buck under heavy load

12vriviera

12vriviera

That Guy with that car
Joined
Mar 31, 2009
Messages
6,846
Just did my buddies ppump swap. with a stock 215hp pump.. No mods, freebies etc..
Pin timed at 13.5 plus 8 (give or take) with 310 bar vp 8x9 injectors..
Runs great, starts ok.. But e went to pull a hill with about 17k on it.. And it started bucking rather badly.. Dropped a gear and revved out (2800rpm, i know) and it was fine, but not right still..
Does it sound like it needs more timing, less?
Don't have a super accurate way to measure timing yet, going off marks we made on balancer and pin timing...
Thoughts?
 
You have it at roughly 21* timing? We typically time our ppump 24s around 25*, I know mine loved 30* timing on the sled and didn't seem to have issues on the street or dyno. I would up the timing personally and see if that helps.
 
When we had it at tdc and pin timed.. It didn't want to run at all.. Hold it on the floor it would hold 1500rpm and build boost without moving... Added the 8 or so degrees and it drives good all around... Till this...
 
It could be the pump itself, I have a 180 on my truck to start out and it did ove 500HP on the dyno, hooked to a sled about a month later and it wouldnt come off the sled to save its ass. Wont knwo til its rebuilt but we think the governor is fukked.
 
We are going to try for more timing tomorrow.. And see how it does.. Its completely stock virgin pump.. Later this year i think i can talk him into sending it to DPE and getting it checked out and some 4k's..
Just wanted an opinion on the current issue..
 
Yup! I will just tell him not to tow heavy!
I think a little bit of afc and plate adjustment might help some too.. Will see about that shortly.
 
Pushing past a stretched spring on the ofv... Over 20 i would say for sure...
 
i have had this happen a couple of different ways. one is at around a given rpm and peddle input. this was gov issue.. tight 4k's
the other is towing heavy, i have it now. when your pushing hard any, i mean any peddle movement starts an occilation that start bucking.. its a combo of flexing of the frame, 5th wheel hitch, etc and pulling hard with alot of power.. i have no doubt its my aggressive driving locked converter with alot of weight and power making this happen..
im not sure about your buddies deal but i have a hard time thinking it has to do with tuning other than maybe the govs..
 
Timing hasn't slipped, doesn't drive anydifferent.. I will turn in the stock springs a click or 2 and see if that helps the next time as well..
 
Not a fan of tighting stock springs up if its a dd, but u can try tighting them up to see if it helps hold the gov in.

I tighten my dads stock springs up before we put the pump on the old 12v and if ur down low in the rmp's (lugging it) its bad jerky.

I think its a gov issues also!
 
I have the same problem as Adam towing heavy pushing it hard. I can still drive through it by going out of od or going faster.
 
Throttle linkage definitely needs rebuild or replaced.. But e adjusted most of the slop out if it.
Added 3 or 4 degrees of timing to it today. According to measurements and marks on balancer (accurate as a hand grenade i know) we are now at 22 or so...
Idles way better, pulls great. He is going to pull a load on Monday so we still see how that does...
Will let you guys know!
 
After timing was bumped up, we modded the afc, ground the plate and adjusted accordingly, way more drivable, had 20k on the trailer, and it pulled super nice! No issues at all. Next mood will be a set of 4k gsk and he will be done, with the pump anyways :) trying to talk him into compounds!
 
Very nice. I almost like the idea of a PPump. But I need to buy a house first.
 
You must log in or register to reply here.
Back
Top