dyno figures don't seem right after rebuild

**tokes_Vhdrift** · 30-01-2020, 03:15 PM

Originally Posted by ynot8

one thing is for sure, you got the 'knob head' bit right.....

Two things mate, two. I’m a knob head but I was right wasn’t i...

**ynot8** · 30-01-2020, 09:10 PM

Originally Posted by tokes_Vhdrift

Two things mate, two. I’m a knob head but I was right wasn’t i...

Only thing confirmed so far is,
1. you are a knob head

Further testing will either confirm or dismiss a knob heads internet diagnosis.
I'm currently in the process of trying some changes, after-which the car will be returning to the same dyno for comparison.
I can then make an informed diagnosis.

**cava454** · 30-01-2020, 09:54 PM

Time will tell who was right. I still think you should of called Pete. But each to own.

But unless it’s back to back, the dyno comparison will be always be skeptical.

**ynot8** · 31-01-2020, 09:35 AM

Originally Posted by cava454

Time will tell who was right. I still think you should of called Pete. But each to own.

But unless it’s back to back, the dyno comparison will be always be skeptical.

Biggest issue I have at the moment is how low in the rev range it is topping out at, which suggests more than anything else that something isn't right. It might be intake or exhaust restrictions, I don't know at this stage. I think the dyno will offer a fairly good indication if that component has improved or not.

And to be honest, I really don't care who ends up being right or wrong. I'm not interested in the ego stroking 'I told you so' games.
That's why I have asked for people's advice, suggestions. There are lots of differing opinions and have taken it all on board.
My goal is to figure out what the problem is.

**Deuce.** · 31-01-2020, 01:17 PM

Originally Posted by ynot8

Biggest issue I have at the moment is how low in the rev range it is topping out at, which suggests more than anything else that something isn't right. It might be intake or exhaust restrictions, I don't know at this stage. I think the dyno will offer a fairly good indication if that component has improved or not.

And to be honest, I really don't care who ends up being right or wrong. I'm not interested in the ego stroking 'I told you so' games.
That's why I have asked for people's advice, suggestions. There are lots of differing opinions and have taken it all on board.
My goal is to figure out what the problem is.

My money is still on exhaust. Makes sense to me that it would peak sooner and flatten out if you have "more all around" but the pipes are holding it back. I have seen this a few times before.
But at the end of the day I wish you the best of luck in finding your answer quickly and efficiently Darren.

**cava454** · 31-01-2020, 06:58 PM

What’s the current exhaust setup.

**ynot8** · 31-01-2020, 09:48 PM

Originally Posted by Deuce.

My money is still on exhaust. Makes sense to me that it would peak sooner and flatten out if you have "more all around" but the pipes are holding it back. I have seen this a few times before.
But at the end of the day I wish you the best of luck in finding your answer quickly and efficiently Darren.

thanks mate, it's on the list of things to try. I got the exhaust made up when I first built the car in 2001. So it's had a good life either way and served it's purpose. I've wanted a proper mandrel bent system for a while and I'll go a bit bigger.

Originally Posted by cava454

What’s the current exhaust setup.

Pacemakers with 3 inch single going to a single 3 inch muffler and resonator.
Not mandrel bent and the Y-piece is a bit rough.
I love the sound (hoping not to change it much), but according to the exhaust size vs hp chart, a 3 inch single is right on the limit

**Deuce.** · 01-02-2020, 04:48 AM

Originally Posted by ynot8

Y-piece is a bit rough.

This would be my biggest concern.
I dislike most y-pipes. I changed mine to equal(ish) length twin 2.5" to the first muffler (single) which is under the rear passenger floor.
You could really feel the gains.

**Castiron355** · 01-02-2020, 09:56 AM

Originally Posted by ynot8

thanks mate, it's on the list of things to try. I got the exhaust made up when I first built the car in 2001. So it's had a good life either way and served it's purpose. I've wanted a proper mandrel bent system for a while and I'll go a bit bigger.

Pacemakers with 3 inch single going to a single 3 inch muffler and resonator.
Not mandrel bent and the Y-piece is a bit rough.
I love the sound (hoping not to change it much), but according to the exhaust size vs hp chart, a 3 inch single is right on the limit

So what size from the pacemakers to the muffler?

I have 3-inch from extractors merging to 3-inch muffler, then to single 3-inch out the back.

My collectors at the extractors are only 2 1/4in. These will be upgraded to 3 in as well.

Sent from my iPhone using Tapatalk

**struggler** · 01-02-2020, 10:28 AM

I have only had a look at the first and last pages of this thread but it would appear you have a restriction somewhere.

The cam isn't perfect and I would have kept the cast heads but at the end of the day that combo should go OK.

I wouldn't get too tied up in chassis dyno figures but the peak at 5300 is too low.

A single 3" will work fine but the muffler is the limiter, not the pipe size. Drop the system at the diff and take it for a drive. If it doesn't pick up then peer into your antique muffler and see whats going on.

