Trouble with a blown GM 1600 twincam
 

Hello guys. I'm a noob from the UK, I've been an observer of the site for a few years.
I run a european variant of a GM engine known here as a C16XE. I have a specific cast manifold & garrett T25 charger. I got it running on the std management (Bosch ECU) with a decompression spacer between the HG & raised fuel pressure from a rising rate reg.

After a run to a show weekend this weekend, I experienced some probs on the highway coming home. Due to not knowing much about setting up new turbo installations I was taking it steady & not allowing much,if any prolonged boost. Due to needing more vac sources under the hood, I didnt run a gauge but suffice to say, I experienced a judder whilst ascending a section of highway at approx 70mph & backed off. Cresting the hill I coasted down & things didnt feel good. I came off at the exit & coasted into a residential area & she stalled. I got it running after it cooled slightly & got home on minor roads, down on power & very gently.

heres the run down.

Now idling high (1550 rpm)
No oil on plug tips
No smoke from exhaust
Coolant OK & not contaminated
Doesnt appear to be breathing heavily

Power output is still very low & engine splutters & is hesitant. Please help me diagnose what I have done & maybe what setup functions I can carry out in future. My BLOX vac manifold & manual boost controller have now arrived...

Thanks for reading my long post.

It really sounds like you blew off a vacuum line somewhere after the throttle plate. Go through all of the vacuum lines, make sure they are not cracked, and are properly connected to where they need to go.

Cheers. I'm hoping it's nothing major. That gives me hope.

I got a buddy stopping by in a moment to help me have a look & do a comp test. I'll post up the results.

Well my mate seemed to think there was no need for a comp test after hearing it start. He was right.

We found the air filter & AFM pretty soaked (its a under a hood louvre), A lengthy rocker breather kinked & holding some oil (engine has been sitting) & a sticky idle valve.
It wasnt spluttering at all & after some fettling we had it pulling quite nicely & feeling normal again. We looked for any leaks around the inlet & boost pipes but spraying brake cleaner whilst it idled didnt highlight anything, but I reckon I can hear another noise above the spooling/whoosh from the turbo. Like a distant whine of air being sucked in, so the inlet & TB etc is all coming off to be checked & sealed back down after a thorough clean up.

I need a decent fuel press reg if anyone wants to mention what kinda thing I can use that is decent & dependable. My current one isnt giving me the pressure I want 3.5 bar, but adjustment from one end to other barely moves it from 4 bar to 5.

Just a couple pics so anyone interested can see my car.

Attachment 8060

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nice car
what year is that?

Glad you got it working better! So often it's the minor things that cause the issues. But be aware, if they happened once, and you didn't redesign what failed, it'll happen again.

Unfortunately, leaks on charge piping are difficult to find. You won't find them under vacuum, as the pipes have suction, so it actually sucks the hoses down tighter. The best way I know of doing it is to rig an air compressor fitting into the system somehow, and put about double your normal boost level into it. The pipes should hold without a problem, and if not, they need to be fixed! There are many ways of fixing them, you can use better flexible tubing (4-ply silicone is what I use), you can use T-bolt clamps, and in addition you can put a bead on the end of the hard pipe. Together, these will alleviate any problems you have! But at a price....

You've got a VERY clean car!!! It looks good too, it's got very tasteful modifications done. Just enough to look sporty, not enough to look overdone. I like it.

thats a sweet car..

Thanks for the comments guys. The car is a Vauxhall Nova (not to be confused with your Chevy Nova LOL) It's a 1990 model year. They were very popular in the mid 90's over here & are possibly one of the UK's most modded hot-hatches. Now they are mainly owned by enthusiasts like me as in most peoples eys they are old & unrefined.

Me & my mechanic pal tinkered with a few things on it this afternoon, got the FPR working properly (stripped it down), cleaned out the idle valve etc & it is running far better than it was before the weekends mishap. Much better!