253 running issues after top end overhaul

[Panama]

hey guys, i know its not a commodore but i'm having trouble getting my hj 253 manual to idle and run after replacing head gaskets, intake manifold, cam, dizzy, coil and carb.

its running a single plane redline manifold, a rochester quadrajet, a points-less distributor and the cam is a crane cch-276. it has pre pollution heads.

i checked that the timing mark is right for tdc by watching the rockers on cylinder one so the h/balancer isnt slipping, the cam rotor points at cyl 4 when this happens which is oppisite cyl 1 on the dizzy so that means the dizzy isnt 180 out.

i've also disconnected the distributor advance vac line and all the vac lines off the carby and blocked them off for now to make sure its not a leaky vac line

i can get it to run at like 1500rpm and an insane amount of ignition advance (crank mark sits at the bolt head on the timing cover that is between the 2 bolts for the fuel pump) but as soon as i try to lower the idle or timing it dies.

its also difficult to get the engine to start, i need to pump the accelerator a couple times then crank with my foot to the floor. if i dont do it this way it turns over and then i get a single rhuum and it dies straight away.

any ideas as to what it could be thats giving me these dramas?

[SL/ENUT]

Fuel staving a bit? Or the spark isn't big enough.

[Panama]

i heard you need to use a 12v source for the elect ignition so i tee'd it in from the fuel cut solenoid still being used thats left over from it being dual fuel. i was looking at the see thru fuel filter i have and thinking maybe i should get a new fuel pump...

[strgas]

recheck your lifter preloads sounds like lack of compression . has the block been decked and the heads shaved much ? manifold been machined ?

[DAKSTER]

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.

Quadrajets are also known to have a problem with the original plastic floats, they could absorb fuel and the float would sink, so it didnt shut the fuel off, causing flooding. There are brass versions you can replace these with if you have a plastic one.

If its a secondhand carby, its also common for the steel primary throttle shaft to cause wear in the aluminum casting material in the throttle body. This causes an air leak and can even cause the primary throttle blades to not close properly, causing idle problems. You can buy aftermarket teflon bush kits to fix this.

[Panama]

nope, block and heads looked to be in tolerance. manifold is new. i used new lifters but pre-oiled them inside and out then torqued down rockers to specs. it's had full oil pressure now though so i can recheck the rocker torques. would the cork gaskets be ok to reuse or should i get new ones? when turning over by hand (with ratchet on alt) compression feels decent but i haven't measured it or anything.

[Panama]

Is the Rochester a new addition? 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.

the one that's on the motor is supposedly "straight off a running motor and the jets/ needles should suit your motor" but the guy who told me that dicked me around with the cam and manifold. took him 4 months to get me a crane cam for a motor only used in australia and i think he wrote the book on excuses.

didnt late model 253's come out with quaddies? i thought it would be ok since i'm using a cam that needs "improved carburettion". i have another quaddie in the shed that i'm waiting for a kit for. i have it stripped and cleaned on the bench but waiting for kite. that one i know came off a running 308.

i'm tempted to switch to a holley but i've already got these parts. once the kit comes for the other quadrajet i'll be putting that one on whether i've got the current setup running or not cos it will be freshly rebuilt.

[DAKSTER]

We are going back 30 years now lol but i remember 253s having two barrel strombergs. The 308 certainly had a quadrajet. Its possible the later model 253s had quadrajets , I cant remember, but I do remember the first thing we would do if we bought a car with a quadrajet was remove it and buy a better carby.

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.

'improved carburetion' should be provided easily by a Holley 4bbl 500.

Bigger isnt necessarily always better.. still remember laughing at a mate who stuck an 1150 dominator onto a 308 and turned a major beast into a thirsty kitten..

[Panama]

We are going back 30 years now lol but i remember 253s having two barrel strombergs. The 308 certainly had a quadrajet. Its possible the later model 253s had quadrajets , I cant remember, but I do remember the first thing we would do if we bought a car with a quadrajet was remove it and buy a better carby.

Bigger isnt necessarily always better.. still remember laughing at a mate who stuck an 1150 dominator onto a 308 and turned a major beast into a thirsty kitten..

i know a lot of people are of the oppinion that quadrajet = shit, and tbh i'm beginning to be swooned by the aftermarket support both in parts and tech advice for holley's. the manifold i have will fit holley as well without an adaptor plate so it's very tempting. but i dont know if its the carb or something else.

yeah i know theres such a thing as over carbing but i thought later first gen commodores like the vh had quadrajets on their 253's?

you're bang on about this engine being originally a stromberg. when i got it someone had banged on an adaptor plate and holley 350.

when it dies and i quickly turn the dizzy back or give the throttle a blat (depending on what i was fiddling with) it doesnt reignite.

[machone]

We are going back 30 years now lol but i remember 253s having two barrel strombergs. The 308 certainly had a quadrajet. Its possible the later model 253s had quadrajets , I cant remember, but I do remember the first thing we would do if we bought a car with a quadrajet was remove it and buy a better carby.

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.

'improved carburetion' should be provided easily by a Holley 4bbl 500.

Bigger isnt necessarily always better.. still remember laughing at a mate who stuck an 1150 dominator onto a 308 and turned a major beast into a thirsty kitten..

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....panama if your having to run your car at a whole lot of advance make sure you really do have your dizzy in the right place with the rotor pointing to no1 spark plug lead and the timing mark is tdc....also make sure your piston is on the up stroke not on the down...you can check this easily by taking no1 spark plug out scrunching a small piece of paper placing it into the spark plug hole dont push it all the way in just cover the hole enough so it stays there.... then turn the engine by hand the paper should pop out thus telling you its on the upstroke once its popped out then move the crank to tdc mark.....then check to see if the rotor arm is on no1....also if you have changed the manifold make sure the gaskets have not slipped this will also cause the timing to be erratic to check run crc or oil around the manifold you should hear the revs change if its leaking.

[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/u...s/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

[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

[VR38]

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

Well actually alot of performance GM cars were fitted with a Holley... if it is correctly serviced and tuned to the motor then there will not be much either way, holley, rochester, carter, weber etc etc.

[VC308]

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

this. i had the same problem. the dude who dialed my cam in set it out enough that i had to advance the dizzy one tooth.
we then did the timing & set the carb on the dyno, it was perfect.

Beau.

[Panama]

but if i spin the dizzy around it should compensate/negate the need for the rotor shaft to be set one geartooth in advance? i can physically spin the dizzy 360degrees.

[DAKSTER]

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.

Ari I have a lot of respect for the stuff you do. We have had both disagreements and agreements, but at no point have you or I degenerated into insults. It doesnt suit you, and its certainly not something I intend to degenerate to.

You may have had good experiences with Rochesters, but I have had nothing but bad. I'm only offering my opinions based on my own personal experience, same as you.

If you need to disable half the carby to make it suit, its hardly the ideal carby is it? 230cfm is not enough for a 253, 750 is too much, so obviously its a bit more complicated than that.

Of course there is the added benefit of a Holley being simple and reliable too, which a Rochester isnt. As people are pointing out, no-one seems to know how to tune a Rochester properly.

I know you dont agree, but surely we can agree to disagree on this one, without insults?