fooling my small block

[stroker mike]

Will a tight lobe seperation compensate for the loss of velocity described when you put 340 2.02 heads on a 318?? Large runner/port volume reduces velocity in this combo but a cam on a 108 or a 107 will use the overlap to draw more mixture in, right? but close the intake cycle faster to keep up dynamic compression? Theoretically a tight LSA should balance that loss of velocity within reasonable parameters, right? I have the 318 with 340 J heads, 2.02/1.60 valves and I'm trying to pick a cam for my combo, I have a factory high stall converter, 2.75 first gear, and 3.55's. The cam I was looking at is an Isky 216/445 on a 108. My second choice is a crower #31918, with a 214/224 at 444/467 on a 112. The crower grind will slip in, which is a prerequisite for me at this time, and there is plenty of room for the isky, the only two issues I have are price and LSA. I have run small 50-75 shots of N02 before, but this is only for fun and not criteria. I want a nice lopey 108 sound, too, that's nice. But, people say that with the 108 nitrous is a no no. The true criteria for me is an optimal use of what I have to work with, and the final choice has come down to this, and I could use some more input from the ones who've been here. Thanks again! People tell me not to overthink it but I can't help it, I work too hard on my car, and to earn the parts I get so I hope noone is getting tired of my endless queries!

 

[flyfish]

Ahhh, Mike…Not again! That NO2 (nitrogen dioxide) is going to kill your motor. I think it was about a month ago (on moparchat) that I told you about how nitrogen dioxide along with water vapor will make nitric acid inside your motor…you need to switch that thing over to nitrous oxide(a.k.a. N2O)….well, its 3:30 in the morning and I’m getting slap happy…sorry folks...back on topic.

I can answer the last part of your question regarding the lobe separation and nitrous. Don’t worry about it. With that small of a shot you are totally fine. I have run my car with 180 shot for many years with no issues…and a MP 509 cam (with a 108° lobe separation). Good luck with your 318.8)

 

[BJR Racing]

Mike,
LSA being tight really doesn't have much to do with the port velocity, but by moving the intake centerline back to the 112 that you have stated then the overlap will decrease. Which the intake valve opens and closes eariler, and by opening eariler will pull more in the cylinder, and because of it also closing eariler that the cylinder pressure will increase. Helping make poor velocity heads better performers. But you also said that you wanted sound, or lope, but this will decrease as the centerline is moved back. But the torque and HP will be stronger in the lower ranges.
The best way to change this is to use 318/302 heads on the 318 and use the cam that you want as then you will have port velocity and lope. Large port heads kill the sound of a engine unless there's a large cam installed, just as small port heads amplify the sound.
For example, my 404 ci big block engine with a .480 cam and 184 cc heads rumbled like it had a big cam in it and it was only 230 @ .050 and it had stock size valves in it. Then I put a 402 ci engine in and it had 213 cc heads and a 240 @ .050 cam with stock size valves and the sound was almost stock tame sounding even with 10* more duration @ .050 and less CI's.
The port velocity wasn't as good in the 213 heads as it was in the 184 heads and the response wasn't as good either, even though the 402 engine made more peak HP it lost TQ and I have to turn it harder. Hope this helps.

 

[340mopar]

flyfish, I think NO2 is a typo, I believe he means N2O


Chuck

 

[stroker mike]

I joked about being dyslexic on the bottle, looks like I'm the one that's slap happy!!LOLOL!! N02, N20, I think my brain is formally protesting all this cam research I've been doing, and I still haven't made a decision!! G'nite guys, I'm for some sleep!!

 

[flyfish]

flyfish, I think NO2 is a typo, I believe he means N2O


Chuck

I was just missing with Stroker Mike from a previous post where he had a typo on the nitrous oxide chemical formula…..yup, I’m that much of a dork that I notice these things…Oh well.:-D:-D:toothy10: