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Members thoughts on mild 186s engine build

Started by _186sHK_ , Feb 27 2017 07:08 PM

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#1 _186sHK_

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Posted 27 February 2017 - 07:09 PM

I have been getting a lot of good info off this site for a while, so I thought I’d post up some info on the 186s engine build in my HK, and get your guys thoughts and opinions on it.

Right from the start I wanted it to look close to stock from the outside so that meant using the standard exhaust and inlet manifolding and the WW Stromberg 2 barrel.

The motor was bought off Trademe (NZs version of ebay) and the bottom end was half arse rebuilt, we zeroed the deck height, put new bearings throughout, but used the cast pistons and rings that it came with as they hadn’t done much work. With the chambers at 49cc the compression is around 10.2:1

I put a Tighe cams 310 grind hydraulic flat tappet cam in it (268 advertised duration, 212 @ .050, .445 lift with a 1.5 ratio rocker), it’s supposed to peak at about 5200rpm.

I spent a lot of time on the head trying to gear it towards low lift flow and good airspeed (as good as it can be with a siamesed port anyway). I ended up cutting a 30 degree seat on the inlet (1.68 valve), with 45 and 60 degree blends down into the bowl, as I found this flowed better at lifts up to .450 than the traditional 45 seat and blend geometry. (I built a basic flow bench to try and verify my work).

I did a lot of chamber de-shrouding (more than what was necessary I think), cut the bolt boss out and machined for a cap screw, blended the bowls and shaped the guides.

At this point the inlet flowed 185cfm@ .550 lift (at 28”water). As I was shooting for a 5200 rpm peak, I thought this would be more than what I needed ( a few different online calcs suggested about 160cfm would be right) so I started filling the port with a two part epoxy called Belzona. At half the fill I ended up with (about 4mm in the bottom of the port at the face, tapering to nothing at the short side radius) it had no negative effect on flow, so I kept filling to about 8mm at the face, this reduced the port volume considerably and made it peak at 165cfm@ .450 lift.

Unlike the port lumps they put in the chevy 6 heads I did not find any gains in using the fill to increase the size of the short side radius, this could be a function of my weird seat geometry so I wouldn’t really take it as conclusive.

The finished port volume (when the manifold fill is taken into account as well) is actually less than a standard head, and the average airspeed across the port face at 160cfm is 170fps, without the fill it calculated out at 117fps.

The exhaust is a lot more conventional, with pretty standard seat geometry and really only cleaned up in the bowl and guide area.

For the inlet manifold I radiused the inlet manifold plenum to port entry and made a spacer to smooth the carb to manifold transition.

I slimmed down the throttle blade shaft in the carb and smoothed out a few of the sharp edges.

Before I did the manifold and carb mods, with the manifold and carb attached to the head it was flowing 145cfm (as opposed to the port by itself at 165) and after the mods it ended up at 155.

The exhaust is the standard two piece manifolds with 1 ¾ secondary’s that are 21 inches long. The rest of the system is a single 2 ¼ pipe to a chambered muffler in the standard position lying sideways under the boot.

It runs a standard points dizzy and 9v coil, the std advance curve seems about right.

The car runs an m20 Aussie four speed, 3.55 lsd banjo and I haven’t weighed it, but im guessing it would weigh about 3100-3150lbs with me in it.

I haven’t had it on a dyno, but finally got it to the strip in the weekend and it ran a best of 16.83 @ 81.37. Over the course of the day I adjusted timing up and down and fiddled with the jetting as well, so I think it must be around right.

What are everyone’s thoughts on the combo? I think its making around 140hp at the crank, I guess I was hoping for it to go a little better, but really I don’t have much gauge for comparison as most of the power figures and strip times are for more aggressive motors with bigger cams.

Does anyone have any figures for any similar builds with similar cams to mine?

Just in finishing I’d like to say thanks to Old Johnno for his website, it was a real good source of info, and also anyone else who takes the time to post stuff up about the holden 6,

Cheers,

Dave

Edited by 186sHK, 27 February 2017 - 07:12 PM.

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#2 _186sHK_

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Posted 27 February 2017 - 07:13 PM

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#3 _186sHK_

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Posted 27 February 2017 - 07:16 PM

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#4 Ice

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Posted 27 February 2017 - 07:41 PM

Cant help you some will come along and will though
but id love a pic of the HK

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#5 _186sHK_

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Posted 28 February 2017 - 07:10 PM

Cant help you some will come along and will though
but id love a pic of the HK

Cheers mate, here's another couple pics,

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#6 _Bomber Watson_

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Posted 28 February 2017 - 08:58 PM

A few points.

1/ frOck me your car looks wikedly cool. I love it. The only change ii would make would be to paint the spare tyre hump black.

