Twin cam = dohc?

[dohca]

4a-f and 4a-fes are twin cam.

except one cam is cog drivin off the other.

toyota uses dohc as well as twin cam.

my old celica had dohc turbo on the side.

but twin cam turbo on the steering wheel

go figure.

[Chickenman]

Thats what I wanted to know dude! Thanks, So twin cam on the economy engines is different, not true dohc. Ka Pai.... you get a minty

[dohca]

yes 4a-f series engines are true twin cam.

just there way of driving the seperate cams is slightly different to a 4age or 3sge etc

i belive the 1gfe is similar

the belt drives the right cam, the right cam has a cog on one side which drives the other cam

if there is two cams its twin cam.
can also come in a vast array of valve arrangements ranging from 8 valve to 24 valve.

[Malcolm]

to elaborate slightly, I believe most, if not all Toyota "F" series head (narrow angle valves) utilise a single cam gear on one cam, and cogs on the inside, under the valve cover, to move the second cam. I believe that this is because the cams are too close together, and if you had the correct sized cam gear on each camshaft, they would touch, or not fit at all, and the only way to get around that would be to make the cam gears smaller and the crank gear smaller (remembering that the crank gear must have exactly half as many cogs as the cam gears)which may be physically impossible as it's minimum diameter is limited to that of the crank shaft end. Then they would also have make the water pump gear smaller, and the oil pump gear smaller etc, and all this is a lot more work and expense than utilising the system they use.

[GUDGRL]

and i thort my 4A-FE was single cam. U learn something new every day!

Question (ill put this out on the tech forum too)

ive got a fully standard ae101 levin with a 4A-FE engine that has 171kms on the clock.
is it worth buying a 20v silvertop engine for $350 (not sure on kms) and chucking that in?
Also how much roughly do you reckon the conversion would cost?
im selling her atm coz of the kms and the engine, but if its a good idea to chuck tht engine in then ill get onto modifying her.

[Malcolm]

for the most part the conversion should be plug and play. Find the right person to do it and it shouldn't cost much more than $800.