what it sounds like when its not quite right. the only way to know is to hear it when it is right).

[DSPTurtle]

Are you using locknuts or wavy washers and regular nuts on the intake studs?

[Ronnie's.930]

I'm surprised that the engine does not misfire at those extremely lean AFR@X-RPM numbers you posted above (other than idle), and also would have thought your fuel consumption would have been at the absolute minimum (better than 14 mpg, in other words).

[T77911S]

nylock nuts with flat washers.

yea, you would think it would be popping but it is very very nice on the road.

[DSPTurtle]

Sounds like your studs are backin out of the heads. You could experiment by pulling one stud out, coating the threads with blue loctite, reinsert it through the manifold, get it close to proper height and let the loctite setup. Sometime the nylocjs will overcome the blue as you tighten them down. Wavy washer and regular nut will put much less stress on that joint as you torque them to 16ftlbs and probably work better for you.

[JFairman]

"Sometime the nylocks will overcome the blue as you tighten them down. Wavy washer and regular nut will put much less stress on that joint as you torque them to 16ftlbs and probably work better for you."
That makes sense. The factory didn't use nylocks on the intake manifold and I've always wondered why.

[T77911S]

i checked the studs this last time i had the manifold out. they were not moving and had not moved a bit.

the nylocks where on there when i go the car.(so i put new ones on). i just put back on what was on there.

so you think using regular bolts might do it?

M8 1.25 right? i will pick some up today

[S1000RR]

The go to book on fasteners

Carroll Smith's Nuts, Bolts, Fasteners and Plumbing Handbook (Motorbooks Workshop): Carroll Smith: 9780879384067: Amazon.com: Books

[alwaysflat6s]

S1000RR: Great reference. Carroll Smith wrote the absolute BEST books on [mostly racing oriented] vehicle technology.

[T77911S]

I was thinking about this again today, when i tightened the nuts the other day, they all made a loud "crack" when they started to turn.

i bought nuts today. $8 for a bag of 100

[Tippy]

"Carroll Smith's Nuts".....could've been worded differently......I mean really......

[T77911S]

removed the nylocck nuts and put on regular nuts. drove it 4 hours today. checked a few of them that are easy to get to and they were still tight.
i dont get why the nylocks would keep getting lose.

all the studs stick up above the nuts the same so i think it is safe to assume none are pulling.
the car sounds good. it did not sound like it does when the nuts come lose.

[JFairman]

I removed my intake manifold for the first time since getting the car yesterday and the nuts were all regular nuts with flat washers under them. The manifold nut that's under the bowl of the CIS air flow meter housing had low yeild loctite on it. Probably blue loctite. Makes sense cause once the CIS is on there you can't see it or get at it.

[WERK I]

Nylocks should not be used anywhere heat cycling takes places. The heat changes the characteristics of the nylon, causing the nylon to hardened and become brittle. The nylon may also shrink under these conditions, which will cause the nut to loose some of its tension on the stud. I only use nylocks on the valve covers...no where near the temperatures the heads experience.
If you take a sharp pick to one of the old nylocks that were used and compare to a new nylock, you'll probably find a big difference in the resiliency of the nylon.

[T77911S]

thanks for the help. since the nylocks were on there when i got i may never have changed them.

i saw that book in a store just dont remember where. i thought how crazy to have a book just on fasteners, perhaps not so crazy now.