253 running issues after top end overhaul

[Guzzoline addict]

Get rid off the single plane manifold,theres no way a 253 has the airflow/airspeed to run a single plane.Its problerly running hell lean.Put a stock, twin plane manfold on it and it will have twice the power.

 

[DAKSTER]

i ran a rocky with my 253 for years its one of the best mods for a 253 early model commodores had rockys it depends on what jets standard jets are fine and with a redline manifold all will be cool....

Shame you didnt try a decent carby, you could have saved a lot of fuel and gone faster.. one of the best mods for a 253? meh...

Get rid off the single plane manifold,theres no way a 253 has the airflow/airspeed to run a single plane.Its problerly running hell lean.Put a stock, twin plane manfold on it and it will have twice the power.

I would have said thats an exaggeration on all counts, but I agree the stock manifold is probably a better option.


None of this is helping the original problem though, which is making the motor run properly. Do you have a different carby setup you can bolt on to test?

Also, if you are having to advance the timing so far just to make the petrol go bang.. is it possible you are a tooth out on the dizzy? As Guzzoline said, I'd be double checking. Easy mistake to make and not always as obvious as it could be.

 

[SL/ENUT]

Holleys aren't best at all of a 253/304 or 308. The quadjets are though. When tuned right, use less fuel than any Holley. Thats fact.

As per original topic, maybe the timing is out. Usually they run good at 8 btdc, try at 10 or 12.

 

[ari666]

Is the Rochester a new addition? And was it new?

Not saying its your immediate issue, but it cant be helping. No good for a 253. I'd be switching for a 4bbl Holley 500, much more suited to the motor. The quadrajet is way too big, especially if someone has been playing with the jets.

most retarded thing i have ever heard

 

[ari666]

The Rochester was nominally 750CFM, much too big for a 253. I guess they could be jetted down, and maybe thats whats been done if they put them on later models, but I cant remember a single one of my mates ever having a quadrajet on a 253..

soooo many retards throwing this crap out all over the internet. its just a shame people actually believe it.


a quaddy is a 230CFM carby till you let the secondary metering flap open. if you dont want it to open, then you tighten up the spring holding it closed. it takes about 5 mins. no better carby in the world. perfectly suited to a 253.

especially when you are companring it to a junk holley.

 

[Pub247]

I'm guessing you put the cam in? did you set it up properly dial in?

I agree about the quaddy if they were rubbish carbs they would have never put them on from factory one that is tuned right and in good condition will deliver better fuel economy and with no power loss side effects.

Holleys are way overated imo

 

[GenFree]

Rochesters have a bad name because no one knows how to tune the damn things correctly.Get a good tuner and you will never go holley again unless absolutely needed.

A good chester will always holeshot a holley given both cars have the same setup/power.

You cant then say"yeah,its got a 650 d/p mannn,loves the juice"lol.

 

[Panama]

yeah i fitted the cam but i i didnt dial the cam in, as i dont have a dial guage.

i couldn't get a hold of an oem manifold that wasnt corroded for the price that i got this brand new one. i was advised that single plane would be better for the small engine with a large carb and cam. i cant remember the exact reason.

all i have is 2 rochesters. they appear to be different models though and the one i originally wanted to use i'm waiting on a kit from the u.s.

the stripped and clean one looks like this model:
http://i169.photobucket.com/albums/u217/ari666os/P8282859.jpg

the dizzy could be a tooth out but i cant see why spinning it around to suit wouldnt cure that? i dont think its out though.

it might be a vacuum leak. i might try using blue tac over the throttle plate shaft. it looked a bit moist after i sprayed carb cleaner in there.

 

[ari666]

yeah i would look at vacuum leaks mostly. make sure the choke the blocked off there the heat riser usually comes out of. make sure your brake booster isnt leaking etc etc in fact, just block off all your vacuum hoses altoghter.

so you have a pre pollution head, but does the manifold suit? i.e. is the egr crossover blocked off? i see you read my quaddy thread, did you follow all the steps toward the end of the thread?

are the idle mixtures turned out 6 full turns? timing running 10 or so degrees with the vac advance disconnected? fuel pressure can be as low as 2 or 3 psi for it to idle. mine used to run faultlessly on 3.5psi. the idle bleeds all clean? fuel filter clean? does it have that little metal cylinder-thingie filter on the front? (personally i put a screwdriver through them, but some ppl have heart attacks when they hear that)

 

[Panama]

manifold is to suit pre pollution.

yeah all the vac lines are blocked off except brake booster and the large charcoal cannister one. dizzy vac line is disconnected and blanked.

does it suck vacuum thru the choke horn?

yeah i cant get it to idle as low as 800, and its a manual, and also i set it to 6 turns like you said. i dont have a fuel pressure guage but i can see it flowing in the clear plastic filter.

i dont think it has the strainer in it, cos i took that massive adaptor off to liquid thread tape it when i put it on the car.

i just had another fiddle with it, i cant find any vac leaks on the manifold runners, or the base of the carb or the throttle plate pivot rod like i'd hoped. i think i might just wait for my kit to arrive, then if it runs properly with the fresh carb on it i'll sledge hammer this one. lol