Stopping the knock: Lower compression and ported heads...

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I guess it depends upon what you call "straight up". To me, straight up is always installing the intake centerline at the lobe separation angle. If a cam is ground with a 110 LSA then installing it with a 110 ICL would be straight up. Even if the cam manufacture grinds it with 4 degrees advance, straight up would be 110 ICL. Installing a 110 LSA cam with 4 degrees advance ground in it, at 106 ICL, would not be straight up, but 4 degrees advanced. That may not be the only way to understand it, but that's how I keep it straight in my mind. I guess that's because I don't give a damn where the cam is ground, I'm gonna install it where I WANT IT.

All they do in effect by grinding a cam 4 degrees advance is place the locating pin or keyway in a different spot. Sometimes when they grind them 4 degrees advance and you install them dot-to-dot you will find the ICL to be 102 to 112. It's why you hafta degree your cam in every time.
 
I guess it depends upon what you call "straight up". To me, straight up is always installing the intake centerline at the lobe separation angle.

x2

The builder should degree in order to ensure the ICL is exactly where they want it in relation to the piston's position. Degreeing takes into account the component machining (dowels or keyways, slots or holes in the gears, etc), the quality of cam grinding, & the timing set accuracy so we can put it where we want, vs where it might end up otherwise.
 
Agreed on straight up= same as LSA. Anything other is advanced/retarded.
Also agree that tighter quench is the proper route.
My point is this-
All the factors point to it should not have any problem running on 92 octane.
The cam may have been degreed, but nobody seems to be sure if its correct.
Cranking compression is higher that what it should be, indicating something isn't right, and possibly the camshaft is too far advanced.
The cam card clearly says installed at 106° ICL will be 2° advanced, with IVO @24.5 and [email protected] measured @ .050" lobe lift with it set there.

Telling a guy that advancing it up too 8° is a good idea is IMO a problem. Granted, we all want to help the guy but that's just bad advice for the OP.
Along those lines, you need to remember, most cam manufacturers grind 4* INTO the camshaft. So, even if you install and degree it "straight up" it is likely advanced 4* already. SO, if you installed it advanced, you can probably add 4* to wherever you installed it, which would raise cylinder pressure even more
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CPMotorworks said:
Agreed on straight up= same as LSA. Anything other is advanced/retarded.
Also agree that tighter quench is the proper route.
My point is this-
All the factors point to it should not have any problem running on 92 octane.
The cam may have been degreed, but nobody seems to be sure if its correct.
Cranking compression is higher that what it should be, indicating something isn't right, and possibly the camshaft is too far advanced.
The cam card clearly says installed at 106° ICL will be 2° advanced, with IVO @24.5 and [email protected] measured @ .050" lobe lift with it set there.

Telling a guy that advancing it up too 8° is a good idea is IMO a problem. Granted, we all want to help the guy but that's just bad advice for the OP.
Click to expand...

Let me defend my friend here.

1st, Rob wasn't telling him to advance the cam eight degrees. He was saying that if a cam with 110 degree LSA was ground 4 degrees advanced and that if when installed at 106 that you considered that to be straight up and then you advanced that cam 4 degrees, you could possibily now have the cam eight degrees advanced.

Again, he wasn't saying do it, only that it could be that much advanced under those circumstances. Anyhow, that was my interpretation of his post.
 
Thanks for the clarification. The way Rob wrote it I misunderstood it, my apologies to Rob. I just don't think it would do anybody any good if they read it the same way I did, and advanced a cam 8° because it sounds like a good idea.
I have seen more than a few people get confused over reading cam cards and trying to degree camshafts properly, some of them long time car guys.
 
Rob has been one of the main players trying to help FD about how to fix this...I think we kinda let the cam aspect fall on the wayside because of assumption that it was degreed as spec'd and the fact it's larger than the one it replaced. But, it would make perfect sense to assert the cam may be advanced and is generating too much pressure.
 
Nevermind. I ain't getting this far into this one again.
 
IQ52 said:
Let me defend my friend here.

