Ported Head, General Info Needed

[thomasrally 3]

Hi all

 

My 1600 forest spec rally car has a fairly standard engine at the moment producing 140 bhp@flywheel and I'm curious how much difference a worked head could possibly make to my torque and power, what kind of gains could I expect and any recommendations based on the below info?

 

Here's the current spec of the engine:

 

Standard bottom end

Standard head skimmed to provide 10.5:1 compression with 3 angle valve seats

Kent PT22 Cam

Vernier pulley

Twin40 webers

Maniflow 4 branch with competition 2 1/4 system, single tailbox

[DrSarty 90 1 Cars]

I'm not sure anyone can give you a quantitative answer/figure.

 

You certainly have a good spec there, especially as you have the triple-cut valve seats which definitely seems to make a difference in the 16v world, so I can't see it being a bad thing with 8v heads.

 

I've never seen factory vs worked flow tests on 8v heads either, although I have seen some comparisons of XU5/9 heads versus XU10J2 heads on Guy Croft's website. It may include some useful info there.

 

What I would say is, one shouldn't necessarily expect a leap in peak figures. Even a minor increase in peak tq/bhp would be good as long as along with it comes some better average torque, better throttle response and smoother power delivery.

 

Most torque curves have some dips in, and it's possible that a little head work - cleaning up factory anomolies etc - may iron those out. I've also heard though that one can over-do it with head work, in so much as polishing and opening up things too much can be detrimental to power.

 

I think the real solution is trial and error. And another 'trick' that may work is having your dizzy refurbished/re-curved.

 

What will almost 100% definitely get you gains is fully mappable management running ITBs. The £200-£300 you could spend on the head now could be put towards the mappable set-up and give you a larger improvement and flexibility for the future.

Edited March 23, 2010 by DrSarty

[thomasrally 3]

I'm not sure anyone can give you a quantitative answer/figure.

 

You certainly have a good spec there, especially as you have the triple-cut valve seats which definitely seems to make a difference in the 16v world, so I can't see it being a bad thing with 8v heads.

 

I've never seen factory vs worked flow tests on 8v heads either, although I have seen some comparisons of XU5/9 heads versus XU10J2 heads on Guy Croft's website. It may include some useful info there.

 

What I would say is, one shouldn't necessarily expect a leap in peak figures. Even a minor increase in peak tq/bhp would be good as long as along with it comes some better average torque, better throttle response and smoother power delivery.

 

Most torque curves have some dips in, and it's possible that a little head work - cleaning up factory anomolies etc - may iron those out. I've also heard though that one can over-do it with head work, in so much as polishing and opening up things too much can be detrimental to power.

 

I think the real solution is trial and error. And another 'trick' that may work is having your dizzy refurbished/re-curved.

 

What will almost 100% definitely get you gains is fully mappable management running ITBs. The £200-£300 you could spend on the head now could be put towards the mappable set-up and give you a larger improvement and flexibility for the future.

 

We're lucky in the fact we're working with a local engineering company who are doing all our head work for free in return for some advertising and using our car as their 'advert' for their competition head work so not actually needing to spend 'real' money as such so hopefully soon we'll be posting back here with some good results!

 

The test head shows a gain of 11% extra air flow on their flow bench

[DrSarty 90 1 Cars]

The test head shows a gain of 11% extra air flow on their flow bench

 

But that doesn't always mean you can get at it.

 

You may need seriously lairy cams, which need further head work to make them fit and perhaps solid lifters and revving to 8,000rpm.

 

I doubt there's any free ride, but I think many of us here would be fascinated to see what results you get.

[Rob Thomson 6]

It's vaguely interesting that different tuners think differently about the benefits of more flow through the rev range.

 

Have a read of Dave Baker's website:

 

http://www.pumaracing.co.uk/gentune.htm (and the other tuning pages too).

 

Personally the head is where I'd start any engine build, it's the heart of a normally aspirated engine. More flow potential is more-or-less always good, and not just at the very top end.

 

Incidentally, I know someone locally who rallies their 1.6 GTi. It's a very similar spec to that mentioned in the first post, with the exception of a proper Longman head. I was cynical when I was told it develops 160 bhp until I had a ride in it. It absolutely flies. Sure, it's a bit peaky but on the stages it never drops below 5k so who gives a toss about that.

[thomasrally 3]

It's vaguely interesting that different tuners think differently about the benefits of more flow through the rev range.

