I heard that you shouldn't really go larger than a 390cfm 4 barrel? Why do you think it's too small, does it just sound like you have alot of hesitation, when you punch it? Do you know who makes a carb. that will fit the 300, that's larger than 390 cfm? What do all of you guys think is too large for the 300? (well, besides the obvious, like those 700 cfm monsters)

Chris
1982 F100 Flareside
300" T18 4speed
Blue & Silver

 

Steakman, Edelbrocks 500 cfm carb would probably still work on a 300, in my opinion.

 

Steakman, Edelbrocks 500 cfm carb would probably still work on a 300, in my opinion.

 

WOW! That's awesome! I always thought that the 390 was too small, I mean just look at the thing, it's kinda scrawny, plus those secondaries look too small to do any help, and it's bad when the girls think it's cute. :-) Thanks for the info, I'll just continue to save up my money! By the way, one last question, will that 500, or 450 for that matter, hook up to the manifold for the 390? Do you have to have one custom fitted?

Thank you!
Chris
1982 F100 Flareside
300" T18 4speed
Blue & Silver

 

While mine was on the dyno a Wide open throttle it started to build Vacumm at anything about 3500 rpm. the guy running the dyno told me that that is caused by too small of a carb because the carb isn't flowing enough air so the engine is still tring to suck more air and creates a vacumm again. at 4000rpm I had 4hg of vacumm and 5000 rpm it was pulling 7hg of mercury. this is with the holley 450 on it. I now have put a edelbrock 600cfm on it and there is a noticable difference from 3500rpm up than with the 450cfm on there, and get slightly better milage too. But I'm running 9.5 to one compression, 260* .447lift cam, pocket ported/gasketmatched heads and true dual 2" pipes with super turbo mufflers, it breaths really good...... I was told by a old inline six racer that anymore cam than a decent torque cam and you lose torque faster than you gain HP.

 

BTW: I'm running a Offenhauser DP 360* intake, which will mount any holley base carb from a 390cfm to the 850cfm monsters......

And if you got a vacumm gage in your truck/car and the vacumm goes above 5hg at redline you need more carb....

 

Cool, thanks alot! Just another reason I like this site, I always get the real world view on things, before I buy them!!!

Thanks again Bog'n!

Chris
1982 F100 Flareside
300" T18 4speed
Blue & Silver

 

[font size="1" color="#FF0000"]LAST EDITED ON 23-May-00 AT 09:26 AM (EST)[/font][p]My 1994 F-150 4.9L w/3.55 gears and a 5-speed gets 16-18 mpg; I do a lot of city and highway driving and that's about what my average is. Still, it kills me to fill up both tanks right now with the way gas prices are, about $37-$40 each time.

 

Do any of you have experience with Rhoads variable duration lifters?
The reason I ask is I have a Clifford 270 EFI cam and kit sitting in the garage right now, which will eventually make its way into a blueprinted/mildly modified 300.
I have heard differing opinions on these lifters varying from "why introduce another uncontrollable variable" to "best thing since beer".
I would like to be able to run this big a cam but not lose any bottom end, either, and I wonder if the Rhoads (or equivalent) is the answer.
Eddie

 

I have a 94 4.9L efi with a 5 speed
right now i'm getting about 14.5mpg in the city
I've kept it tuned up, but i've never had my injectors cleaned. maybe that will help bump it up a bit.

 

I had a 240 straight six in my 1968 F100 shortbox, with the factory Dana 60 with 4.10 gears and the locking rear diff. highway it got 17 miles a gallon, town down to about 12-13, I took it out and put a 360 in when I took it on a trip. the dipstick read just fine for oil, partway into the trip it got a tapping sound, it got worse and worse, I checked the dipstick and it was low, when i got back from the trip low and behold the dipstick read wrong, full was 2 quarts low, the engine ran close to 130 miles each way on about 1.5 to 2.5 quarts of oil, and I took it home and changed the oil added the 5 quarts it should have and found out that the dipstick reads higher than the mark for full (if that makes sense, "full" was actually 3 quarts) that really sold me on the dependibility of a straight six, and if you dont believe me, when I drained the oil pan and put it in a milk jug for recycling there was half a gallon of oil that came out, I'm not making that mistake again... but 17mpg highway with 4.10's and 3000 RPM at 60mph to 65mph with a 68 240 with 145,000 or so I dont think it was ever rebuilt because it still had the tag that read 240 on the coil mount still

 

Ive got a 79150 4x4 w/300cid. Nothing special all stock and I get about 15-16. I feel very blessed.

 

before my carb started giving me fits, the trck would get 20.1 mpg if i drove it like a grandpa! driving it normally like i do it got an average of 18 mpg. now that the carb is going, i get about 9-10 mpg.

David
85 F-150 300 I6
C4 3 speed auto 2.47 FDR

 

My truck is an 88 5 speed, with (I think) 3.73's. Honestly I do not know and never checked. Its a shortbed, short cab, 2wd, with "0" options. I get between 11 and 14 mpg on the summer (non-oxygenated) gas. In the winter, with that MTBE/oxygenated, poor-excuse-for-fuel they sell in the winter around here, its more like 9-11 mpg. I do not drive harshly either. And, factory MPI FI. No hotrod parts either; its all stock. This crappy mileage is why I am converting to a 302 or 351...might as well have an 8 if I am going to be getting 10 mpg anyhow.

 

My truck is an 88 5 speed, with (I think) 3.73's. Honestly I do not know and never checked. Its a shortbed, short cab, 2wd, with "0" options. I get between 11 and 14 mpg on the summer (non-oxygenated) gas. In the winter, with that MTBE/oxygenated, poor-excuse-for-fuel they sell in the winter around here, its more like 9-11 mpg. I do not drive harshly either. And, factory MPI FI. No hotrod parts either; its all stock. This crappy mileage is why I am converting to a 302 or 351...might as well have an 8 if I am going to be getting 10 mpg anyhow.