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Comp cams

Started by _Bluejinx202_ , Oct 19 2012 04:01 AM

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114 replies to this topic

#1 _Bluejinx202_

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Posted 19 October 2012 - 04:01 AM

Thinkin about going to a wide lobe centre on the boat. The comp listings show all marine cams to have 110-112 LSA. I'm running 242@50 108 LSA now. I've got heaps of low down grunt, I just run out of torque at low 5000's and I want to get into the 6000's looks like comp have the lift qualities I need for my head too.

Any suggestions for grind before I call them up?

is wider sep going to help?

Who do I speak to to order a Holden six comp cam?

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#2 greens nice

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Posted 19 October 2012 - 01:33 PM

you can go through performance wholesale.
that is where i get mine.

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#3 _Ned Loh_

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Posted 19 October 2012 - 04:10 PM

Thinkin about going to a wide lobe centre on the boat. The comp listings show all marine cams to have 110-112 LSA. I'm running 242@50 108 LSA now. I've got heaps of low down grunt, I just run out of torque at low 5000's and I want to get into the 6000's looks like comp have the lift qualities I need for my head too.

Any suggestions for grind before I call them up?

is wider sep going to help?

Who do I speak to to order a Holden six comp cam?

2 cents. If you are using an agreesive lobe profile, then yes you should go for wider than conventional LSA.

What ratio rockers are you using? The reason I ask is that I looked at comp profiles not very long ago and it was going to be very hard to get one that worked with my current roller rockers (1.7) and head (valves/springs).

Who flowed the head?

Edited by Ned Loh, 19 October 2012 - 04:16 PM.

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#4 _Ned Loh_

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Posted 19 October 2012 - 05:19 PM

Ps. Chassis dyno right?

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#5 _Bluejinx202_

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Posted 19 October 2012 - 06:28 PM

I wish it was a chassis Dyno. Nah, that's on the engine Dyno at mikes Dyno (308 shop) I have 1.5 rockers and the head was flowed at high port cylinder heads in ferntree gully

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#6 _STRAIGHTLINEMICK_

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Posted 19 October 2012 - 07:10 PM

G'day mate, It is difficult to make more torque at 5500-6000rpm without losing bottom end torque ,you need low rpm torque in a ski boat.There are good local cam grinders who can do a cam that is as good as the best. I can see that the head flow does not peak untill .600".Who is the cam ground by and what is the current valve lift .Also when you were building the engine did you check max valve lift before intake valve hits the block and if the valve springs ,retainers and valve guide boss have clearance to .600".Your answers will help decide which way to go.Also did you calculate compression and what exhaust system are you running,Mick

Edited by STRAIGHTLINEMICK, 19 October 2012 - 07:12 PM.

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#7 _Bluejinx202_

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Posted 19 October 2012 - 09:05 PM

G'day mate, It is difficult to make more torque at 5500-6000rpm without losing bottom end torque ,you need low rpm torque in a ski boat.There are good local cam grinders who can do a cam that is as good as the best. I can see that the head flow does not peak untill .600".Who is the cam ground by and what is the current valve lift .Also when you were building the engine did you check max valve lift before intake valve hits the block and if the valve springs ,retainers and valve guide boss have clearance to .600".Your answers will help decide which way to go.Also did you calculate compression and what exhaust system are you running,Mick

Not sure what the piston to valve clearance is, the cam is a 'Clive cam' and I'm pretty sure I've only got 480 lift after clearance.. Clive told me that my lift was limited due to standard lifter diameter? Everyone else seems to be over 500 on standard lifters? My compression is 11.3:1 and I am using x2 cast headers into a single three inch system.

Is piston to valve clearance an issue at say 530 lift? I spoke to performance wholesalers that's arvo (thanks greens nice) they suggested I use a 250 in/255ex @50, 550-18 lift, and 109 LSA. (duration was something close to that anyway if not exact what he said). He said 109 or 110 centers it no to go too wide or I'll end up wasting low down torque. I said I'd get back to him next week.

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#8 _Bomber Watson_

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Posted 19 October 2012 - 09:22 PM

I've got .555" lift and the valve dosent touch the block or slug....

