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Clevo missing when cruizing

5K views 38 replies 7 participants last post by  xemeanmachine 
#1 ·
Hey all, got another one for ya

This ones really got me stuffed. I got a recond 600 vac sec holley for the 351. Haven't changed anything else on the motor. The XE is now back to bagging tires off the line if need be which i'm happy about. It still has a slight flatspot on light acceleration which i'm sure is just an accel pump adjustment.

The primary jets i've changed to 63's, they were 66's.

Now, under load the motor is fine, pulls like all hell... but when cruizing at say 60km/h you can notice a bit of a uneveness... kinda feels like someone tapping the break pedal. Its very random, like theres no pattern to when it happens. If you open the throttle a little bit and start accelerating, the problem is less to no more. If you drive at 60km/h and leave it in 2nd, its even more noticable to the point you can here the motor surging then starving kinda thing.

Any suggestions??

Pete
 
#27 ·
xemeanmachine said:
Yeah i'm positie he said he drilled them out, aprently 3 sizes???? The jets that were in there were 63's so god only knows what they are now.

I remember him also saying something about it could be the carby/manifold combination causing it to surge?????????????

I was running a 600 on that same manifold before, and it never surged. Does anyone know of any places in brisbane that has knoledge of clevo's?? bearing in mind that the car is an utter pig to drive at the moment, so somewhere on the northside would be handy?
I bet they are talking about drilling the fuel restrictors in the metering block. If it has an excessivly lean idle, and can't be tuned out, they will drill the fuel restrictors out a few thou.
They usually drill if there is a bigger cam causing lower vacume, and the motors wants to stall when putting into drive.
 
#29 ·
TruBlu351 said:
He only has a very mild hydraulic cam which should be AOK with stock settings. It was excessively lean @ WOT (not idle), so I'm sure its the main jets that were drilled out.

What was the air fuel ratio xemeanmachine?
His problem is at idle(or atleast in the idle circuit,). Any load, just off idle, and it hesitiates. I still thinks its an overly lean idle circuit. A 600 vac is mild carby in my opinion, and i have found with quite mild cams, the slight drop in manifold vac stops the fuel being drawn at idle. And in gear, idleing under load makes it far worse if there is a lean problem.

edit, make sure you arn't "really" lean on the main jets first. If it has been totally bodged up, really lean main jets can cause a hesitaition too.
 
#30 ·
The general consensus is that the carb must be at fault. The 600 VS is always difficult to get right i.e. no sec metering block or fuel line bowl connection etc, no capacity to upgrade the engine. If you can afford it get a 650 or 750DP new or sec hand then at least you’re heading in the right direction!
BTW have you tried redcliffe dyno and performance?
 
#31 ·
I'm not too sure on how to tell the a/f ratio. On the sheet they gave me, right at the bottom it has a lambda graph. It starts off at about 0.9, increases slightly, then starts a gradual decrease down to about 0.84.

The graph also starts at 100km/h.

Not sure if thats what you were after.
 
#32 ·
xemeanmachine said:
I'm not too sure on how to tell the a/f ratio. On the sheet they gave me, right at the bottom it has a lambda graph. It starts off at about 0.9, increases slightly, then starts a gradual decrease down to about 0.84.

The graph also starts at 100km/h.

Not sure if thats what you were after.
.84 sounds a bit rich if anything, and getting up to .9 or a tad more at wot is fairly good.
 
#33 · (Edited)
xemeanmachine said:
I'm not too sure on how to tell the a/f ratio. On the sheet they gave me, right at the bottom it has a lambda graph. It starts off at about 0.9, increases slightly, then starts a gradual decrease down to about 0.84.

The graph also starts at 100km/h.

Not sure if thats what you were after.
Yep, thats it. Lamda is just another method of displaying the AFR in a stupid kind of way. The actual ratio is what's easy to interpret unless you have a conversion table.

When Lamda = 1, it means the AFR is 14.7:1 or stoichiometric (best economy ratio for normal cruise power in our older type engines). When under full power, it needs to be slightly richer, about 13.2:1 or 0.9 lamda. Your decreasing lamda of 0.84 really means an AFR of about 12.3:1, which is nothing horrific, but as xdclevo said, a little rich, and not where max power is found.

Looks like your mates went a bit too far with the drill bits ;)

This website has a table that converts Lamda to an AFR.

http://www.splitsec.com/products/arm1/arm1ds.htm

Instead of displaying rpm, they just show the speed of the dyno rollers, which is easily reverse engineered to rpm if you know your diff ratio and tyre size.
 
#34 ·
WOOOHOOOOOO!!!!!!!!

I took the metering block off and soaked it in kenco for about 10mins then washed it off with water and blew about 120psi of air through it. Put all the jets and idle screws, powervalve etc, and put the carb back together. It now idles better than before, and guess what.... THE SURGING HAS GONE!!!!!!!!!!....

Thanks for all your help again guys, muchly apreciated :)

Pete
 
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