Now that I've got my new engine run in my torrie and put on a few thousand Ks I've started to notice some issues. The engine is a completely rebuilt pre pollution red 308 with standard everything and a mild cam, running 9.3 compression. The two issues are:
1) The carb appears to be over-jetted as its running rich. It's a rebuilt Rochester quadrajet but I think the bloke I got it off may have put too large of jets in it as the whole car appears to be running just a bit too rich. Does anyone know the standard jet size used in these carbs on 308s? How easy are new jets to buy and can a simpleton like me who's never played with a carb before swap them out at home?
2) I'm beginning to hear just the slightest of pings when I really open it up, I've had a mate quickly run an engine light on it and said its 15 degrees before TDC. I had the dissy rebuilt by performance ignitions in Melbourne (Bosch commodore dissy) and they said it needs to be at 10 degrees before.
Now I could always take it back to my mechanic to sort out but he is hesitant to play around with the carb at the same time so sending it to him to take some advance out but leave me with a car that's running rich is not ideal. So my best option would be to probably have a go at taking advance out of it myself to save some $$$ and a trip to my mechanic...but again I'm not 100% sure of myself and don't want to stuff it up. So any advice on this would be great!
Also, if there's anyone who lives on the eastern side of Melbourne who can lend me a hand in exchange for a box of beers (or cash!) that would be awesome!
Thanks in advance for the help everyone.
Quadrajet and tuning advice needed
Started by
_74LH_
, Dec 13 2015 05:03 PM
22 replies to this topic
#2
_Bomber Watson_
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Posted 13 December 2015 - 05:46 PM
Pulling advance out of an engine thats running well rich will likely make it worse, It will appear way more well rich.
Are you sure the very slight pinging your hearing isnt an exhaust leak?
What is the total advance? Innitial advance on an engine thats detonating when your under it is a pretty useless number unless your running a locked dizzy, and it seems your not.
Cheers.
#3
rexy
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Posted 13 December 2015 - 06:08 PM
Which suburb are you in?
#4
_74LH_
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Posted 13 December 2015 - 06:14 PM
It's a brand new exhaust from headers all the way through, done at a quality shop too so I'm positive it's good. Will check it to be sure though.
I'm no expert on the matter of ignition. All I know is the shop that built the dizzy said to set it to 10 degrees before tdc and currently it's at 15 before. For all I know what I'm hearing might not be pinging but it sounds awfully like it.
Cheers
Hawthorn, happy to travel
I'm no expert on the matter of ignition. All I know is the shop that built the dizzy said to set it to 10 degrees before tdc and currently it's at 15 before. For all I know what I'm hearing might not be pinging but it sounds awfully like it.
Cheers
Which suburb are you in?
Hawthorn, happy to travel
#5
rexy
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Posted 13 December 2015 - 06:49 PM
Sent you a pm.
#6
_74LH_
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Posted 13 December 2015 - 08:50 PM
Does anyone on here have a knowledge of what the standard jet and hangers sizes were? I know that the 253 and 308 variants were different to one another. However for the 308 there seems to be a few different opinions on what they were. It seems they differed depending on the type of 308 (red, blue, black).
Does anyone have a recommendation for a pre pollution 308 with standard heads, standard manifold, standard inlet manifold, mild cam and a comp of 9.3:1? I just want to make sure the set up is right
Does anyone have a recommendation for a pre pollution 308 with standard heads, standard manifold, standard inlet manifold, mild cam and a comp of 9.3:1? I just want to make sure the set up is right
#7
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Posted 14 December 2015 - 04:03 PM
By the time you read the High Performance manual on Quadra-Jet tuning you will soon come to the realisation that you will not have all the jets/needles etc to experiment.
You will also realise that a cam change will throw out the standard jeting.
I bought a re-manufactured Quadra-jet specified for a Known engine configuration and it was "close"
finished it off with a dyno-tune from a quadra-jet specialist. Never looked back. Track days proved it.
I suggest you get it dyno-tuned from a Quadra-Jet specialist.
#8
_The Baron_
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Posted 14 December 2015 - 05:22 PM
Looking to "tune" mine a little better, but finding an expert in SA with bits to trial seems too hard now days. Mine runs on the lean side until the secondaries open as proven on both a chassis and engine dyno. Problem is it sits on the primaries most of the time and could really do with a tab more fuel on light loads. It can ping (I can just hear it) when running up hill if the fuel is a tad old (98 RON). I have also pulled a few degrees out of the timing to settle it down.
I am at the point where I will pull the rods & check the primary jet and order the next size richer for both from maybe HUME. I have a spare carby to practice dissembling before I touch the good one. Once I have some bits, I will need to drop it on a dyno for proper tuning.
All constructive comments welcome.
P.S. this is a later 603 to suit a commercial WB as recommended by Mr Carby back in the early 90s. I bought one new from GMH and sent it to Mal Rose (Mr Carby) who performed a few tweaks to improved flow and it is still in mint condition.