2/ From my research your findings on the port filling are accurate, the ski jumps everyone uses in chev heads are useless in a Holden head. Oldjohnno famously said that although the ports look similar, they couldnt be more different, or something like that.

3/ Awesome home made flow bench.

4/ Its great to see that you tested the manifold on the head and checked the modifications you made as you went along, most people get a head that flows x then do whatever to the manifold and assume it flows y.

5/ Your times seem about right. If not really good for your cam profile, which would have something to do with your attention to detail above.

I ran 17.6 with a similar cam profile about 12 years ago in my far lighter LJ, albeit with far less attention to detail or critical thinking used, more a case of following general internet rules, so I honestly think you time is very reasonable.

At the end of the day its as quick as a VN SS.... With far less cubes and far less technology.

Edited by Bomber Watson, 28 February 2017 - 08:59 PM.

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#7 LC-GTR-1969

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Posted 01 March 2017 - 05:27 AM

Love your work mate- and I love how you have approached your build... You are definitely a thinking man...

These port lumps have interested me for a while now. Great to see some testing and data on it...

What epoxy did you use mate?

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#8 _Lazarus_

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Posted 01 March 2017 - 10:07 AM

The 186S made 145bhp with a stock head and smaller cam so something doesn't compute if your estimated hp is close. Stick an old Yerra Terra head on it and see what happens.

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#9 TK383

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Posted 01 March 2017 - 11:32 AM

For what you are aiming to achieve the head looks good.

But the cam is too small, like way too small.

You're on the right track, smaller ports will most certainly work better under 5000rpm & produce a much stronger TQ curve - but in order to make it work you need to feed it more cam. Big head -> smaller cam, smaller head -> bigger cam for the same rpm band.

Don't be shy with the cam, the work you've done on the head will take care of the low rpm drivability, give it another 15 or so deg at .050" & watch it come alive.

I'd suggest maybe 228/230 on 106-107 centres, less lift on the exhaust (it'll have to be a custom grind) - these thing over exhaust something fierce, but you need the exhaust duration for a good signal to the intake, so you stretch out the blowdown phase with reduced exhaust lift.

For a reference we make around 180hp from the HQ race engines with a stock single barrel intake & carb.

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#10 _186sHK_

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Posted 01 March 2017 - 06:19 PM

A few points.

1/ frOck me your car looks wikedly cool. I love it. The only change ii would make would be to paint the spare tyre hump black.

2/ From my research your findings on the port filling are accurate, the ski jumps everyone uses in chev heads are useless in a Holden head. Oldjohnno famously said that although the ports look similar, they couldnt be more different, or something like that.

3/ Awesome home made flow bench.

4/ Its great to see that you tested the manifold on the head and checked the modifications you made as you went along, most people get a head that flows x then do whatever to the manifold and assume it flows y.

5/ Your times seem about right. If not really good for your cam profile, which would have something to do with your attention to detail above.

I ran 17.6 with a similar cam profile about 12 years ago in my far lighter LJ, albeit with far less attention to detail or critical thinking used, more a case of following general internet rules, so I honestly think you time is very reasonable.

At the end of the day its as quick as a VN SS.... With far less cubes and far less technology.

Cheers mate,

Like I said above I wouldn't say my findings on the port lumps was conclusive, as my bench is a floating pressure type and at .450 lift will only pull about 16.5" water (then you convert this to a 28" figure by way of a calibration plate). Because of this its possible that the results would be slightly different at a true 28" ie the flow might separate off the short side, create turbulence etc.

It also might pay to mention I haven't actually tested the calibration of the bench, other than testing a standard head and comparing my figures with other published figures for a standard head (it was within a few cfm at all lifts). The obvious flaw in this is that even different standard heads could easily be +or- 5cfm.

I think I've got the manifold/carb combo flowing about as much as it can (on the flow bench), I think the manifold is held back by the sharp 90 degree short side radius on the front and rear runners, I could fill the corner with weld and radius it some more but at the moment I don't think outright airflow is limiting the motor anyway.

Love your work mate- and I love how you have approached your build... You are definitely a thinking man...

These port lumps have interested me for a while now. Great to see some testing and data on it...

What epoxy did you use mate?

Thanks,

I used Belzona 1111, it was pretty good to work with, maybe was a bit runny at first, but as it started to set you could work it pretty well. I sandblasted the surfaces to key them up, and so far the car has done about 4000 miles and the epoxy is showing no signs of coming out.

It is also pretty expensive (I scammed mine off a mate) probly a couple hundred bucks worth to do what i did.

The 186S made 145bhp with a stock head and smaller cam so something doesn't compute if your estimated hp is close. Stick an old Yerra Terra head on it and see what happens.