 

Have a read of Dave Baker's website:

 

http://www.pumaracing.co.uk/gentune.htm (and the other tuning pages too).

 

Personally the head is where I'd start any engine build, it's the heart of a normally aspirated engine. More flow potential is more-or-less always good, and not just at the very top end.

 

Incidentally, I know someone locally who rallies their 1.6 GTi. It's a very similar spec to that mentioned in the first post, with the exception of a proper Longman head. I was cynical when I was told it develops 160 bhp until I had a ride in it. It absolutely flies. Sure, it's a bit peaky but on the stages it never drops below 5k so who gives a toss about that.

 

I can definately believe it, these things with a bit of power are an absolutely rapid bit of kit and I think the only thing really holding back the potential of the current engine now is the head so I'm hoping to get to around the 155bhp-160bhp mark with the car weighing 850kgs with a close-ratio gearbox and 4:8 CWP

[DamirGTI 342]

If you're on to do this on a DIY basis , first , id strongly suggest some research buy some engine tuning books - read/study them carefully , ask someone familiar with this the precise subject for advice (Mr. Guy Croft is extremely helpful ..) .. practice on a scrap head ..

 

http://forum.205gtidrivers.com/index.php?s...p;hl=inlet+port

http://forum.205gtidrivers.com/index.php?s...p;hl=inlet+port

http://www.guy-croft.com/viewtopic.php?f=1...t+205+gti#p3614

http://www.guy-croft.com/viewtopic.php?f=2&t=45

http://www.guy-croft.com/viewtopic.php?f=1...t+205+gti#p5723

http://www.guy-croft.com/viewtopic.php?f=13&t=869

 

Damir

Edited March 23, 2010 by DamirGTI

[Rob Thomson 6]

What ignition system are you running? A mechanical dizzy's a bit limited once things start getting exciting. Mapped ignition helps massively with driveability without the additional expense involved with swapping to injection.

[thomasrally 3]

Still running a standard dizzy at the moment, whats involved in putting a mapped ignition system on instead then and what type of costs are likely doing it?

 

I'm very tempted to put rear proflex on this at some point too, with 160bhp and running rear proflex these things would be pretty damn hard to beat!

[boombang 2]

Still running a standard dizzy at the moment, whats involved in putting a mapped ignition system on instead then and what type of costs are likely doing it?

 

I'm very tempted to put rear proflex on this at some point too, with 160bhp and running rear proflex these things would be pretty damn hard to beat!

 

Few setups you can use, but ideally ditch the dizzy completely and run coilpack(s).

 

Omex 200 sort of setup is £500 odd plus mapping & your sensors.

 

Also need either a 16 valve type flywheel or a trigger wheel crank side (flywheel neater but they are heavy).

 

I'd go straight for full engine management (spark and fuel) and just use the spark side for now - later date can go over to ITBs and full on injection.

[Rob Thomson 6]

I guess you're talking a grand, maybe a little more, to do it with new bits. You need an ECU (and you might as well get one that'll support injection later), a wiring loom, a coil pack, new leads, a throttle-position sensor (which needs attaching to the carbs) and a crank position sensor. And then a couple of hours of mapping.

 

You won't gain all that much in the way of performance, but it'll probably be a lot nicer to drive and more reliable too, and give you scope for more development later.

 

Have you seen Rippthrough's Fox dampers....?

 

http://forum.205gtidrivers.com/index.php?s...=109266&hl=

[thomasrally 3]

No I hadn't seen or heard of them before, have they actually been tested on a rally car yet do you know? From reading the thread it doesn't look like they have been used at all yet?

 

I'd want something which is completely tried and tested so whilst they maybe upto the job I think their still in their infancy of proving themselves on a rally car?

[welshpug 1,661]

I doubt they will have issues proving themselves on a rally car if Phill has specified them correctly, the standard of the units will be sufficient given FOX make dampers for these things amongst a variety of other machinery;

 

[thomasrally 3]

I doubt they will have issues proving themselves on a rally car if Phill has specified them correctly, the standard of the units will be sufficient given FOX make dampers for these things amongst a variety of other machinery;

 

 

Ah didn't know that so now it's drawn my attention!

 

Are they 2 or 3-way adjustable like proflex etc? If so then I might ber very interested!

[Baz 421]

Funnily enough i have that exact spec. Only it's not all together!

