The stock tulip intake valves vary on the cc's. I've measured 3.7-4.4 cc's on the ones I've measured. Some being deeper, some being more shallow.
Help me out here, where did the .026 clearance # come in? If you are running the .045 gaskets and .010-.015 in the hole, then.... Long story short, deck the block if the pistons are in the hole. I would zero deck or .005-.010 out. Originally, I was going to suggest shave the heads .010-.015 if your P/H clearance was at .026 to pick up some compression, but if you have the room, deck the block.
this a new built hate to pull motor and deck block, i can mill the heads. .026 came from .011 piston in the hole, taking off the .045 gaskets and putting on a .015 steel head gasket. highest piston .011 to deck. plus add .015 head gasket = .026
Ah ha! I had a feeling, but wanted to make sure we were on the same page. Go with the thin gasket, but may as well take a tic off the heads since they have to come off. Were they milled before or stock surface? FYI, I have some cam info I want to share, will reply cam thread soon. I have been doing some testing and have some first hand info for you. Stand by. FYI, F85 is right about timing, but keep in mind, less timing making max power is ideal-knock not being an issue.
For reference, LS motors typically like 26-28 degrees total, SBC's like 34-36 total stock type heads. Nails like around 30-32 typically.
If the engine is together I'd save your precious time and leave it alone. I'm saying the engine that likes a few degrees less timing is telling you something. There's a reason you can't dial in a few more degrees. You could be at the beginning stages of in-audible detonation and just seeing no further improvement with more timing. If so, that's your safe line. Also if so, adding .7 compression just to back off your timing would make this a huge waste. Again, I don't know much more about the two example engines other than above.
I agree with everything you say, however, if he is having det with just 28 of total timing with that little timing with that little compression, something is not right.
yes thin gasket and .010 off heads should work out, .04 were milled off the heads before. I confused you guys by talking about 2 different motors. the big stroke 446, 10.4 comp likes 28* and am wondering about knock with that much comp. the smaller stroke 410, 9.15 comp is at 30* timing. I have tried up to 36 * timing with no signs of any knock, but pulls better all the way around with 30.* that will be interesting about your cam info and testing.
I was using the comparison between the two engines and their timing to illustrate a point. I'm guessing that one doesn't like more timing than 28* because it is near detonation, still yet inaudible. There's more going on than cylinder pressure. Temp in the chamber is the spark starter. Are your exhaust valves seating full contact and wide(r) than previous or interference angle and narrow? Same valve material as you've run? (Reg. steel rejects heat quicker). The two example engines have the same cam timing and stall speed? Are you running a consistent or low water temperature? This is why I don't attempt to push cylinder pressure curve limits with small cammed, low rpm engines. Everything around the engine and many other factors determine octane tolerance. I think I read here that Buick didn't like .025" in Nails for some reason...
Is a high dynamic compression ratio the concern in this case? One fix for too much compression is a bigger cam! Hey Dual Quadism, good to have another builder here! Looking forward to your cam testing results.
For the stroker engine, have you considered a thermo-coating the chambers? That should help get rid of hot spots in the chamber that can cause pre-ignition or detonation for a bit more octane tolerance. I have never considered it for that before but I think it may help? Wouldn't hurt to ask a place that does that kind of work. The idea for using the thermo-coating is to keep the heat more in the chamber when it fires for a bit more harder push. It also helps transfer less heat to the heads so a side effect would probably be a bit more octane tolerance? Not sure though, never thought about looking into this for that. But now that I'm thinking about it that might help with a future project I have been researching. Lets us know what you find out if you look into the above. GL
Possibly, and already mentioned Agreed. There's been little mention of so many specs, I'm only looking at symptoms described and offering what I see when daily driving them. This might be strip only and carefully controlled, don't know.
the 10.4 motor had a 230-235 @ .050 on a 109 LSA solid. just put in a new cam a few weeks ago a 236-240 @.050 on 109 LSA. solid.
I agree, 10.4:1 with an iron head is really pushing it, but your cam favors that so combo obviously works. You are probably detonating going over 28 degrees, but not much you can do about it other than maybe try a colder plug or worst case, put the thicker head gasket on it and drop it down to 10:1ish. Alum head will go 10:5-11:1 no problem with no det, for reference. 300sbb' post on coating the chambers is a good recommendation, also.
Do those cams close at the same degree? Even if not, at speed the bigger one could be building more cylinder pressure near peak torque. The question being, how does this engine with possible detonation compare at intake closing with the one you are contemplating raising compression .7? Now that you are at this point in the thought process, and thinking about things like plug temp and hopefully exhaust valve temp....
Have you calculated your dynamic compression based on this? Normally I consider that calc to be a crude starting point but in this case it appears more important because you have found a limit with timing to a similar engine (chamber). I feel like the conversation is going in circles, these things are normally planned out long before parts are chosen and machined, rather than the effects of such asked with varying opinions ensuing... Either way it goes, it's exciting to see another Nail go down the strip or highway.
