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.
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.
10.70 @ 125.00 on the black fun top
408 Cube Cleveland.
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.
Ok, i've richened it up by 1/2 a turn each side, and it seamed to idle a little better. Took it for a drive and the surging is still there. got it home and took it another 1/4 of a turn and it started to idle worse again. Its got me stuffed haha
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