Current pistons are good (issue is worn bore on #4)...I'm leaning towards sleeves and new rings, as JP replicas are apparently a bit 'soft' (i.e. not high quality), plus machining of some description will be required regardless...happy not to modify the head to get CR right.

Searching for alternative cam bearings, will make life much easier if I can dip the block.

see if you can get these cam bearings 3C6127N from Repco (about $42)

U need to talk to Pete..... He's the man.

Where do I find this Pete?

Go the Gemini Pistons and rods as they will accommodate the press fit gudgeons.

There are many things you can do to "blue-print" the motor upon assembly but I've included some of the most obvious ones below which are not difficult.

Weigh pistons and rods all individually and take material off the bottom of the rods to match them in weight. Mix and match heavier pistons with lighter rods. You should be able to get them down to within 1gram of each other using a cheap set of electronic kitchen scales.

Gt orph is right, don't get the block acid dipped as it will wreck the cam bearings but you can ask for just a "hot tank" which removes gunge etc. but doesn't wreck the cam bearings.

Get all the bits that go round and round balanced as well, it makes a heap of difference.

As you assemble it use plasti -guage to check all clearances on the mains and big ends. Thrust washer clearance should be the minimum in the range given in the specs - 4 thou from memory. Check compression ring gaps - from memory, top ring gap should be 12 -13 thou and second ring 10 thou..

While you're at it get a small die grinder (air powered or a small electric "dremel " tool) and radius the back of the valve seat which is often sharp - a small rounding of the turn here will improve gas flow. De-dag all the rough casting in the ports as well , paying attention to the top of the inlet ports as that is where the majority of gas flow occurs. Also smooth out the "short turn in the bottom of the port as it changes direction into the back of the valve seat. Dont' "polish" the inlet ports - looks nice in piccies but doesn't work - about a 120 grade abrasive is as smooth as you want but polish the exhaust ports as much as you like. Spend a day doing this headwork and it will pay dividends.

I haven't included everything here but these small "one-percenters", when combined make for a very sweet motor.


A G150 motor goes from 1471 cc to 1584 with Gemini rods and pistons and comp ratio of 9.1 :1 but as your Gt started as 1584 cc you might need to go oversize depending on bore wear. I believe that 40 thou oversize will give you 1622cc.

Somewhere on this site you should be able to find all the specs that I adhered to in building the Yellow Peril's motor about ten years ago using Gemini Rods and pistons - pm me if you need to know more.

Good luck with it.


YP

Cheers YP,

Thanks for the advice! I've got a mechanic doing the work for me, he builds performance engines (usually V8's). Unfortunately, when I'm working I seem to be working 12 hours days, when I'm not, I'm broke...so I'm getting someone with better mechanical skills than me to knock it on the head while I have a few bucks to spare.

He has a hot tank, but reckons it will still destroy the cam bearings. I'll drop in one Saturday and clean it by hand if I have to.

I'd have to admit, the more I think about Gemmy bits the less I'm attracted to the idea - how do I make up the lost compression? I'm not interested in machining the head to suit, although will have a quick snoop around to see if it's worth matching ports. All said, the motor is nearly 50 years old, the more I mod for performance the more the car needs to be upgraded, higher stress other components are placed under, things begin to be pushed to their limits and break etc, etc. I don't wanna do it again, so this will be a pretty standard build.

Cheers,
Duane

Hi Guys
All good advice
I sound like a broken record but you can still get cam bearings from USA under Chevy Luv 1972-74 or Isuzu 1817cc
http://www.ebay.com/itm/GM-ISUZU-OPEL-1 ... 726wt_1362

http://www.ebay.com/itm/Chevy-LUV-1981- ... 785wt_1124

http://www.ebay.com/itm/1972-1975-1-8L- ... f1&vxp=mtr

So can go for it with tanking
Cheers
James

another thing to consider would be getting valve seats done to suit unleaded fuel.

you may well find the head needs work done anyway, eg slight twist etc. Only downside i know of skimming the head for gemini conversion is that there is probably not enough left to do another skim later on. Hardly a problem though i guess, given limited use of a Bellett.

Cheers James...but all these listings show 3 bearings, my camshaft has 4...what's going on?

Hi
From memory
G150 and G161 cams are NOT interchangeable as different number of bearing surfaces
however size and listing of bearings interchangeable
Therefore need to buy 2 sets
To be absolutely sure put different cam shafts together and compare

(Similar to how you buy sets of mains for G161 and throw away smaller caps when rebuilding a G150)
Cheers
James

a bit off topic but does anybody know if the 1800 SOHC head will fit on a G200 DOHC block?

And the chain drive still work etc..... i guess Qn is, is a SOHC block near enough to same as a DOHC block so that a hybrid could be built ?

glenn

Hi Glenn
I had a similar discussion with 'isuzu performance' in USA
And he said the twin cam G200w and sohc G180ss blocks are interchangeable
But I wouldn't bet sheep stations on it
Cheers
James

interesting..... I guess one needs to look at both blocks very closely to get a better idea. In that case one could go other way, fit DOHC head on SOHC block.

Thanks James...cam bearings are on their way! We'll have a look when they arrive and see if it is safe to proceed removing the old ones...then the work will really begin!

No problema
They had better do the trick or my street cred will be shot

I bought some from US of A and they are now in my G161 - all good
Cheers
James

Cam bearings received and delivered, so the work can continue. We decided to reuse the original pistons and re-sleeve the block.

Water pump is proving an issue...paid a small fortune for a seal from Japan, but bearing and housing are stuffed. May try re-weld the housing and wait until a suitable replacement appears one day...hopefully a bit of modification and we can fit an off-shelf bearing from something.

Port matching and balancing will be pending cost estimate of the total rebuild - unfortunately I don't have the money to do everything I want to do.

So far the motor's a work of art, looking forward to getting my car back and going for a squirt!

so the bearings are the right fit? looking forward to seeing the finished product mate!

The cam bearings are the correct ID and OD, but are much wider than the Bellett's (especially #4)...we're going to machine them down and hope for the best.

Getting sleeves for the bore is proving an issue as well, so may have to go the Gemini route for pistons yet. Not if I can help it, but money is tight, so may just have to.

Oz kindly donated an OHC water pump for experimentation too - we are going to gut it and see which components can be used to refurbish the OHV pump, so the mystery and speculation may soon be over!

Hi All
I had sleeves fitted to my G161 a couple of months ago
They where G180 84mm rather than G161 82mm but cost about $350
If you are going gemini pistons and rods and don't want to sleeve as well then consider boring to 84mm.... Much better torque, revy motor and perhaps less cost
Re cam bearings ensure you match the cam tolerance to the bearings in relation to torque resistance to turn
They can be a little tight and may therefore become a big issue re wear, heat, failure
Please keep us informed re water pump
Cheers
James

The sleeves required are 81.5mmm, an odd size, so the cost goes up - that's why I think I'll most likely ditch the sleeves and go with Gemini pistons. Budget is tight, so if I can save $400-500 using Gemini pistons I'll be able to afford to balance the motor, or have replica exhaust headers made.

Re: cam bearings...I assume you've fitted these James? If I turn them down it should decrease the surface area a little bit (as oil holes are much larger, plus there's 2 of them in each bearing), so should spin more freely due to loss of resistance, yes?