20R/22R hybrid swap writeup

[kyle_22r]

recently, i blew a head gasket. had the head machined, got it all back together, fired it up, and found that i now had a broken valve guide and the head had to come off again

i had a 20R head sitting in the backyard from my original engine, and figured i could try the hybrid that everybody has talked about but you find very few people who've actually done the swap.

i started out with one of engnbldr's complete head rebuild kits with new guides, springs, keepers etc, and bought a set of oversized 20R stainless valves and a 268C cam. i decided i wanted to stick with my 22R carb rather than going back to my 32/36 weber or worse yet, a 20R carb so i ponied up the $30 or so and bought a carb adapter from LC engineering.

the holes in the adapter don't *quite* line up with the ones in the 20R manifold(due to the 20R carb having a smaller secondary and the primary is closer to the secondary) so i got out the dremel and matched them to the adapter.

i also got a set of topline aluminum rockers off ebay. since my 22R is from an '82 celica, it had cast iron rockers, and the 20R had 6 iron rockers and 2 aluminum ones(probably from a repair). i think it ended up being about $100 for a set of 8 + shipping.

i had johnson's machine in tumwater do my machine work on the head. they did the installation of the valve guides, cut the seats for my oversized valves, do a 3 angle valve job with some mild bowl work and surface the head, since it was pretty nasty after 26 years.

as for installing the head, it plops right on the block, i used an OEM 22R head gasket. basically pretend you're installing a 22R head. torqued my ARP studs to 80lbs adjust the valves etc. your 22R distributor will work fine, and EGR is the same(though you're probably not keeping if you're doing this swap anyway). i noticed my LC egr plate on the manifold interfered with the carb adapter, so i took a round file and egged out the hole in the plate closest to the manifold and made a gasket that doesn't stick out as far.

remember, you need to use the 20R intake manifold, since the ports are round vs the 22R intake being square. from the factory, a 20R uses a water-choke carb so there's a water port on top the manifold next to the throttle linkage. the 20R doesn't have the bypass port on the water plate underneath like the 22R, so i took a piece of 5/8" radiator hose, and ran it from the port on the top of the manifold to the pipe on the back of the timing cover.

most 20R water necks will interfere if you have a mechanical fuel pump, so use your 22R water neck.

as for driveability, i kind of wish i had done some more port work. seems to have lost a little on the low end(most likely from the smaller intake ports) but it seems to like to rev. i also have the stock horrible exhaust manifold, but i'll be replacing it with a thorley header before too long. might also look into a single sidedraft setup if i ever find one on the cheap. in conclusion, i'd say unless you have a 20R head lying around or want to do a bunch of port work, it might be easier to just build up a 22R head. i like to rev my engine to the moon, so i'm learning to like this setup

[OliveToy]

So how much did that bump your compression, with higher compression I would think it would have more torque.

[kyle_22r]

from what i've heard it doesn't really bump up the compression much. the benefits mainly come from the port design. the 20R has intake ports that go straight into the combustion chamber, while the 22R uses swirl ports with a big lump in the center that swirls the air/fuel for more efficient combustion, with a side effect of not being able to rev as high.

i could've shaved more off the head, but wasn't too interested in messing with an adjustable timing gear with the motor in the truck.