JMHO

**tokes_Vhdrift** · 01-02-2020, 03:41 PM

Originally Posted by ynot8

Only thing confirmed so far is,
1. you are a knob head

Further testing will either confirm or dismiss a knob heads internet diagnosis.
I'm currently in the process of trying some changes, after-which the car will be returning to the same dyno for comparison.
I can then make an informed diagnosis.

Let’s just stick to me bagging myself out for now, u can come back at me later if u feel the need.
So here we are on the internet asking for advice, after not liking the earlier advice givin about the combo.... anyway let’s try and help as it’s a Holden v8 and we need to keep them alive! Sounds like your dyno guy is pretty cool and happy to help, so remove them inner valve springs and run it up on dyno see if any change, then drop exhaust and do same thing, shouldn’t cost you anything and might give some answers. Seems like to much spring, and those lifters are horrid, but process of elimination.

**ynot8** · 02-02-2020, 08:41 PM

Originally Posted by Castiron355

So what size from the pacemakers to the muffler?

I have 3-inch from extractors merging to 3-inch muffler, then to single 3-inch out the back.

My collectors at the extractors are only 2 1/4in. These will be upgraded to 3 in as well.

Pacemakers merge with a Y-pipe into a single 3 inch pipe (same diameter as the Pacemakers up until the split merges at the Y). It then goes back to a single 3 inch Lukey offset turbo muffler, then out to a 3 inch resonator.

Originally Posted by struggler

I have only had a look at the first and last pages of this thread but it would appear you have a restriction somewhere.

The cam isn't perfect and I would have kept the cast heads but at the end of the day that combo should go OK.

I wouldn't get too tied up in chassis dyno figures but the peak at 5300 is too low.

A single 3" will work fine but the muffler is the limiter, not the pipe size. Drop the system at the diff and take it for a drive. If it doesn't pick up then peer into your antique muffler and see whats going on.

JMHO

yeah I was more concerned about the low RPM figure it peaked at.
The 286 is supposed to peak around 6000rpm, whereas the previous cam I used was designed to peak around 5500. The previous cam actually peaked at 5800rpm on my setup. So when this cam peaked 500rpm lower, straight away it didn't seem right. I do remember the tuner asking if the valve springs had been replaced. Didn't think too much about it until I investigated further.

Exhaust is next on the list. I've spent a lot of time under the car lately, and everytime I look at it, I think to myself it could be a lot better. And it has been on the car now for around 18 years, so anything could be going on in there.

Originally Posted by Deuce.

This would be my biggest concern.
I dislike most y-pipes. I changed mine to equal(ish) length twin 2.5" to the first muffler (single) which is under the rear passenger floor.
You could really feel the gains.

Yep definitely will be looking at exhaust, will be getting done properly this time, even if it means driving the thing to Brisbane. All the exhaust shops out here don't seem to do a lot of performance exhaust work.

Originally Posted by tokes_Vhdrift

Let’s just stick to me bagging myself out for now, u can come back at me later if u feel the need.
So here we are on the internet asking for advice, after not liking the earlier advice givin about the combo.... anyway let’s try and help as it’s a Holden v8 and we need to keep them alive! Sounds like your dyno guy is pretty cool and happy to help, so remove them inner valve springs and run it up on dyno see if any change, then drop exhaust and do same thing, shouldn’t cost you anything and might give some answers. Seems like to much spring, and those lifters are horrid, but process of elimination.

I have no interest in bagging anyone out, nor am I interested in playing the 'I told you so' games. I've made that crystal clear right from the beginning.
Just because I didn't act on your advice, doesn't mean I didn't like it. I simply was not prepared to pull a freshly built engine apart, swap cam and heads over based purely on advice given by a person I know nothing about. There has been so much different advice offered (often conflicting advice), I can only take it all into consideration and then make my own decision.

Before building this engine (or seeking advice from anyone on the internet) I discussed at some length, my requirements with a well respected performance engine builder. He understood the combo I had, and made recommendations (based on my requirements) on a suitable camshaft and compression ratio. I trust his advice and experience. Doesn't mean I won't remain open minded about it, but for the moment I'm looking at experimenting with components that don't require pulling the engine to pieces again. If I exhaust those options with no positive results, then I will further investigate any possible conflicts between the cam and cylinder heads and decide what I do from there.

Now moving forward onto more productive discussion....

Valve springs, I replaced them last weekend with the springs that Crane recommends for the cam. I took it for it's first run last Sunday and again last night. The valve train noise is now almost non-existent and it may just be 'seat of the pants' but the tacho seems to swing up to 6000+RPM with so much more ease. The entire engine sounds and feels more responsive and less restrained at higher RPM. Even the exhaust note has changed. In fact it sounds and feels much closer to what it did with the previous cam. So whilst at this stage I can't confirm with any certainty if it's had an effect on the peak power and RPM, it sure feels and sounds a lot healthier. So I think that's the first step forward.

The tuner guy is cool, the tune needs a bit of a tweak on steady cruise around 60kph in 4th gear, so I was always planning on dropping back in to see if he could have a look at that, might discuss the changes I've made with the valve springs, get him to hook it back up on the dyno and give it another run. Then go from there.