Loss of power between 4.2k and 4.5krpm

[Mudderoy]

1995 block/head in my 1998. .060 over with Crane Cam. I was warned that the stock valve springs might not be strong enough but in the majority of cases, they were just fine. I suspect my old (but verified good) springs don't have the umph necessary.

Accelerates fine up to 4.2k then slower until 4.5k rpm then takes off again.

I am seeing "online" that some people are using the Mopar dcc-5249464. I'm losing oil through the valve seals so if I'm going to replace those I might as well do the valve springs even if it doesn't resolve this strange loss of power issue.

Has anyone used these Mopar springs on a 4.0?

http://static.summitracing.com/global/images/prod/mediumlarge/dcc-5249464_w_ml.jpg

:link: (http://www.summitracing.com/parts/dcc-5249464)

[xj-jake]

I don't have any experience with these but... If I remember correctly guys that are or were building sbc's were using the valve springs out of the Z28 motors which had the same design as the ones you are showing here. They were stiffer which kept from floating valves etc. It was popular with the race car guys around here. Maybe someone with better knowledge can chime in but this is what I recall.

[abebehrmann]

Man, I rarely even rev over 3k! And that's only when I'm in a hurry. (Insert grandpa joke here)

[Pookapotamus]

Hi Muddy!

Not too sure if your springs are the issue, my stroker reves like crazy from 0 to red line, and I am sure Jenssen's does the same, not sure what springs he is running and I am running Harley springs in mine.

What is your fuel pressure at the rail when this happens? What injectors are you running? what intake? Throttle body?

And here is a tough one? what is your quench? Did you have the head decked? Are you running premium?

The spring being soft would mean that at even higher rpm the would continue to fail, not regain after 4500 your problem must be something else? Unless I am talking out my bum!

Give us some more information!

Pook

[4.3LXJ]

I agree with that Pook. I think it is something besides valve springs. I lean towards a computer programming problem personally.

[Pookapotamus]

Dare I say cause its red?:rolleye0012:

[4.3LXJ]

Dare I say cause its red?:rolleye0012:

Might be on to something there Pook. Maybe we should get the paint gun out :smiley-taunt002:

[XJ Wheeler]

Going with Pooks info you might wanna check out your A/F ratio during this range on that torque app you have running.

Sent via messenger pigeon - i talk, he types.