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From: Las Vegas - Just stop perpetuating myths please.
So I found my Ed Staffel book on the sbc. He lists a max average piston speed for sbc with different reliability of parts (strength, quality). And he says for a street built performance sbc max ave piston speed should be kept less than 4,000 ft/min. Which for a 3.75" stroker is 6,400 rpm.
To go higher rpm takes lighter/stronger parts.
Thought you may want to look into max ave piston speed for your build.
Good luck and let us know how it works out - it helps us all.
With you compression test most likely not. The other 7 were high so I would try it. If compression was low or "all over the place" I would pull other pistons. You do want to make sure ESC ( knock sensor) is working.
So what i ended up doing was pulling all other 7 pistons and bringing them to the machine shop. I have a new set of pistons and rings on order.
It would have taken me a few hours to remove rings, inspect pistons, buy new rings, reinstall them, etc. While im this far down, I'm just taking every precaution necessary. I need to remember how lucky i am that all the block needs is a quick hone.
250 bucks for pistons and rings plus their labor is so worth me not doing this again. The car is going back to the dyno tuner once it's running.
When i did the compression test, it was my first time doing it on a sbc. I vaguely remember one other cylinder taking its sweet time to hit 180 then 210. This route covers my *** and also takes out that uncertainty in the back of my mind every time i punch it that another piston or 7 MIGHT be ready to break.
I'll have him check knock counts when its on his scanner.
I have a 219/219 cam...I bought it used. I do not know if it has 4 degrees advanced built into it.
Would setting a base timing of 8 degrees plus 4 degrees of cam timing built in have the potential to harm a motor?
Just need to prevent this from happening again...
New pistons will be installed soon but I'm considering pulling out the radiator and taking the cam out. Either having the cam looked at and spec'd out or buying a new cam that I know what it is and reinstalling.
Thoughts? This keeps snowballing. Getting sick of it.
From: Las Vegas - Just stop perpetuating myths please.
Advancing the cam closes the intake valve sooner trapping more of the fuel/air charge which increases cranking pressure. Your measured 210 psi (if done correctly) is as high as you want to go on pump gas. What I want to add is even if you fixed the throttle blades open to test, a cold block will make less cranking pressure than a hot/operating temperature block do to better ring seal when hot.
You can degree a cam while in the car - I've done it - though cumbersome. And it's a great learning experience while at the same time you can verify TDC on #1 and nail your timing tab marks for future tuning.
Do you what your static compression ratio is? A thicker head gasket could be used to lower it. Since there is no damage to piston head I still believe it was more something with piston itself. The high cylinder pressure is a concern requiring highest octane fuel you can find. Advancing cam timing tends to increase low end torque while retarding can reduce low end torque and help top end. It really has little to do with ignition timing. I would contact cam manufacturer regarding adjusting cam timing either way. Also some cams are made from specific timing sets. If you don't use the recommended set, you will need to degree cam to get correct cam timing.
I don't know the comp ratio. It's 10 degrees or10.5 to 1.
Almost ready to start it. Gotta install the tensioner, belt, prime it, then install dizzy. If it starts, fill with coolant, get it to the exhaust shop for true duals, and hope I never touch it again.
Gonna take it to the Tuner To give it a once over.
Well it runs. Idles well. I think I'm off a tooth of the distributor cause it's turned more than before but I'm at 6 deg advanced timing. I'll either move plug wires or fix it right
hot idle oil pressure is still 10 to 15. I'm not too happy about that. The only bearings not changed were crank and cam bearings.
There seems to be a slight metallic tick like a rocker is just nicking my valve covers.
Minor issues hopefully. Still want to check out the old Pistons to see if I wasted 400 bucks for all new ones.
Engine is at the machine shop. Engine broke on the dyno. Same cylinder 4 ringland failure. Cam bearings, Crank bearings were shot. Ended up figuring out compression ratio was 11.4:1. Cam was indeed 4* advanced and never degreed in.
I have another thread regarding the old unknown cam. Needed new cam and lifters. Bought new rods. Will need new pistons. Add in flywheel, clutch, and PP, as well as some trans upgrades for the zf6, I'm well over 3k. Sucks to suck but i need to get it right this time.
Check out the other thread. I want to get this right.
Yikes! So sorry to hear that! Frustrations abound! Makes me wonder if dyno tunes are more risky than valuable! It's doubtful that a street driven car will ever push the engine as hard as it gets pushed on the dyno.
Yikes! So sorry to hear that! Frustrations abound! Makes me wonder if dyno tunes are more risky than valuable!
It's doubtful that a street driven car will ever push the engine as hard as it gets pushed on the dyno.
If it was blowing on a dyno and the engine is new, I would suspect the builder. I really like to do a "one stop shop". That way the tuner doesn't blame the builder and the builder doesn't blame the tuner.
For my grandmama, yes. I punch it on the ramps. If I can't do that, I think I'd get a sedan. Oh, what the hell, I punch the sedans too. Never mind.
I punch it on the ramps. If I can't do that, I think I'd get a sedan. Oh, what the hell, I punch the sedans too. Never mind.
Yeah, I punch it on the ramps, too, but my on-ramps aren't 1320 ft. long! A dyno pull is full throttle at max load for a longer period of time than my local cops will tolerate! (Unfortunately.)
I didn't say that an engine shouldn't need to survive a dyno pull, I just said that a dyno pull puts an abnormal load on an engine, and you just might find a weakness in the engine that might otherwise never bother an engine in a normal street driven car. I hear many more stories about engines blowing on the dyno than I hear of engines blowing in "normal" street driven cars.
Originally Posted by Deepa
Engine broke on the dyno. Same cylinder 4 ringland failure.
The problem is detonation too much heat, too much timing, not enough fuel, too high a compression ratio. On SBC typically cylinders #3 and #4 are the first to detonate, the coolant flow around those cylinders seems to be the worst and they will detonate before the others do. When you run a engine with 11.4 compression and the 219 cam with a superram you need to have good fuel, correct timing, correct AFR, and cool water temps near 160 degrees. If any of these are off the engine can detonate and damage like his pictures show is the result.
The problem is detonation too much heat, too much timing, not enough fuel, too high a compression ratio. On SBC typically cylinders #3 and #4 are the first to detonate, the coolant flow around those cylinders seems to be the worst and they will detonate before the others do. When you run a engine with 11.4 compression and the 219 cam with a superram you need to have good fuel, correct timing, correct AFR, and cool water temps near 160 degrees. If any of these are off the engine can detonate and damage like his pictures show is the result.
I agree with all. 210 psi is too much for street motor (what is lobe sep angle) 11.4:1 will not play nice with pump gas. look at a crate motor from a good builder, and do your own tuning.
look at a crate motor from a good builder, and do your own tuning.
That costs more money than a junkyard motor. Now you want to do your own tuning on that and risk it? Learning to tune, if you want to do it right will involve hours at a dyno. For a one off, why go through all that trouble and risk? Now if you are changing heads and cams every week, fair enough.
If you really want to learn, get a junkyard motor. If you break it, so be it.
