4G32B/4G37 hybrid

[16LGS]

Hi all, interested in your views on this one.

I have a chain drive 4G32 in my tarmac rally car, 1770cc, 10.5:1, good port work, 45 DCOEs, #5 cam, decent headers. It goes okay, but like everybody I need more grunt! I've looked at all the options (eg 4G62, 4G54 etc) but for several reasons I'd like to stay with a 4G32. Going to belt drive is okay.

Looking at the 4G32, I think the main restricting factor is the valve sizes - no matter what else you do with these engines, you can only get so much flow through those small inlet valves. And there's really bugger-all room for bigger valves in the head.

So I've had a good look at a 4G37 head. Seems to me it would flow much better, having significantly larger inlet valves. Obviously putting the 4G37 head on a 4G32 belt drive block would drop compression dramatically, so you need the 4G37 pistons (of which I have a set). Because the 4G32 chain drive block can be bored to 1770, I'm guessing the 4G32 belt drive blcok can be, too. So the hybrid I have in mind is:

- 4G32 belt drive block bored to take 4G37 pistons
- nicely ported 4G37 head, shaved head if need be to raise compression
- #5 cam, using one of those chain-drive-to-belt-drive adaptors (I'm told that 4G32/4G37 cam blanks are totally unobtainable, and the #5 cam is absolutely the bee's knees, so I want to use that)
- Twin 45 DCOE's and headers from current engine (will fit with slight mods)
- plus all the standard building techniques - blueprinting, balancing, light flywheel and so on.

Any of you guys have any experience that allows you to comment on this one way or another?

Interested in your feedback!

Cheers

[astronturbo77]

are you talking about the 4g367 out of a nimbus? if so i think they are possibly a sirius engine? have you tried a 4g35 head (1770cc 4g32 engine)

[colta51]

i dont supose if this all goes well you will want to sell ya 4g32 head..? just thort i wood ask..

[Rally_2.6LC]

Sounds like an awesome idea. I had thought of doing work to my 4G32 as well to get some good power out of it, however im going the 4G54 path (but dont get me wrong, i havent been able to destroy my 4G32 in 4.5 years but 3 4g54's have shat themselves in 2 years haha).

Would be good to hear of your progress.


Cheers Matt

ps you say your current 4G32 is a 1770, what pistons are you running if they arent the 4G37 pistons?)

[75wagon]

Read this:
http://japanesenostalgiccar.com/forum/v ... php?t=5444

Dave...

[16LGS]

Thanks all, good feedback and encouraging. I've found a 4G37 donor engine, $150, just have to get it back from east of Melbourne somehow. A 4G32 Colt engine should be easy and cheap to find. The big question is "Can it be bored to (I think) 80.6mm like the chain drives?"

Re the 4G35 head, (1) are they actually any different to a 4G32? and (2) Where can I find one?

Yep, if it gets off the ground my current engine will be up for sale, maybe just the head. I have a couple of spare heads including a brand new round port 4G32 head that I've been saving up for 25 years!

I thought about the 4G54 option, I had a rally car with one in it a long time ago. I could never get its dynamic response right - high polar moment of inertia with that lump up front, although it had plenty of grunt and potential for lots more. But I want to keep my current car within the rules (or somewhere close!) AND I want to stay in the smaller capacity classes, so 1600 to 1800 is the go...The pistons in my current engine are C2 kit flat tops...

[astronturbo77]

a 4g35 is a chain drive 1770cc saturn engine. came factory with twin carby and no.2 cam i believe

[A112H]

4G35 is a 1.7l 1686cc engine that was ony offered between 1972 and 1976 in A55 GTO's and never released here, good luck finding one of those.
Here is a story of someone who did but the story ended unfinished, maybe Dave Trees or Hoonboy know the out come of this story?
http://www.bmsc.com.au/forums/rallying- ... -4g35.html


Hoonboy info
http://www.hoonboy.com/4g35.html

[astronturbo77]

ive personly seen one, and may try and buy it... i assume the 4g37 is belt drive only?

[75wagon]

ive personly seen one, and may try and buy it... i assume the 4g37 is belt drive only?

4G37 belt drives are out of the Non Turbo Mitsubishi Cordia's and also the Nimbus's. So they are cheap as.

Dave...

[astronturbo77]

i see what you are getting at dave with the link you have posted about the 37 head having better flow charactistics, and it makes sense putting it on the 32b block. but the 37 i believe is a sirius engine not a saturn engine??? can anyone confirm this?? of is it just a belt drive varient of the saturn engine?

why not just put a starion 4g63 engine in it?? they are a better alternative to a astron as they are lighter, but still make decent power..

[75wagon]

but the 37 i believe is a sirius engine not a saturn engine??? can anyone confirm this??

Confirmation: http://en.wikipedia.org/wiki/Mitsubishi_Saturn_engine

Dave...

