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Lack of power for stroked 4.3L VR

Moredhel84

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Hi guys,

Been racking my brains the past fortnight trying to work out why my stroked Buick 4.3L VR is only putting out 147RWKW. Now can’t give you exact specs but can tell you what the engine builder told me. Port/polished heads/inlets, reconditioned Bosch injectors, V8 TB, CAI, saloon spec cam, stroked/bored to 4.3L, custom Chip-Torque tune/dyno, extractors and 2x 2¼” exhaust all connected to a 5spd Getrag manual with HD clutch, still got the stocko diff + ratio.

Been in contact with some of the guys at FIT looking at high ratio rockers/lifters thinking maybe that’s where I’m going wrong but they reckon this should not be the problem as the cam and heads have been worked already and the rockers will only add 7RWKW at best. Tony at FIT seems to think its some kind of tuning problem or maybe the cam is out a little.

By all means the car isn’t slow but for the money I spent (close on 12K) I was expecting higher results. Reason for the high pricing due to the fact that this is actually the second rebuilt engine in a month. First got rebuilt by the Brock Shop with no stroker but pretty much everything else. It died in LESS then 1 week, not covered by warranty ($5K gone) as they claim the torque converter played up causing the converter to push the crank back into the engine causing excessive amounts of end-float which ended up eating the engine and the auto. Now every mechanic I’ve spoken to reckons this is a load of crap and if anything it would have been the engine killing the auto not the other way around but as I took it back to their shop as soon as it died, I have no way of proving this as they pulled everything apart before telling me what happened and then told me I need a new engine and gear box. Long story short, took it to my cousin who’s a manager for a Kmart Tyre and Auto and got him to put the 5spd in with HD clutch and send the engine in for another rebuild this time with the stroker crank. BTW the engine builder came back to say that the Brock Shop built the engine to its up most limits, in other words, they were giving me figures of 200FWKW (far from it according to the current graph) with no stroker but when my guys took the engine apart it was a case of quantity over quality with the engine pretty much over-extended and not designed to take as much power as it had.

Sorry about the long rant, but losing that quantity of money for gains I didn’t achieve has gotten me a little bit annoyed. In final if anyone can suggest why or why not I’m getting this power it would be greatly appreciated (attached dyno graph).

Thanks,
BJ

PS. To anyone else considering going to the Brock Shop up in Brisbane, one word for you…don’t. When I rang up the department of fair trading, was informed that they know of them quite well and all the mechanics I’ve spoken to agree, they falsify dyno charts to give higher readings and in the end their work isn’t up to scratch not to mention their customer service is below abysmal.
 

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smaddock

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I would expect more power than what you've got. My only thoughts would be possible inlet manifold restriction (I don't think they flow too well), or maybe cam not degree'd in correctly.
Bout 6 months ago I rebuilt the top half of my engine myself, and didn't degree in the cam, and accidently moved the crank sprocket 1 notch too far one way (can't remember which way), and when the guy tuning it said all he could extract was 106rwkw, I was quite peeved to say the least. The next weekend I took it apart and degree'd in the cam, next weekend back on dyno it reeled off 143rwkw without a touch up to the tune. Gained another 10rwkw after tune...
I'd be checking the cylinder 1 lifter rise @ TDC to see if it matches cam manufacturors recommendations, and possibly look at custom inlet manifold with bigger throttle body (possibly gen3 t/b or twin t/b's).
 

1991_Vn2nV

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4.3L stroker crank came from Bradey Cranks im guessing, here in Adelaide. The Bradey 4.3L crank is a toy when compared to the C.O.M.E. 4.2L crank.

Not really good for any more than 180 at the fly, and thats with a memcal tune, and extractors and exhaust...

The dual exhaut would give you more power as would the port polished heads and injectors. Also the CAI, Throttle body and cam would add more power.

But you are putting out roughly 200kw at the flywheel...So your results are not that bad, maybe 30rwkw off. So i'd probably say its just a problem with tuning or cam specs as well. If it is the Bradey Crank say so and I will get you the info on the tune and cam run on the demo car at St Mary's here in Adelaide.
 
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Raptorsc

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Mate

Feel sorry for you, not sure how best to help, the torque is all down hill from 3000 rpm really isn't it, that must provide a clue to what is wrong. Had the torque kept up then the rwkw figure would have been much more impressive.

Your tuning choice is fine (chip torque), no problem there, must be a deficiency in there somewhere. Maybe cam timing, maybe something in the exhaust, can be so many things
 

Moredhel84

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Hmm, well thanks for all your excellents replys, adds a little food for thought expspecially the whole dodgey Bradey crank, i'm just waiting to hear back from my cousin in regards to if thats the one or not, he doesn't think it came from Adelaide but he's double checking with the engine builder himself. Also waiting to hear back from the Brock Shop in regards to their "222degrees super saloon cam?".

In regards to the CAM timing being out, being as the engine was built by a professional wouldn't this have been checked before passing it on? Accidents can happen though i guess but like raptorSC said, havn't really heard anything bad about ChipTorque. Will wait for the results on the CAM specs and crank and will get back to yous. Once again thanks for the feedback.
 

Moredhel84

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Sorry just one more thing I should add, when the engine was on the dyno it had only just been run in. Was running Shell Optimax (didn’t have the car for 4 months so wasn’t the one who filled it) with mineral oil still in there. The exhaust has the back muffler on there also (going for the full straight through dual pipes when rear bar back on, X pipe with muffler from diff back atm). Been told by a couple of people that this shouldn’t attribute to 10RWKW+ in loss but more opinions the better.
 

greenfoam

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Just looking at the graph I think you could do with a bigger cam to move the rpm range over to the good side of the graph a bit :)? it does ramp up pretty quick and looks like it could make heaps more power if it wasn't running out of puff at 5,000 rpm. Something restricting it, maybe it needs a more agressive cam, better flowing heads, the exhaust might even be too small. What size is the exhaust?, you might want dual cats and dual 2.25's or a 3 inch for that much power
 

Moredhel84

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I've emailed the Brock shop in regards to specs for the CAM, was originally told it was a "222 degrees super saloon cam", sounds like a hyped up name and considering it was the Brock shop who put it in, it probably is. But will forward specs as soon as I get them. As for the exhaust, it’s already a twin cat 2.25" pipe from extractors which goes to the X pipe after diff into a muffler and back out to dual 2.25" tips. Going to get the X pipe and muffler removed to go dual all the way when I get my rear bar back on as at the moment mechanic reckons a little constrictive and way too quiet for my liking.
 

MBS206

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That graph is all over the place, with a big spike, then a drop, then ramping up again.
I beleive it's all in the tune!
Are you able to give us a dyno sheet with your AFR on them?
Also, are you able to get a copy of the fuel map and ign map?
 

burnz

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get the serial of the cam contact manufactuer
a ask for dialup
use crow cam dial gauge and dial the cam.
2, posable wonge cam for displacement
 
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