1725cc racer

[muzzagod]

Hi all, I live in Brisbane, Australia and am doing up a 1725cc motor for some Sprint & a little hill-climb racing. I want to bore it out a little bit (say 3 1/4" ) and am also considering say 100 thou extra stroke. have any of you guys done this? If so, what pistons did you use? Also con rods?

So far I have looked at Mitsubishi 4G64 and 4G52 pistons. Also the Toyota r21 engine pistons. I'd like to use 1.5mm wide rings (not 2mm wide).

Con rods - what about Chev 350 ones at say 5.7" or 6"?

At the moment I run a lumpy (sort of) cam, twin 40DCOE carbies, std. bore and 44 year old pistons with new rings, slight port & polish, fully balanced etc.

Any thoughts or ideas would be greatly appreciated.

Thanks,

Murray

 

[Jim E]

For rods you want the 250 chevy 6 cylinder units, the V8 rods are not wide enough on the big end. I think there is also a ford rod that can be used. Actually you are in the hot bed of big bore and stroked motors there down under

 

[alpine_64]

Murray,

There are quite a few motors in AU that run 2120cc they are the starion turbo based rods and pistons, there are guys running volvo rods and pistons and i have heard of other combos.

Might be worth contacting bob (kean keon sp?) in NSW or simon noske of all hunter spares in melbourne.

 

[Tom H]

I used Chevy rods from the 6 Cyl. Those rods have a smaller big end than the stock 1725 and allowed me to regrind the crank with 0.100" added stroke. I also did the Vizard mod on the head, bored it out to 3.248 , which is 82.5 mm so I could use common standard metric rings.

I had custom pistons made by Venolia, in order to match the exact compression height and dish on top to give me the CR I wanted. The custom pistons were only slightly more expensive than standard ones.

There are 2 articles on Chevy Rod conversions on 1725's in the Marque magazines on this site. Do an advanced search on Chevy or Marque and you'll find posts about these articles

Tom

 

[atallamcs]

Something different

Engine:
Sunbeam Alpine 4 Cylinder 1725cc
Venolia Pop-top Pistons
Eagle Connecting Rods (Ford Pinto 2300cc)
Crane Cam - custom grind
Datsun 1600cc Valves
BMW 1600 Schrick double valve springs
Sumbeam Alpine 1600 oil pump
Custom deep sump oil pan with baffle
Mocal oil cooler
3 qt Accusump
Gilmer Belt drive water pump
Weber 40 DCOE Carb
Custom intake manifold
Custom high efficiency raditor
Mallory dual point distributor

* 135 hp at 6200 rpm *

 

[Bill Blue]

Bill, could you "edjucate" us about the Ford 2300 rods? I've never heard of them used in the 1725.

BTW. 135 hp @ 6300 is something I'd probably paint on the side of the car!

Bill

 

[alpine_64]

Engine:
Sunbeam Alpine 4 Cylinder 1725cc
Venolia Pop-top Pistons
Eagle Connecting Rods (Ford Pinto 2300cc)
Crane Cam - custom grind
Datsun 1600cc Valves
BMW 1600 Schrick double valve springs
Sumbeam Alpine 1600 oil pump
Custom deep sump oil pan with baffle
Mocal oil cooler
3 qt Accusump
Gilmer Belt drive water pump
Weber 40 DCOE Carb
Custom intake manifold
Custom high efficiency raditor
Mallory dual point distributor

* 135 hp at 6200 rpm *

Bill, you say you used the 1600 pump.. why would you be using that.. i would assume you have fiited it with the MG mod to make it higher volume.. but why early pump in a late car?

 

[atallamcs]

engine

Hi Michael,
I have no idea why the racing shop and previous owner went that route. But judging from the $10,000 of receipts there must have been a reason. That is a lot of money for the engine alone. Your guess is as good as mine, better probably.
Bill

 

[muzzagod]

1725cc improvements

Hi guys,

Thanks for the info - keep it coming . . . .\\Murray

 

[atallamcs]

Engine Mods

Sorry I cannot answer your questions. The race shop is no longer, hence I remain in the dark.

The only engine mods I did once receiving the car was to change the intake manifold, add some quality headers, add a larger Weber, (45DCOE), add a light weight racing alternator, twin cooling fans and engine vibration dampner similar to what the factory suggested years ago.

 

[old grumpy]

Look at muzzagod playing around!!

http://www.youtube.com/watch?v=tiz7VF_Lig0
http://www.youtube.com/watch?v=Qg8ZlkNCcJk&NR=1

 

[old grumpy]

Why only 3 1/4" bore?
I am using st. Volvo pistons 3 1/3"

 

[muzzagod]

I eventually went to 84mm bore, had to get special head gasket made. Dyno man said 113 hp at rear wheels. lots more getup and go now.

 

[Jay Laifman]

First, I recall hearing that the 1600 crank allowed higher RPM.

Second, when we rebuilt my engine, I worked with a Lotus specialist. He found that if we went 55 over, he could use a set of rings that he was very partial to for his Lotuses. I'm not saying that 55 over is the greatest (but 24 years later, it is still going strong). But my point is that the rings may be your deciding factor.

We got custom made Jahns pistons to use his rings.