Breaking up

I guarantee it was floating the valves, not to the point of breaking up, just not making the power ot should have. I ran a 224 cam with the same style lobes with a set of springs with 350lbs open. Took it to 6200 with no issues. The car didnt pick up much power with more boost, and when i pulled the heads apart, the valve stems were mushroomed at the keepers from float. I run the same cam, but with 600lbs open to 7000rpm now, making over 1000hp. I dont think your breaking up problem is valve spring related, but i bet it is still getting valve float.
 
TT/Ameasap said:
The old combo had 1.6 rockers and same cam with 941's. I could go to 5800-6000RPM Anything after that was valve float, but the car ran great at 5800.
Click to expand...
Same here same cam with 1.55 rockers 941 springs, ported irons and could hit 6k rpm no problem. swapped to ta heads and went to 1.65 rockers and it doesnt want to rev. One number up on ratio typically means 20 to 30% increase needed on spring psi.
 
I tried new plugs and it still breaks up at 5200RPM in 2nd gear. BTW my AFR is 12.5-13.0 in that range, so with no boost introduced, im good with that reading with E85. I checked the cam sensor cap for wear and the shaft for play. That all seems good too.
Could the spring pressures decreased in the short time that I had the car running good?
Im really leaning towards the springs now. I went from 1.77/1.5 to 1.94/1.6 valves and 1.65 RR from the old combo.
 
Do you have the near zero travel hydraulic lifters like the comp 885's?
 
That is an aggressive lobe cam. It needs a real spring. I would be running the travel limited lifters too.
 
Yeah word on the street is that the 853's might not be able to keep up with an aggressive valvetrane setup
 
But they kept up before. I even marked them so they stayed in the same bores when I did the head swap.
Here is me floating the valves at the track at 6200RPM in 2nd and letting off. ... I have no rev limit. (Old combo) car was only trapping 125.

 
I chased the same problem you are having with GN1 heads with a stroker cam 224 545 lift cam from FT and done everything in the book trying to fix the breaking up at boost about 5200 rpms at 17 lbs of boost , springs big and beehive and conventional springs nothing worked, I had to go to a smaller lift cam and pac 1201 valve springs and used the same Morel lifters and my trouble was over , turn it 6300 if I want to and 25 lbs of boost with alky . You have too big and aggressive cam for your heads and valves , I have come to conclusion smaller is better and faster when it comes to a Turbo Buick engine , hope you get it straightened out Just my 2 cents .
 
I have a 224 roller from RPE with 540 lift, springs specd by him. I can shift at 6700 and pull clean ....I too think that the cam is too big for my engine but it idles very well.

Bryan
 
Bo, have you tried to swap your TPS? Maybe a dead spot that your not noticing on low RPM.
 
I checked it a while back, but I can check it in the morning. I would die if that was it....lol
 
The only reason I'm thinking something simple is because it changed, and wasn't doing it before. The simple things are usually the culprit on these cars but they like to drive us crazy!
 
TT/Ameasap said:
But they kept up before.
Click to expand...

The gurus were telling me that when the open valve spring pressures start to get much past 410-430lb, it's time to start looking at the 885's instead of the 853's. If your gonna end up over 450lb with new springs you'll probably need the hot rod lifters too.
 
Fwiw worth i changed from TA 1125 springs to 1160 (same outer spring just a stronger inner) and gained 600 ish rpm before it would break up at 5200ish and after spring it does it now at 5800. So a stronger spring helped but still think it needs more. Iirc you cant use a 1.50 od spring as it will hit the t&d rocker arms and a 1.385 od was it.
 
Last edited:
Im thinking if I can reduce the rocker ratio to 1.55, that should move me up considerably. If that gets me close, I can always shim the springs a little to get me where I want to be. Im hoping this will avoid new lifters, springs, retainers,push rods,ect.
 
Considered that as well but the cost of 12 new rockers will be more money than all the springs and such. A real pisser that the heads arent assembled with the right springs when the cam specs are given.
 
You must log in or register to reply here.

Similar threads

T
No start no spark no inj pulse
Replies
3
Views
264
BEATAV8
BEATAV8
S
can't get past 5psi
Replies
18
Views
1K
shmed
S
H
GREMLIN CONTINUES TO BE PRESENT MAKING DRIVING UNSAFE
Replies
15
Views
580
MikeS
M
G
High BLM
Replies
7
Views
1K
GNVAIR
G
C
TR6 problem.
Replies
3
Views
679
Clark6
C
Top