The V8 Owners Forum -

Dissy should run from the lower vac port shouldnt it??
I thought the top port gave more vac as rpm inreases??

mgbv8 wrote:Dissy should run from the lower vac port shouldnt it??
I thought the top port gave more vac as rpm inreases??

It should be connected to the timed port. Which one of the two small ones that is escapes me as the Eddy 500 just does not suit the vac system anyway! (So I've forgot which one it is)

The vac is more dependent on the throttle position than the revs although high revs when the throttle is shut (over run) will generate the most vacuum.

mgbv8 wrote:Dissy should run from the lower vac port shouldnt it??
I thought the top port gave more vac as rpm inreases??

As far as I can ascertain, the the top port gives virtually no vacuum at tickover, loads at cruise, then lower as the throttle opens more. This is the same as the SU.

I have been running around on the RPI set up and have the silver springs and the nearest to carb hole on the accel pump, still with no vac connected. Still not really happy without the vac, so will be connecting that back up soon

I still have a slight hesitation so will have to get some 68/57 rods.


RPI don't sell them, Repower haven't got any so they cancelled my order , and several email sent out to other places have yet to be answered

Anyone know where I can get some?

Richard P6 wrote:

mgbv8 wrote:Dissy should run from the lower vac port shouldnt it??
I thought the top port gave more vac as rpm inreases??

As far as I can ascertain, the the top port gives virtually no vacuum at tickover, loads at cruise, then lower as the throttle opens more. This is the same as the SU.

I have been running around on the RPI set up and have the silver springs and the nearest to carb hole on the accel pump, still with no vac connected. Still not really happy without the vac, so will be connecting that back up soon

I still have a slight hesitation so will have to get some 68/57 rods.


RPI don't sell them, Repower haven't got any so they cancelled my order , and several email sent out to other places have yet to be answered

Anyone know where I can get some?

From what you have described the top port sounds like the timed port. If you have set the timing up to anything like the figures that I give in the wiki articles you will have issues if you use the vac system (The motor will kick back just as you start to open the throttle)

I still think that the rods that you are after are too lean, getting hold of rods these days seems to be getting quite hard. JRV8 might stock them.

Pete

Don't worry Pete, I won't be connecting the vac back up with the timing at 13 BTDC.

I am busy moving factory units at the moment and am trying to get enough time to fit some spoilers on the P6 - had some made up by a GRP chap I know so not much time to do anything else.

The set up I have now is too lean so will try some others to see what they do. The 68/57 are richer than I have now so will see what they do when they arrive - Partsorama are getting me some.

It's all good experience

Richard P6 wrote:

mgbv8 wrote:Dissy should run from the lower vac port shouldnt it??
I thought the top port gave more vac as rpm inreases??

As far as I can ascertain, the the top port gives virtually no vacuum at tickover, loads at cruise, then lower as the throttle opens more. This is the same as the SU.

I have been running around on the RPI set up and have the silver springs and the nearest to carb hole on the accel pump, still with no vac connected. Still not really happy without the vac, so will be connecting that back up soon

I still have a slight hesitation so will have to get some 68/57 rods.


RPI don't sell them, Repower haven't got any so they cancelled my order , and several email sent out to other places have yet to be answered

Anyone know where I can get some?

Richard, I can get you the rods if you still require them. Summit in the USA list them in stock, part number EDL-1418.
I have a son and daughter who work for an airline at least one of them is in the states almost every week. I can get Summit to send the order to their hotel for collection.

The rods are listed at $7.99. Last time I ordered I paid $11.99 internal (USA) shipping charge per consignment, I think this is because I used a UK credit card they made this charge???. They list free shipping on mainland USA in their catalogue.

You can add any other small items if you wish with no extra shipping charge. PM me if I can help.

PS, If any one else would like rods or jets please PM. The $11.99 shipping charge can then be spread. As they are small items my kids won't mind bringing them home.

Paul

Muscle-Manta wrote:Richard, I can get you the rods if you still require them.
Paul

Many thanks Paul.

Partsorama have actually ordered them for me at £11.90 inclusive of delivery and vat.

Thanks for the offer though - nice to know there is another avenue if needed.

Richard

Richard P6 wrote:Don't worry Pete, I won't be connecting the vac back up with the timing at 13 BTDC.

I am busy moving factory units at the moment and am trying to get enough time to fit some spoilers on the P6 - had some made up by a GRP chap I know so not much time to do anything else.

The set up I have now is too lean so will try some others to see what they do. The 68/57 are richer than I have now so will see what they do when they arrive - Partsorama are getting me some.

