Why so much inital timing???
I actually live here in California, I know what the gas quality is, so please already..
That was a common rule of thumb I repeated when in reality if you're going with after market heads and let say even a roller...you wouldn't give up cylinder pressure if you were bright.
I read your posts and all ill say is...you like to argue for sake of arguing.
His cylinder pressure is low, that's why he can crank up the timing...and you know it.
He's not giving up anything. 8:1 DCR on a street motor with iron heads is good. Even you said you should aim for 8:1 - 8.5:1. Then you find out you're wrong, his DCR isn't in the shiter and he's at 8:1 and you keep arguing? Who likes to argue for the sake of arguing now? Can he run more DCR? Yes. I said that from the start. Is it worth it? No. What will he gain from .5 DCR? Maybe 5 horse. What does he risk? Detonation. Timing issues. Tune issues. Gas issues. Etc etc etc.
His build is obviously a well thought out build. With time and attention to detail. Does it squeeze out every last horse? No. Will it run every day for a long time? Yes.
And if you took me right, that's all I was saying...it could be better but its fine if you like it. But that is the answer to your question, lower than ideal dynamic compression imo.
I thought you said ideal DCR was 8:1-8.5:1. He's at 8:1. So its not lower than ideal in your own opinion.
If you're so smart...why in the hell are you asking a question you should already know the answer to...lmao
If you're so smart why can't you get 3 replies into one post? lmao
Most calculators use the IVC-at-the-seat, but I see 1 or 2 use 15* beyond the .050" angle on the intake closure cycle. The latter will estimate an 'effective' IVC that is 5 to 10 degrees earlier than actual IVC-at-the-seat (which is a smaller ABDC number), and will give you a higher DCR computation.
The 15* addition is an ok way to guess. But generally the smaller cams (under 220duration) will be more 12*-13* where as bigger cams (over 250/260) will probably be in the 18*-20* range. So you can see, for 8 out of 10 street motors, guessing 15* will get you close. That's why I much prefer getting the actual IVC at seat, for best accuracy. The power is in the details on engines.
Thats the point at which I get the highest vacuum reading in gear at idle. It's also around where the RPMs stop increasing when adding timing. Also, it seems to fire up and idle a lot faster at that point, than say the 20* where I had it before when I was messing around with it, with better throttle response too. Am I off base? Thanks for the input btw. Didn't mean to start a **** storm. Just never had an engine that seemed to 'want' this much initial before. I runs great though, with no hiccups. Once I finish tuning a couple different carbs I have for it, I'll be taking it out to the track for some testing.
That's a good way to go about it. Generally add timing to get best vacuum/rpm. Then shut it off for 20, try and start. If it starts no problem. Get it up to operating temp. Then shut it off for 10, try and start. If it starts no problem, get it up to operating temp. Then **** it off for 5. If it starts no problem. That's where it should be.
Ideally, you would be able to take it to a dyno and figure it out. Best vacuum/rpm should also be best horsepower. But you don't know unless you dyno it. I will say this. If you play around with the timing. You will find an initial that it just runs awesome at. I remember with my car when I first got it I was tuning and I played with it, brought it up from 18-22. It was night and day. Throttle response was much more immediate. It barked a lot harder. And just absolutely wanted to run hard. It was the definition of scalded dog. If you looked at the pedal it would squawk the tires. You can and will notice the difference in better initial timing.
