Question about SBF 302 with stock cam

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Guessing the cam doesn't have enough lift or duration to support the bigger heads etc. Or the springs are week and you start getting valve float at high RPM.
Check your springs and get a cam to match. Then degree it. After that's done, get the EFI flashed for your combination and you will be pleased with the results.

Hard to say. Id guess valve float. The spring specs on the QCH website don't really make any sense so i don't trust them. They're claiming 335lbs at .600 which would be beyond coil bind.

Seeing your MAF air mass drop quickly an is all jagged leads me to think its valve float.

If youre running out of head or intake it will round off a bit smoother. Heres a log from my car, my sample rate doesnt look to be as fast as yours but you can still get the idea.

EDIT: i do remember having maf clipping/pegging problems with a similar MAF as yours. Ill see if i can dig up a log from that.

Model A guy said:

Guessing the cam doesn't have enough lift or duration to support the bigger heads etc. Or the springs are week and you start getting valve float at high RPM.
Check your springs and get a cam to match. Then degree it. After that's done, get the EFI flashed for your combination and you will be pleased with the results.

Click to expand...

Krem12 said:

Hard to say. Id guess valve float. The spring specs on the QCH website don't really make any sense so i don't trust them. They're claiming 335lbs at .600 which would be beyond coil bind.
View attachment 787041

Seeing your MAF air mass drop quickly an is all jagged leads me to think its valve float.

If youre running out of head or intake it will round off a bit smoother. Heres a log from my car, my sample rate doesnt look to be as fast as yours but you can still get the idea.
View attachment 787042




EDIT: i do remember having maf clipping/pegging problems with a similar MAF as yours. Ill see if i can dig up a log from that.

Click to expand...

I was delighted with the information from this resource. 400 HP With A Stock Cam! - MotorTrend
I was sure that I could get at least 300-350 hp on the crankshaft. In addition, I did not want to lose torque at low rpm.
Thanks for the suggestions to check the valve springs, maybe some are really poor quality. I need time to test this hypothesis.

If the valve springs will a satisfactory condition, then I will consider using 1.7 rocker for the exhaust valve or both. The Intake valve 2.02 has a high probability of contact with the piston.

Im running a stock bottom end (including Cam) E7 heads, 1.6 roller rockers, dual plane, holley 600, shorty headers and 2.5 exhaust out the back (no cats). Last time It was dynod it had 225hp at the rear wheels that could translate to about 250 +- at the crank. side note, needed two valve cover gaskets stacked to clear the rockerarms with my cast aluminum covers.
Not bad considering. It matters more how everything works together.
Your goal is well attainable with the items you describe!

Hello again! In continios....
I analyzed log files, and I found the next moment (see pic.)
After 5k rpm MAT temp going to the moon . It's mean that intake valve spring can't close, and combustion prossed go out to intake.
The MAT sensor was installed in lower intake runner's way before fuel injector.

VizorSRF said:

Hello again! In continios....
I analyzed log files, and I found the next moment (see pic.)
After 5k rpm MAT temp going to the moon . It's mean that intake valve spring can't close, and combustion prossed go out to intake.
The MAT sensor was installed in lower intake runner's way before fuel injector.
View attachment 787217 View attachment 787218

Click to expand...

Thats what we call bad Valve Float. Stronger springs should show a big improvement!!

Some news available for you I found many mistakes at my engine combination. But I am not sure in my conclusions.
Mistake 1. My cylinder heads was assemble for use Hydraulic Flat Tappet Camshaft. My engine has Hydraulic roller Camshaft. It's mean that valve spring in heads is not strong as need for me. I measured [email protected]" and [email protected]" and only 229lb on 0.444 lifting for my stock cam. Finally the valve height: Standard + .100, but I need + .200 You will see it below...



Mistake 2. I bought Magnum Rocker arms https://www.summitracing.com/parts/cca-1431-16 with designed as left rocker at picture.

Notes: Not designed for use with guideplates. For use on models with rail type rocker arms. I dont know why I installed https://www.summitracing.com/parts/cca-4816-8
This rockers has contact to Spring Retainers on the work. My solution by grinding machine was not good or not enough.


Mistake 3. I not checked right position of contact roller tip to valve. My push rod leight was 6.25" see pic below, but after checking I resolved to use 6.0" leight at the future.


What do you think about it?

P.S Do i need to buy new valve spring or I can just install valve spring shims +0.16" for make more seat and opening pressure?
Push rod need new 100%

Hello!
New parts arrived to my garage



May be I will try to order 1.7R arms.