Jetting help needed for turbo holley

[richiew]

Been helping with a turbo setup using a 650 double pumper holley and need some jetting help,specs are 2276,cnc comp elims 46/40 with a little clean up,fk46 on 114 lobe centers,8.5/1 compression, 1 5/8 header,cb to4 .69 on the exhaust side, it has 73 jets on the primary side and 78 on the secondary at the moment,so any help from anyone who has worked with this setup would be great,cheers richie,uk

PS carb came from Rick Sadlers old pro turbo car so pressumably had any mods needed already done to it

[Marty]

If it is a mechanical secondary, the jetting should be more "square" like you have it.
If it is a vacum secondary, keep the primaries smaller (like a 64) and the secondaries larger (like a 88).
A wideband will help our GREATLY in jetting them correctly.

[richiew]

Hi Marty,yes its a mechanical secondary,have an LM1 hooked up ready to go,so far just bedded the cam,and put 25 miles on it to check its all ok,any suggestions on a starting point,cheers richie,uk

[Marty]

Start with what you have.

[Matt Davis]

67 pri  -  76 secs would be a good start. What are you limiting boost to?

[pcarney8008]

Hey guys ... I had a similar question..
I just recieved free an 850 double pumper and jet size would be appreciated...
2387cc...7.5 comp...255@.050 and 589 lift with 112 lc... comp elims...46x38...
1 5/8 header and T3/T4 hybrid ...
3.88 with 3.40 -1 , 2.21 -2 , 1.48 -3 , and 1.04 -4
what jetting approx. would be greatly app.
Whats up Richie ?

[richiew]

Mat,will be running about 23/24psi to start with then turning it up when its sorted,what fuel pressure should we start with?cheers richie,uk

[Matt Davis]

I like 6 1/2 - 7psi. If you have a Holley regulator, monitor it after every pass. They are notorious for spiking then going low then rising again. Or for a piece of mind, use a Mallory Reg.

[richiew]

mat,will have to look at the needle valve as when we tried more than 5psi it started leaking out of the throttle pump shooters? so i have it at 4.5 at the moment,float levels seem good,it does have the holley regulator on there,cheers richie,uk

[Mat Sanchez]

Fancy swapping regulators? Mine's jammed at 6.5 (according to the guage). 

[richiew]

Okay update.

We tried it today,15lbs of boost,27 degrees total timing with te boost retard taking 3 degrees out,jetted as was with just over 6lbs fuel pressure,detted real bad,this was with sunoco 118 mixed 50/50 with 99 octane pump gas,took 3 degrees timing out,mixed the fuel at60/40 still detted,took 2 more degrees timing out,better but still slight pinking,now got 75 jets in the primary,same secondary as we dont have anything bigger till tommorow,put the fuel ratio up to 80/20,will try again tommorow as its raining now and to slippery to continue,any suggestions or thoughts welcome,cheers richie,uk

[Mag00]

 You might try Straight 118 to get it dialed .. then if you feel froggy , back off on octane...Octane is your friend .

[Matt Davis]

I start tuning at 26 deg's and 67-68 on the primarys and 74 or so on the secs and I've never had a det problem.

I usually run a VP110 or VP112 to get it running and as I add more boost I up the octane, the jets and back down the timing to 22/24 deg's. Start small work big. VP C-16 (117 motor octane) isn't the answer for every turbo engine. Especially ones that aren't in the 25+psi range. Too much octane will make your engine lazy.

I run VP fuel, so you would have to check the VP site for actual motor octanes compared to that of the Sonoco that you are running.

[richiew]

Thanks mat,we are getting there now,still needs more fuel but we will have to wait till next weekend now for more jets etc,cheers richie,uk