 

If you're hunting for more, i'd go for a slightly larger cam, the PT22 is only 281deg iirc, the carbs etc would have no trouble running a 300 even tbh.

 

I'd also say more compression wouldn't hurt.

 

And, has the dizzy been re-weighted to match?

 

Of course as mentioned it'd be ideal to run mappable ignition too.

[Rippthrough 98]

Just spotted this - at the minute the Fox's don't have the external adjustment a set of Proflex, etc, can provide, as I can only specify them with a compression adjuster on the reservoir, obviously all the internal comp/rebound/bleed + blowoff stacks are all adjustable/customisable though.

As Welsh says, they've been a big name in the off-road rally world for about 40 years, and they make millions of dampers per year - the Penske dampers actually evolved from an early design he bought from Fox.

I'm just working on machining a new canister I intend to offer as an upgrade which will seperate the external adjustment into high-low speed compression, and should have an option for rebound adjustment shortly after.

 

They're aimed more at a stepping stone between Gaz/Koni/Billies and the Penske/Proflex/Ohlins setups though, so I'm trying to be careful not to put too much money into the units and keep them a nice mid-range solution.

However - I can offer some internal springing in the Fox's, to assist the rear torsion bars, which I haven't seen anyone but solution F offer yet.

Edited March 24, 2010 by Rippthrough

[thomasrally 3]

Funnily enough i have that exact spec. Only it's not all together!

 

If you're hunting for more, i'd go for a slightly larger cam, the PT22 is only 281deg iirc, the carbs etc would have no trouble running a 300 even tbh.

 

I'd also say more compression wouldn't hurt.

 

And, has the dizzy been re-weighted to match?

 

Of course as mentioned it'd be ideal to run mappable ignition too.

 

hi baz, to be honest this cam gives fantastic torque between 3000-7000rpm which is perfect in the woods and i dont find it peaky either so it works pretty well for my setup though whats the deal with having a re-weighted dizzy - performance improvement and cost?

 

Oh and where!?

[rescue dude 0]

hi baz, to be honest this cam gives fantastic torque between 3000-7000rpm which is perfect in the woods and i dont find it peaky either so it works pretty well for my setup though whats the deal with having a re-weighted dizzy - performance improvement and cost?

 

Oh and where!?

 

 

Here.

[Rippthrough 98]

Thomas, would you have been buying the Proflex new or used? If new, I might have another option for you shortly if you're wanting something with all the adjustment under the sun

[thomasrally 3]

Thomas, would you have been buying the Proflex new or used? If new, I might have another option for you shortly if you're wanting something with all the adjustment under the sun

 

No idea to be honest ripp but if a perfectly fine pair of second-hand proflex came on the market at the right time then I'd deffo be interested! Not quite ready yet as have a few things to finalise on the car then proflex/ast/avo/ohlins/whatever else on the rear should be pretty much the last piece of the jigsaw!

Edited March 28, 2010 by thomasrally

[Rippthrough 98]

I'm making some fancier dampers for the Pugs shortly, just tooling up now,4-way, same as we use on the rally cars, I'll send you a PM when I'm a bit closer unless you have something sorted by then.

Edited March 28, 2010 by Rippthrough

[davidc 0]

I'm making some fancier dampers for the Pugs shortly, just tooling up now,4-way, same as we use on the rally cars, I'll send you a PM when I'm a bit closer unless you have something sorted by then.

 

What sort of dampers will they be ?

 

How does 4 way work ?

 

 

 

Cheers,

David

[Rippthrough 98]

Slight thread hijack

 

Low speed compression + rebound

High speed compression + rebound

 

Hence 4-way adjustable.

They'll have either remote or piggybacked canisters, not decided yet, I might add a couple of bypass circuits too so they're 6/8 way adjustable.

[thomasrally 3]

Slight thread hijack

 

Low speed compression + rebound

High speed compression + rebound

 

Hence 4-way adjustable.

They'll have either remote or piggybacked canisters, not decided yet, I might add a couple of bypass circuits too so they're 6/8 way adjustable.

 

 

your like hijacking ninjas the pair of you

 

we start another thread when the head is done and on the car anyway ripp whats your company/background in terms of competition suspensions then?

[Rippthrough 98]

your like hijacking ninjas the pair of you

 

we start another thread when the head is done and on the car anyway ripp whats your company/background in terms of competition suspensions then?

 

They'll be based on a modified MVS design.