loss of boost after rebuild!!

[dkbanjo]

I recently rebuilt the engine in my 5.0. it only has a couple hundred miles on it now. The problem is that I used to have 10psi of boost@6000 and with the new set up I only get around 6 maybe 7ps. I checked all the hoses and changed the pcv valve, my only suspicion left could be the bosch bypass valve because the car did sit for almost two years. Could it dry out and leak?

This is what I had before...
holly systemax intake
v-1 sc
30lbs injectors
75mm throttle body
1 5/8 longtube headers
stock e7's
stock cam
stock bottom end
stock valvetrain
3.90 gears
255 fuel pump


This is what I have now
holly systemax intake
v-1 sc
30lbs injectors
75mm throttle body
1 5/8 shorty's
ported the exhaust side of the e7's
e-303
306 longrod w/ srp pistons
dual valve springs w/hardened pushrods
and retainers
and an Edge racing 3200-3400 stall converter
3.90 gears
255 fuel pump
aluminum driveshaft

I don't think these changes would increase airflow enough to lower my boost 3-4 psi, what do you guys think? thanks for any input.

 

[clement]

you ported the heads and put a cam in with more lobe area and dont think that would cause this? i would bet there is nothing wrong with it.

 

[dkbanjo]

SO I SHOULD JUST PUT THE NEXT SMALLEST PULLEY ON IT(WHICH WOULD BE THE SMALLEST FOR THE V1) TO GET MORE BOOST BACK? AS LONG AS I DON'T OVERSPIN IT

 

[GRIPitNripIT]

Just b/c your not making as much boost doesn't mean your not making the same or more power. If you ported the heads, added long tubes, or altered the engine so that it would flow more air, you just made the engine more efficient. If you had a 10psi kit on a stock engine, then put the same kit on a engine with ported heads and long tube headers you will only see like 7psi, but the hp will be more then when it was on the stock motor.

 

[clement]

if all your interested in is a boost number put the stock cam and unported heads back on.

 

[dkbanjo]

I completely understand about the boost on a more efficient motor. They are just air pumps. I just didn't think it would make that big a difference in boost numbers. The car is definitely faster. It revs much quicker too. I just added a cam and ported the exhaust side of the e7's. i actually switched from long tube to short tube(the long one just never fit right on my car, they would hit the chassi).

 

[Rick 91GT]

If you want to increase the boost, just add a larger crank pulley and keep the stock pulley on the Vortech.

 

[clement]

or an anderson powerpipe

 

[dkbanjo]

Well, I went to Vortechs website and used their calculator for impeller speed and I don't think it would be safe to use the 2.62 size pulley. If I were to run it I would not be able to rev passed 6500 for only about a 1-2 psi increase and it would also increase my discharge temp. I'm running the 2.87, which is the next one up and only getting 6psi. The power pipe is a good idea. What would u guys think about upgrading my V1 SC to a V1 Si trim for more CFM's and a higher max impeller speed. I think it cost's about 300-400$.

 

[Chrome_Rust]

Boost is nothing more then a measure of restriction through an engine. If you allow more air to pass through the engine unboosted the ammount of restriction that the engine will see will be less, hence lower boost numbers. On an E7 head the exhaust is the major restriction. Since you cleaned them up it is no longer a restriction.

When i used to play with Thunderbird SC's, installing headers, larger pipe, and flow through mufflers would generally lower the boost number to the 10-12lb mark. But the car would be noticably faster.

If all you are worried about is a boost number, weld your intake valves shut. That will give you all kinds of boost.....

Charlie

 

[Rick 91GT]

Well, I went to Vortechs website and used their calculator for impeller speed and I don't think it would be safe to use the 2.62 size pulley. If I were to run it I would not be able to rev passed 6500 for only about a 1-2 psi increase and it would also increase my discharge temp. I'm running the 2.87, which is the next one up and only getting 6psi. The power pipe is a good idea. What would u guys think about upgrading my V1 SC to a V1 Si trim for more CFM's and a higher max impeller speed. I think it cost's about 300-400$.

Like I said if you want more boost increase the crank pulley size, this way it will not over spin the blower and cause you more belt slippage issues.

