34 replies to this topic

[dgear1984]

Hello,

 

Starting to rebuild my 1275 mk1 cooper s block.

 

The block is 60+ and I will be fitting a 12g940 1805 head which will have been ported, cc'ed, unleaded seats and valves etc.

 

I have a brand new Piper 270 camshaft which was recommended to me by the engine builder/machinist.

 

Should I fit my standard 1.3 forged cooper s rockers or the 1.5 forged rockers I have with that cam. I am aware of checking the springs do not get coil bound etc..

 

Thanks Dave

[minimadles]

If your looking for every last bit of horsepower go for the 1.5s but as your using a 270 I guess that all out power is not the aim I would use the 1.3s and set up your rocker geometry to the optimum eg pedestal height and pushrod length

[dgear1984]

If your looking for every last bit of horsepower go for the 1.5s but as your using a 270 I guess that all out power is not the aim I would use the 1.3s and set up your rocker geometry to the optimum eg pedestal height and pushrod length

 

not aiming for huge power but usable engine for normal driving in my mk1

 

Will have to do some research into how best to setup the pedestal heights etc..

 

thanks dave

[Gr4h4m]

I would go with 1.3

[jaydee]

+1 on the 1.3 rollers

shim them so at half lift the rockers sit at 90° to the posts

[minimadles]

To be fair your standard pedestals are probably at the right length the way it works is the higher the rocker shaft fulcrum point the less effective valve lift you have your aiming for a true 1.3 ratio and the rocker pad centred over the valve tip at half valve lift. Not worth much in outright power but worth checking and doing for the sake of valve train longevity

[dgear1984]

+1 on the 1.3 rollers

shim them so at half lift the rockers sit at 90° to the posts

 

Thanks I will shim them accordingly.

 

What would be the disadvantage of using the 1.5?

 

I have a brand new set of 1.5 and the 1.3 I have need rebushing and have shot pillars, although I could use the pillars from the 1.5 and check the heights.

 

[jaydee]

 

What would be the disadvantage of using the 1.5?

 

 

Drivability lost at bottom end, very little gain and top. Plus extra strain on cam and followers.

1.3 are good to preserve valve guides and make the cam works as it should, just remember to use the coorect valve poundage (avoid silly springs, take 160lbs as a limit for such camshaft)

Edited by jaydee, 08 December 2013 - 08:42 PM.

[dgear1984]

Thanks, looks like 1.3 are the way to go.

 

Just ordered some new 1.3's

 

I figured it that was far easier than rebushing and I can sell my used 1.3's on (along with the new 1,5s by the sounds of it)

 

Hopefully I can get my block back next week so I can start building over the xmas break

[minimadles]

Pm sent

[carbon]

dgear - be careful to keep the 1.3 pillars with the 1.3 rockers, and the 1.5 pillars with the 1.5 rockers. Reason is the position of the rocker shaft on the 1.5's is moved slightly closer to the pushrods.

 

You can see the difference if you put them along side each other.

[dgear1984]

dgear - be careful to keep the 1.3 pillars with the 1.3 rockers, and the 1.5 pillars with the 1.5 rockers. Reason is the position of the rocker shaft on the 1.5's is moved slightly closer to the pushrods.
 
You can see the difference if you put them along side each other.

Thanks, I will have to look into this rocker thing a bit more I think.

Funny really, people here reckon 1.3

The company I got the cam from said get 1.5's

Engine builder didn't really give a comment about 1.3 or 1.5 when I quizzed him

[Dusky]

Keep 1.3. With 1.5 you will lose bottom end bhp and gain (if you have luck) a bit bhp on top end rpm's

[dgear1984]

got details of the full spec now, built the bottom, top end to go....

 

cooper s 1275s thin flange block +60

21253 pistons

521 rods

480 crank mains +10/bigs std

new damper with cooper s pulley

ACL steel backed bearings and thrusts

fully balanced

12g940 1805 head flowed and ported by Rob Walker

35.7 and 31mm unleaded valves with 3 angle hard seats and bronze guides

piper billet cross drilled bp270

light weight steel duplex gears

GLP138 oil pump

lightweight flywheel

270 back plate

orange cover

new 1.3 forged rockers

rocker spacers/shims

1128 gearbox with 1040 ratios and x pin diff with 3.44 and hardys

Twin HS2 on aeg347 manifold (will be putting some H4 on at some point)

Maniflow LCB (lm004s11r)

Maniflow stainless 1 3/4 twin box

 

 

 

just need to find some steel 1.3 posts

 

 

 

Edited by dgear1984, 26 December 2013 - 06:57 PM.

[dgear1984]

got details of the full spec now, built the bottom, top end to go....

 

cooper s 1275s thin flange block +60

21253 pistons

521 rods

480 crank mains +10/bigs std

new damper with cooper s pulley

ACL steel backed bearings and thrusts

fully balanced

12g940 1805 head flowed and ported by Rob Walker

35.7 and 31mm unleaded valves with 3 angle hard seats and bronze guides

piper billet cross drilled bp270

light weight steel duplex gears

GLP138 oil pump

lightweight flywheel

270 back plate

orange cover

new 1.3 forged rockers

rocker spacers/shims

1128 gearbox with 1040 ratios and x pin diff with 3.44 and hardys

Twin HS2 on aeg347 manifold (will be putting some H4 on at some point)

Maniflow LCB (lm004s11r)

Maniflow stainless 1 3/4 twin box

 

 

 

just need to find some steel 1.3 posts

 

 

 

 

What would be the best compression ratio to go for? Head is still at machine shop.

 

Im thinking about 10:1 would be best as I only plan to use super 97 fuel

 

Thanks