pcf_mark

iTrader: (1)

We have an early LS7 engine running on BS3 with a Katech cam. The engine has about 4 hours light running time. Today we hit the dyno and the driver's head gasket blew under a partial power run. Brand new crate engine - anyone have this issue? Any suggestions as to the cause? Good fuel, running at 170 degrees at the time. It had run as hot as 220 in the past for a few minnutes while I was struggling to get the cooling system bled.

trumperZ06

Who installed the cam ???



If it's a Katech crate engine, give Jason a call.

pcf_mark

iTrader: (1)

This is NOT a Katech engine - Katech camshaft installed in an otherwsie stock LS7 with BS3 engine management.

trumperZ06

Hhmmmm.... I haven't heard of any head-gasket problems with the C-6 Z06... LS7 engines. There have been a few problems with the LS7 engine... but no reports of blown head gaskets, as far as I know.

1999ssls1

iTrader: (71)

How do you know the gasket blown for sure?

pcf_mark

iTrader: (1)

I have antifreeze in #3 cylinder. Very light evidence of knocking on some plugs but nothing substantial. I think the tuner is honest and knowledgable leaving me to think maybe I had a problem from the crate.

John B

iTrader: (10)

If you bought the motor through SDPC I'd give them a call for warranty work!

71CamaroLS1

I hate to say it, but it's pretty easy to create detonation using an aftermarket ECU, particularly if the tuner has little experience with the BS3 on LSx series motors and tried to use ignition advance more appropriate to old style small blocks (anything over about 28 degrees). And the BS3 requires a quite fussy calibration procedure for it to understand where TDC on the motor is, which if you get it wrong can also lead to excessive spark advance and detonation. And at least on the version of the BS3 I have, there is no provision for using knock sensors, so you're jumping without a parachute when you push the timing up.

I use the BS3 on my '71, and it's very sophisticated and functional, but the documentation is less than crystal clear on some of these issues. OTOH, support is usually very responsive if you email them.

One more point - the Katech cam closes the intake valve quite a bit sooner than the factory cam, which is likely responsible for the low end torque of that cam, but also increases the dynamic compression ratio and therefore increases the risk of detonation further.

the_merv

iTrader: (88)

I wouldn't of put it on the Dyno right out of the Box unless it comes broken in..

pcf_mark

iTrader: (1)

Thanks for the feedback. Lucky for me the tuner is in contact with John at BS3 who helped develop the baseline tune that was pre-installed in my ECM. I am starting to think about maybe my TDC mark could be wrong but the detonation was limited to the back cylinders and we are running only 28 degrees of timing. Any flaw we should be looking for when taking the head off?

Candyredz28

iTrader: (4)

I love your Monte Carlo, the 4th gen Monte carlo is just like the Camaro everyone wants the latest year because of the little improvements.

71CamaroLS1

Well, if the detonation was serious enough it may have melted part of the piston tops, which will show up as a pitted look. As long as it's not too bad, the pistons should still be OK on that front. The other thing that can happen to pistons under detonation, particularly cast pistons, is fractured top ring lands. This would typically cause some scoring of the cylinder walls, and would also show up in a compression or leakdown test.

If there's melted aluminum on the plugs, there can also be aluminum on the valves and valve seats, which will have to be polished off or it will ruin your valve seal.

This all sounds very dire, but hopefully your head gasket was the canary in the coal mine and everything else will be pretty much OK.

Best of luck.

pcf_mark

iTrader: (1)

I have the head off and it is much worse. The number three cylinder is cracked about 3" long. The plugs are chewed up like it was knocking like crazy. Tuner says the bleed for the heads was not hooked up right and the heads over heated causing detonation which tore up the pistons which then cracked off pieces and this cracked the block. Sounds a little hokey because it was hooked to the over flow tank. Even if it was plugged the hose would have blown off - it is not even clamped on. I do not know who to believe but it ran hot from the very first start up. Now I need to find a short block or someone to rebuild this one. Any suggestions on what could have caused this level of detonation other than a crazy bad timing setting which seems to be right on?

See5

iTrader: (53)

"bleed"?

71CamaroLS1

Sounds like cyl #3 hydraulic locked from the coolant in the cylinder, and the pressure split open the block. This will also pretty much wreck the rod and crank.

The coolant bypass, as I understand it, is there to make sure there are no air pockets stuck in the cylinder head coolant passages, which would indeed create hot spots in the head that could cause detonation. But there's nothing complicated about hooking it up - mine just runs to a tap in the top radiator hose. If yours isn't blocked, I don't think it should have caused a problem.

Without knowing all the data, it's hard to say what caused the detonation, but I still wonder about the timing. One thing that occurs to me is that the procedure for finding TDC on an LS7 is probably different than on an LS1, because the LS1 has a 24x reluctor wheel and the LS7 has a 58x ... but if you checked the timing on the running engine and cross referenced that against what timing the BS3 thought it was providing, and they matched, that would pretty much eliminate ignition advance errors, unless your TDC mark is off. Off the top of my head, I don't remember where TDC is marked on these motors - the damper isn't keyed, and can slip on the crankshaft, so a mark on the damper wouldn't necessarily be reliable.

Was there a data log from the BS3 on the dyno pull? It might have things like coolant temp, actual A/F ratio, MAP sensor readings, which could provide some clues.

71CamaroLS1

One other thing occurs to me - we had a heck of a time bleeding all the air out of the coolant passages on my car. My tech said they all (LS1s) do that, and we actually ended up jacking the front of the car way up to assist in the process. If you had major air pockets blocking a coolant passage, that might be it.

Does the other cylinder bank show the same problems? If not, that's a pretty good indication it's related to cooling on one side ...

gun5l1ng3r

So how are we to know when there is no more air in the cylinder heads?

71CamaroLS1

This problem seems to crop up in retrofit conversions, for whatever reason. The cylinder heads themselves are supposed to be purged by the coolant crossover t-fitting. But there was a number of iterations of fill coolant, wait for big bubbles, run engine, fill more coolant, etc until coolant levels stayed constant.

Here's another thing I just remembered from my '71 conversion: you have to allow some circulation through the heater lines for the cooling system to work properly. I fitted an aftermarket HVAC system which shuts off heater coolant circulation when the heater is off - and when the heater was turned off, coolant temps went up drastically in just a minute or two. I put a t-connection between the heater lines before the shutoff valve, and the problem was immediately fixed. I think the water pump goes into cavitation if that heater line circulation doesn't occur.

427

iTrader: (3)

The bleed line on the cylinder heads must be hooked up to something "uphill" on the cooling system with no restriction to flow. This will let the cylinder heads fill with water and clear the air out of the system. If this is not done properly the engine will be hard to fill with water, and engine damage will likely result.
We can repair the block and replace the pistons for you if you like, call me for more info.
Do you have a picture of the engine with cooling system installed in car?



Kurt

lovescamaros28

Maybe because you didnt properly break in the engine.A lot of break in procedures call for not running an engine over 3500 rpms for the first 500 miles.I would guess you just put the engine together added oil and thought it was good to go until the next 3000 mile oil change interval?