 

[dkbanjo]

IF I AM ALREADY MAXING OUT THE IMPELLER SPEED IN MY SC, WHY WOULD I PUT A BIGGER CRANK PULLEY? WOULDN'T THAT JUST OVERSPIN IT TOO JUST THE SAME AS A SMALLER PULLEY ON THE SC ? HENCE THE REASON I'M ASKING IF I SHOULD UPGRADE MY V1 SC TO A V1 Si. I DON'T JUST CARE ABOUT BOOST I CARE ABOUT EVEN MORE SPEED.

 

[Chrome_Rust]

Well posting in all caps is not going to get you anywhere, use some proper etiquette... We'll just leave it as you forgot caps lock was stuck on...

Moving on,
Upgrade to the V1 Si.
There, done.

 

[dkbanjo]

THANK YOU, I'M AT WORK AND THE REGISTER ONLY HAVE CAPS.

 

[Rick 91GT]

I shoudl have posted...Add the 7" crank pulley and put the larger pulley back on your head unit....

The issue with the Vortechs (all of them) when you get too small on the blower is belt slippage and you take the effiecency out of them. I have actually seen more boost and more power by slowing the blower down. The powerpipe is a good idea, always.

Where are you shifting?

A v1-sc with a standard 6" crank, 2.87" blower and a 6200rpm shift point is 44717.77

The same set-up with a 7" crank (ASP makes a 6rib version www.aspracing.com) 52170.73

all still under the 53,000rpm max, which is just a guideline....

Personally I like the 7" crank, 3.12" blower on that set-up, I wouldnt think the car would make power past 5900rpm or so.

Did Edge know about the blower, it could also be a converter issue... What are your intentions with the car, if you decide to upgrade the head unit you shoudl just upgrade to one that fits now and down the road.

 

[dkbanjo]

I shift at about 6000 rpms, though in the water box it sometimes quickly revs to 6500. That's why I was hesitant to come so close to the max impeller speed at 6200 and also was considering the discharge temps with spinning it that fast. My stock pulley is 3.33"(which i have) and with a 7" crank it would be 44963.96 rpms at 6200. If I kept the 2.87" and just changed the crank to 7" it would be at 52170.73 at 6200. Right now its spinning at 44717.77 at 6200 with the 6" and 2.87. If i just changed the crank to 7" I think would probably gain about 3 psi. I would be at about 9psi at 6000. That might be ok. Let me check and see how much the crank pulley cost's and and see if Its worth it or just upgrade. My plans for the car is basically to just go race at the track. I might change the heads sometime down the line or add nitrous, but its not a boss or dart block. Its a rebuilt stock block with upgraded pistons and valvetrain. So i don't plan on going over 450hp. I don't even know where I'm at now. Oh ya! and edge did know about the S/C. It was the last item I bought for the rebuild. It was custom made for my set up.

 

[93GTStang]

So your still running the 6 rib setup? If yes I would stick with the 3.33 like said above with the 7" lower or just get the stock S-Trim pulleys (3.33/6.87) and have the 8 rib setup. Alot for sale on the forums and ebay. Then just get the idler and spacer new from any Vortech dealer or maybe used. I would not be revving it that higher either, if you have an MSD box stick a lower RPM pill in it. Is that 6500 on a REAL tach or the stock one? Because 6300 is the stock limit unless you have a chip.

Personally, you should have a HP or ET goal in mind and shoot for that. Boost #'s are pointless unless you are trying to track down belt slip. Then I'd be using a GM MAP sensor and something like a DataQ to log with.

 

[dkbanjo]

I'm still using the stock tach. It can still jump passed the rev limit even if it kills the spark. I am still running the 6 rib set up. I am using the "no slip" glue for S/C belts. It stays at a solid 6 psi at 6000 no jumping around. I checked out the belt, pulley, and idler combos and I think the 8 rib 6.87/2.95 might be a good idea. now to see if anyone has this combo used lol.

 

[dkbanjo]

My hp goal is around 450, but what really matters it my ET. I don't know what a tangible goal would be with my car without a boss or dart block. I have my current set up on this thread. I have a good base (i think).