gb95zconv

If they said that I wouldnt trust them with a preformace engine work. The oil should be changed and inspected after 200 or so miles ....filter contents should be looked at to see if any thing unusual is in it...ie excess metal particals indicating a problem.

Before I started doing my own work the shop I went to for a cam install insisted that I bring the car back after 200 miles of moderate driving so they could change the oil and check everything out ...including looking for any leaky gaskets. After they checked it and everything looked fine they said go out and give hell....then I put the nitrous on and broke a piston

dave1w41

Amateurs.


The heads are bolted to the block. You guys think that nice solid piece of iron is going to protect you? When it comes to an engine, nothing is as solid as it seems. Applying torque to components distorts them. Applying too much torque to the intake manifold distorts the engine block. Another thing that I left out was cylinder head machining without machining the bottom of the intake. In order to get it to seal you have to apply more torque; and more torque = more distortion. This is why those fasteners have a torque sequence and specification. The threads in the head can take several times the clamp load that it requires to seal the intake. I cannot count the number of intakes that I have seen torqued with a 3/8" impact. You have to picture the engine from a "distortion" perspective as a giant wad of very hard jello.

If what you guys were saying was true, you could torque all of the bolts to whatever specification you wanted as long as it was above the minimum required to keep the bolt in. You could just throw the bolts for the deckplates and maincaps in at whatever torque you wanted before you align bored/honed the crank journals or finsh honed the bores. There is a reason that you torque them to a spec and then hone and machine things, to compensate for the distortion that occurs when the fasteners are tightened.

Just look at the number of failures that occur after a cam change. Is every tech that does that a slopply dirt-thrower? Most are, in fact, 90% of the post-install failures (heads, cams, etc.) on otherwise healthy engines are due to dirt and grit dumped into the engine by sloppy techs. (abrasive discs, scotchbrite pads, sand, chunks of RTV.)
But something has to account for the other 10% of those failures and the other 10% are caused by another failure of a sloppy technician - failure to follow proper torque sequences and values. Oil pumps don't just "fail" because someone took an intake manifold off or put a cam in the engine. Bearings don't magically lose their surface by rubbing on the crank journal because someone stuck a cam in the engine. If you put 60 ft-lbs of torque on the intake manifold it will distort the block by pulling the heads toward the center of the engine. It may do nothing but it may cause the bearing journals in the block to distort and change the clearance between the bearing and the crank. Remember, the static clearance if the main bearing is completely round is between .0008" and .0015" that is about 1/5th the thickness of a caucasian human head hair. It takes almost nothing to close that space down to .0001" and kill the bearing from lack of oil.

If an engine is a piece of crap when the valve covers are removed a good tech will know it and call the owner and tell them: "this may not work, you may kill the engine by doing this mod; are you sure you want to do it?" That should account for the rest of the failures in my book - engines rarely just "fail" most often, they are killed.

94formulabz

Most of the distortion from overtorqing soemthing is going to be the bolt stretching because it has a tiny fraction of the cross sectional area and effective yield strength of the block. The importance of the torquing sequence is for sealing. Slightly overtorqueing the intake bolts is not going to cause distortions thoughout the bolt down to the main bearings. Using a breaker bar or something, yes, that would be stupid. I'm talking about a small amount of overtightning.

dave1w41

Intake manifolds only have about 20 lb-ft of torque on the bolts. A lot of people go at least triple that. - That isn't a small amount of mistorquing.

94formulabz

daym, 3x! how do you figure most people go that heavy? Your saying they just leave the impact wrench on whatever setting they were on i guess.

Anyways, i have a hard time believeing you will have a resulting distortion that large at the bottom of the block. The block probaly has 500x the cross sectional area of the bolt. The bolts will just stretch, and the block compress horizontally a negilible amount.

97bowtie

Actually, I believe LT1 intake manifold bolts are to be torqued to 34 lb ft.

dave1w41

Actually it is 37 lb-ft. or 50Nm but that is after doing a "first pass" to 10Nm. How many people have you seen make two passes let alone use a torque wrench or a sequence?

Dave Feerst

I used a torque wrench on mine and did both stages, on all I could i used the torque elbow. the block is cast Iron, not ductile iron, it should crack before it flexes. im not saying its impossible. but i would think it would take more like 100 foot pounds to do it. and i dont see that many people being that stupid.

ucnu112

This thread isn't very reassuring...

should I be scared putting a hotcam in my 130k lt1? What steps do I need to take to ensure that I don't suffer an 'early' death, like some others have?

Fred

craigffb

I'm thinking the same way as Fred. I wanted to go with a cam, but now I'm not sure it's worth it. I have about 106k on mine.

Dmx4ever3

well i spend all my money getting it in making thinks right dyno tuning it and so on but humm for what??? now i don't have a car to drive i need to get the engine pulled to fix it but ahhh wtf im thinkin nows a good time to make it into a 383 stroke

tom3

I've done several.
if you're clean and follow the specs, there are no problems. Just be real **** about keeping everything clean

marshall93z

i've got 230,000 on mine ad its not going to stop me from doing a cam. xe230/236 and a little head work shouldnt hurt anything!

Z28Nut

A mechanic friend highly recommends getting the bottom end freshened up along with a head/cam install to prevent spun bearings or worse. He explained its from over/under/re torquing the heads and intake. I believe him 'cause at work I supply a machine with water tubes (we make radiators) and they kept blaming my tubes -- they were all in spec, dead on the mean or target dimension. After six weeks of jumping through hoops and fighting with management, they discovered the base plate in the other machine was distorting because different operators were torquing it down by feel. This would distort a several hundred pound block of steel by .01-.03mm. This is alot harder and much more solid than an engine block with its cylinder bores and water jackets and oil galleys.

I vote for the torque distortion theory. I also think a big part of that factor is lazy mechanics -- the guys that don't give a crap about your car and take shortcuts when retorquing the heads and intake, especially when the motor is still in the car and a pain to get to certain bolts with a torque wrench.

My .02

GUMP

I have torn my motors down for the IHRA a bunch of times. Normally I have to pull the intake and one head for inspection. All of this is done in the open at a busy race track. I have never had a motor fail after tech. I would have to agree that cleanliness is everything. If you are carefull, you will not have problems.
Now, throw a cam into a high mile motor and you will probably find it's weak spots pretty fast. It all depends on how the motor has been maintained.

Best Regards,

Daren