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#9 _STRAIGHTLINEMICK_

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Posted 19 October 2012 - 09:37 PM

_{Inake valve to top of block clearance can be more of an issue than valve to piston at over about 500-520.The intake valve can hit the top of the bore,scribing a line using a head gasket as a template and grinding a chamfer to just above the top ring usually gives enough clearance.Each cylinder must be checked as bore centers can be all over the shop.250 @ 50 at 110lsa will have less low end torque and a little more top end power than you have now. Camtech have a fast acting solid 250 @ 50 with .532 lift with 1.5 rockers (grind no 637) ,ask him to grind it with 110lca.}

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#10 warrenm

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Posted 20 October 2012 - 06:50 AM

.609" doesn't touch. :3gears:

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#11 _Ned Loh_

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Posted 20 October 2012 - 08:20 AM

Odd that comp recommended a dual pattern cam with those head flow figures. Can't see why they'd be giving the exhaust a bit more duration? Did they explain it?

Valve to block can be an issue or not depending on a variety of factors.

If you are increasing lift 50 thou check out everything is ok at that lift.

I would have guessed more hp from that head, even with current camshaft. Are you certain nothing else in the combo is holding it back?

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#12 _STRAIGHTLINEMICK_

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Posted 20 October 2012 - 08:20 AM

.609" doesn't touch.

G'day Warren,is that with angle mill or head moved across or small intake valve??.I found most red motors with milled heads and large intake valves have this problem at more than .520" or so lift and on some the bores arn't even in line.

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#13 _STRAIGHTLINEMICK_

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Posted 20 October 2012 - 08:25 AM

Odd that comp recommended a dual pattern cam with those head flow figures. Can't see why they'd be giving the exhaust a bit more duration? Did they explain it?

Valve to block can be an issue or not depending on a variety of factors.

If you are increasing lift 50 thou check out everything is ok at that lift.

I would have guessed more hp from that head, even with current camshaft. Are you certain nothing else in the combo is holding it back?

I agree ,if everything is right you should see roughly 240 hp on an engine dyno

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#14 _oldjohnno_

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Posted 20 October 2012 - 12:20 PM

Odd that comp recommended a dual pattern cam with those head flow figures. Can't see why they'd be giving the exhaust a bit more duration? Did they explain it?

Not odd at all. The balance between intake and exhaust duration has got very little to do with the relative port flows and everything to do with the efficiency of the exhaust system as a whole. As well, it works in the opposite way to what you'd expect, with better exhausts being able to utilise more duration.

If you have a very efficient system - ie. properly tuned headers etc that give a strong negative pressure pulse during overlap - then this permits you to use additional duration relative to the intake lobe. This will extend the rpm range beyond the peaks without any real losses lower in the range.

If on the other hand your exhaust doesn't really "work" - eg "wet" cast marine manifolds or badly tuned headers - then additional duration won't help the top end and you'll actually end up losing power to reversion. This is one reason why marine cams tend to have a wider LSA - to limit the overlap.

The port flow doesn't have much at all to do with exhaust duration, though a relatively good exhaust port would run just fine with quite a modest amount of lift.

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#15 _Bluejinx202_

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Posted 20 October 2012 - 02:24 PM

I'm not sure of the effiency of the X2 headers I'm using, but I've seen some pretty strong engines using them so I've been looking elsewhere first

Had a look at the 637 mick... 532 lift then I bet take the 22 clearance off that down to 510, my head would like more would u say?

Edited by Bluejinx202, 20 October 2012 - 02:29 PM.

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#16 _STRAIGHTLINEMICK_

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Posted 20 October 2012 - 03:03 PM

I'm not sure of the effiency of the X2 headers I'm using, but I've seen some pretty strong engines using them so I've been looking elsewhere first

Had a look at the 637 mick... 532 lift then I bet take the 22 clearance off that down to 510, my head would like more would u say?

Maybe , still early to decide. Do you know the advertised duration of the current cam ?,are yu using 98 pump fuel ?Are you using a spacer under the carb?When u said 3" exhaust,is that open pipe,thru a muffler or thru water?Apologies for all the questions.

