Thread: Detonated Dreams

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Valve train noise can be affected with engine temperature and load. Too much lash will grow even bigger with engine temp up to normal, as compared to a cold reading. Also too much lash on the exhaust will sometimes tick louder under load as it has to open against increased cylinder pressure, but most of the time who can hear that when the engine is screaming unless you have a stock and quiet exhaust system, which i assume you do not. The valve lash can grow more with aluminum heads as the expansion rate of aluminum is so much greater than cast iron. Good luck on your engine and know that when you find out what was wrong you will be that much more educated and satified with your car and you will have information that you will be able to pass alone to the next guy! I would like to know what eventually fixed this problem!
that cast iron.

I was under the impression, that if you have hot spots inside the firing chamber, it is pre-ignition. The motor won't last long with this condition.
Might check for the proper reach of the spark plugs.

^^^so his plug spotting could be bits of combustion chamber and/or piston?

Everyone should read this thread about Dynamic Compression Ratio. It is the best explanation/discussion of DCR I have seen.

http://www.chevytalk.org/fusionbb/sh...php?tid/92966/

awesome link^^^ thanks

Originally Posted by 78c10

^^^so his plug spotting could be bits of combustion chamber and/or piston?

Highly likely.

I will apologize in advance if someone has already said this...

Hyper pistons do not hold/absorb heat like forged do, they send it to the head/chamber and top ring, yes this does increase temps at the top ring requiring more gap [to avoid butting] so the rest of the ring package is lowered to avoid having to increase their gap as well.

JMOanything beyond .042 thou quench distance from the head is a wash if trying to make use of quench benefits, like avoiding detonation...

I would like to know what the actual dynamic psi is-as in cranking psi ?

If you are over 185psi, then that explains it to me.



There is an old sbc x head that has more material around the plug to help centralize the ignition/burn and avoid uneven lighting off- 2 fronts colliding.

I like the the slipping balancer ring idea, just wonderer if since the efi set up retards the timing for you if that would matter?
that cam is a lil small for the compression on pump gas with those heads and their plug angle that is miles away from where it should be. .JMO

yep they reflect some heat not all hypers need more ring gap KB yes and i will stand by thinking they hold more heat around the top ring land were i seen many fail and NOT from lack of end gap if they fail and have much end gap you tell me why? if you can not get the heat out of the top ring thru the block then the top ring land as deep as the radial ring cut is going to run abit hotter ???? speed pro alloy seam to hold up better .i do not know if the machining on the fly cuts on the KBs are to sharp and need to be rolled (i roll most of my pistons if they are sharp) with there hi sil alloy to hard making them fail but i have seen many and i will stick to the 4032 or 2618 or for lower buck builds the speed pro hypers. even a HD cast piston before a KB hyper i used them ...i do not care for them.... if i am wrong its ok with me what i have been doing has worked very good for me

The KB have ridges above the top ring for heat dissipation.
Yes the the edges have to rolled/smoothed.
And I didn't say they didn't hold some heat, just said they absorb as much as forged pistons do, which translates into the pin/rod and into the oil temp.

Why do they fail?
Cause guys run too much timing with them for 1, for 2 people use these things out of app. when they should be running a forged piston, and then the ring gap factor...

I have heard many good things about the mogul/speed pro, too bad they don't expand their app's....

KB has many different head configured pistons to choose from.

btw..thats what it's about right? share our experiences and use what we like, but put the info out there for others to aid in making the right choice.

well KB are making a cheaper forged line and i have used them and will use them again . the KB s hypers i know about the ridges. there is sharp break on fly cuts with no radus. a good break off point. no big deal i use more forged piston stuff any ways just think there hypers are not that good for the money . and i bore just one or two blocks a year

So we ordered Comp Cams 12-366-4. Should give a DCR of 7.95 with quite a bit more duration. Hopefully it solves the problem.

Stay tuned for the outcome.

Intermediate update, with the heads back on and the previous cam still installed, we turned the engine over to see what the Pressure/PSI was in each cylinder. We are between 180-185 PSI. Sounds like a lot. Maybe we are on the right track. More to come....

Wow! That is a lot. 120-140 is more like it.

Panic time? New cam gives the same cylinder pressure. It has 4 degrees advance ground into it. Our timing gear only allows 2 degrees in either direction. Is that the answer? ....retard it the 2 degrees and see what we get?

Panic time? No. Install the cam straight up. Most Comp cams have 4 degrees advance ground into them. You can retard it two degrees if you want, but you should not have any problems with installing it straight up. I didn't, and I am running a higher DCR than you. If you are unsure, call the CompCams Cam Help tech line (800-999-0853) and ask them. I think they will tell you not to retard it. You are not going to get a good reading on your compression until everything is installed. The compression test seemed high to me, but I only take a compression test when I suspect a problem with a cylinder. DCR is a better indicator--trust it.