F or 2F: Lowest possible idle speed?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

B

bikemaniac

10 Year 15 Year
Joined
Feb 3, 2010
Threads
96
Messages
183
Location
Copenhagen, Denmark
Hi,

As for F and 2F engines: What would be the lowest possible idle speed still being adequate for sufficient lubrication? Basically I would like to know if it is possible to make a F or 2F sound like this V8:



Look after 1:20. Is this a distinct V8 sound or can an I6 sound similar?

Thanks, Lucas
 
I love flatheads; still own one (a motorcycle).

IMO, you'll never get an I6 to sound just like a V8, they just have a different balance and rhythm.

Personally, I wouldn't run an F or 2F below 650 rpm. The plain main bearings must have a certain amount of oil pressure to work; why risk it?
My bikes have roller bearings on the crankshaft and rods; you can run them as slow as you want and with minimal oil pressure. The Indian oil pump is more of a gravity-feed regulator than an oil pump by modern standards - but the F-series motors need oil pressure for the bottom end, not to mention the cam and flat tappets.
 
When I worked in a old Buick dealership back in the late 70's, the old time mechanics said they used to have competitions on how low they could get the RPMs on straight 8 Buick engines. They said it was all in how consistent and accurate the valve adjustments were. I don't recall the actual numbers were but it was surprisingly low.
 
V8's will always have a distinctive sound. While sometimes other engines come close, it will never have that same throaty bellow. End of story. As they say, there's no replacement for displacement. My 4 cylinder Tacoma (with a flowmaster and sounds plenty strong) doesn't sound like my 40 with an F engine (and headers; it sounds even more strong), which doesnt sound like my dad's 1968 Super Sport Chevelle (which absolutely thumps). That being said, it is possible to get the most grumble out of any given engine. You can change any engine's exhaust note in basically two ways: a new exhaust system (headers and muffler, specifically) which will change the way it resonates and flows; or, a new camshaft which will alter the timing of the valves and their lift, which in turn alters the sound. As to idle speed, I think it's impractical to go below about 700 RPM with one of these ol F or 2F motors, as has been said already. They're tough and stout, but aren't performance tuned by any stretch of the imagination.
 
Personal opinion. Nothing factual to back it up. But I have run and torn apart and rebuilt both F engines and 2F engines. The 2F has much better oil flow than the F engine.

I can run my 2F at 650 rpm and still have decent oil pressure (assuming tuned properly and no misses due to various issues). There is no way I would have, or could have run the F engine that low.
 
If you're only doing it for a minute or two at a time, it shouldn't be a big deal. Heck, Me and a whole bunch of people watched @orangefj45 wheel @greenfox's 72 F engine on its side for a good 5 minutes at Katemcy 7or 8 years ago. Ryan said there was no long-term damage. It was an unforgettable sight.

I set one of my buddies '78FJ40s at 450 after a tune up, purring smooth as a kitten. He called me the next day thinking he had a new electrical problem because his turn signals wouldn't flash when he stopped the truck. I laughed and explained to him the RPM was too low to energize the alternator. He had me turn it back up to 650.
 
Lastly, FWIW, I have @Mace's old 40 series flowmaster in Ruftoys with a tri-Y header. At 500rpm, it has fooled a LOT of Landcruiser owners who mistook it for a V8.
 
65swb45 said:
Lastly, FWIW, I have @Mace's old 40 series flowmaster in Ruftoys with a tri-Y header. At 500rpm, it has fooled a LOT of Landcruiser owners who mistook it for a V8.
Click to expand...

Funny you should say that. My FJ40 (with flowmaster) has been mistaken to have a SBC many times based on the sound at slow speeds. They obviously did not follow me uphill!
 
65swb45 said:
Heck, Me and a whole bunch of people watched @orangefj45 wheel @greenfox's 72 F engine on its side for a good 5 minutes at Katemcy 7or 8 years ago. Ryan said there was no long-term damage. It was an unforgettable sight.
Click to expand...

