Chevy 454 p30

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chevywontmove

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Hi , I'm new to the forum so please accept my apologies for the level of understanding that i will probably show !
I have taken over a "project " and i am really struggling getting the Chevy 7.4l engine to fire. (back story) I was told the Motorhome was driven on a short journey to undertake a re-fit. On the way the engine overheated and failed ,upon inspection the heads (one of ) had failed. It was towed back to base. A mechanic was called and he has stripped the top end,all the vacuum hoses,removed the heads and pressure tested them. One has failed as predicted. Thus i have taken on the project, which is where i have started from. Purchased a pair of matching heads which match the engine numbers. Purchased a gasket set from Realsteel plus the another gasket set as the heads had a slightly different water jet from realsteel. Replaced the heads and manifold with the correct torque and gaskets and replaced the carb. Dropped in the distributor as i thought at the correct position and tried to start her up. All i have got so far is a backfire with no sign of firing ??? I have plugged the vacuum ports excluding the distributer, intake port and rocker cover ? but i am at a loss ? Is there anyone out there who knows someone that either has a picture of the vacuum set up in idiot form or knows someone that loves to have a dabble with these 1988 mk4 Chevy bbc 454 7.4l beasts. I am in Leeds (Yorkshire) if anyone can help (I'm Happy to pay !) i would appreciate any help with this .
Sorry for the essay above, i thought it better to include most points good and bad !
 
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Would you be better off going on an American forum that deals with Chevy engines?

But the old V8 is pretty simple if it’s naturally aspirated.

If you’ve got compression, fuel and a spark shell fire up.

As a guess I’d say the dizzy is out 🤷‍♂️
 
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Hi , Thanks for that . Really i would love to for someone who has some knowledge of these engines to come out and have a look . Thank you though, i already have done what you said.
 
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Have you got a spark

Have you got clean fuel in the bores

Have you got the dizzy set correctly

If all the above it will fire up I’m sure.
 
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Have you set the engine at tdc and the dizzy just before points would open.

Pour petrol into the carb, don’t rely on the tank and pump

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So Sorry !! All new to this !
I have tried all the normal stuff and petrol is flowing ? I think it is a timing plus vacuum issue but i haven't got the experience ?
 
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Throttle body injection? If so and all timing correct could be stuck injectors, they don't like to sit, look, carefully, down the throttle body when cranking watching for fuel flow. Backfire means some is present but perhaps not enough? I managed to get some going once with ample wd40 and an air line, likely not the recommended method. rvoc.co.uk, sister site to fun may offer more, as mentioned above?
 
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Dodgey said:
Throttle body injection? If so and all timing correct could be stuck injectors, they don't like to sit, look, carefully, down the throttle body when cranking watching for fuel flow. Backfire means some is present but perhaps not enough? I managed to get some going once with ample wd40 and an air line, likely not the recommended method. rvoc.co.uk, sister site to fun may offer more, as mentioned above?
Click to expand...

Injectors as inside the carb?
 
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I had the same Chevy 7.4 in our RV. (shown in avatar picture). It worked well when we had it, just as well I know nowt about these beasts.
Phil

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I have a workshop manual, if you want a copy pm me your email.
To send a pm hover over my photo and click start conversation.
 
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Dodgey said:
Throttle body injection? If so and all timing correct could be stuck injectors, they don't like to sit, look, carefully, down the throttle body when cranking watching for fuel flow. Backfire means some is present but perhaps not enough? I managed to get some going once with ample wd40 and an air line, likely not the recommended method. rvoc.co.uk, sister site to fun may offer more, as mentioned above?
Click to expand...
I doubt a 1988 engine will be fuel injected but I'll stand corrected.
 
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Could be so many things.
As mentioned above.
Are plugs wet (fuel) after cranking
Do you always have a good spark
Are you sure plug leads are on in the correct order
Do valves need to be gapped, or have their timing done, checked
Do you have compression
How old is the fuel that you are using

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Cylinder number 8 valves rocking would put cylinder number one at top dead centre. The points should then just be starting to open.
 
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It sounds like you are fishing in the dark any one with a bit of mechanical knowledge should be able to time this up and check your firing order, there must be lots of places around you as Rodley motors were the biggest v8 dealer in the UK not that long ago.
Good luck
 
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Many years ago had the same symptoms with a mates car .. everything seemed fine, comp, fuel & spark ... eventually turned out to be a cracked inlet manifold.
 
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icantremember said:
Many years ago had the same symptoms with a mates car .. everything seemed fine, comp, fuel & spark ... eventually turned out to be a cracked inlet manifold.
Click to expand...

A V8?

I would of thought even a crack in the inlet it would still show some form of life 😊

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icantremember said:
No not V8 just a 4 ... it was probably more than just a crack, I didn't see it.
Click to expand...

I can see a crack in a four cylinder being a real pain.

Years ago when I were a nipper I had a leaky inlet manifold.

She still ran ok if you used the choke and would tick over without 😊
 
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