1.25 rockers to 1.4 rockers, HP difference

cnfabo Custom Title Time!

1,353 posts · joined Apr 2008 · 26 Feb 2009, 8:55 am

#697391

i have 1.25 rockers with my k8 cam and have been thinking of changing them too 1.4's. is this even worth the effort?

and what sought of increase would i be looking at?

i know the heads will have to come off the check valve and piston clearence and make sure my valves wont bind .

my heads are steve timms stage 2's..

vw54 Administrator Always Waiting 4 Friday

16,723 posts · joined Aug 2002 · 26 Feb 2009, 12:24 pm

#697420

u will have to change or check the push rod length as well

I read it on FACEBOOK so it must be true

http://forums.aussieveedubbers.com/viewtopic.php?tid=91278&page=1#pid848630

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http://forums.aussieveedubbers.com/viewtopic.php?tid=4832&page=1#pid452603

http://forums.aussieveedubbers.com/viewtopic.php?tid=60650&page=1#pid574409

westi what the

1,610 posts · joined Aug 2005 · 26 Feb 2009, 7:37 pm

#697476

it realy depends on what your heads flow,at the different lift's.
and yeh there are heaps of little things that need to be checked along the way.
rocker geom/lenght. coil bind and piston clearence.blah blah blah.

what heads are they.044's ,comp elim,
it might be well worth it if the heads flow more at the lift that you are chasing,what's your engine spec's.
comp.exhaust size.extractor primary size.carbies/venturies.and head flow chart.
give me a ring if you don't want to share with the world.

down sharon.

cnfabo Custom Title Time!

1,353 posts · joined Apr 2008 · 28 Feb 2009, 7:51 am

#697712

heads are o43 steve tims stage 2's, 42x37.5, 74x94, 44 idfs, 9.1 comp, 1 5/8 headers, the muffler is custom built. its a fatboy style one, dont know the actual size but its big, 2 inch pipe coming off the headers into the muffler.

going off a article about steve timms heads in hot vw's, the springs are good enough for .555-inch lift, seat pressure 140-ft-ibs. flow at 185cfm @ 25 inches,. he has 2 chamber designs and the chambers varie from 57cc-62cc.

when i bought the heads i was told they flow at 168cfm.

westi what the

1,610 posts · joined Aug 2005 · 28 Feb 2009, 11:15 am

#697746

a good rule of thumb is always if you can't get it out(exhaust gas)you won't be able to get any more in.
i have seen a set of tim's heads and done alittle testing on them but i am no expert by any stretch of the imagination.
but what we found with the set we had was that they needed high lift to work properly,not properly just make the hp we wanted,but the spring's weren't able to do it .we were told when we bought them that they were good for more lift than they actually were.
so i would proberly take the somewere to be checked before you go down that path.
you will be doing alot of work for very little gains,if you have to change springs and all the other stuff that goes with it.pushrod's,blah.blah.blah.
but everylittle bit counts.
what kinda pw is it making know and were do you want it to be.
i only ask because the gains from more lift can be done with porting/exhaust tinkering/timing/fuel etc.etc.
i reakon that it's worth doing if you don't have to change to much to make it worth while.

down sharon.

55slug Seriously Crusin Dubber

169 posts · joined Jul 2006 · 28 Feb 2009, 2:48 pm

#697770

The cam is designed to run with 1.4:1. I would bump up the compression to 9.5:1 and go to 1.4:1 rockers. Go with bugpack 4041 springs (i think thats the number), they allow a bit more lift due to a lesser wire diameter, so you get a bit more to coil bind. Just need to check all clearances and set up the springs correctly (can be time consuming).

FWIW I ran a K8 with similar heads at 9.5:1 on 95 petrol (NZ) with no evidence of detonation. You may find the compression increase alone will really get the cam working better.

cnfabo Custom Title Time!

1,353 posts · joined Apr 2008 · 28 Feb 2009, 8:30 pm

#697813

westi, i have been told if i put a stinger on and it feels better then my exuast is restricting it a bit. going off the timms article these stage 2 heads are ported as big as they can be before needing welding. a freind of mine has a 90.5x98.6 with 043 heads wich he ported and has ran a 14.6 so far. he has same headers which he has cut the stock 4 into 1 back a bit so it is now opened up more and has a bigger mendral bend into the muffler which is smaller but no baffles. he said it feels less restrictive.not sure how much HP but i have done a 15.8 @134kms, strong head wind,full weight car. but i would like to be in the 14's, without slicks , just turn up and drive. thats not to much to ask for.

55slug, my vw mechanic man thinks the same,maybe the cam needs a bit more compression,and 1.4's.. my engines still running in at the moment.a few more runs then ill decide what to do. but yeah im not happy with those times.

keep the info coming boys and thanks heaps..

55slug Seriously Crusin Dubber

169 posts · joined Jul 2006 · 1 Mar 2009, 9:01 am

#697867

I doubt a 1 5/8 header, muffler will be restricting. I have run 13.5s @ 100 mph through a CB performance 1 5/8 and fatboy. I doubt very much if your exhaust is the problem. The heads I ran this with were not huge ports (see photo)

When you think about it, with 1.25's you are lifting the valve off the seat later, you are currently restricting duration and lift. I also ran a 86b webcam (about the same as a k8) with oval port cncs with 8.9:1 compression, it really sucked in the power department... 15s was the best I could squeeze from it (82 x 90.5).

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 · 1 Mar 2009, 9:36 am

#697873

Have to agree with 55slug. I run 104mph 140 rwhp with 1 5/8 and muff. If the cam is for 1.4's run em, but there's lots to check...not just a bolt on.

Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

cnfabo Custom Title Time!

1,353 posts · joined Apr 2008 · 2 Mar 2009, 7:55 am

#698088

thats what i was thinking too, if the cams made for 1.4's why arent i using them.hhmmm.

would anyone know what HP increase i would acheive.im asking because i might even go down the road of changing my heads.