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Guest svsdino

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Guest svsdino

Hi All

 

What a day to have to go to your rolling road appointment, somethings I've noticed apart from never wanting to drive in the rain again, now I've changed from clamshell wings to cycle wings is they chuck crap everywhere! the doors wouldn't stay fastened, i never knew you had to have someone button you up as you can't do it from inside and my bloody windscreen wiper arm broke as it fouled the roof popper!!

Anyway, I have rebuilt my top end over the winter and i'm quite pleased with the results although they don't seem to match other peoples results. I'm running a 2.0 pinto with Vulcan big valve head, ZX6 bike carbs and FR32 cam with the RH 4 branch manifold.

She acheived 97bhp at the wheels on arrival, when Mark checked the ignition timing it was out so he retimed it and got her up to 119 at the wheels and 144 at the flywheel.

The afr results were 12.5 to 13.5 across the rev range of 2250-5000 but dropping to 11.5 at 1000-2000 revs. This is leading to rich running at "bimbling" speeds ie 35-45 4th gear, backed up by choking up, backfiring on the overrun and needing a good rev to clear it.

My question is does anyone else suffer poor running at low revs? I can live with it but living around the New Forest with blanket speed limits of 40mph does mean that i'm slap bang in choking up territory.

I went to Read Performance in New Milton, great lads, can't recommend enough really, Mark was very clear in explanation and set it up for road rather than 5500rpm track use. Very pleased.

Edited by svsdino
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Guest svsdino

A friend of mine fitted the cam, he had never fitted a vernier pulley before nor a fast cam so it may be out. What put me off was the estimated cost of Read performance dialling it in, they said it could take hours!

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Guest svsdino

I'll have a go at setting it up myself I think, I know he's set the rocker gaps to 0.25 across them all instead of .3 for the exhaust so while i'm at it i'll check the cam. They were reluctant to do it at Read Performance because they say they don't want to appoximate it, they will only dial them in with gauges etc and it takes time. I'm not really looking for that level of setting just a good tractable car.

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I've used most of the rolling roads in my area of the past 20 years and only ever found a couple of them really willing to put the work in to get the most out of your engine for a reasonable outlay. But to be fair to them it can take time to fully set-up a car (Ignition and Cam timing, adjusting the fuelling, not to mention fixing items that are wrong or broken) and many people don't want to pay a garage for a few hours work.

 

Did they go through all the simple checks like that the carbs were balanced and idle mixture was set. I'm also slightly surprised that they didn't swing the vernier a couple of degrees either way to see if the cam timing was having an effect (Assuming a vernier is fitted?) - but again it comes back down to time = money.

 

Finally don't worry too much about power figures as it's impossible to compare figures obtained from one rolling road to the next, or even the same rolling road with a different operator as there are just too many different paramenters to take into account.

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Guest svsdino

To be fair, no they didn't check the carbs were balanced nor that the idle mixture was set, they had a probe up the exhaust measuring AFR though. He did say that I should remove the plugs and check to see if there was any mixture issue on a particular cylinder and if there was to come back.

I feel now that I probably should have pressed them a little harder to diagnose a bit more, it was just that he seemd happy that the set up i've got was doing what he thought it should.

I have got a Quafe vernier pulley, it probably isn't the easiest to adjust so i'll see what difference i can make to it.

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FR32 has full inlet lift @ 108 degrees after TDC

A couple of degrees retarded would reduce bhp but increase torque earlier in the rev range

FR32 produces peal bhp at about 5600 but will rev forever

144 at the fly is good

I suspect your compression ratio is sub-optimal

10 to 1 would be an improvement

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I think what Paul meant was your compression ratio needs increasing to 10:1 to see better bop figures.

The only way i know of to work out what comp ratio you're running is to calculate it from your cylinder bore, stroke, deck height and combustion chamber sizes.

 

You can't accurately calculate a compression ratio by doing a compression test....I've asked this question before!!

 

http://www.rhocar.org/index.php?showtopic=33478&hl=compression

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You can get a ball park compression indication by cranking compression

If your expected to get say 170psi on a standard cam a higher duration cam will give less

I note that Burton Performance have engines ready for client collection in there shop with tags saying 190psi

Dave Baker Puma Racing likes to see 200psi

 

The caveat is that cast pistons don't like more than 10.5 or so to 1

 

As a minimum you want to see cranking compression at the same as a standard wngine

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