No cylinder pressure

I always have reservations about diagnosis I didn't perform..... the rough run would be from a cylinder or cylinders not producing.... the poor brake performance could (without benefit of looking for myself) be an effect of low manifold vacuum not offering enough assist for the power brakes.

BTW, when asking for assistance, a little information goes a long way to helping form a reliable assumption...

Jim Warman snipped-for-privacy@telusplanet.net

I'm also hesitant about giving a seat of the pants diagnosis:

But, no cylinder pressure. Low brake boost might be from low vacum. Sounds like an intake valve went bad or bent in cylinder 8 to cause the no compression, and low manifold vacum.

Refinish King

Refinish King opined in news:kw4bc.13594$ snipped-for-privacy@fe03.usenetserver.com:

I agree...probably bent intake; but if the shop was half worth it's salt, it would have TOLD you what the problem was.

Unless you got the diagnosis for nothing.

At least they could put air into the cylinder with that piston in firing position.. if it is a bent intake, it'd go into the manifold

From the original post, it's tough to say what the shop did in the way of diagnostics....... additionally, we don't know motor size, mileage ,general condition nor how much the OP was willing to pay for the diagnosis.

Doing the heads on a motor with mediocre ring seal will turn a car into a mosquito control device....

Too many unknowns to judge what the shop is worth and how the diagnosis was reached...

Jim Warman snipped-for-privacy@telusplanet.net

Alternatively:

A decent shop has what's called a: "Leak Down Tester"

Like I have, Which you bring the particular cylinder in question to TDC on the firing stroke, inject air with the leak down tester, and it will give you the percentage of air leaked pars the area leaking, and you can hear it from the exaust or manifold.

But I concut on the intake valve.

Mister Backyard Mechanic shoots, and he scores!

Refinish King

On the other hand:

If you have a reputation to protect, if you accept the job. Whether you took it on for free or as a paid job. If you do it half assed, you did it half assed. You have a responsability to your reputation and your customers, whether you took it as a pro bono or an hourly job to:

1: Do it to the best of your abilaties, and give a concise detailed report.

2: No matter if you get the job or not, look like the professional! At all costs, because there are too many hacks working at reputable places. Tarnishing the reputable technicians and making us all look like grease monkies that swim in grease pits.

I for one refuse to be stereotyped in that group!

3: By doing the above, who can question your candor?

Refinish King

news:kw4bc.13594$ snipped-for-privacy@fe03.usenetserver.com:

Thanks for the input guys and sorry for not providing more info. Always wished I spent my time learning cars instead of computers. Anyway, a little background. It's an all black automatic '93 LX 5.0 with some modifications. From the invoices of the previous owner it has: TFS heads, TFS track, TFS cam, TFS spacer, 3016 injectors, TFS 6.7 pushrods, FMS rockers, Walbro fuel pump, Accufab 70 w/ spacer, BBK cold air intake, Trickflow intake, and it has a neat looking FMS triangle brace over the engine. I believe the headers are BBK shorties and flowmaster mufflers. Like I said, i'm not a car guy so I'm not sure what all that means. The odometer reads around 70k. Inside, it is immaculate with only a few alterations: an autometer tach, and a B&M racing/ratchet shifter (which made me feel really stupid when i first drove it, because i couldn't figure the damned thing out). The exterior has a Cervini cobra R hood, Saleen wing, it's been lowered a couple inches i thinkg, and, as far as i can tell, has '96 cobra wheels. I have some pics up at

if you want to see it. Almosteverything is pristine, except for some of the hoses, which are dryrotting. The shop that I took it to gave me a paper with a chart that showed 0 compression on the 8th cylinder. They told me that it could just be a leaky header gasket or that the piston is damaged. I thought maybe it was the gasket because i had just changed that. Or i thought it was a vacuum leak because i had just replaced a hose because it broke from dryrotting, but i couldn't see any broken hoses. Anyway the shop wanted $600 just to replace the header gasket and "many times more than that" if it was a broken piston. That seemed a little shady to me. Should it even run with a busted piston? Wouldn't there be pinging? So I just took it home and have been trying to get someone that knows what they're doing to look at it. I think i've found someone, but i just have to get it towed to his place. He's charging me $250 + parts to fix.

Thanks again for the comments. Hopefully I'll get it working soon!

JD

JD opined in news:WvDbc.58$ snipped-for-privacy@news.uswest.net:

No reason you cant learn cars AND computers... it's not a decision of "either/or".

It's "head" gasket.

Do you mean YOU changed it.. or you meant you HAD it changed?

When was that and what do the guys that did it say?