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Lacking performence after installing new 531 head

V

VolvOrr

New member
Joined
Aug 1, 2020
Dear turbobrickers

Last week I installed a 531+vx3 instead of 530+T cam on my b200ft AW71 240.
The head was complicity re done and I used new gaskets everywhere.
When the old head was removed I checked that when in TDC that all the marks on the pulleys
are correct and that the rotor on the distributor is in the right place.
I checked that there is no vacuum leaks and that my turbo compressor wheel spins freely.

I think that the engine doesn't produce enough vacuum, it's between minus 10-13 psi when in neutral and with no AC or anything like that, when putting it in drive vacuum goes to around minus 9-10 psi.
The car runs like crap below 3500 rpm.
I mean really bad, way worse than a NA b200 to the point that when I press the gas pedal
the car doesn't want to accelerate, even when the turbo push 5-6 psi the car is still really slow.
Before I changed the heads the engine felt quite agile on low-mid rpm.
Another weird thing that happened is that when I unplugged the MAF and tried to start the engine it started fine, but when giving it a little bit of gas it turned off.

Any idea what can I do to fix the problem?
Cheers!
 
Might also want to do a leak down test and make sure the valves aren’t too tight allowing a vacuum leak into a/the cylinder(s).
 
Did you adjust the shims, or was the shop supposed to do it?

You can check with the valve cover off, or do a compression test if you have a compression gauge. For checking shim clearance, if valve hushers were installed, you need to push down firmly (by hand) on the shim&bucket to get the feeler gauges in.
 
Things to check:
1. Vacuum leaks. Are all of the caps/plugs/hoses hooked up on the intake manifold? Is the MAF to TB plumbing leak free and connected properly?

2. Check cam timing, verify that TDC on the crank pulley is actually TDC with piston #1 at the very top of the stroke.

3. Compression check or leak down. This will tell you if there's an issue with the head (leaking valves, valve lash, etc)
 
I checked 10 times that the engine is in TDC and that all of the timing gears are in the right place.
Today me and my mechanic also did a compression test. we think that his compression gauge reads too low, it showed 95 psi on all 4 pistons
but when we added oil to one of the cylinders and did it again it didn't jump too much, and on a different 240 with a NA engine it showed similar results.
I checked also for vacuum leaks by spraying carb cleaner on every spot it might leak, and we didn't find any leaks.
We checked fuel pressure and it was good, 3.44 bar on ideal.

I advanced the cam gear 1 tooth forward and it made things better at low/mid rpm.
but still not as good as before the swap.
 
VolvOrr said:
I checked 10 times that the engine is in TDC and that all of the timing gears are in the right place.
Today me and my mechanic also did a compression test. we think that his compression gauge reads too low, it showed 95 psi on all 4 pistons
Click to expand...

I think that's your problem. Was that pressure reading done with the throttle wide open?
Cranking pressure should be around 140-160psi ob a b230f, not sure on a b200ft though.
 
Yes, we did the test with wide open throttle.
I need to check the compression with a different gauge though.
Because this gauge gave very low results on another engine too.
And my engine doesn't show signs of a low compression engine

About valve clearence, the head was done by a shop, and the guy who did it said that he set up thr valve clearence to 0.35mm and that they looked in good shape
 
Try a leak down test instead of a compression test. You’ll be able to hear the air escaping past a valve, or possibly into the crankcase as excessive blow by. My guess though, is that the valves are too tight. Or, possibly the combustion chamber is that much larger on a 531 head vs a b200 head.
 
For every 10 thou the head is milled down, the slack in the timing belt causes approx 1 degree cam retard. Maybe that head has been skimmed a lot. You would have to measure the head height to know.
 
So after a few days of driving the car my main problem is that it's really slow at low RPM.
It's worse at start before warming up, I get zero torque and if I go WOT from a stop, the car boggs and even when the boost start rising to 5-6 psi at 2500RPM in first gear it's still not accelerating like it should.
At 3500RPM and above the car pulls strong but its barely drivable before that.
I use premium gas and I checked that when in TDC everything is in the right place.
Also, yesterday the car started only after some stubbornness when turning the key, took longer than usual to start the engine.
It looks like spark timing is really retarded, what can I do about it?
 
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not sure if cheating or not, but I installed an adjustable cam gear today and advanced the cam and it helped with low end acceleration.
And I'm getting around 15 psi of vacuum when there is no load (in neutral and no AC).
I also changed the FPR to an adjustable one, and set it to 3 bar when in idle and when the vacuum hose is not connected to the regulator.
 
We may be talking about a case of over-camming here. Combining that with reduced compression ratio from the larger chamber of the 531 head and it's a double-whammy. If you've checked all the obvious stuff and it's ok, put the T cam back in and see what happens.

Many years ago I had an '80 Malibu with a 283, way too much cam, and nowhere near enough compression. It was TERRIBLE up to about 3000 rpm, then it came on like crazy (in a relative sense). Dicked with it for a few years trying to make it work before I finally took cam out of it and swapped on a set of stock 283 heads (much smaller chambers). Idle vacuum went from 11 in to 17, and it was way more tractable, even with less gearing.

I don't know why these cam/compression mismatches tend to come on at about 3000. Maybe somebody around here does.
 
I've been having similar issues with mine after installing an iPd turbo cam along with an NA 530 head that was recently resurfaced. The odd thing is the car had already started feeling sluggish before I swapped the head and cam, but I'm not sure if that's related at this point.
I ordered an adjustable cam gear from STS machining last week and I'm going to see if that fixes the lack of power under 3000 RPM. It moves like it's in 4th gear from a stop, then the power seems to just switch on after 3k.
 
The 531 isn't good for low grunge.
This head perfomance is at high revs.

The better choose below 3500 is a 530.

The combustion volume of a 531 is more than of a 530.
VX3 cam is a screamer one.
Your combination: 2.0 + 531 + VX3 is only made for high boost AND high revs.


Good luck, Kay
 
I can verify that 530 is good to the 3500 rpm. Long before 3500 rpm, i like to put next gear. These b200 blocks seems to have good torque at low engine speeds, which is something that i like. Long time ago when my Volvo was my daily-driven car, i remember that with heavy trailer i used to drive long hills with 3000rpms, around 3000rpms these engines feels really strong. Not so many hp, but good torque at low speeds.
 
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