I remember that well, and even took some photos:







 
dual exhaust and a cam and you won't be certain what you're hearing...I have had a 2F chugging at about 200, but only to look for vacuum issues and only for a minute or 2.
 
Dual exhaust!! Now you're talking Rod Wiggins from the old SNLV crew. I think @4Cruisers remembers him.

Great pics @1911. Takes me right back.
 
When I first installed Jim C's freshly rebuilt carb back on my '78 it purred like a kitten at 540 rpm but I set it up and timed it at 650..........
 
65swb45 said:
Dual exhaust!! Now you're talking Rod Wiggins from the old SNLV crew. I think @4Cruisers remembers him.

Great pics @1911. Takes me right back.
Click to expand...
Yep, I remember Rod from the two short years we were members of SNLC. The club was probably the part of living in Las Vegas we missed the most when we moved back to northern New Mexico.
 
The 77 we picked, had up a MAF(we think) cam, header and pretty normal muffler. Darn thing sounds like no 2F I have had, more like lumpy V8 at idle
 
I'm upping this thread because I'm surprised to see numerous posts stating that it's not good for the engine to go lower than 650rpm idle speed.

Actually the 1971 F engine FSM states the idle speed is 500rpm (except for the US but I guess it's for emission?).
1654107086659.webp


Even the 2F FSM states 650+-50rpm (except ECE and US....) so should be fine to run at least as low as 600rpm?



After decades with a carb that would not idle under 900rpm what a pleasure to have it set at 530rpm currently... I still needs to get used to it, at every red light I think I stalled because I can't hear my engine anymore xD
Oil pressure seems good at idle, stays around the 2/3 mark as always.
Alternator not energizing is a true issue, it's not always the case, I think if it was charging when getting down to idle it stays energized but otherwise will not start charging. Although I have no issue with blinkers I noticed the honk would pull down the V low enough that it does not produce any sound (except the relay clic), small issue.



The engine braking is just astonishing with this idle speed, it's a true pleasure offroad and feels a lot more confident. On road you can do some eco-driving using a lot less your brakes xD

I calculated that with my 1974 with the first version of the H41 with 5.3 first gear, 2.3 transfer, 3.7 diff and 500rpm idle, it would theoretically idle in low first at 1.6kph / 1mph.



So, why not following Toyota spec on a F engine?
 
flx said:
I'm upping this thread because I'm surprised to see numerous posts stating that it's not good for the engine to go lower than 650rpm idle speed.

Actually the 1971 F engine FSM states the idle speed is 500rpm (except for the US but I guess it's for emission?).
View attachment 3022651

Even the 2F FSM states 650+-50rpm (except ECE and US....) so should be fine to run at least as low as 600rpm?



After decades with a carb that would not idle under 900rpm what a pleasure to have it set at 530rpm currently... I still needs to get used to it, at every red light I think I stalled because I can't hear my engine anymore xD
Oil pressure seems good at idle, stays around the 2/3 mark as always.
Alternator not energizing is a true issue, it's not always the case, I think if it was charging when getting down to idle it stays energized but otherwise will not start charging. Although I have no issue with blinkers I noticed the honk would pull down the V low enough that it does not produce any sound (except the relay clic), small issue.



The engine braking is just astonishing with this idle speed, it's a true pleasure offroad and feels a lot more confident. On road you can do some eco-driving using a lot less your brakes xD

I calculated that with my 1974 with the first version of the H41 with 5.3 first gear, 2.3 transfer, 3.7 diff and 500rpm idle, it would theoretically idle in low first at 1.6kph / 1mph.



So, why not following Toyota spec on a F engine?
Click to expand...
If you had a mechanical oil pressure gauge on your engine, you wouldn’t be asking this question.
 
White Stripe said:
Open header 2F sounds pretty good at idle. Turns heads at the drag strip-well, until u go down the track that is.
Click to expand...

It'd still turn heads.....

At first very slowly as you make your pass. Then quickly side to side at short intervals after.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom