broken 4af with a workin 3ac and a 7a bottom end

[laundryhamper]

So I have an 88' corolla dx wagon with a 4af engine that i just rebuilt the head. The bottom end has just crapped out . I havn't taken it apart yet but i predict a spun bearing with damaged crank, rods, pistons and block.

I also have sitting around a fully working 3a-c from a tercel. I also have a block, crank, rods, pistons, and bearings from a 7a engine.

I want to get an engine together so i can get my car back on the road. Can I fit my "f" head and all engine accessories onto the 7a block and bottom end and fit that into my 88' rolla.

I understand that would bring about a bump in displacement due to stroke. I do'nt know what this will do to the compression ratio or if there will be interference between the pistons and valves.

The 3a engine has a smaller bore so I doubt that I can use the F head which works with the existing carbs and exhaust in the car. I also found that the stroke on the 3a is shorter than the 4a so using its crank is out.

I believe the 3a-c is useless for my problem. Will the combination of the 7a block and the F head work with a reasonable CR?

Thanks

[freakinbox]

well since those are all different displacement engines it'll be simpler to just buy another 4a engine, 4af/e, or a 4age

[toyotaspeed90]

the 7a block will work fine..... you'll just need to make some adjustments on fuel delivery

[laundryhamper]

Good to know I can use the 7a with my old head. I take it by fuel delivery adjustment you mean tuning the carb so it doesn't run rich or lean w/ the new displacement. I'm cool with that.

I read from some search that the piston dish on the 7a pistons was 12 cc's and the 4a-f pistons have a 8 cc dish. I also found that the CR for the 4a-fe is 9.5 and another source said the 7a-fe was also 9.5.

I plugged in the numbers assuming the above CR's and piston dish volumes and calculated 9.7 CR for the 7a block and pistons w/ the 4a-F head. The 7a block and crank with the 4a-F pistons and head yields a CR of 10.4.

9.7 CR means I can either retard my ignition timing and/or use 89 octane in place of 87 like I had been using prior. Somebody correct me if I'm wrong or add any suggestions.

Can somebody verify the stock CR of both the 7a-fe and the 4a-f and the piston dish volumes as I have found conflicting data for these measurments.

So far its looking like I'm going to pull the old block this weekend and begin assembling the 7a bottom end.

[freakinbox]

all I am saying is for what it's going to take you to build it up you could buy a 4age... I don't know how much a 7afe is

[laundryhamper]

Sorry if it isn't clear from my first post, but I already have the 7a bottom end in almost new condition. I don't want to buy a junkyard 4a-f if I don't have to because of the uncertainty of how much life is left in it.

This is the most super budget rebuild ever. If I need to get another engine...I may or may not scrap the car and either go w/o a car or find another car for <$300. This corolla is my 2nd $150 running toyota and I just spent about $100 on a new head gasket set and lapped the valves and replaced the valve guide seals. For $250 the car ran strong and did not burn oil.....however it did leak it and did die due to my neglect. (shoulda replaced that crank seal)

From your responses freakinbox and toyotaspeed90 it seems that this will work with not too much more $$$ invested. I'm still open to anybody's $0.02 if I am assuming something incorrectly.

Thanks

[toyotaspeed90]

well..... if you use 4afe pistons in the 7a block... you'll have a higher CR.... if you use 7a pistons (even with the 4af head) it'll be the stock 7afe compression......

[freakinbox]

I am saying use the block you have... but you will need internals and those are cheaper if you find an engine. And fyi when I say 4age is cheaper you can get the ones that are imported with around 40 000 km (24854 miles).

At this point you still need a crank and connecting rods. Oil pump? water pump? all the shit to make the engine run. Not sure what you have on the 4afe that is interchangeable and what on the 4afe is still good. Not to mention all the gaskets and such.

You can get a 4age for around 300 - 400, your looking at more than that to rebuild it in my opinion.

[laundryhamper]

Thank you for your feedback. At this point I am set to do it. I do have the 7a crank, rods, pistons, and bearings. I'll use the waterpump and accessories from the 4a-f as they are all still good. The only question is the oil pump but considering I have everything else including a huge box of assorted gaskets to do multiple rebuilds I'll just look for only the pump or hopefully the pump is still usable.

again, thanks

[freakinbox]

yeah when you said you had a 7a block to me that meant just that, only a block.
I'd check to make sure the accesories from the 4af are good for the 7af your building since there were small changes even with the 4af - later 4afe's