BIGGER Engine Problems

[dthrock]

After going back and forth with the shop over my engine, they finally admitted that the car probably had a wiped cam. When I asked what we could do about it I was told that race engines dont have any warrenty. It didnt seem to matter that the engine was like this when I picked it up with 18 miles on it. He doesnt seem to want to take any responsibility for it. I think he ordered the wrong pushrods for it and they where to long. Here is the specs from the machine shop. See if there is anything out of wack.

Connecting Rods:
Big end Bore: 2.3745
small end bore: .9385
small end fit press: .0012

Heads:
chamber volume(cc): 47.5 cc
valve head size: Int: 1.710 Exh: 1.500
spring installed height: 1.710 1.710
spring coil bind 1.185 1.185
spring pressure closed 105# 105#
spring pressure open 265# 265#
retainer to guide / seal clearance .495

Cam:
brand TA Perf Part# TA-260-H Grind 32057 (206/206)
lobe lift: in .275 ex .275
valve lift in .440 ex .440
duration at .006 in 260@ ex 260@
duration at .050 in 206@ 206@
lobe seperation 114@
intake lobe center line:
Cam Card called for: 110@
Cam degreed in at: 108.5@
piston to valve clearance: in .170 ex .190
compression ratio: 8.46
test information: Compression 150#
------------------- Oil Pressure 60#
-------------------valve adjustment: in H ex H ??? <-- donno what that means

The shop wanted non adjustable stock length push rods to put in. When I went to order them from TA they asked me for a length. I went back to the shop and asked again about length and he told me to get stock length. I think they were to long and wiped the cam. Opinions on all this please? And what responsibility should the shop have for fixing this FUBAR?

Dave

 

[FJM568]

Are you running a hi-vol oil pump??? I wiped a lobe on my new motor and was running a hi-vol oil pump with CC981 valve springs with pretty much the same seat pressure specs as what you have listed for yours...IMO, I think the spring pressure was too high to get the lifter spinning properly during break-in, and the Hi-vol pump didn't help any...

I am in the process of replacing the cam and putting lighter valve springs in along with putting a std oil pump back on...Basically, in your situation, I would do the same...Heck, if you still have the old stock valve springs, I would use them to break the new cam in and then change them to some heavier springs, like the CC 980's but definately not as heavy as the ones you had on there...


BTW, this line here in your post...

-------------------valve adjustment: in H ex H ??? <-- donno what that means

means hydraulic, there is no valve adjustment on these motors unless you have adj roller rockers...

Everything in your post(except my opinion of the valve spring pressure) looks fine...

 

[cruzn57]

flat cam

I am some what new to the Buick scene, But have been building motors, (all kinds, not just chevys!) for a couple weeks now!
It is my experience that you must break in a cam properly, usually the manufacture will offer some sort of suggestions as to which method he recommends.
Regardless, the major factor I have found in cam shaft failures, is incorrect cam lube, and /or improper lubrication upon start up, normally you are to bring the RPM to about 2000 rpm or so, for a duration of 20 to 30 minutes, the cam shaft receives its oil from the side clearance on the rods, (as the rods are spining, the excess oil is splashed on the cam lobes) oil is also pushed down from the lifter, but the amount is much less than the rods will supply.
Idling for an extended period of time on a new motor, will most likely result in cam shaft failure!
Excess valve spring pressure will contribute to premature failure.
I have not experienced cam failure , from too long of a push rod, its possible, but not likely.
So......... ask T/A what they recommend for break in proceedures, and lube.
good luck!
Keep the shiny side up!

Cruzn57

 

[Dave Simpkins]

Cam gone south

I believe CRUZN is onto something ... but DTHROCK doesn't say if his pusrods are deformed. If they are the culprit (too long) I'd think they would show signs of being compressed longitudinly.

Find a trued flat surface and roll the rods ... look for wobbles.

 

[S10xGN]

piston to valve clearance: in .170 ex .190

Is this correct? I have .480" clearance with the pistons at TDC! If I were running a slightly smaller cam, there would be NO interference if the chain slipped or broke. These numbers seem to express pop-up type pistons instead od our dished jobs.

 

[dthrock]

Well as expected it turned out to be a wiped cam. The 1, 3, and 4 intakes are gone. The shop that did the break-in agreed to do the rebuild at no cost if I buy the parts.

The cam is going back to TA Performance so they can send it back to the manufacturer for warrenty. Not sure if they will cover it or not yet. And I thought this engine rebuild was going to be fun.

Dave

 

[gnx7]

This may sound like a PITA as far as cam break in..... but here is what a few of us local guys do.

assemble new engine with high mileage stock GN springs (100K mile). This way the seat pressure is much lower than stock rating and mucho lower than any high perf spring. Start engine and vary RPM from 2500-3000rpm for 20-30 minutes and never hold it at any constant rpm. The cam gets lubricated from crank splash. The cam physically hardens during this period. Many of us also have the lifters side cut machined prior to assembly. In essence a machine shop cuts a small 1/16" cut in the side of the lifter and this allows more oil to trickle down and lubricate the cam lobes. Cost was $1/lifter.

Watch for any leaks and add water as necessary. Bleed air from the heater hoses (highest point) during warm up. After breakin is complete let engine cool down. Drain oil and install new filter/fresh oil. Now you need to pull all the plugs and fill cylinder with compressed air and replace valvesprings with the intended high performance units. Kirban's I believe has a valvespring compressor tool to change them while engine is in the car. Sounds like a PITA.... but no failures to date.

If you need info on the machine shop that side cut the lifters email me. I just bought generic GM lifters directly from them and had them side cut machined. Saved on shipping costs. This machine shop is the same place that did work on Terry Ryan's 10.20@132mph car and Ryan Guy's 9.99@135mph car. They know what they are doing.

GNX7

 

[Ormand]

Valve to Piston Clearance

S10, do you have GN heads, or TTA heads? The TTA heads have a deeper dish, don't know how much deeper.

Push rods too long would make the engine not run/idle, since the valves wouldn't close all the way. It the push rod was long enough to compress the valve spring all the way, the push rod would bend, too. It does sound like a break-in problem.

 

[S10xGN]

Re: Valve to Piston Clearance

Originally posted by Ormand
S10, do you have GN heads, or TTA heads? The TTA heads have a deeper dish, don't know how much deeper.

My heads are genuine GN (8445) heads...

Push rods too long would make the engine not run/idle, since the valves wouldn't close all the way. It the push rod was long enough to compress the valve spring all the way, the push rod would bend, too. It does sound like a break-in problem.

Don't think that's it - the engine *was* running for several months built as it is right now, except for me pulling the front cover several times to "fix" oil leaks

 

[TurboJim]

Originally posted by S10xGN


Is this correct? I have .480" clearance with the pistons at TDC! If I were running a slightly smaller cam, there would be NO interference if the chain slipped or broke. These numbers seem to express pop-up type pistons instead od our dished jobs.

How'd you do that? Almost 1/2" of clearance between a TDC piston and a fully open valve? I dont think soooooooo.... must be a SMALLLLLLL cam....

 

[S10xGN]

Nooo, I don't think so... It's a Comp roller with .520 lift. Stock GN ported heads and TRW forged replacement pistons. With the piston at TDC and check springs in place of the Comp 941's, I pushed down on the valve stem until the valve contacted the piston and got 0.480" on my dial indicator (referenced on the valve retainer).