Joined: Sat Feb 18 2006, 01:31PM
Location: your mom's new "Friend" in Lawrence, KS
Posts: 81
Im running and 850 Holley on a 415 inch small block- 650 dropped major power across the whole range even though the air hat on dyno said it was only pulling 618 cfm (i think the higher velocity of smoller venturies wouldn't let the fuel stay suspended in the air as it made the turns into the manifold). I just depends on what you wanna do with motor. ive seen 383 chevys make mor with a 1030 cfm than 750 even though the formula says a 650 would be sufficient. mordern intakes are showing now that the old rule of (that engine is overcarbed) just donesnt hold up anymore. PLUS with the amazing advances in booster tech, big carbs are not dogs down low anymore.
Joined: Mon Feb 20 2006, 08:12PM
Location: Ontario,Canada
Posts: 950
I also run a 4 hole 1 inch spacer under my carb.. I found it helps the bottom end, and made the throttle a lot more crisp... I thought it was worth the $15 on ebay I paid for it..
Volumetric efficiency depends on a lot of things; on an aging smog engine it would be around .70, an all out (naturally aspired) racing engine .90, turbo/supercharged can go above 100%.
This is no absolute truth, but gives an indication of carb sizing.
Also, carbs like the TQ are an exception, due to the regulated secondaries.
Personally, I like the TQ since it can really achieve good performance without too much sacrifice in economy (thanks to the spreadbore design with small primaries).
Joined: Wed Oct 12 2005, 12:14PM
Location: Antarctica
Posts: 702
MopesdoFly wrote ... Im running a 9800 series thermoquad On the gremlin Seems to be a very good carb thinking Of putting one on the super dodge in summer The newyorker has a thermoquad also but I was told it is different because it's a leanburn carb (Is there a difference between an older thermo And one off a leanburn car ?) less Cfm or internal sizes
I tried to put a 77 or so TQ on my 73 but couldnt get it adjusted properly. Cant remember though what's the difference exactly.
Joined: Sun Feb 26 2006, 08:46PM
Location: Kingston,Ontario
Posts: 5622
sjak_brak wrote ...
MopesdoFly wrote ... Im running a 9800 series thermoquad On the gremlin Seems to be a very good carb thinking Of putting one on the super dodge in summer The newyorker has a thermoquad also but I was told it is different because it's a leanburn carb (Is there a difference between an older thermo And one off a leanburn car ?) less Cfm or internal sizes
I tried to put a 77 or so TQ on my 73 but couldnt get it adjusted properly. Cant remember though what's the difference exactly.
The LeanBurn carbs do not have a port for the distributor vacuum advance.(The leanburn system does not use a vacuum advance distributor). The jet sizing is different also and so are the metering rods. They also have electric idle solenoids on the right hand side--no idle screws on the left side. Depending on year,the fuel feed line is in a different location as well. !cowboy