4a head swap

How-to's and repair secrets for your 4WD can be found here. Have a question? Ask it in here!
Post Reply
Posts: 42
Joined: Sun Feb 05, 2017 5:42 pm
My tercel:: 1988 DLX Tercel Wagon w/ weber

4a head swap

Post by SirFoxx » Thu May 18, 2017 8:44 pm


I have two quick questions. First is, if I have a 4a head redone and swap it onto my 3a, will I lose any power?

Second question is about my rear wiper arm. I bought a new wiper blade for my rear wiper, and I noticed that my wiper arm doesnt press down hard enough to fully engage the blade. Did I buy the wrong blade, or is something wrong with the arm?

User avatar
Highest Ranking Member
Posts: 3210
Joined: Tue Apr 02, 2013 10:02 am
Location: Farmington, NM

Re: 4a head swap

Post by irowiki » Thu May 18, 2017 10:20 pm

Might have to take the arm off and bend it a bit.
81 Coachmen RV, 65k miles
95 Camry Wagon, 135k miles
04 Camry Sedan, 213k miles

User avatar
Highest Ranking Member
Posts: 774
Joined: Sat Jan 01, 2011 1:49 pm
My tercel:: Multiple

Re: 4a head swap

Post by rer233 » Fri May 19, 2017 4:41 am

Is the spring-loaded pivot for the arm free? I've had a bunch of 'em rust up and become stiff over the years. Sprayed some PB Blaster on the pivot, worked it back and forth by hand 'till it freed up, and all's well. As for the 4a head, I think the combustion chamber volume might be a little greater than the 3a, so yeah, you might loose a little power. Why not stick with the 3a?
if it aint there, there's a good chance it won't break!
83 SR5 Silver/Blue (Snowmobile/work beater)-totaled but drivable
85 SR5 Blue
88 SR5 White (the 'good' one)-not anymore-totaled
87 fwd silver wagon a/t
87 4wd dx Cream (a/t- not anymore- now m/t)

User avatar
Highest Ranking Member
Posts: 9775
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: 4a head swap

Post by Petros » Fri May 19, 2017 10:00 pm

the 4a engine has more displacement, both the 4a and 3a engine have the same compression ratio. this means the combustion chamber on the 4a head has to be slightly larger or it would have a higher compression ratio.

It is not difficult to compare the cumulonimbus chamber size, easiest is to measure width, length and depth. More accurate would be block it up level and fill from an accurate measuring device like a graduated cylinder (used in chemistry class). you measure the volume of the combustion chamber directly this way. you can also determine how much surface to mill off the head to get the volume the same, or to even raise the compression ratio to a higher level (I do not recommend going over about 10.5:1, max. which will require premium pump gasoline).

it will still run ok, but with slightly less power with the lower CR. it should be more ping resistant on regular fuel however.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

Post Reply