Got a 400 and a bit SBC going together. (4.145X3.75) Street/Strip motor with the emphasis on strip. Street driving will be very limited. Motor should make about 700 hp with a maximum rpm of 7500. Hopefully lower.
Was thinking of running a Vac pump for the Hp gains. Have seen vac pumps make an easy 15 hp on 4.03"X3.48" motors at 6500 with standard rings.
Would it be reasonable to expect 20 or so hp from the 400 with standard tension rings? Is it worth running low tension rings in a motor like this. How much HP could they be worth.
Cheers
Fatman
Vac. Pump Questions
Moderator: Team
Typically the big gains are made with low tension rings. It's a package deal, the rings, ring gaps, the pump, this pistons.
If you've seen big gains with std. rings then the pump may have been helping a tired engine.
The only issue I have for a partial street application is oiling the pins. and skirts. Unless you have oilers in the rods you need to limit the vacuum for long run durations. I'm sure many people have their own methods, but it's for the long term health of the pins mostly. For a street deal you should limit it to around 8-10" MAX. If you had an adjustable valve you could kick it up for the track use.
On a wet sump race engine that will pull around 18-20 inchs, I will harp on the customer to keep the vacuum pump line disconnected except when making a run, to allow the pins and cylinders to get a good soak of oil prior to the run and the big hit of vacuum. Since that decision I've seen the cylinder wall and pin wear decrease dramatically.
If you've seen big gains with std. rings then the pump may have been helping a tired engine.
The only issue I have for a partial street application is oiling the pins. and skirts. Unless you have oilers in the rods you need to limit the vacuum for long run durations. I'm sure many people have their own methods, but it's for the long term health of the pins mostly. For a street deal you should limit it to around 8-10" MAX. If you had an adjustable valve you could kick it up for the track use.
On a wet sump race engine that will pull around 18-20 inchs, I will harp on the customer to keep the vacuum pump line disconnected except when making a run, to allow the pins and cylinders to get a good soak of oil prior to the run and the big hit of vacuum. Since that decision I've seen the cylinder wall and pin wear decrease dramatically.
Std ring packages and Vacuum pumps have netted little or no increases in the cases I have seen. If I was planning on running a Vac pump, I would be running 0.043" rings with gas ports. The new Moroso 4 Vane Design pump is supposed to be one of the best out there at the moment, steer away from the 3 Vane units, most I have heard of have netted very low Vacuum figures. As mentioned previously, run a relief valve or bypass in the system, and activate it when you are not making a pass, especially on start up.
AL...
AL...
Vac pumps
Thanks for the input
A few more details that i should have probably included in the first place. Motor is wet sump, dart short deck block, pistons do not have gas ports, will possibly be run on alcohol.
Don't want to run huge amounts of vacuum, would rather be safe than sorry. Is there a minimum amount of vac needed for the low tention rings?
The motors that i mentioned that saw a gain with standard rings were new motors that were on the dyno. Motors were tuned without the vac pump and the vac pump added right at the end. One was a 357 Cleveland, the other was a 355. Both Wet sump.
Thanks again
A few more details that i should have probably included in the first place. Motor is wet sump, dart short deck block, pistons do not have gas ports, will possibly be run on alcohol.
Don't want to run huge amounts of vacuum, would rather be safe than sorry. Is there a minimum amount of vac needed for the low tention rings?
The motors that i mentioned that saw a gain with standard rings were new motors that were on the dyno. Motors were tuned without the vac pump and the vac pump added right at the end. One was a 357 Cleveland, the other was a 355. Both Wet sump.
Thanks again
Last edited by Fatman on Tue Nov 20, 2007 7:07 pm, edited 1 time in total.
steer away from the 3 Vane units, most I have heard of have netted very low Vacuum figures.
what kind of numbers do you usually hear about ? i'v made 17-18 " pretty consistenly with the one i have, but i do go to great pains to seal it up. its always pegged on 15" ( relief setting) during a pass.
i can tell you it did take a crash when a shaft and rotor gave it up , and car lost about 0.05 in the 1/8 mile afterwards, and smoked some too. i use 1.5 mm / 1.5 mm / 3mm . never smokes with the pump running.
what kind of numbers do you usually hear about ? i'v made 17-18 " pretty consistenly with the one i have, but i do go to great pains to seal it up. its always pegged on 15" ( relief setting) during a pass.
i can tell you it did take a crash when a shaft and rotor gave it up , and car lost about 0.05 in the 1/8 mile afterwards, and smoked some too. i use 1.5 mm / 1.5 mm / 3mm . never smokes with the pump running.
Carefull with the New Moroso pump, as it's a monster when pulling vacuum. If your engine is sealed good, you can almost count on a relief valve being used.
The last engine I put one on had 18" at idle and about 28 at high rpm....with the same pulley setup I was using on their std. 4 vane pump pulling about 12 and 18wot..... I reduced the ratio in HALF, and the engine still was seeing about 14 at idle....
Nice pump though. Moroso did well with it.
The last engine I put one on had 18" at idle and about 28 at high rpm....with the same pulley setup I was using on their std. 4 vane pump pulling about 12 and 18wot..... I reduced the ratio in HALF, and the engine still was seeing about 14 at idle....
Nice pump though. Moroso did well with it.
Uratchko Racing Engines
248-755-5556
248-755-5556
Being a budget-minded guy, I have successfully used this pump for my last 3 engines (street/strip 540BBC, 2 406s street/strip). They work fantastic, and pull ~10" vacuum.
GM 24505066 air pump, 95 Corvette
GM 12117025 Plug
1) Remove the large black plastic cover from the pump. There are three tangs and silicone sealer holding the two halves.
2) Remove the dense foam surrounding the pump housing. In the event a large amount of oil is aspirated, the foam will cause pump meltdown...don't ask
3) Remove the small green solenoid entirely from the circuit.
Hot=ORG
GND=BLK
I would strongly suggest using a relay with this pump; it pulls a bit of current. HTH.
GM 24505066 air pump, 95 Corvette
GM 12117025 Plug
1) Remove the large black plastic cover from the pump. There are three tangs and silicone sealer holding the two halves.
2) Remove the dense foam surrounding the pump housing. In the event a large amount of oil is aspirated, the foam will cause pump meltdown...don't ask
3) Remove the small green solenoid entirely from the circuit.
Hot=ORG
GND=BLK
I would strongly suggest using a relay with this pump; it pulls a bit of current. HTH.
He who is in me is greater than he who is in the world.
Hi Fatman
Hi Fatman
Was talking to Shane from COME Racing today on this very same matter
He told me that i should go to the jap wreckers and just buy vac pump off a mazda or the like and run it at half engine speed and it will be cheapest 20 hp out
Im doing that tomorrow as Shane has heaps of dyno tests and he reckons majority of the time it produces the results.
Trev
Was talking to Shane from COME Racing today on this very same matter
He told me that i should go to the jap wreckers and just buy vac pump off a mazda or the like and run it at half engine speed and it will be cheapest 20 hp out
Im doing that tomorrow as Shane has heaps of dyno tests and he reckons majority of the time it produces the results.
Trev
No, but I've witnessed one on a 572 make an additional 20whp.PFM wrote:n2xlr8n,
Do you have any HP gain numbers for this pump? Do you run it all the time after start-up or is it a 10 second deal. I guess if you managed to overheat one it was running all the time. I'm thinking it may be a good fit for one of my projects, I need to see it on the dyno.
PFM
I run it continously. I can't imagine the benefits of not using it all the time.
It overheated because I grenaded the engine and it filled with schrapnel
It's a good low-cost alternative, IMO.
He who is in me is greater than he who is in the world.