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1.5 Roller rockers
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Author:  douglas42l2 [ Wed Dec 21, 2011 4:59 pm ]
Post subject:  1.5 Roller rockers
1.5 Roller Rocker questions

I have an 1100s (1275) short motor bored 40 thou using a large journal crank ground to Cooper s specs (stroker) crank giving 1360cc capacity. ARP conrod nuts/Centre main strap/new piper 255 camshaft/ Hypatec pistons/lightened conrods/flywheel/balanced.I will be using David Rosenthal's custom made inlet manifold designed for Yamaha R1 carburretors. It is to be used as a road car. I have 1.5 full roller rockers but am unsure whether I should be using them or using 1.3’s.

It seems to be a fact that the advantage of going to 1.5 rockers is that it is the equivalent of going 'up' to the next specification of camshaft without the need to physically change the camshaft.
Does that mean that going to 1.5 rockers could possibly be the difference between a car that idles smoothly and performs in certain way to one that might idle roughly, consume more fuel, and be a 'pig' to drive ? Is this one risk that someone is taking by going to 1.5 rockers ?

If the car is to be used for street use and usable torque is the aim, does going to rockers also move the usable torque up the rev range ? I ask because I have heard that unless consistently revving at least over 5500rpm roller rockers are useless/pointless. This is because they only come into play above these rpms and that below these rpms it is actually costing you in terms of usable power (as power has moved up to higher rpms) that because of this it would be preferable to use 1.3 rockers ?

I understand non original rockers are designed to eliminate ‘friction’ but if all things were equal meaning that that you had everything identical and used 1.3 ratio rockers and 1.5 roller rockers and drove, serviced, the car EXACTLY the same, does having quality rockers reduce or increase cylinder head, engine wear and tear ? What affects, if any, are their on the cylinder head guides,valve stem seats, etc

David Rosenthal has mentioned to only use 1.5 rockers if using those where the posts are repositioned to take the side load off the valve stems. Is this what full roller rockers are designed to do as opposed to 1.5 rockers (not full roller rockers) or is he talking about the quality of rockers made or another issue ?

What is the practical difference between roller rockers and full roller rockers ?

Given all the above what are members personal preferences opinions regarding whether I go to 1.3’s and if so to roller rockers or to full rockers ?

Answers/advice much appreciated
Author:  justminis [ Wed Dec 21, 2011 9:50 pm ]
Post subject: 
For a road engine with that cam stay with 1.3 rockers, preferably 1.3 roller rockers.

The difference between full roller rockers and roller rockers is that full rollers have a needle roller bearing in the rocker that runs on the shaft instead of a bush. A bush is preferable on a road motor, the needle rollers are for the racers, as are 1.5 ratio rockers.

I built a 1360 (73mm bore) with the Piper 255 cam a few years ago and it was a great road engine, pulled like a teenage boy from 1500 rpm upwards.
Author:  drmini in aust [ Thu Dec 22, 2011 7:35 am ]
Post subject: 
re your other Qs...
1.5 rockers (whether forged or roller) do increase cam wear, particularly on `pointy lobe' cams. I wore a Camtech 619 (VP3) cam out in 45,000 miles- valve lift dropped from .480" to .270" approx on 3 lobes. [edit] and this was with the hi-lift springs C-AEA526 which were not coil bound.
I'm not sure exactly how pointy your Piper 255 is... but most UK cams don't have a nice big nose radius like say an RE13 or RE83 does.

Supposedly the forged 1.5 rockers also give more valve guide and valve stem wear, however I have had the same valves and bronze guides in my 1360's head for over 50,000 miles now, and they are not worn. This time, I just replaced the Viton valve stem seals (inlets only).
Author:  smac [ Thu Dec 22, 2011 9:54 am ]
Post subject:  Re: 1.5 Roller rockers
douglas42l2 wrote:
Does that mean that going to 1.5 rockers could possibly be the difference between a car that idles smoothly and performs in certain way to one that might idle roughly, consume more fuel, and be a 'pig' to drive ? Is this one risk that someone is taking by going to 1.5 rockers ?


I ran my 1380 with RE13 cam, light flywheel and standard head for a while. Bit of a lumpy idle, but very drive-able around town, and pulled well to 6500rpm (didn't like to go beyond as bottom end was stock).

Now running ported big valve head and 1.46 rockers....result? Completely different engine. Idles at 1400-1500rpm (who can tell...), a ning nong to get away from the lights, and forget driving at under 2500 in anything other than 1st gear (lurch lurch).

So to answer you......yes, it will change the way the engine behaves. But I certainly wouldn't call it a risk!! 8)
Author:  awdmoke [ Thu Dec 22, 2011 10:22 am ]
Post subject: 
I had 1.5 roller rockers on my 1430cc with a big head and MD290SP cam. Idled fine, plenty of low/mid torque & reasonable top end made it a great daily driver & occasional track use car.

Of course I discovered it had coil bind (incorrect springs fitted by PO) which caused massive cam wear. Sorry I don't have pics, but the wear on the lobes could be measured in mm
Author:  Mike_Byron [ Thu Dec 22, 2011 10:35 am ]
Post subject: 
Yep - always a fine line balancing what you would a car to be and what is practical on the road.

The reality is that mostly you have a car potentially very quick but you rarely get to use that performance and its just plain hard work driving it around.

Mike
Author:  74snail [ Thu Dec 22, 2011 3:27 pm ]
Post subject: 
Mike_Byron wrote:
Yep - always a fine line balancing what you would a car to be and what is practical on the road.

The reality is that mostly you have a car potentially very quick but you rarely get to use that performance and its just plain hard work driving it around.

Mike


As Mike said, the reality is that unless your building a track or rally car and you need it reliable up to 180kph , its much more fun and practical building a car with a wide useable torque band and thats comfortable sitting on 100kph, with the rising cost of 1275,s there is a quiet revolution of people going back to basics and really enjoying a well built small bore , the sort of people I see getting out and about using their cars , the sort of people who I know will have a Mini on the road for Christmas

Now going back to Cams VS high lift rockers / roller rockers , the ones I know work very well are the Corolla rockers that Mr Green makes as he has calculated the load spread, and they would be probably first on list if I wanted higher lift , now over to Cams , most of the original cam grinders all based their cam grinds on the standard ratio 1.25 , Waggot , Speco Thomas to name a few

From the air intake through the SU where your making the first stoichiometric ratio ,a swinging or fixed needle, to the CFM through the manifold , to the inlet air velocity and the size of the inlet valves , the size of the chambers and your compression ratio , the exhaust ports and port matching to the gasket , all of that has to be taken into consideration before you choose a cam and a change in rocker lift

.
Author:  Morris 1100 [ Thu Dec 22, 2011 5:06 pm ]
Post subject: 
Forget the 1.5s and just go straight for a seven port head.
Author:  smac [ Fri Dec 23, 2011 4:58 am ]
Post subject: 
:lol: Ning nong??

Heh I don't even remember what I said now..... :roll:
Author:  Morris 1100 [ Fri Dec 23, 2011 3:42 pm ]
Post subject: 
Sorry, I should have been more specific, I thought you already had a Ken Elder 7 port head...

douglas42l2 wrote:
Sorry - i should have been more specific......

Am looking at using motorcycyle carbs on a crossflow head (namely the ken elder 7 port just released). If somebondy has used them on ken's 8 port head they should be compatible with the 7 port.
Author:  douglas42l2 [ Sat Dec 24, 2011 11:39 am ]
Post subject:  rockers
Not using an elder head - was considering it . I know there has been plenty of talk and big claims have been made for it but no real world examples that i know of.

Motorcycle carbies are for a 5 port.
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