4A-GE engine mix - question

[Maren]

Hey,

my name is Maren and I am new to this forum. Actually, my car is an MR2 MK1 but as it shares most engine parts with the AE and the AE crowd is much bigger than the MR2's, I decided to register here

However, I am troubling with the build-up of my new engine and could need some help from people with more experience. I tried to search already but didn't find an answer.

My car had an MAP-based Bluetop engine which rapidly wore due to a very stupid mistake (that's what the oil is needed for... )

I found an replacement which sounded good: rebuild Bluetop from an AE based on a 7-rip block, about 20.000km old. Unfortunately, it has been build with 18mm piston pins (and one stuck), some residues on one piston skirt which looks like metal, partly shiny polished cylinders, blue shaded crank, worn conrod bearings, etc.
So this one is crap, too.

Now I tried to find the best option to get an engine back into my car. I was running Megasquirt and Catcams before and currently I am working on one of the Bluetop heads (polishing according to the TRD bible) while a friend is making a manifold to run motobike throttles. So performance is an issue.

I have several options now, but the one I like most is buying a new shortblock for a smallport engine and combine it with the Bluetop head.

I could also rebuild the 7-rib block with smallport conrods and pistons to get the higher CR but I think it won't be much cheaper and I won't have the oil squirters then

Does somebody know if this fits together, SP block and BP head? Will I get the higher smallport's CR then or is it same as before due to the BP head?

Hope somebody can help!

Maren

[Ivan141]

Yes, smallport and bluetop block&head will mix. Compression is all down to the pistons, so in theory, you'll get the higher compression. But smallport blocks are hard to find. Furthermore, compression is not all that much higher than euro bluetop.. it's mostly the american dudes with the low compression pistons that have much to gain there.
If you're building a bottom end anyway, it might be interesting to consider a 7AGE.

[Maren]

Thanks for your reply, Ivan.

Actually, I always thought that EU-Spec engines have the same low CR of 9.4:1? So, if not, how much is it?
Most websites come from the US, that's maybe the problem.

I'm not sure if it is still available, but I was thinking about ordering a brand new shortblock. Considering that I would have to pay a few hundred Euros to an engine builder for reworking the cylinders and maybe also the crankshaft plus buying pistons, rods and bearings, the ready-to-install shortblock is not much more expensive (due to my job I have a good source for OEM parts).

I know I will have to shave the head and install a lower head gasket anyway as due to my work in the combustion chamber the capacity increased.

As ususal, it shall cost as less as possible and bring the best benefit

[oldeskewltoy]

A bit of research will help you quite a bit. First, have you seen the largest MR2 forum? http://www.mr2oc.com/

Besides that MR2 site, there is also http://www.club4ag.com.


Ivan141 is correct, parts of Europe got the 10 to 1 pistons. You'll know by if the car was originally equipped with a catalyst. No cat - 10 to 1, cat - 9.4 to 1. France required the cat, so they got the 9.4 to 1 engines


You need to decide WHAT you want, and then build it. It is easy to get diverted from your goals, so *IF* you do your research first, you will spend less, and enjoy it more.

A smallport head will make more torque EARLIER in the power band. That means equal mods, the smallport will be quicker in the first 60', then a largeport.


Finding a "good used engine" is rare these days. I recommend you build it from the ground up, that way you KNOW everything about it

Maren Wrote:I know I will have to shave the head and install a lower head gasket anyway as due to my work in the combustion chamber the capacity increased.

How much has the chambers been increased? I've done a LOT of 4AG head porting - http://www.aeu86.org/viewtopic/ost-porti...s/t/10896/




Depending on how careful you were, the chambers may only be 1cc larger (37cc, instead of 36cc) That 1cc enlargement only needs a .25mm cut on the head to get the chamber back close to stock, so a .25mm cut off the block(makes a perfect mounting surface) will give you a little extra compression - total with 37cc head and block cuts and using a "stock" 10 to 1 piston = about 10.3 to one when finished.

[Uzelac]

Got similar question, if anyone can help.

I'm not that in CR and displacement but would like what will i get with:

- stock BP block (was 4AGEC, 9,4:1) o/s to 81,5mm
- wiseco hicomp o/s 81,5mm pistons
- redtop head skimmed 1mm, no digging/porting

What CR should i get, can anyone figure with this info ?

Please, spare me reading about cc, skimming, domed and other pistons and similar stuff

Thanks

[oldeskewltoy]

Uzelac Wrote:Got similar question, if anyone can help.

I'm not that in CR and displacement but would like what will i get with:

- stock BP block (was 4AGEC, 9,4:1) o/s to 81,5mm
- wiseco hicomp o/s 81,5mm pistons
- redtop head skimmed 1mm, no digging/porting

What CR should i get, can anyone figure with this info ?

Please, spare me reading about cc, skimming, domed and other pistons and similar stuff

Thanks

not sure about others... I need a few more bits of info

1) need to know the dome volume of the Wiseco piston.
2) need to know chamber volume after head cut - guessing would place volume around 34cc
3) need to know what thickness head gasket?

[Uzelac]

http://www.wiseco.com/Catalogs/SportComp...Toyota.pdf

They say:
- dome dish is 5.9cc

i say
- not sure about chamber volume, head was stock and cut 1mm, thats all i know
- head gasket is 1mm, will use thicker if needed, that way i will adjust CR, hope i wont need to dig the head

Thanks!

[oldeskewltoy]

http://www.rbracing-rsr.com/compstaticcalc.html

bore = 3.208"

stroke = 3.031"

head gasket = .039" (1mm)

deck height - on a non milled block, this usually = .030"

Combustion chamber volume... with just a 1mm cut... it is somewhere between 33.5 and 34.5cc. Stock chamber is 36.25cc

A rough estimate would therefore put static compression between 11.5 and 12 to 1.

[Uzelac]

Thanks

I was hoping stock chambers are bigger.
How much would i gain if i remove casting marks, i've seen there are nice ridges around valves.
What is easiest way to enlarge chamber by 1cc ?

Thanks

[oldeskewltoy]

the side walls of the 4AG head are pretty thick, I've actually added nearly 3 cc to a stock head, so you should be able to add 1cc to a cut head.

stock head on top, "opened chamber" head below - note gap, or lack of it, between chambers



*BE FOREWARNED* it is VERY easy to screw things up royally.... if you add too much... there isn't a lot you can do... also as you add, you need to measure each chamber to make sure it is only 1 cc.