[A112H]

I think the early Nimbus (1985ish) were a 4G37 Saturn 1.8l??
I think the 4G62 was the Sirius 1.8l in later Nimbus and Cordia's

[astronturbo77]

hmm i wonder why i thought they were a sirius engine.......

anyway proceed...

[16LGS]

Gotta love all this great feedback and discussion. Great stuff..

The 4G37 was in the first model Nimbus (or Wombus or Nimbat as we called them at the time) and yes its a Saturn. My take on it is that MMC wanted some more grunt out of the 4G32, and needed better flow to get it - but the chambers were too small to enlarge the valves, so they went to a larger chamber in order to get larger valves in, and domed the pistons to get the compression back up. Im keen to get the 37 head and pistons into a 32 block, as the 32 block (at least the early L300 ones or super-rare early GE Sigma ones) is non-silent shaft and therefore lighter than a 37 block (even without the shafts).

CAMS do permit the 4G62 SOHC as an alternative to 4G32, but that would mean fabricating intake manifolds, and extractors, and starting from a zero base in terms of camshaft. Going to the 4G37 avoids all that.

So now I'm on the hunt for a N-S configuration 4G32B, condition largely irrelevant...any ideas/

Thanks guys

[75wagon]

Gotta love all this great feedback and discussion. Great stuff..

This site truly is gold to blokes like us.
We all have different needs, but ask a question and it usually gets answered?
Got to love that...

Dave...

[cheaterparts]

CAMS do permit the 4G62 SOHC as an alternative to 4G32, but that would mean fabricating intake manifolds, and extractors, and starting from a zero base in terms of camshaft. Going to the 4G37 avoids all that.
Thanks guys

maybe a bit more work with the 4G62 but prob easier in the long run -

[16LGS]

Thanks Cheaterparts, I think you're correct - 4G62 would be the long term solution. But with two car projects, a boat project, and a house project, time is of the essence. I only do a couple of events a year so the simple way of getting a bit more grunt is probably the most achievable way! And the cheapest....

[pistorf]

4G35 is a 1.7l 1686cc engine that was ony offered between 1972 and 1976 in A55 GTO's and never released here, good luck finding one of those.
Here is a story of someone who did but the story ended unfinished, maybe Dave Trees or Hoonboy know the out come of this story?
http://www.bmsc.com.au/forums/rallying- ... -4g35.html


Hoonboy info
http://www.hoonboy.com/4g35.html

There were loads of 4G35s imported to aus in the late '70s and early'80s by API and the likes. I had one in my Galant at one stage.

[75wagon]

There were loads of 4G35s imported to aus in the late '70s and early'80s by API and the likes. I had one in my Galant at one stage.

4G35 is a 1.7l 1686cc engine that was ony offered between 1972 and 1976 in A55 GTO's and never released here, good luck finding one of those.
Here is a story of someone who did but the story ended unfinished, maybe Dave Trees or Hoonboy know the out come of this story?
http://www.bmsc.com.au/forums/rallying- ... -4g35.html


Hoonboy info
http://www.hoonboy.com/4g35.html

There were loads of 4G35s imported to aus in the late '70s and early'80s by API and the likes. I had one in my Galant at one stage.

API, I had forgotten about them.
I bought an A14 and a rally 5 speed off them for my Datsun 1200 Coupe years ago.
I wish I could get my hands on a 4G35 now... would compliment my wagon perfectly.

Dave...

[davetrees]

CAMS do permit the 4G62 SOHC as an alternative to 4G32, but that would mean fabricating intake manifolds, and extractors, and starting from a zero base in terms of camshaft. Going to the 4G37 avoids all that.

A 4G32/37 hybrid wouldn't be CAMS-legal for rally use ..... not in PRC, anyway. Cylinder block & head must be original.

Then again, if they look close enough to identical externally, who would know ?

[16LGS]

True story Dave, although if I make application I cant imagine why it wouldn't be an acceptable substitute - same manufacturer, number of cylinders, camshafts, valves, dimensionally interchangeable and all that....then again, given the vagaries of CAMS....

[davetrees]

They might come at approving the complete 4G37 as a 4G32 replacement ..... but I doubt they would approve a 4G37 head on a 4G32 block !

The approval of substitute engines by CAMS is generally based on providing competitors a cheaper & easier means of increasing engine capacity (hence the approval of the L20 motor as a substitute for the L16 & L18 in many Datsuns, or the 4G62 in Galants/Lancers) ..... so I reckon an application for approval of the 4G37 would have to stand a reasonable chance of success, seeing a similar capacity engine (4G62) is already approved ?

[16LGS]

I reckon there's a couple of options to overcome the dilemma - (1) Seek CAMS approval for a 4G32 belt drive as a replacement for 4G32 chain drive (shouldn't be an issue) then build a 4G32 belt drive with 4G37 head and custom pistons to remain within the desired engine capacity class (and regain compression lost with the 4G37 head), or (2) Seek CAMS approval for a 4G37 as a replacement for 4G32 chain drive, and run in the higher engine capacity class. As always it seems the cheaper option is the least desirable!