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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
 
#3 ·
It sounds similar to what is termed surging. ie: not missing, but as you described, slight cycles of accleration and deceleration.

If this is the case, it is normally caused by a lean situation in the carb. It's not a jet issue as the main circuit is hardly working at cruise.

Just wind your idle mixture screws out 1/4 to 1/2 turn each and go for a drive.
 
#6 ·
xemeanmachine said:
Hey TruBlu351, when i had a vacume guage on the motor, I adjusted the idle mix until I got the highest reading. Should I still be taking it a bit further like you suggest?
The vacuum gauge method works well for tuning. Get it just right and then fatten the mixture a little and see how it goes.

Just wind them out from where they're at now. If it works great, if it doesn't you may have to persue another avenue.

Some cars, depending on cam/heads/combo etc, just need a personal tune/tweek to make them work the best.
 
#7 ·
xemeanmachine said:
Hey TruBlu351, when i had a vacume guage on the motor, I adjusted the idle mix until I got the highest reading. Should I still be taking it a bit further like you suggest?
It is good to have a strong vac, but i go on what the motor likes. I like the best combination of idle in park and also in drive.
When i have a nice "non stinky exhaust", good idle in park and drive together and no bogging or hesitation, i am happy.(I think i am here finally)
The best advise above is do a small change, then go for a drive. You will then see how the changes affect all of your driving.
 
#8 ·
Another quick thought also, it may help, or it may not,
Grab a can of WD-40 or similar (even carby cleaner will do) and spray along where the head / intake manifold join, while it's idling.
If it seems to idle better when spraying, this will indicate a leaky intake manifold gasket, which will play tricks with idle mixtures, and contribute to surging also.
 
#9 ·
Thanks guys

9psi, i've already done those checks, theres no leaks there and she idle's fine. The problem is only when cruizing. I'll have a play with it on the weekend and richen it up a tad and see what happens.

Is there any way all of the outputs on the dizzy going to the plugs can ark?
 
#13 ·
xemeanmachine said:
Yeah mate, did that yesterday while tinkering. Primary is just dribling out of site whole with the screw out. Secondary dribles a tad bit more than the primary.
Is that about right??
Try lowering them a bit. Maybe level is slighty too high. After it gets up and running, and has used some of the fuel it is ok.?? Worth a try
 
#15 ·
xemeanmachine said:
I'll try backing them off a tad. Should the secondary bowl flow more out of the site than the primary??
I would set front and back the same. Get the motor running and have it so the fuel does'nt dribble out at all, but if you rock the car slightly, fuel will spill out. The BG carby i run has the plastic extensions from the metering block which helps prevent the fuel pumpin out the breathers.
Fuel shouldnt come out of the sites while the motor is running. It should "nearly" come out.
 
#16 ·
I will adjust it back a bit when i get home from work and let you guys know how it goes :) Thanks for all ya help


P.S Its being put on a dyno wednesday. I'm hoping it will get over 165hp at the treads. What should I be hoping for with the following.

351 clevo
2v closed chamber heads
mild cam(not sure of specs, but enough to give a slight lump at idle)
600 holley
Edelbrock performer manifold
why try extractors
2.5inch single sports exhaust

Oh and no clutch fan anymore, twin AU thermos

Let me know what you think... I know its only very mild
 
#19 ·
Yeah, you should be safe in assuming at least 165hp @ treads.

As mentioned, cam dependant, no reason why your combo wouldn't do 200rwhp.

Before if goes to the dyno tomorrow, pull the spark plugs tonight and inspect each one. Look for one darker/oilier than others. Could point to a dodgy plug or ignition lead.
 
#20 ·
Well, where do i start...... it went on the dyno and they found the plugs to be a problem, so they were replaced. The graph shows a total of 159hp at the treads, but aparently its leaning out towards the top end.

I took it in there with a flatspot on accelleration, surging while cruizing and shitty performance.

I got it back with an even bigger flatspot on accelleration, worse surging while cruizing, shitty performance, and a blowen power steering line.

Needless to say i'm not F*ing happy.

The bloke that dyno'd it said "u've really gota look for the surging now, ya can't even notice it" ITS WORSE THAN BEFORE.

I will be calling them again today and explaining to them AGAIN what I told them yesterday.

I also don't think that the $285 it cost me was worth it at all.
 
#22 ·
The guy that actually did the work said that he had to drill the jets out 3 sizes to get enough fuel into the motor for a respectable lambda reading.

I called them this morning and when I told him that the problem is still there if not worse he said "nup, can't be" and then continued to tell me about what he found etc and what he did to make it better. Eventually he referred me to northside carburretors, aparently the guy there will be able to help me out.... then its got to go back to the dyno place to be retuned.

What I don't understand is, at WOT it pulls nicely and doesn't miss a beat. At idle and cruize is where the problem is. Wouldn't logic explain that the problem would be in the idle circut?... yet he didn't mention anything about checking any of that, or at the very least, cleaning out any of the little vent things in the metering block.

When I get home, I might scan the dyno sheet and let you guys have a look at it and see what you's think. To me it looks like its leaning out heaps at top end.
 
#23 ·
xemeanmachine said:
The guy that actually did the work said that he had to drill the jets out 3 sizes to get enough fuel into the motor for a respectable lambda reading.

I called them this morning and when I told him that the problem is still there if not worse he said "nup, can't be" and then continued to tell me about what he found etc and what he did to make it better. Eventually he referred me to northside carburretors, aparently the guy there will be able to help me out.... then its got to go back to the dyno place to be retuned.

What I don't understand is, at WOT it pulls nicely and doesn't miss a beat. At idle and cruize is where the problem is. Wouldn't logic explain that the problem would be in the idle circut?... yet he didn't mention anything about checking any of that, or at the very least, cleaning out any of the little vent things in the metering block.

When I get home, I might scan the dyno sheet and let you guys have a look at it and see what you's think. To me it looks like its leaning out heaps at top end.
You sure he said he drilled out the jets? Just that anyone doing that these days is pretty backward and I wouldn't let anywhere near my car...
 
#25 ·
STROKEXD said:
You sure he said he drilled out the jets? Just that anyone doing that these days is pretty backward and I wouldn't let anywhere near my car...

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?
 
#26 ·
I still think the powervalves opening @ cruise instead of WOT. I know of two clevo's that did it. 1 = mine and the other being my mates. After the powervalve change the surging went away.

[edit]them going up 3 sizes means you now have a 66 primary jet. Which according to holley si about right. 76 is what the secondarys should be around size wise.
 
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