12 replies to this topic

[lcgtr1970]

Hi Guys

I have a 253 running a Crow Cam 5666-8 cam. On top is a 4 barrell Holley 465 that I bought rebuilt. 

This set up seems to run quite rich...

It uses about 21L/100kms and leaves the spark plugs black...also has a few dots of soot on rear of car.

 

The current jets are 58s and the powervalve is 65.

 

What do you think would be a good jet size to drop to for this set up? And what would be a more appropriate powervalve?

 

Thanks 

 

[Rockoz]

Thats a how long is a piece of string question.

Its a mild cam so economy from standard shouldnt be much higher.

But given those numbers its using about 50% more fuel than I would consider reasonable.

My comparison is a VB Commodore with a 253 that I used to get no worse than 14l/100km.

That was usually spirited driving for the most part too.

A 2 barrel 350 Holley was usually the go to for a 253 back in the day.

A 4 barrel was really only going to affect your wallet rather than performance.

Jets and Power Valves probably arent that expensive.

Buy a few different sizes and play, unless you want to spend time and money on a dyno with a good tuner.

 

Cheers

 

Rob

[yel327]

I'd be looking to a Quadrajet setup right for a 4.2, off a blue 4.2.

[Rockoz]

Quaddie will always be the best choice for sure.

But with effort the Holley will work.

Can remember in the pits at Oran Park a couple of teams had aluminium blocks loaded with jets and power valves.

They would do a hard run down the straight, shut it off then tow it back to the pits for a plug check and change of bits of needed.

 

Cheers

 

Rob

[claysummers]

Any vac sec 4 barrel with smaller primaries will out perform Holley 350.


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[EunUCh]

I would be trying another power valve first , forget how they work but i think the number indicates opening point in inches of mercury , generally with a cam the manifold vac drops a bit and it may be that the power valve is opening too early , i would try a 45 power valve.

[Bruiser]

Not too big of a cam
Is the rest of the motor stocko? Heads, exhaust?
Is your ignition and timing all in good order?
It has been said lots of carby problem are ignition related
Even scraping the gunky white buildup off the dizzy cap plug contacts helps
Is easy driving economy what you are talking about, or are
you beaning it a fair bit?
Maybe even the vacuum advance
I wouldn’t have thought 58 jets are that big at all for decent cruising mileage,
they couldn’t be too far off
Cruising along shouldn’t bring a 6.5 power valve into play at all, anyway.
If something is leaking under vacuum it could eat a fair bit of fuel
Don’t panic, that’s just the next little can of worms

[lcgtr1970]

Got a set of extractors to twin pipes, electronic dizzy (new)...heads are mild ..been done at some stage before me got Yella terra valves not sure on work done to them.
Just a cruiser doesn't get flogged.

[Shiney005]

I had a mate with a Brougham drop in last weekend with a 465 on the 308. It was running so rich it was blowing black smoke at idle.  I thought the float level was set too high (or full of fuel) but it was fine. Then swapped out the needle and seat, but still no difference. It ended up being a crack in the metering plate letting fuel through.  This is the third time I have heard of late model Holley castings cracking in the last 6 months.

[rexy]

Check your manifold vacuum at idle.

A power valve that’s half manifold vac will be about right.

 

Buy yourself a big box of Holley jets and start leaning it out.

 

Make sure the idle circuit is properly adjusted first.

[EunUCh]

And when swapping out jets or power valve or whatever do one change at a time so that you know which way you are going with the changes made.

[UCSLE]

I think 58s would be about right  

 

There has to be another problem , shine a torch down the carby when its running and look for leaks and also check for a blown power valve 

 

Beware the most common jet kits start at 64   

[Bruiser]

If it’s wet in the open area in the main body behind the power valve you have a p.v. leak
Check there is only one one round gasket on it too. That’s easily done and a classic