RPM upper limit(max hp)any help?

[MikeZcar]

No access(or money)for dyno, 280zx turbo block, bottom end balanced and blueprinted, ported and polished E31, .475/280 cam big springs and valves, jetted etc SUs, MSD 6AL, looking to put in the Rev limiter chip, anyone with similar motor have a suggestion on RPM limit? It's in my '70 Z with a 3.90 R200 Don't need to completey max it out. Thoughts, suggestions? Mike (PS runs like a scalded dog)

[zguitar71]

I would go to around 7200. I do not think you get much out of the SU's past that. Your cam probably makes power to that range too.

[jmortensen]

I had basically that same build with a .490/290 cam and I could get to 7200 but it wasn't pulling real hard when it got there. I agree you should set your limiter there but you'll probably be losing time if you are shifting that high with SU's.

[boostedz]

With you still using stock style SU's I would think that you would want to lower yoru shift point, I really like the rest dont think you would be getting much power past 6500 rpms. Id say set it at 7k to be safe.

[jackboxxx]

No access(or money)for dyno, 280zx turbo block, bottom end balanced and blueprinted, ported and polished E31, .475/280 cam big springs and valves, jetted etc SUs, MSD 6AL, looking to put in the Rev limiter chip, anyone with similar motor have a suggestion on RPM limit? It's in my '70 Z with a 3.90 R200 Don't need to completey max it out. Thoughts, suggestions? Mike (PS runs like a scalded dog)

They are pretty much right on the money..with that setup. I wouldnt go past 7200rpm maybe keep it a bit lower like 7k. Mines been dynoed up to 7250rpm but my HP peaks out around 6200rpm @ 289hp / 245torq , but by 7200 it drops down to 263hp / 192torq.

Are your SU's bored out at all?

What header /exhaust setup are you going to be running?

JacK

[MikeZcar]

SM needles, all edges cut down to radius including front lip on floating piston in carb throat, throttle bars(butterfly holders)cut down to maximize flow, running Motosport Auto Jet Hot Coated 6 into 2 headers(disappointed in the amount of rust on these in such a short amount of runtime, boo hiss), carbs have individual K & N filters but I want to go back to stock set up(trade someone?) Mike

[gnosez]

I too suggest the 6500 limit. With both my 3.0 and now 3.2L engines anything over 6500 was just wasting gas and time. You need to be shifting well ahead of 6500. But of course it all comes down to your specific set-up. My engines were built to made power between 3200 and 6000rpm and for road courses, not 1/4 mile straights.

[jmortensen]

Sometimes you need to get that extra little bit at the end of the straightaway. If you set your limiter at 6500 you won't be able to continue accelerating once you hit the limiter. If you set it to the max safe piston speed then you can wring it out and there is no disadvantage. Shift points can be determined independently of the rev limiter.

[thehelix112]

MikeZCar,

Can you give us the proper specs on the cam, advertised duration is about as useful as clothes for women. What is 0.05" duration?

Dave

[gnosez]

You are quite correct to point out that a rev limiter set at 6500rpm would not be helpful in getting that last little bit on a long straightaway. I use a 7000 limiter on my MSD box but ratherly ever take the engine over 6500 because I'm not making any more power after 6400rpm.. It sounds great but in reality it's just that, noise.

[Ed]

Motosport Auto Jet Hot Coated 6 into 2 headers(disappointed in the amount of rust on these in such a short amount of runtime, boo hiss)

Jet Hot has a warranty on the headers against rust. I'm not sure on the time limit (it's been a while since I went through this). I think that if it's within 1 year they will recoat the headers no charge. You only pay for shipping. After the year they cover 50% of the recoating charges.

[SER240Z]

Jet Hot has a warranty on the headers against rust. I'm not sure on the time limit (it's been a while since I went through this). I think that if it's within 1 year they will recoat the headers no charge. You only pay for shipping. After the year they cover 50% of the recoating charges.

You might want to check on when you bought the header though, I know that at some point MSA stopped using Jet Hot and started using a comparable company due to cost.

Scott