I guess the various power ratings and how to interpret them will always be open for debate, but for my stuff I always use a couple of different online calcs that calculate it from 1/4 mile mph and weight, depending on what one you use these are pretty similar to what the old moroso slide rule would predict.

For what you are aiming to achieve the head looks good.

But the cam is too small, like way too small.

You're on the right track, smaller ports will most certainly work better under 5000rpm & produce a much stronger TQ curve - but in order to make it work you need to feed it more cam. Big head -> smaller cam, smaller head -> bigger cam for the same rpm band.

Don't be shy with the cam, the work you've done on the head will take care of the low rpm drivability, give it another 15 or so deg at .050" & watch it come alive.

I'd suggest maybe 228/230 on 106-107 centres, less lift on the exhaust (it'll have to be a custom grind) - these thing over exhaust something fierce, but you need the exhaust duration for a good signal to the intake, so you stretch out the blowdown phase with reduced exhaust lift.

For a reference we make around 180hp from the HQ race engines with a stock single barrel intake & carb.

Cheers for the feedback,

After all the work i did on the head/manifold/carb, I had sort of come to the conclusion it is the cam that's holding it back, but that's what i came on here for, to get some confirmation from guys like you that have been there done that.

Im over in NZ, Im not sure how much our HQ series differs from yours, but I have heard the 170-180hp level being talked about over here as well.

Here are the specs for the control cam over here, would this cam work ok?

HOLDEN 149-202 HYD STAGE 7 230/230 (.050dur) 290/290 (AdvDur) 320/320 (Lobe Lift) 1.5 (Rocker ratio) 480/480 (Valve Lift) 110 (lobe sep) Auckland Cams controlled HQ Race cam. 10 to 1 comp ratio, Marsh Motorsport modified cylinder head and springs

Just out of interest have you ever seen any HQ race cars run down the strip?

I seem to recall watching one back here run high 14's in the mid 90's, does that sound about right?

How much higher would a cam like your suggesting make the peak hp rpm? Im a little weary of going much over 5500 with the stock 186 bottom end?

I'm also liking the driveability and fuel economy of the cam I have, so I guess I'll have to weigh up the trade off for what will most likely still be a pretty slow car (by modern standards) , even with the big cam.

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#11 TK383

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Posted 01 March 2017 - 07:03 PM

Looks like your HQ racers get a bigger cam than ours, ours are 214/214 @ .050" - the power comes from lots & lots of little tweaks all worth 1-2hp!

Don't buy a shelf cam, they are ALL wrong - cam grinders assume you're gonna pick a cam that's too big, so they widen the lobe centres to tame it. They also tend to use single pattern grinds, just coz it's easier. Shelf cams are there for the average guy with little knowledge to pick a cam that will show him some gains.

If you want the *right* cam you get it ground - I haven't put a shelf cam in one of my engines for years, I have cams ground to suit the engine.

110 lobe centres is way too wide, 106-107 centres will come on earlier, harder & make more TQ & HP right through, the trade off is a snotty idle & reduced vac for brakes - just bump up the idle speed 200rpm.

Talk to the boys at Kelford.

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#12 _Lazarus_

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Posted 01 March 2017 - 10:48 PM

""Right from the start I wanted it to look close to stock from the outside so that meant using the standard exhaust and inlet manifolding and the WW Stromberg 2 barrel"

With this in mind wouldn't you be better off going smaller ports than bigger cam ?

..

Edited by Lazarus, 01 March 2017 - 10:51 PM.

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#13 MustardGTR

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Posted 01 March 2017 - 11:33 PM

Was it intentional to modify a small chamber head as I didn't think a 186S came out with them stock?

Either way top job with the workmanship.

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#14 orangeLJ

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Posted 02 March 2017 - 10:59 AM

ID be interested in details on your flow bench. Build thread or instructions?

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#15 gtrboyy

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Posted 02 March 2017 - 02:25 PM

Now this is kind of thread cool to read.

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#16 _186sHK_

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Posted 02 March 2017 - 07:08 PM

Looks like your HQ racers get a bigger cam than ours, ours are 214/214 @ .050" - the power comes from lots & lots of little tweaks all worth 1-2hp!

Don't buy a shelf cam, they are ALL wrong - cam grinders assume you're gonna pick a cam that's too big, so they widen the lobe centres to tame it. They also tend to use single pattern grinds, just coz it's easier. Shelf cams are there for the average guy with little knowledge to pick a cam that will show him some gains.
If you want the *right* cam you get it ground - I haven't put a shelf cam in one of my engines for years, I have cams ground to suit the engine.

110 lobe centres is way too wide, 106-107 centres will come on earlier, harder & make more TQ & HP right through, the trade off is a snotty idle & reduced vac for brakes - just bump up the idle speed 200rpm.

Talk to the boys at Kelford.

