Yellow Bullet Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
45 Posts
Discussion Starter #1
After two lifter failures back to the drawing boards . Im in the midst of rechecking clearance issues , alighnment , geomety , oiling ect . Block is at the machinists atm set up on fixture for realignment and fittment of new bushes . Whilst there I have options of upgrade from 875 to 904 . Also at this stage whilst apart have been , myself , thinking of upping the cam core size to 55mm and roller bearing . Definately cant hurt in aiding issues with deflection and so on but is it needed . I dont mind spending if needed but dont like wasting it if not . Dont want to open a tin of worms .Im in two minds and need to make a decision . Sbf , svo windsor 9.2 , solid roller 268 274 @50 112 410 418 by memory atm standard core 1.9 rocker and c3s 7500 rpm . Street car will see strip eventualy once sorted . Thanks in advance
 

·
Registered
Joined
·
45 Posts
Discussion Starter #3
Bigger lifter is definatly on the cards at this stage but I need to make a decision on upping my core size . At this stage lifter bores have been checked on the cylinder I've had last 2 failures on and has told me bores are out 4-5°perpindicular to the camshaft 1-1.5° the other way with a .0015 -.0025 taper from top to bottom recomended to square ûp and re bush.
 

·
Registered
Joined
·
45 Posts
Discussion Starter #4
How much is involved in installing 55mm core and will I come into clearance issues rod to can ect could be a major operation
 

·
Registered
Joined
·
4,798 Posts
I'd look alittle closer at the rest of the valve train
for a cause. Out of control valve train can beat the
lifters to peices quickly.

1.9 rocker ratio is very aggressive, especially on
a valve train run on the street.
1.9 will accelerate the valve side very hard,
it's easy to get the pushrod flexing etc doing that.

Look deeper,, I don't thing the lifter bore correction
is going to be the entire issue.

Curtis
 

·
Registered
Joined
·
45 Posts
Discussion Starter #6
Ill be at the shop tommorow there's some other things I'd like to check , oil timing ,end float , I also notice that there was some indentation at the top of some lifter bushes possible the tie bars had been fouling at some point in time maybe when opposite valve opening causing lifter to jump of the cam need to folow that up dig deeper like you said. Also I am putting a new set of rockers on this time around and am looking at ratio change was thinking 1.75 any thoughts will need to make the lft up on the lobe.
 

·
Registered
Joined
·
13,485 Posts
274 @.050" lifter lift is not that much in comparison as you know if the roller wheel is lareger on your proposed 904 lifter body, then the rate will be a little more agressive.. i never liked the 1.9 ratio, and allways felt that it forces the pushrod to do funny things especially in a canted valve head...with a sideways moving rocker due to the angle of pushrod cumming out of lifter socket.....you need to compare by way of mapping out the actual measured lift curve / duration with what you have / lobe / rocker / pushrod AT the valve...and then select a cam lobe that will effectively give the same result at the valve with a more mundane rocker ratio ( 1.75 ) with the larger lobe.... SBF core size as well as base circle is allready allowing as much as a .450 lobe with base circle...a 55 mm setup is only .030" larger.. where as usually the change is done because a typical SBC or BBC is starting at 1.860 to 1.950" dia bearing..as said.. you probably have a pushrod side loading issue.. not enough spring or too much rocker ratio seen this a lot more agrivated in a 8.2 deck setup with the canted heads.. a BBC has a advantage because the lifter bores are "tilted " to help the pushrod alignment..........fords do not have this...
 

·
Registered
Joined
·
20,096 Posts
do you have a ford block or dart block?
 

·
Registered
Joined
·
68 Posts
I run a 412 lobe on a clevo on the street ,no bushing 1.73 rockers run a pretty light valve train and spin to 7500 no problem.
Makes 742 hp pump fuel 98 octane 4" stroke 13.3 to 1
I don't believe your camshaft diameter is problem I'd be looking at your rocker heights,
Valve spring pressure maybe to aggressive for street
I run I sky 9315 plus
Ofmemory there 225 on seat and 530 on nose and have a 500 ish spring rate
I have run this spring in another combo with similiar lobe has been running for 7' years
Every burnout comp, dyno comp,to a max of 7500 rpm
Any heavier than this they don't last on the street,excessive idle kills roller lifters especially with heavy spring rates and aggressive lobes
Check your set up what power do you want to achieve and rpm can't have a street hp cam and drag cam it's one or the other
 
1 - 10 of 10 Posts
Top