Roush 427R and Quick Fuel QFT 750 jet sizes?

[ha_pe_1968]

Hi!

Anyone around with a Roush 427R and a QFT 750? It would be helpful for me to know what Powervalve and jetsizes you are running. Will post mine today evening. (I know sealevel, temperature and humidity makes some differences but a reference would be great)

Thanks a lot!
Peter

[ha_pe_1968]

Primary main jet:72
Secondary jet: 84
Idle air Bleed: 73/73
Hi speed bleed: 35/35
Pri Nozzle: 31
Sec. Nozzle: 31
Needle and seat: 110
Power valve: 9.5

[Hotfingrs]

Originally Posted by ha_pe_1968

Primary main jet:72
Secondary jet: 84
Idle air Bleed: 73/73
Hi speed bleed: 35/35
Pri Nozzle: 31
Sec. Nozzle: 31
Needle and seat: 110
Power valve: 9.5

9.5 seems high for a PV. I believe most come with a 6.5. I run a 2.5 in my EM and a 4.5 in my ERA.

[ha_pe_1968]

yeah i thought the same...for this type of cam i should run a 4.5 or 4 PV. At the carburator there was a 6.0 installed and it was very lean below 2000 rpm - so lots of stumble. I get an advice to go with the PV to 9.5 and it was a lot better.
But think the right way will be to go with a 4.5 PV and increase the primary main jets.
Thats why i was asking for infos from other members with the same engine.

Peter

[Hotfingrs]

If you're getting a stumble, try increasing your squirters to 33 or 35 and see if this helps.

[Jerry Clayton]

My old days self learned rule of thumb----------starting jet sizes for Holley carbs worked out to be in the region of jet number sorta matching carb CFM ratings----IE-your 750 cfm carb I would begin with around #75 jets in the primaries and more times than not---would start with a 4.5 power valve just to be able to work on the normal driving tune before then advancing into the hard acceleration and WOT stuff----------

[ha_pe_1968]

Hi!

Thanks a lot for the advices. I will buy some PV´s and jets and will then test the emissions again.

Hotfingers, with squirter you mean the Primary nozzle?

Thanks a lot and greetings from Austria
Peter