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> Big backfire, 2.7L CIS from 1976 911
Kansas 914
post Jul 4 2020, 10:08 AM
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I tried to start the car as I normally do but back fired (pretty loud) I tried to re-start (it did this once before a few years ago) but this time it didn't restart.

I pulled the air cleaner cover and saw a hole in the filter and the pop-off valve was in pieces.

I haven't taken the air box off yet but that is next if I can't get the old pop-off valve out. It looks like the engine builder sealed the air box (and the pop-off valve) with some kind of "goop". Fun times...
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Kansas 914
post Jul 4 2020, 11:18 AM
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sixnotfour
post Jul 4 2020, 12:15 PM
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Well, better than the box blowing up...You should be able to pry the base out.. Usually the whole thing pops out... Happy 4th of July
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Kansas 914
post Jul 4 2020, 12:45 PM
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QUOTE(sixnotfour @ Jul 4 2020, 12:15 PM) *

Well, better than the box blowing up...You should be able to pry the base out.. Usually the whole thing pops out... Happy 4th of July

Hi Jeff,

Yep - I hope the box isn't blown. I will work on the pop-off valve and see how it goes.

Happy 4th of July to you and Suzie - cheers!

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rgalla9146
post Jul 4 2020, 01:17 PM
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Put the toilet seat back on ......see if it starts.
Maybe put something on top of it to keep it seated
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914Toy
post Jul 4 2020, 01:19 PM
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Also check the cross-over black rubber boot was not blown off the throttle body or the fuel injection module.
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rgalla9146
post Jul 4 2020, 01:25 PM
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Put the toilet seat back on and see if it starts.
Maybe put something on top of it to keep it seated.
A big backfire is usually caused by a lean condition.
If the plenum survived (fingers crossed) check fifth injector, points and the other usual
suspects
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Kansas 914
post Jul 4 2020, 02:24 PM
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QUOTE(rgalla9146 @ Jul 4 2020, 01:25 PM) *

Put the toilet seat back on and see if it starts.
Maybe put something on top of it to keep it seated.
A big backfire is usually caused by a lean condition.
If the plenum survived (fingers crossed) check fifth injector, points and the other usual
suspects

It did start with the toilet seat on and weighted down - but ran poorly then died.
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windforfun
post Jul 4 2020, 02:30 PM
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Too many spicy tacos. Happens to me all the time.
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sixnotfour
post Jul 4 2020, 02:37 PM
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Got Gas ? in da tank.. $th of july
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Kansas 914
post Jul 4 2020, 02:38 PM
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The old pop-off valve is SECURELY glued in place. I may have to remove the airbox (and all the other associated goodies).

It doesn't look like fun.

I am reading some articles on the Bird Board now - ugh. I love my Type 4 motors even more now...
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sixnotfour
post Jul 4 2020, 03:08 PM
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Type 4 sale.... dont come home with one..REDRUM..
Pulling the CIS assm. on a 914 is way easier than a 911... (IMG:style_emoticons/default/popcorn[1].gif)


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sixnotfour
post Jul 4 2020, 03:11 PM
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Just throw Carbs on it.. (IMG:style_emoticons/default/idea.gif) (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/av-943.gif) (IMG:style_emoticons/default/popcorn[1].gif)
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Kansas 914
post Jul 4 2020, 03:32 PM
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QUOTE(sixnotfour @ Jul 4 2020, 03:08 PM) *

Type 4 sale.... dont come home with one..REDRUM..
Pulling the CIS assm. on a 914 is way easier than a 911... (IMG:style_emoticons/default/popcorn[1].gif)

Thanks Jeff,

I was going to ask you if it is easier in a 914 than a 911. My only problem when reading the "how to" thread on Pelican everything will have to be reversed (right side = left side). (IMG:style_emoticons/default/smile.gif)
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Kansas 914
post Jul 4 2020, 03:33 PM
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QUOTE(sixnotfour @ Jul 4 2020, 03:11 PM) *

Just throw Carbs on it.. (IMG:style_emoticons/default/idea.gif) (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/av-943.gif) (IMG:style_emoticons/default/popcorn[1].gif)

I had thought about ITBs and Megasquirt....... But my wallet ran out of the room.
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porschetub
post Jul 4 2020, 03:49 PM
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QUOTE(Kansas 914 @ Jul 5 2020, 09:33 AM) *

QUOTE(sixnotfour @ Jul 4 2020, 03:11 PM) *

Just throw Carbs on it.. (IMG:style_emoticons/default/idea.gif) (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/av-943.gif) (IMG:style_emoticons/default/popcorn[1].gif)

I had thought about ITBs and Megasquirt....... But my wallet ran out of the room.


Shit that was a big bang...blew the hinges on the flap right off (IMG:style_emoticons/default/sad.gif) .
Check to see the plenum runners are still tight on the heads,they are known to loosen up on the gaskets and leak.
Good luck sorting this,guess its about finding the cause after the airbox is fixed,hopefully no further damage done.
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Kansas 914
post Jul 5 2020, 08:33 AM
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QUOTE(porschetub @ Jul 4 2020, 03:49 PM) *


Shit that was a big bang...blew the hinges on the flap right off (IMG:style_emoticons/default/sad.gif) .
Check to see the plenum runners are still tight on the heads,they are known to loosen up on the gaskets and leak.
Good luck sorting this,guess its about finding the cause after the airbox is fixed,hopefully no further damage done.

Thanks for the suggestion to check the runners - I will do that.

I agree - I hope there was no further damage.

I am under the gun to get this fixed since Red Rocks Classic is being held here (Durango) in September and I have never worked on CIS before.
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Kansas 914
post Jul 7 2020, 10:49 AM
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@sixnotfour

Jeff - I did as you suggested and got the pop off valve out.

The new on is on the way (next week probably).

What adhesive do you like to install the new POV? I have some Honda Bond HT but I think that stays "rubbery" after it cures.

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sixnotfour
post Jul 7 2020, 01:07 PM
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Did you notice,It was actually 180 out of proper flapping flow ?
Any thing is good but if it backfires, you need to check the seal, Ive seen em pop out ,instead of breaking a few times,,,
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Kansas 914
post Jul 7 2020, 01:11 PM
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QUOTE(sixnotfour @ Jul 7 2020, 01:07 PM) *

Did you notice,It was actually 180 out of proper flapping flow ?
Any thing is good but if it backfires, you need to check the seal, Ive seen em pop out ,instead of breaking a few times,,,

Thanks!

I have seen them installed both ways and didn't know which way was right.
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