Yea, I think that's what happened when I ordered the cam, I gave them all the flow figures and specs etc, but I was probably a little contradictory ie here's the head figures but I'm running factory carb and manifolding, I want it to idle decent and don't want to pull over 5500, so it's no wonder I ended up with something on the small side.

I possibly will get kelfords to recommend something, I've had them do a custom nitrous cam for a big block chev I had, and then a re grind for a turbo 3.8 commodore motor as well,they were always good to deal with.

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#17 _186sHK_

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Posted 02 March 2017 - 07:21 PM

""Right from the start I wanted it to look close to stock from the outside so that meant using the standard exhaust and inlet manifolding and the WW Stromberg 2 barrel"

With this in mind wouldn't you be better off going smaller ports than bigger cam ?

I think I get what your saying, but from the outset I was hoping for around 160hp, (this would be enough to run a high 15-low 16) and did what I thought was required with the head to achieve this without going too drastic with the cam. In hindsight to match the cam I've got, the head would have needed little more than a good valve and seat job and a little work on the short side radius, I guess I just got carried away.

..

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#18 _186sHK_

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Posted 02 March 2017 - 07:31 PM

Was it intentional to modify a small chamber head as I didn't think a 186S came out with them stock?

Either way top job with the workmanship.

Cheers,
Yea was intentional, easier to get the compression with the small chamber head, and better quench.
I guess the whole car is only stock looking to the casual observer, has HT front crossmember (rubber bushed) hq front discs (so I could use dropped spindles) hydraulic clutch, and M20 holden 4 speed as opposed to the opel.

ID be interested in details on your flow bench. Build thread or instructions?

Will try post up details over the next few days

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#19 _186sHK_

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Posted 02 March 2017 - 07:35 PM

Now this is kind of thread cool to read.

Thanks, like I said,I've pillaged enough sites for info over the years,I thought it was about time I posted something up that someone might think was worth reading

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#20 _Lazarus_

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Posted 03 March 2017 - 10:21 AM

Wouldn't a Yella Terra Stage 3 or equivalent give you around 160hp with that cam ?

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#21 _186sHK_

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Posted 03 March 2017 - 03:13 PM

Wouldn't a Yella Terra Stage 3 or equivalent give you around 160hp with that cam ?

From what I can find out a stage 3 YT head only flows about 140 cfm, and the inlet ports would be considerably bigger than mine, so less airspeed as well.

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#22 _Lazarus_

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Posted 04 March 2017 - 07:51 AM

Doesn't mean it wouldn't make 160 hp.

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#23 8BALL

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Posted 04 March 2017 - 09:22 AM

When it comes to cars/engines.
Theory is one thing. Actual reality is another.

Only way to truly tell is to try it.

Had many engine combos over the years that people said wouldn't work and wouldnt be anygood etc etc.
yet on the track they worked very well.
Yeah sure not everything works. But until you try something you cant rule it out.

Ive seen YT heads with smaller cam and single barrel carb do same times as yours in hj-hz sedan.

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#24 LC-GTR-1969

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Posted 06 March 2017 - 12:30 PM

Ive seen YT heads with smaller cam and single barrel carb do same times as yours in hj-hz sedan.

That may be the case, but its very hard to compare what others have done in regards to times, with different drivers, different air temps, different gear ratios and so forth.

Whilst I agree that theory does not always relate to real experiences, it is always much wiser to follow the well documented, and understood theory regarding engine design and engine building, than throwing together a package with the hope that the 'unconventional' setup will 'work'.

Don't get me wrong, there have been plenty of times I have gone outside the box, but things like trying to improve CFM and airspeed to suit our desired rpm range, is just a good thing to do (and more people should do it IMHO). It may not make the car all that much faster in a straight line, but it will make it much more responsive and more pleasant to drive at lower rpms (where the engine will most appreciate the increase in airspeed and this better cylinder filling capacity and torque).

Example being me running 40mm chokes in my webers of 36mm chokes. The 40s make more power, and may be slightly faster in MPH at the track, but its only slight... and with the 40s, bottom end drivability and torque suffers (which is harder to validate, as seat of the pants observations are hard to measure).

Just my 2c.

Edited by LC-GTR-1969, 06 March 2017 - 12:31 PM.

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#25 8BALL

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Posted 06 March 2017 - 12:38 PM

If people didn't "throw" a unknown package together with hopes it would work then progress would never occur.

If someone never tried different sized choke or a different diff ratio or even cam or compression etc then actual results would never be known.

He has a baseline thats respectible. But no harm trying for more.
A YT head isn't expensive these days.
Nor is a different cam. Etc.
Just comes down to time (to do it) and if one can be bothered to try.

It may go slower. It may be horrible to drive.
But.
It may also be the best thing he does to the car/engine.