what causes a bent valve? friend thinks i might have one

91foxbodygt · Apr 30, 2008

My car has been a neverending problem, anyways.
had my engine rebuilt, gt40p heads resurfaced, new springs installed
turned on the car
well, it fouls the plugs within 2 minutes.
changed the plugs, timed the car, it made a loud ping, like something hit metal with metal?
the car doesnt stay on after that, it surges then dies unless throttle is pressed
when its driven, it feels like it has power, before it was timed with the gun it felt weak, however there has always been a miss
need some advice guys, thanks

BlownFiveLiter · Apr 30, 2008

You'd need to have some piston-to-valve contact in order to bend a valve. What cam are you running in your car? The Stage 1 listed in your signature? That cam shouldn't be enough to create any clearance issues, if you're running 1.6 rockers. The TFS1 cam can be known to cause some surging issues on some cars, so it may be worthwhile to run down the Surging Idle Checklist in the sticky thread here in 5.0 Tech, to see if you can nail down an issue. What kinda fuel system are you running? Stock injectors & pump? How's your fuel pressure? Any codes stored?

91foxbodygt · Apr 30, 2008

new stock fuel pump, new fuel filter, tfs stage 1, 98 explorer injectors. car was parked for about 3 years, we took most of the old fuel out and added 5 gallons of 93 octane
we swapped stock fprs just to see if the fpr was the problem too, but it wasnt

would really bad timing cause the piston to hit the valve?????

91foxbodygt · Apr 30, 2008

by the way, anyone know what the loud ping could be? my friend said the loud ping was detonation.

Blandnuts · Apr 30, 2008

A leakdown or compresson test would be a good idea.

91foxbodygt · Apr 30, 2008

just bought the leakdown tester today, the compression test measured 150 for all cylinders

Blandnuts · Apr 30, 2008

Well, the bent valve theory seems to be dwindling with 150 for all cylinders. What do the plugs look like?

BlownFiveLiter · Apr 30, 2008

It could very well have been detonation that caused the sound. Minor pinging sounds like marbles in a jar, but a large detonation is going to be clearly audible. Did it backfire through the intake tract at all? That can, and does do some damage to electrical components (IAC, IAT, TPS, MAF come to mind), which could also give you some headaches. If you had a bad enough detonation, you should check your plugs and plug gaps for any sign of damage, too. It's not uncommon to break the porcelain with a severe detonation, or have the plug gap change considerably.

rockytoohot · Apr 30, 2008

It is possible your balancer has spun and therefore your timing will be out. I have seen them spin slightly so you can still set timing although it will be way out.

91foxbodygt · Apr 30, 2008

the plugs are completely black, they were replaced after the big bang but turned black again within a couple minutes. ill replace some of the electrical components with anything i have laying around asap

BlownFiveLiter · Apr 30, 2008

I wouldn't replace any of it without checking its condition. Pulling codes will give you a good start, but you can also ohm out the IAT/ACT and see if it's still within spec. Here's a chart that shows the ohms for a given temperature:

BYRDPE · Apr 30, 2008

Sounds like a timing issue to me. I would bring #1 up to TDC by using the finger in hole method.
I had some of the same symptoms when I did my H/C/I swap. It'll crank but run like crap.

Lunch Box · May 1, 2008

91foxbodygt said:
My car has been a neverending problem, anyways.
had my engine rebuilt, gt40p heads resurfaced, new springs installed
turned on the car
well, it fouls the plugs within 2 minutes.
changed the plugs, timed the car, it made a loud ping, like something hit metal with metal?
the car doesnt stay on after that, it surges then dies unless throttle is pressed
when its driven, it feels like it has power, before it was timed with the gun it felt weak, however there has always been a miss
need some advice guys, thanks

piston rings might be shot time for a rebuilt of the bottem end

1991vert · May 1, 2008

i'd also check the timing...

89lxcoupe · May 1, 2008

is your o2 sensors pluged up and working ! if they are not our plugs will turn black..... or if your iat sensor in the #5 intake runner is bad they will turn black !

91foxbodygt · May 1, 2008

the o2s are connected but they are the originals, more than 200k miles old.
ill check the ohm reading on the IAT sensor to see if its any good tomorrow

mkk50 · May 1, 2008

Could it be from the injectors from the 98 explorer? Just a thought

91foxbodygt · May 1, 2008

Lunch Box said:
piston rings might be shot time for a rebuilt of the bottem end

piston rings arent bad, this happened on a fresh rebuild

my friend drove the car on fouled plugs right after the ping and when he would give it gas like at 2k rpm, it would sound like if it had a missfire

hopefully its just a timing issue

stykthyn · May 1, 2008

if you had 150 on each cylinder your piston rings are fine. I'm going to jump on the bad timing bandwagon.

ls1beater4eva · May 1, 2008

ok im in on this one now i doubt its the rings not with a 150 in each hole, now when you did the rebuild did u change the balancer bc thats what it seems like if your setting the timing by that, i had this kind of issue with 88mouse's car the balancer was just barely spun but we caught it in time bc i couldnt get the dizzy stabbed rite so finnaly i just rolled the motor over till we got to tdc on num 1 and stabbed it and it worked like a charm re set your timeing

what causes a bent valve? friend thinks i might have one

91foxbodygt

Member

BlownFiveLiter

have car, will race....wait, it doesn't run

91foxbodygt

Member

91foxbodygt

Member

Blandnuts

I don't swallow; I only swoosh

91foxbodygt

Member

Blandnuts

I don't swallow; I only swoosh

BlownFiveLiter

have car, will race....wait, it doesn't run

rockytoohot

New Member

91foxbodygt

Member

BlownFiveLiter

have car, will race....wait, it doesn't run

BYRDPE

Lunch Box

New Member

1991vert

89lxcoupe

91foxbodygt

Member

mkk50

Active Member

91foxbodygt

Member

stykthyn

I want to measure mine. It doesn't look that tall.

ls1beater4eva

New Member

Similar threads

what causes a bent valve? friend thinks i might have one

Member

have car, will race....wait, it doesn't run

Member

Member

I don't swallow; I only swoosh

Member

I don't swallow; I only swoosh

have car, will race....wait, it doesn't run

New Member

Member

have car, will race....wait, it doesn't run

New Member

Member

Active Member

Member

I want to measure mine. It doesn't look that tall.

New Member

Similar threads

Privacy & Transparency

Privacy & Transparency