It's all good experience

Like you said, it's all good experience! Keep us all posted.

The worst thing about doing any of this is reading the bloody numbers off the rods and ESPECIALLY the jets, Edelbrock...sort it out!

Pete

The rods are almost impossible to read because the whole number is often not fully stamped on them.

The only way I could read the ones the car came with was to take a picture with a 6.1 megapixel camera, download it and zoom fully into it

Here it is

Richard,

The reading of the jet and rod numbers is a pain, had to go out and buy a strong magnifying glass when I did my recalibration.


As you are running the weakest (silver)step up springs with a fairly mild cam it's possible that it's not staging to rich quickly enough when you initialy open the throttle. which is causing the hesitation.

If you have them try a pair of the pink ones, if the idle remains good the transition to rich may well be improved.

Kevin.

CastleMGBV8 wrote:As you are running the weakest (silver)step up springs with a fairly mild cam it's possible that it's not staging to rich quickly enough when you initialy open the throttle. which is causing the hesitation.

Kevin.

I thought the weakest were the blue ones and silver were the strongest?

I meant to put the strongest ones in and set the accel pump to its highest rating (Closest to the carb) in order to help with the hesitation - which it did btw, but not quite enough.

Richard P6 wrote:

CastleMGBV8 wrote:As you are running the weakest (silver)step up springs with a fairly mild cam it's possible that it's not staging to rich quickly enough when you initialy open the throttle. which is causing the hesitation.

Kevin.

I thought the weakest were the blue ones and silver were the strongest?

I meant to put the strongest ones in and set the accel pump to its highest rating (Closest to the carb) in order to help with the hesitation - which it did btw, but not quite enough.

If you put the stronger springs in the carb will come onto the power step sooner, this will richen the mixture up which is why it might have helped. The problem is that if the engine does not make enough vacuum at tickover then the carb might actually be on the powerstep at that point, that could mess up your idle AFR. (I think that the idle fuel circuit gets its fuel via the primary jet but I would need to check)

A simple test would be to run the engine at tickover with the air filter off and ther small rod/piston covers removed, the pistons should be down the bores, if they are popping up then there is not enough vaccum for the springs that you have fitted IMHO.

The accelerator pump will only richen the AFR for a second or so when the throttle is floored, this is to get round the fact that the air flow will go up soon as the throttle is opened but the fuel flow lags behind. When your rods and jets are right you will find that the pump can be on the smallest 'shot' setting. (or made even smaller with an 'arm-extension')

Pete

The 68/57s are here so I popped them in and went for a drive.

They made the hesitation a lot worse, almost undriveable to the point that I was unsure that I would get home - only went a mile

So I went back to check my figures and noticed that I should have changed the jets from the 83 to the 86

So with the 86 jets back in a running, the hesitation has gone. Smooth acceleration with plenty of power. Still looking slighty lean on the A/F meter so might just try this for a while and then try the 67/55 again.

Richard P6 wrote:The 68/57s are here so I popped them in and went for a drive.

They made the hesitation a lot worse, almost undriveable to the point that I was unsure that I would get home - only went a mile

So I went back to check my figures and noticed that I should have changed the jets from the 83 to the 86

So with the 86 jets back in a running, the hesitation has gone. Smooth acceleration with plenty of power. Still looking slighty lean on the A/F meter so might just try this for a while and then try the 67/55 again.

Where in the range range/throttle position is the AFR showing the mixture to be too lean? Remember you can go as lean as the motor will 'tolerate' when cruising about. You don't what it to be too lean at high revs and WOT, if this is where its lean then you might want to up the secondary jets.

Actually looking at you rod and jet combo I'd guess that the cruise is slighty too lean to obtain good throttle response, well a 86 jet and 68- cruise rod has been too lean on all the lump that I've messed about with.

I bet the acceleration phase is a touch lean with the 55 part of the rod too!

BTW, now at least you know what a 'too lean' mixture feels like to drive! (i.e it's not driveable! )

Pete

Cruising along at anything up to 2,500 shows an A/F of around 14 to 15.4 but just touch the throttle and it goes to 16 momentarily.

WOT is 10 to 11.5 so is not lean at all, might even try some 92 secondary jets in that.

I will drive it around for a while before retrying the 67/55 86 combo, with maybe the 92 secondaries.

Part throttle acceleration seems fine, but I have only driven it around the block, so will see what it does when I drive it to work this week.

Still on the silver springs as my engine seems to produce a lot of vacuum, and using the centre hole in the pump.