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Bad Running Diagnosis Help!... Please

engine

Best Answer zebigfatman , 12 May 2018 - 07:19 PM

Fitted the twins, need fettling but problem sorted!! Thanks for all the help!! Go to the full post


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#1 zebigfatman

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Posted 11 May 2018 - 02:05 PM

Hi all, got my engine in the car a couple of weeks ago. it starts, runs and moves.

 

However if you load the engine much at all/ have the RPM to high for any period, it bogs down (think the car can do 30mph max).

What it feels like to me is, it barely has enough fuel pressure to keep the float chamber filled so when you start driving it it kind of empties, lift off the throttle for a bit and it seems to recover.

 

 

 

The fuel pump and filter are in the boot attached to the rear firewall, the pump is facet like this one:-

 

https://www.ebay.co....4cAAOSwPpZaTgF1

 

 

My other theory is the needle is so very wrong that after a certain point it either leans out or runs rich. And finally the worst possibility is the cam timing being wrong but I don't think this is likely because I thought I was fairly meticulous in setting it up (kent 286 to 104 degrees). 

 

I have all but eliminated the ignition timing, changed the plugs and leads. Turning the distributor in either direction makes it run worse.

 

Carb is a hif38 which I am using to try and run in the engine (will be changed to twins). I have also tried a single HS4 on the engine with the same effects (but slightly worse).

 

I do have a fuel pressure regulator on the car which I am going to take off tonight just to try.

 

Any help or advice would be greatly appreciated!!

 

Cheers!!



#2 ukcooper

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Posted 11 May 2018 - 02:53 PM

needs setting up rolling road, sounds like it rich on choke and building up carbon and running lean. burning the carbon off what's it built up, while running on choke .

#3 zebigfatman

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Posted 11 May 2018 - 03:27 PM

Not sure the car could make it to the closest rolling road with the engine as it is. Plus I reckon 30 along duel carriageway is a really bad idea!!

Just need it to be able to do a sensible speed and I have every intention of getting it properly tuned!

 

Gonna have a bit of a play with it tonight but I'm not that optimistic...



#4 Swift_General

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Posted 11 May 2018 - 03:27 PM

Does sound like a fueling issue. What carbs are you intending to use? I wouldn't be using a carb that small on a 1275 with that cam, and particularly if you don't know what needle/spring you are using unsatisfactory results are perhaps to be expected. Would be better of fitting the carbs now that you are going to use, rather than try and play with a set up that is never going to be ideal. In the meantime check the fuel delivery of them pumb, and also the needle valve/float are operating normally. What is the fuel pressure regulator set to? If the pump produces max 4psi you prob don't need one.

Edited by Swift_General, 11 May 2018 - 03:32 PM.


#5 ukcooper

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Posted 11 May 2018 - 03:54 PM

try a richer needle like a aaa or the one for the hif38 same spec sd AAA, get it running and r/road it its worth the money ...........but if you change anything like exhaust carb needle air filter back box
                it WILL NEED DOING AGAIN..



#6 ukcooper

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Posted 11 May 2018 - 04:09 PM

this might get in the ball park but its not 100%

http://www.winsu.co.uk/ it might get you a starting point -might not as well

#7 dyshipfakta

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Posted 11 May 2018 - 04:52 PM

What is the exact specification of the engine someone may be able to suggest a needle to get you running.

#8 zebigfatman

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Posted 11 May 2018 - 05:09 PM

Wow, thanks for the replies! Engine spec is

1310
286 can
1-5 rockers
Ported head
Lcb, with a custom exhaust
Carbs are constantly being changed due to this problem but ultimately twin hs4's

#9 Arthy

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Posted 11 May 2018 - 08:54 PM

If it's any help I'm running a 1330, with an SW8 cam and ported head with twin HS4's on the AAA needle. Seems to run good but will get it set up properly soon, but it pulls real good and the plugs are a good colour!

 

I would have thought an HIF38 would be able to handle such engine spec though, maybe not the best but at least run decently? I'm sure they're rated to 90HP or so? 



#10 zebigfatman

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Posted 12 May 2018 - 12:07 AM

I thought the carb should be able to at least get the car to a usable state as well.

The reason I was not using the twins was getting the mixture set up should be significantly easier with a single.

I have bought a job lot of hif44 parts (3 disassembled) off ebay, but they are mirror images to normal HIF carbs (linkages on the opposite side) and all of the throttle linkages are missing so not much use at the moment.

 

Anyhow, I am going to try the twin hs4's tomorrow. will report back then!



#11 zebigfatman

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Posted 12 May 2018 - 07:19 PM   Best Answer

Fitted the twins, need fettling but problem sorted!! Thanks for all the help!!

#12 dyshipfakta

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Posted 12 May 2018 - 11:25 PM

May have just been an air leak on the manifold nether the less congrats enjoy it





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