DIY tune or Rolling Road?

moppit · Post by **moppit** » Tue Apr 05, 2016 10:15 am

My new Rover V8 3.5 (ported heads) with Edelbrock 500, Typhoon cam needs sorting out after installation. Previously the carb was set up for my old 3.5 with piper 270. To be honest the old engine felt quicker and it now seems uneven.

I changed the jets after reading Kevin's recommendation on this forum and tweaked the idle for max revs. The plugs are no longer sooty which is step in the right direction. Power not much improved though. Kevin (Castle MGBV8) said this..
"The mixture screw should be approx 1 3/4 turns out from fully closed.

Do you have the handbook, if not you can download from the Edelbrock site.

The carb does need properly setting up but it is quite simple, the float level need to be set correctly, they are often way out from straight out of the box.

Rods and jets I used on my 3.5 engine with stage one heads and Real steel hurricane cam, 9.8/1 compression.

Primary rods, 1441 (062 x 052) & Jets 1421 (080)

The main jet on the secondary may need reducing but will only affect running at wide open throttle. you could try 092 jets.

Fuel pump. ideally you want a pump to provide max 5.5psi the standard SU pump is only approx 3 psi. this will also only really affect wide throttle openings buit if the carb goes too lean it can damage the engine.

Is the engine otherwise standard and what air filter are you using?

Kevin."
The dilemma is should I just give up and hand over to the guy down the road (Airey Tuning) or persevere and tweak myself? Airey wants £300 which seems a tad pricy (includes jets).

This weekend I plan to re-check timing, fuel pressure but am toying with the idea of fitting a AF sensor kit, buying more jets/needles etc. but this would be a learning curve for me.

sidecar · Post by **sidecar** » Tue Apr 05, 2016 10:27 am

Personally I would purchase a decent exhaust gas analyser such as an LC1 or something better. Then I'd learn how each circuit on the carb works, I'd then set it up myself.

Your 62-52 rods with an 80 jet sets the carb up 19% leaner than the base setup on cruise and 21% leaner on the acceleration step. I have never managed to get a 3.5 to run with such a setup, I have found that the 3.5's that I have worked on have needed the carb leaning of a maximum of 8% from the base setup on the cruise circuit. Anyway each to their own!

moppit · Post by **moppit** » Tue Apr 05, 2016 10:33 am

If I'm honest I took a random punt on this but clearly wrong. Is it worth having another go with something richer or is this a fools errand without AF measurement?

Sort of reluctant to start drilling holes in my shiny new exhaust system how does the sensor seal on a tube?). Wish there was a long probe version like the one the MOT guy uses...

moppit · Post by **moppit** » Tue Apr 05, 2016 10:42 am

Would it be worth doing this...

"Blowing my own trumpet here but I've done quite a few RV8 lumps with this carb. A setup that works well for the 3.5 lump is 86 primaries, 67-55 rods, silver springs, secondaries around 83. (This is not a great setup for the 4.6 lumps)

This will give you an AFR of around 14.5:1 on cruise, 12.5:1 during acceleration and 13-13.5:1 at WOT. "

Forget who said this

but it is something well within my capability to change and see how it goes...

sidecar · Post by **sidecar** » Tue Apr 05, 2016 10:47 am

moppit wrote:If I'm honest I took a random punt on this but clearly wrong. Is it worth having another go with something richer or is this a fools errand without AF measurement?

Sort of reluctant to start drilling holes in my shiny new exhaust system how does the sensor seal on a tube?). Wish there was a long probe version like the one the MOT guy uses...

Really there are only two circuits that you can setup without analysing the exhaust gases...

1. The tickover circuit. You can set the two fuel screws to a rich setting, maybe 4 turns out, then wind in each screw going back from one screw to the other, wind them 1/4 of a turn at a time. The engine speed may pick up slightly as the engines starts getting an AFR that is nearer what it needs. At some point it will just tip over the edge and go too lean, the engine speed will just drop a fraction. Winding both screws out 1/4 of a turn from this setting will get the two screws setup correctly.

2. The second circuit that can be setup by the seat of the pants is the cruise circuit. You can start with a rich setup then keep swapping it out for a leaner and leaner setup until the engine response whilst driving goes bad, then just go back to the setup that is one stage richer.

With regards to probes up the exhaust I'm not too sure if they are any good, I believe that the LC1 had some sort of attachment that allowed for this but I have never seen it.

The one thing that you do need is a large supply of jets and rods, this can be a bit tricky as the calibration kit contains many parts which are not much use really!

southernd · Post by **southernd** » Tue Apr 05, 2016 1:43 pm

I've just been through this entire process and learned a hell of a lot about carbs but more importantly, how few people really know what they are doing.

