mrtstang

Well i'll definitely let you all know after i hit the track. BTW, what rpm do you shift at?

nickmckinney

Glad to hear its running good.

Most engine builder's freak when I say 0.035" is fine for these motors, sounds like these didn't even meet that spec on your motor. Imagine more duration or advance.

If it was up to me all PI NA motors would get a 233/230 cam with 108LSA and advanced to a 106 intake centerline. Thats about the best performance spec for a plastic intake PI head motor IMHO but requires a piston notch.

Bill Putnam ran the fastest stock longblock and cams time of 11.9 with a gutted car and VT Stage 1 cams which have specs nearly identical to these. He found shifting at 6800RPM made the best times so you should definitely look to shift higher than 6000. Its not how far after the peak, its the area under the curve for the gear shift that is important.

Keep us updated with the new track times and get that thing to rev out already.

nickmckinney

Nuthin but love bro

BTW - best dyno story I have is Ed Justin (yellow02GT)

He lost power EVERYWHERE after swapping cams I speced, same dyno he always used, has like 50 runs on it.

He gained nearly 2MPH at the track.....................

Next best is a NMRA guy I did the motor for: one dyno shows 260RWHP, another shows 300RWHP, car weight and times shows 280RWHP average according to my calculations.

Dyno "numbers" are BS in my book, all dyno graphs should come with a + or - 10% tolerance rating on the printout. Yet people get all wacked out over 5 HP on a 300HP graph. Take it to the track and see what it does.

mrtstang

I'll definitely keep you updated Nick. I don't think i'll go as high as 6800 with the stock springs (that just scares me a little lol) but i'll try 6300-6500 and see what happens.

WannaBeGearHead

Go 6800. A little valve float never hurt

lizzyfan

Try shifting where your powerband meets at first
Usually 5500-5800

tbirdscwd

Well 6800 is a little out of the range of realistic with your mods since you probably don't make **** for power at that point. Not to mention a stock bottom end is gonna be screaming for mercy. Valve springs aside there is absolutely no point in shifting that high with your setup. Your power probably drops off no later than 6400 and probably starts leveling off way before that with a stage 2 N/A cam

I shift right around 6k even though I continue to make power well past that point. The perfect shift is a compromise of shifting as close to peak power as possible and ending up as close to peak torque as possible in the next gear. Even if you make decent power til 6200 it may not net the best results by shifting that high.

edit: do you have a dyno graph you can post for us? I know numbers don't really mean much but it would be nice to see where you are making peak power and torque. BTW, you should be trapping at least 107-108 with your setup if those cams are as good as everyone says they are.

mrtstang

I do have a graph, but i don't have a scanner to put it up. Basically, they peak at 5500. My tuner only took the car to about 5800. Up until that point there was no drop in power at all.

I used to get my best results with stock cams shifting at 5800-5900 (old peak used to be around 5000-5200) so i'm thinking around 6200-6300 would be a decent guesstimate. I guess i'll need to play around a bit and see what works best.

nickmckinney

Taking it up to only 5800 is a problem. NMRA rules motors running near 8000 RPM on the stock plastic intake will still peak in the 6000 range, its not the peak that matters but how fast does the power fall off after the peak. If you are still making within a few percentage of a 5500 peak at 5800RPM for example your shift point is going to be well above 6000 and the car needs to be tested up there. Valve float is very evident on the dyno, and to be honest I have not seen valve float with the stock springs and cams bigger than these even at 7000RPM NA.

Usually plastic intake NA motors have torque peaks around 4000RPM so to shift and have the next gear come in around peak torque the shift point is going to be up there. Try www.4lo.com for a good RPM calculator for shifts.

tbirdscwd

Thats a very good point Nick about power drop off after peak. Although I'm willing to bet his power drops off well before 6800. I'll have to try shifting higher the next time I go to the track. My power peaks at around 5600 na, but it stays basically level at that point til about 6450.

edit: my peak torque comes in at around 4500rpm, but I make damn close to the same amount as peak all the way down to about 3800. For me to hit peak torque on my shifts I would have to shift around 7000, which is why I why I was saying "as close as possible." Shifting past peak power is fine if it gets you closer to your peak torque in the next gear as long as you aren't dragging out the rpms past the point where your power drops off.