#9
TerrA LX
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Posted 15 December 2015 - 11:14 AM
Maybe it needs a good tune?
#10
Posted 15 December 2015 - 11:34 AM
Unfortunately you do tend to need a good selection of parts to tune them well - you can get kits with a range of APT springs but generally jets, rods and hangers need to be bought separately. If you have big changes to make sometimes its simpler to go to extremes (e.g. change several jet sizes at once rather than just one) and then work backwards since you should have a good idea of where in the middle you need to be, if that makes sense...
Early 308 Quadrajets had 76 primary jets, later ones were 71, as noted above your cam change may make this irrelevant. The primary rods are not changed. The secondary jets are not changed but the rods are. Set the correct float level and sort the primary jetting and APT (and idle/off idle adjustment) first then move on to the secondaries. You will need to remove the top section of the carb to make alterations to the primary components.
There is some online info here:
http://www.tocmp.com.../QJet/index.htm
(but one of the popular books would be better)
#12
_74LH_
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Posted 15 December 2015 - 07:28 PM
Spoke to the bloke who built the carby today. He said as its a pre pollution 308, he consequently sold me a pre pollution quaddy to suit. Which came with 76 primary jets.
He said the first thing to do is get the timing and advance dialed in properly then see what the carb is doing. Which sounds fair enough to me.
He said the first thing to do is get the timing and advance dialed in properly then see what the carb is doing. Which sounds fair enough to me.
#13
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Posted 15 December 2015 - 07:36 PM
He said the first thing to do is get the timing and advance dialed in properly then see what the carb is doing. Which sounds fair enough to me.
Spot on, and then you can set the idle mixture correctly...
#14
_74LH_
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Posted 28 December 2015 - 10:32 AM
OK update time,
Took it to my mechanic, he initially took it back to 10 deg BTDC, which didn't seem to make a hell of a lot of difference when I took it for a spin. So he then took the vacuum advance hose out of the distributor and capped it with a bolt, and that immediately got rid of the pinging and the car ran a lot smoother at highway speeds and under load. Unfortunately doing this has made it a bit sluggish poking around town and at low speeds so I turned up the idle to compensate for it, which isn't ideal but it worked well enough to drive it 900+ ks to NSW from Melbourne in one day and back a week later....
So I'm now thinking there could be an issue with the distributor? Thoughts anyone?
Oh and Merry Christmas to the extended torana family out there!
Took it to my mechanic, he initially took it back to 10 deg BTDC, which didn't seem to make a hell of a lot of difference when I took it for a spin. So he then took the vacuum advance hose out of the distributor and capped it with a bolt, and that immediately got rid of the pinging and the car ran a lot smoother at highway speeds and under load. Unfortunately doing this has made it a bit sluggish poking around town and at low speeds so I turned up the idle to compensate for it, which isn't ideal but it worked well enough to drive it 900+ ks to NSW from Melbourne in one day and back a week later....
So I'm now thinking there could be an issue with the distributor? Thoughts anyone?
Oh and Merry Christmas to the extended torana family out there!
#15
_LS1 Taxi_
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Posted 28 December 2015 - 10:34 AM
Sounds like the dizzy needs graphing.
#16
_74LH_
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Posted 28 December 2015 - 11:08 AM
Dammit...gave them the cam specs the first time too....ah well ill take it back and see what they can do
#17
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Posted 29 December 2015 - 06:39 AM
Sounds like the carby may need a good tune and check if there is a vacuum leak at the distributor.
#18
A9X
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A fortunate run
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Posted 29 December 2015 - 10:08 AM
give it to ian tate, he'll sort the dizzy and quaddie.
#19
_74LH_
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Posted 29 December 2015 - 01:02 PM
give it to ian tate, he'll sort the dizzy and quaddie.
Oh awesome...been looking for someone who can do it all at once. Does he have a dyno?
#20
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Posted 29 December 2015 - 02:23 PM
yes he does
and he knows his way around them both.
#21
yel327
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Posted 29 December 2015 - 08:47 PM
Make sure you have the right carb for the gearbox too. If you use an auto carb on a manual it'll vacuum advance at idle.
What is the carby number?
What is the carby number?
#22
Ice
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Posted 29 December 2015 - 11:45 PM
What are you saying Byron if i buy a rochester carb it must be to suit an auto in my caseMake sure you have the right carb for the gearbox too. If you use an auto carb on a manual it'll vacuum advance at idle.
What is the carby number?
im looking at one atm not sure if its the right one will some numbers help to tell what it came off
#23
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Posted 30 December 2015 - 06:23 AM
No Gene, from 1/75 auto and manual are the same carby as the same vacuum port required for manual vacuum advance is needed for canister purge, so from 1/75 the carbs have both vacuum ports and on a manual the auto port has a bung on it.
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