The standard RPI rods are way to lean, if nothing else the heat from the engine gives this away. My engine is identical to yours and it was slow and miserable to drive. I did some work myself, my fuel pump pushes out 6.5psi so I have regulated that too 3 and replaced most of the ignition components for peace of mind, they're not expensive.

I ended up taking it to Airey tuning yesterday and it took him 5 minutes to sort it, the car was running stupidly lean as sidecar has said. I've just done a trip from Southampton to Brighton this morning and the car is a flying machine but more importantly, the engine fans barely came on.

I'll be upgrading to injection this summer though, more for the fun of doing it than anything against the Edelbrock.

moppit · Post by **moppit** » Tue Apr 05, 2016 2:11 pm

Thanks Southend,
How much did you end up paying out of interest?

Having had a look at the manual I think I understand it more now. I've ordered the 1486 tuning kit and will try a version 6 combo(P18 of the carb manual) as per sidecar's recommendations above. If that does not improve things significantly then a new dizzy cap and leads will be next (I'm due a refresh anyway), maybe an Innovate LC1 or PLX C6 AFR if I can figure out how to fit it.

I'm determined to learn more about this as I've had the car 20 years now and I feel I ought to...
The £300 for Tom's services buy's a lot of extra toys to further my knowledge...
As for fuel injection - yes of course this makes sense but the cost and complexity of a solution that would fit under my very, very low bonnet puts me off. When finally on song a carb is pretty decent compromise and a very low cost solution.

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as you can see I have not figured out how to post pictures either...copy and paste the link for my setup...

stevieturbo · Post by **stevieturbo** » Tue Apr 05, 2016 2:31 pm

Really...widebands are so cheap these days, you're just pissing into the wind trying to tune without one

Yes it can be done, but why on earth would you bother ? You'll waste more time/money on fuel etc than you will buying the kit in the first place.

sidecar · Post by **sidecar** » Tue Apr 05, 2016 2:33 pm

moppit wrote:
Having had a look at the manual I think I understand it more now. I've ordered the 1486 tuning kit and will try a version 6 combo(P18 of the carb manual) as per sidecar's recommendations above.

Eh?, I did not think that I had made a recommendation!

moppit · Post by **moppit** » Tue Apr 05, 2016 3:25 pm

Sorry it was from an older post and related to your Cobra? We're going back some time but it came up on a search...

moppit · Post by **moppit** » Tue Apr 05, 2016 3:42 pm

stevieturbo wrote:Really...widebands are so cheap these days, you're just pissing into the wind trying to tune without one

Yes it can be done, but why on earth would you bother ? You'll waste more time/money on fuel etc than you will buying the kit in the first place.

You make a good point...

sidecar · Post by **sidecar** » Tue Apr 05, 2016 3:45 pm

moppit wrote:Sorry it was from an older post and related to your Cobra? We're going back some time but it came up on a search...

LOL, no worries! Be aware that if I was talking about my engine then its a 4.6 and the larger RV8 lumps seem to need the carb setup leaner compared to the settings for the 3.5 engines. All sizes of engine seem to want to run similar AFR's but the carbs need to be setup differently in order to get the same fuelling. It will all be down to the vacuum that the engines pull.

sidecar · Post by **sidecar** » Tue Apr 05, 2016 3:49 pm

stevieturbo wrote:Really...widebands are so cheap these days, you're just pissing into the wind trying to tune without one

Yes it can be done, but why on earth would you bother ? You'll waste more time/money on fuel etc than you will buying the kit in the first place.

southernd · Post by **southernd** » Tue Apr 05, 2016 10:07 pm

I paid the £300, it is a lot of money which I wish I'd spent before I'd put so much of my own time in! If I had my own garage space instead of working in the road I'd have finished the job myself. That being said I'm now looking for a house with a garage, I'm not working by the roadside again.

Richard P6 · Post by **Richard P6** » Tue Apr 05, 2016 10:15 pm

stevieturbo wrote:Really...widebands are so cheap these days, you're just pissing into the wind trying to tune without one

Yes it can be done, but why on earth would you bother ? You'll waste more time/money on fuel etc than you will buying the kit in the first place.

Hi all

I've been trying to set my weber 1404 up for a while now. It drives ok, but I feel there's a lot more there, and also it's very 'fumey.' I fitted a stack lambda gauge which runs from 10 to 16 but the main problem with this is, cruising along the road, and trying to watch the gauge at the same time.

These widebands, LC1/LC2 etc, that I have seen mentioned on here, can you drive around and then look to see what's been happening, and if so where's the best place to get them?