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#17 _Bluejinx202_

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Posted 20 October 2012 - 03:30 PM

Maybe , still early to decide. Do you know the advertised duration of the current cam ?,are yu using 98 pump fuel ?Are you using a spacer under the carb?When u said 3" exhaust,is that open pipe,thru a muffler or thru water?Apologies for all the questions.

Not sure of advertised duration but can find out, only spacer is the 12 degree wedge for the carb angle and the ex is x2 headers with a two int one collector and a three inch pipe with so water spraying into it but no muffler

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#18 _STRAIGHTLINEMICK_

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Posted 21 October 2012 - 07:55 PM

James, from the info you have given your engine should make a bit more hp ,firstly i would ensure full throttle mixture is about 12.5-12.9 (i assume you are using 98octane),total timing should be about 34deg from 3000rpm up.Install a sec vac spring as soft as possible without slowing acceleration.A 1" open carb spacer may help (it did for me).The high static comp readings and lack of top end hp may suggest an advanced camshaft.You could try retarding by 2-3 deg to move power where you need it .This can be a frustrating process as you need to try one thing at a time and if no improvement change it back before you try another.Let us know how you go.Good hp hunting. ,Mick

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#19 _Bluejinx202_

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Posted 21 October 2012 - 09:45 PM

My timing gears are single keyed helical alluminium Jp gears. In order to retard the cam timing I need to replace them I'm assuming. To retard a cam from memory the crank gear is the one that gets moved, and also remember getting that gear off is a prick of a job. Is it ridiculous to just get another cam ground with less advance in it. I'm pretty sure my cam has 2 degrees advance.

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#20 warrenm

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Posted 22 October 2012 - 06:46 AM

G'day Warren,is that with angle mill or head moved across or small intake valve??.I found most red motors with milled heads and large intake valves have this problem at more than .520" or so lift and on some the bores arn't even in line.

Angle milled, 1.68" inlets.

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#21 warrenm

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Posted 22 October 2012 - 06:55 AM

My timing gears are single keyed helical alluminium Jp gears. In order to retard the cam timing I need to replace them I'm assuming. To retard a cam from memory the crank gear is the one that gets moved, and also remember getting that gear off is a prick of a job. Is it ridiculous to just get another cam ground with less advance in it. I'm pretty sure my cam has 2 degrees advance.

The preferred method would be adjust the timing gears instead of changing cam & lifters. It's a pity no one makes an adjustable(Vernier style) cam gear.
It's a pity I haven't got a milling machine, you could adjust the advance or retard at the track or the beach in a short space of time.

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#22 _Inj gtr202_

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Posted 22 October 2012 - 07:06 AM

The preferred method would be adjust the timing gears instead of changing cam & lifters. It's a pity no one makes an adjustable(Vernier style) cam gear.
It's a pity I haven't got a milling machine, you could adjust the advance or retard at the track or the beach in a short space of time.

Pm me the blue prints... :spoton:

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#23 _STRAIGHTLINEMICK_

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Posted 22 October 2012 - 05:22 PM

Angle milled, 1.68" inlets.

Yeah mine is not angle milled and has 1.71" inlets,I think the angle mill makes the difference.

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#24 _STRAIGHTLINEMICK_

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Posted 22 October 2012 - 05:25 PM

My timing gears are single keyed helical alluminium Jp gears. In order to retard the cam timing I need to replace them I'm assuming. To retard a cam from memory the crank gear is the one that gets moved, and also remember getting that gear off is a prick of a job. Is it ridiculous to just get another cam ground with less advance in it. I'm pretty sure my cam has 2 degrees advance.

You still may be able to get offset key for the crank or I can supply some helical adjustable gears to make the job easier if you need them.

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#25 _Bluejinx202_

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Posted 08 November 2012 - 09:53 AM

Decided that if the engine is coming out, it's going to be for a big change not a little one. I've been persisting with the same cam grinder for a while now and I think I'm just ready to try something new. Unless someone here tells me I'm about to make a great mistake, I think I'll order the comp cam this arvo. I'm a little concerned that the notes that relate to the lobe family say "most aggressive lobe available, 3/8 pushrods, shaft mounted rockers recommended, extra oiling advised"

I'm looking at a 6250 in 6254 ex at 110LSA

Comments or cautions would be appreciated..