Pulley change and boost problems...

[gbvetracer]

Well we changed the pulley to the smaller 2.7 and instead of getting the power and boost expected, we are only seeing 14 lbs of boost. (and therefore low rwhp gains) Its amazing to us that with ALL the pulleys sold, there isnt a CONCENSUS by now from the installers and tuners, that the belt MUST slip unless other changes are made. Why doesnt EVERYONE know this stuff? And why doesnt the vendors sell the appropriate parts to remedy the problem? In case youre wondering, we used the Hennessey pulley...but its the same pulley as many others are using. Shorter belt? Larger idler pulley? Power sterring spacers? Whats eveyone else doing to solve the OBVIOUS problem here? thanks for your comments....

 

[Gierkink]

The Roush pulley kit comes with a new shorter belt and it's only a 2.8 inch pulley.


Rob

 

[jamie]

I am using the 2.7 pulley and don't have any issues and I think most people who are using it don't. Maybe you have an issue with your belt, I would put on a new one and I think your problem will be solved.

 

[dbk]

I am using the same pulley and have no problems. I've also been present when the same pulley was installed on other cars, and know a couple of local guys who have installed this pulley on a couple dozen cars and they've experienced no problem either.

 

[californiacuda]

Could the boost gauge be reading incorrectly? try another source to read boost.

 

[911teo]

Could the boost gauge be reading incorrectly? try another source to read boost.

True... but he also said the rwhp gains were low... there must be a problem with the belt.

 

[Fubar]

There were about 10 of us that did the "Pulley and Tune" here in Dallas. I don't think anyone had problems. I did notice a slight "chirp" in the belt when it was cold outside. That problem has disappeared tho.

When you say the gains were small, do you know what the baseline is? or are you looking for the kind of numbers everyone else has posted. We have discussed in other threads how different Dyno machines can give radically different readings.

I certainly don't mean this to sound like I'm talking down to you... just trying to get some more information so that I might be able to help.

 

[kumar]

There were about 10 of us that did the "Pulley and Tune" here in Dallas. I don't think anyone had problems. I did notice a slight "chirp" in the belt when it was cold outside. That problem has disappeared tho.

When you say the gains were small, do you know what the baseline is? or are you looking for the kind of numbers everyone else has posted. We have discussed in other threads how different Dyno machines can give radically different readings.

I certainly don't mean this to sound like I'm talking down to you... just trying to get some more information so that I might be able to help.

did you guys use any particular shop in Dallas or was it when the GT Guys were in town?

 

[californiacuda]

Another thing to do, might be to put some vht(drag track surface prep-glue) on the belt just to see for a few minutes if it you saw more boost.

 

[427Aggie]

Kumar we had the GT guys in town for actually about 4 days and they worked non-stop.

Personally if your going to do it...Henn...in Houston has done several of the Texas guys cars and they have all seemed happy.

I trust Rob at Keith Craft Motorsports with my car but you have to have someone that can pull the old pulley and press the new one on...and Rich and Dennis said they have been known to be crooked.

Have you checked to make sure that the pulley was pressed on straight?

Matt

 

[gbvetracer]

Belt is new....

Dallas Mustang and most other sources that tune these cars ALL now say they needed to run shorter belts. Were looking at the boost numbers from the Dyno NOT the gauge in the car... With only 14lbs of boost, its no wonder were not seeing rwhp over 600. Its about 550 on a Mustang Dyno. Now the question is will an 86" belt solve the problem EVEN after we cut the stop off the belt tensioner.

 

[dbk]

gb,
I just watched two cars on the dyno with just the 2.7 and a tune with no belt change do +-10 of 600rwhp. I'm not saying you don't have a problem, but there are a TON of people running just these mods putting out that power level with no belt change.

 

[427Aggie]

Going back to the ones that were done while the GT guys were here in Dallas. Not one belt was changed! Mine did 596hp/605tq on 91 octange.

Something else is wrong here...

Matt

 

[Hennessey Performance]

we have sold over 100 of the 2.68 GT pullies and not had any belt slippage issues with the stock belt. i wish i had an answer for this one but i dont. i will gladly refund the pulley in full if you want to send it back. i wonder if your belt tensioner is less than 100%?

 

[SYCO GT]

As someone who is planning to have the GT Guys install a smaller pulley and tune in a couple weeks, I appreciate all the people that took the time to post their positive experiences. On many forums, it seems it is so easy to critique and share horror stories, but one nice thing about this forum, is that people spend the time to share their honest and good experiences.

- Randy

 

[Shadowman]

I see the mention of belt slippage however none about the possibility of a leak. It does not take an extreme leak at the base gasket or ?? to significantly alter the boost developed. Furthermore I do not read where you hear the belt slipping as I feel certain that you would.

I know that most do this swap with the reusing of the OEM base gasket however it is possible that your gasket simply did not reseal.

I can share that the supercharger sits on 2 aligning dowels and the process to secure it takes numerous back and forth tightening of the bolts for this process to be properly completed.

I am not questioning what one did but rather offering another possibility because the results received as the result of a smaller pulley are mechanical and very real; this is not a subjective issue.

All the best

Shadowman

 

[Black GT]

I have the 18psi pulley and no belt change and mine put down 642rwhp. Check something else there is something wrong maybe a leak somewhere.

 

[ViperJoe]

I have the 18psi pulley .....

What diameter would that be?

 

[AMB]

Pulley

Anybody that changes the pulley NEEDS to change the BELT or use larger idler pullies etc. etc. !!! Both Roush and KB do that !!! Anybody that just installes the pulley WILL have belt slip !!!

AMB

 

[Fubar]

Anybody that changes the pulley NEEDS to change the BELT or use larger idler pullies etc. etc. !!! Both Roush and KB do that !!! Anybody that just installes the pulley WILL have belt slip !!!

AMB

I installed the pulley. The belt is not slipping.