Air blowback through to Air Filter Box

Scotzman · Dec 15, 2013

P38 Blowback - YouTube

Hi, hope someone can help. Started getting a really harsh rasping, thought it might have been the transfer chain....after a little work, found the noise was coming through the air filter.

My wife who was in the car before the noise started recalls we took a roundabout rather sharply...might have knocked something loose? Checked the leads for good connection, seems to be fine, although there seems to be new plugs fitted, leads look, rather old.

Anyone got an previous experience/suggestions?

Only had the p38 a week, driving me nuts lol

Thanks in advance for any help. The above link takes you to a vid I uploaded onto YouTube.

Cheers

Dougie

Datatek · Dec 15, 2013

Scotzman said:
P38 Blowback - YouTube

Hi, hope someone can help. Started getting a really harsh rasping, thought it might have been the transfer chain....after a little work, found the noise was coming through the air filter.

My wife who was in the car before the noise started recalls we took a roundabout rather sharply...might have knocked something loose? Checked the leads for good connection, seems to be fine, although there seems to be new plugs fitted, leads look, rather old.

Anyone got an previous experience/suggestions?

Only had the p38 a week, driving me nuts lol
Thanks in advance for any help. The above link takes you to a vid I uploaded onto YouTube.

Cheers

Dougie

You already had a thread running on this, why start a new one? I gave you some possibilities on your other thread but plugs leads can be added to the list.

Scotzman · Dec 15, 2013

Data, sorry, hadn't realised you had answered. Tried to upload the link onto the previous thread but couldn't, hence the new one. If one of the mods can join them , that would be good.

Would any of the suggestions you have made be gradual, or instantaneous ?

Cheers

wammers · Dec 15, 2013

Sounds like a bent valve.

Saint.V8 · Dec 15, 2013

Dropped valve possibly, due to knackered spring maybe...

Definatly whip the rocker covers off and take a goosey

tom1disco.300 · Dec 15, 2013

either a bent valve or a snapped rocker, as this would cause back blow through the intake pipe,iv just found that on a 2.5 n/a witch i was told the bottom end was blown! but all it needed was the rocker cover taking off and investigating! this would mean it would have to be the exhaust rocker that has broken! if this is the case it will only run on 7, and if you cant tell, rev her up a bit and blip the throttle,if she stutters a bit the its a cylinder down,or maby more, but she would be way down on power!

gfromleeds · Dec 15, 2013

+1 valve not closing properly
Whats it run like? Ie rough smooth ect.

Scotzman · Dec 15, 2013

Thanks for all the replies.

1) the car starts and idles ok..sitting about 750rpm
2) there is a serious lack of "pick up" when the accelerator is pushed, and the noise you hear on the vid is what I get until the gear shifts down
3) when the car is cruising and I'm just keeping the momentum up (very little accelerator) there is no noise. If I'm driving on the flat, with no need to be heavy on the accelerator, you wouldn't know there is a problem.
4) it was instantaneous, so possibly suggesting something went pop
5) I am currently getting about 8mpg according to dash
6) how easy is it to fix if it is suggested, bent or dropped valve?

Cheers

Dougie

wammers · Dec 15, 2013

Scotzman said:
Thanks for all the replies.

1) the car starts and idles ok..sitting about 750rpm
2) there is a serious lack of "pick up" when the accelerator is pushed, and the noise you hear on the vid is what I get until the gear shifts down
3) when the car is cruising and I'm just keeping the momentum up (very little accelerator) there is no noise. If I'm driving on the flat, with no need to be heavy on the accelerator, you wouldn't know there is a problem.
4) it was instantaneous, so possibly suggesting something went pop
5) I am currently getting about 8mpg according to dash
6) how easy is it to fix if it is suggested, bent or dropped valve?

Cheers

Dougie

Think you had better take the rocker cover off first and have a look. It's certainly not a dropped valve or it would be very ill indeed. There would be a little more than a slight blow back through the inlet.

StuckAgainSteve · Dec 15, 2013

Does sound like a single broken valve/rocker type knock going on there under all the other noises.

Do a compression test?

Scotzman · Dec 15, 2013

https://www.youtube.com/watch?v=XNz1tCk6vSg&feature=youtube_gdata_player

Another vid! Dont have the right socket to get the rocker cover off, and heading down south for the rest of the week. Could anyone recommend a good independent around the Lanarkshire or glasgow area?

sassanach · Dec 16, 2013

my apologies for the thread hijack...

what would a decent figure be on a compression check?

wammers · Dec 16, 2013

sassanach said:
my apologies for the thread hijack... what would a decent figure be on a compression check?

Anything over 130 PSI should be ok most important thing is that they are all within 10 PSI of each other.

Scotzman · Dec 20, 2013

All, took the rr down to Gibsons in Ayrshire. Turns. Out the camshaft has gone, getting it replaced. Been quoted £900...sound reasonable?

dove · Dec 20, 2013

Depends what they re doing to it,you can get standard cam for around £70, high lift for around £240,lifters around £80 ,timing chain kit around £40,gaskets around £20,shim kit £20,while you are in there might as well put a better cam in.labour will be expensive as you have to take inlet manifold off and timing cover,easy enough to do if you are handy with spanners,

Scotzman · Dec 21, 2013

Hi Dove

It's not really the parts, I think it is the labour @ 50 per hour.

Apparently the cam has to come out through the front, so the front end and radiator has to come out first.

Had to go sometime given the mileage, so at least I know it's good for a while

Druim · Dec 21, 2013

Scotzman said:
Hi Dove

It's not really the parts, I think it is the labour @ 50 per hour.

Apparently the cam has to come out through the front, so the front end and radiator has to come out first.

Had to go sometime given the mileage, so at least I know it's good for a while

Yeah, then it's just all the bits around it to go

Saint.V8 · Dec 21, 2013

Yep, the Cam sits in the valley of the Vee....to remove you have to take the rad and condenser out, front grill, timing chains and cover etc and it slides out of the Valley through the front!

rewmer · Dec 22, 2013

Can I just throw this into the mix ? Blowing back through the airbox to me means an inlet valve is not sealing. Seeing as valves are naturally closed through spring pressure and are only opened by the cam lobe how can a worn cam cause the problem..?
Just asking ?

Datatek · Dec 22, 2013

rewmer said:
Can I just throw this into the mix ? Blowing back through the airbox to me means an inlet valve is not sealing. Seeing as valves are naturally closed through spring pressure and are only opened by the cam lobe how can a worn cam cause the problem..?
Just asking ?

How about if an exhaust valve is not opening? There would be pressure in the cylinder when the inlet opened would there not?

Air blowback through to Air Filter Box

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