1st, Rob wasn't telling him to advance the cam eight degrees. He was saying that if a cam with 110 degree LSA was ground 4 degrees advanced and that if when installed at 106 that you considered that to be straight up and then you advanced that cam 4 degrees, you could possibily now have the cam eight degrees advanced.

Again, he wasn't saying do it, only that it could be that much advanced under those circumstances. Anyhow, that was my interpretation of his post.
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Exactly what my point was. Thanks, Jim.

I am gonna sit back and watch. The car's not mine. I really have no skin in the game, as obammy might say. Clearly others know more than I. I didn't come in to get pounded on for my ideas so, yall have fun, ya hear?
 
RustyRatRod said:
Nevermind. I ain't getting this far into this one again.
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Can't say as I blame you...I was only mentioning that you dug deep in attempts to assist a couple times before. But, I don't tknow how much was explored before in relation to cam timing. Not that I'll have anything productive to add. There are already several veteran engine builders in here who've forgotten more than I'll likely ever know about building big block Mopars and all their particulars...so, I'm here for the:happy1:
 
I did degree the cam and was surprised to find that with the timing set bolted in at the ZERO mark, (No advance or retard) The cam came in at 106 degrees. I got a total number of 212 and divided by 2.
I was having trouble with the degree process because I had a flimsy piston stop and was having a ***** of a time establishing TDC. I did it with the heads on and the spark plugs in place. I didn't know that the plugs needed to be out to allow the engine to spin over easier!
I bought a beefy solid brass piston stop (well almost solid...it has a bleeder hole through it) and was able to establish TDC. Again, I had good luck because the timing marks on the balancer were exactly right. The degree process went pretty smooth once I got past a few stumbling blocks.

I do intend to REdegree the cam. At this point, I'd be stupid to overlook anything.

I want to apologize for being so annoying about this. I've heard time and again that a combo such as this should be fine on pump gas, but here I am with these problems. I'm to the point where if these new changes do not help, I'll end up pulling the engine for a piston swap.
 
I'm gonna bet you're not the only one frustrated...your predicament is perplexing to a growing number of folks...

And I just want to know what's really behind your problem.
 
Please don't start another thread. I think you guys are on to something. I can't wait to see what the solution is.
 
txstang84 said:
I'm gonna bet you're not the only one frustrated...your predicament is perplexing to a growing number of folks...

And I just want to know what's really behind your problem.
Click to expand...

I don't want to go off topic with a "Poor, poor, pitiful me..." sorta rant, but.....
 
The heads should be finished on Tuesday. The man is doing them in his off-time and told my machinist that he is reducing his price since he has taken so long! That was nice to hear. He is doing a valve job and a light surfacing to the deck too. I asked for him to cc one chamber on each head to get an idea on where they spec out. They were 84 ccs according to the Edelbrock chart, but after being "lightly surface milled" a few times, they could be less than that. Of course, if the porter hogged out the chambers after unshrouding the valves, it could be even-steven.
 
I cleaned the pistons and rechecked the measurement the pistons sit below deck. When I first buit the engine in 2004, I thought I recorded a .017 number. For some crazy reason, this time every cylinder came to .012. I wonder if the machinist decked the block .005 when I had it in for honing in 2011....
The different number changes the CR from 10.73 to 10.84 to one.
 
The heads are coming home tomorrow. I got to look at them today. MAN I like the look of clean & polished aluminum! The man was finishing up the valve job and reassembly. He said that they came in at 83 ccs. Over the weekend I cleaned the tops of the pistons and rechecked the height below deck. I've listed a .017 number but this time every hole came in at .012. The .017 number was from 2004 when I first built the engine. I'm thinking that when I had the engine in for honing in 2011, maybe the guy resurfaced the decks. I'm going to ask tomorrow, but after 2 years, he may not remember unless it was standard practice for him.
I did some calculations. The .075 head gasket will give an even 10 to one compression ratio while the .086 will give 9.77.
I'll post some pictures of the heads tomorrow. Thanks.
 
Good luck. Sounds good. Fwiw, Pay attention,to every detail upon re -assembly.If you have a question,post it .... (and PATIENCE is required...).
 
I've read some people suggest to REdegree the cam. I am actually considering it.
 
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