Dealing with Low Vacuum?

[Doc76]

Interested to know how you guys have dealt with this and what you’d recommend

For starters I have a completely new braking system. Stock 93 mustang booster, 15/16” MC, front disc Mustang, rear disc FFR brake kit.
I’m trying to work through an engine selection but seems all the crate engines have too low vacuum to feed this brake system reliably.

Short of a hydraboost and reworking a bunch of stuff, has anyone experience with an electric vacuum pump in the Mk4?

For the record I have looked at custom builds with a cam that would address this but all the builders in western Canada have a very long leadtime.

[J R Jones]

Back in the seventies we road raced Boss 302 and Boss 351 engines that had the huge intake runners and low vacuum. We had been running non-boosted brakes.
The physical demands of National and Trans Am level competition is substancial, so we went to a (Ford) street brake booster to reduce driver fatigue.
The duty cycle of WOT to maximum braking resulted in little or no brake boost. We found that Chevrolet had a vacuum issue with high performance engines and vacuum doors for the headlights. Their fix was a vacuum storage tank system. We bought the tank/valve, spliced it in parallel, and it functioned perfectly for brake boost. I speculate that it was like having a very large vacuum booster.
jim

[Jim Doak]

I chose this engine from BluePrint specifically because my build includes vacuum-assisted brakes: https://blueprintengines.com/collections/ford-compatible-small-blocks-302-c-i/products/bp302rctc

It's a 302 and according to the dyno sheet that came with the engine, it produced 383 HP and 370 ft-lb of torque, which is enough for me. And if you read the Notes section of the Web page, you'll see that the engine "is designed to work excellent with power brakes".

[Doc76]

I chose this engine from BluePrint specifically because my build includes vacuum-assisted brakes: https://blueprintengines.com/collections/ford-compatible-small-blocks-302-c-i/products/bp302rctc

It's a 302 and according to the dyno sheet that came with the engine, it produced 383 HP and 370 ft-lb of torque, which is enough for me. And if you read the Notes section of the Web page, you'll see that the engine "is designed to work excellent with power brakes".

I have considered the BP 347. Nice setup fully dressed. That engine, like the FPz2363 doesn’t supply enough vacuum.

[Jeff Kleiner]

I have considered the BP 347. Nice setup fully dressed. That engine, like the FPz2363 doesn’t supply enough vacuum.

Where did you hear that?

Jeff

[Norm B]

A 347 with a camshaft that won’t provide enough vacuum for a brake booster will not be much fun on the street. Are you planning to go racing?

Norm

[CraigS]

Another option is go to a 408. More cubes means you can get a given HP# w/ less cam.

[rich grsc]

You don't even have the engine, and yet you find problems. My 331 with a fairly aggressive cam and stack EFI has more than enough vacuum for my brakes. Like Jeff, don't know where you come up with this stuff

[Ford & Jeep Fan]

These Reservoirs with a check valve really do help https://www.ebay.com/itm/225645361466?_skw=vacuum+canister-+reservoir&itmmeta=01JREAP2R6NHFTPZZVDR67Z1RM&hash=item348982f93a:g:VUQAAOSwlxRab7-0&itmprp=enc%3AAQAKAAABAFkggFvd1GGDu0w3yXCmi1ci4Zbye FsnZk0n8L3uKB3LRrVq4ckTQ5SAw1Tv07JlHKn%2BPn4M%2FVH ibxYPLmrwrroejn0OfIG6oBWlgjAY6hYsmw1dk%2FnJnyMg4nY CBmPt7mvc5ZH1Hwzf%2BtFWDFeqmWRr0MZZ%2BDlflXHacg9ik v4uN%2BzlG9W5CrXejTJpUQuQP1bdWf5zXKETivGH2SUN4EPLg roh6ZlEl2Tb0qHFwoZhXn35ViMQZ24JZYRQcgw2U8x5SCNPowY XuBReZIjU4w7FK01%2FQ0KYhCcTwOs%2F5lwargEbjNGR4UKcR FGGXvD5xgytbS4qXak2p5QmIRm%2BakE%3D%7Ctkp%3ABk9SR6 ys2MrDZQ

THere are also identical chrome ones on Ebay for the same $54.95

[bobl]

I installed an electric vacuum pump for a diesel pickup. Been running it for 9 years and 20k miles. It works great for normal driving. I'd probably add a vacuum canister if I were racing it.

Bob

[Doc76]

Where did you hear that?

Jeff
From Ford Performance (tech line) on the Z2 (they don’t list that detail) and BP tech support on the 347
Also spoke with FFR today who confirmed that as being the case when the inHg is that low.
I’m told I need 18inHg to feed the brakes on my configuration.
Neither supply close to that. (10-13 inHg)
All three sources said those differences will be noticeable.

[Doc76]

A 347 with a camshaft that won’t provide enough vacuum for a brake booster will not be much fun on the street. Are you planning to go racing?

Norm

Not planned no (maybe the odd track day) but don’t like redoing things rather do it now than later if needed.

[Doc76]

Another option is go to a 408. More cubes means you can get a given HP# w/ less cam.
I’m open to that.
Do the blocks get wider?
My understanding, from FFR, is the 351 and 408 get wider and require new headers as a result. With my 302, headers are already very close to the drivers foot box.

[Doc76]

I installed an electric vacuum pump for a diesel pickup. Been running it for 9 years and 20k miles. It works great for normal driving. I'd probably add a vacuum canister if I were racing it.

Bob

Good to know thanks
I see you’re 347 and pushing +500hp. Are you doing that on an OEM block?

[StangRacer]

Doc.. a vacuum canister like JR and others have mentioned would probably do the trick. But before doing that, I would try things out. You may be surprised at how well it works...

[Ford & Jeep Fan]

From Ford Performance on the Z2 (they don’t list that detail) and BP on the 347
Also spoke with FFR today who confirmed that as being the case when the inHg is that low.
I’m told I need 18inHg to feed the brakes on my configuration.
Neither supply close to that. (10-13 inHg)
All three sources said those differences will be noticeable.

You have got to be kidding. 18 Is not doable with a performance cam of any size at all.
I think you will find with the light Weight of a FFR vehicle You really will NOT Need as much "power" in your power brakes.

[bobl]

Good to know thanks
I see you’re 347 and pushing +500hp. Are you doing that on an OEM block?

Yes, but let me clarify. It's not a crate engine, it is built with good parts and tuned very well. I'm an engine builder/tuner by profession (retired). I have a dyno and made around 25-30 pulls on it before it even saw the car. I also have a backup engine just in case. LOL. I would not build an engine at this power level on a stock block for a customer.

Bob

[bobl]

From Ford Performance (tech line) on the Z2 (they don’t list that detail) and BP tech support on the 347
Also spoke with FFR today who confirmed that as being the case when the inHg is that low.
I’m told I need 18inHg to feed the brakes on my configuration.
Neither supply close to that. (10-13 inHg)
All three sources said those differences will be noticeable.



Just as a reference my stack injected 347 has around 10-11 inches of vacuum. Mainly because of the small plenum of the 8 stack. I found the brakes worked, but required too much pedal pressure. The electric pump makes around 17" of vacuum and made a huge difference.

Bob

[Doc76]

Just as a reference my stack injected 347 has around 10-11 inches of vacuum. Mainly because of the small plenum of the 8 stack. I found the brakes worked, but required too much pedal pressure. The electric pump makes around 17" of vacuum and made a huge difference.

Bob

Do you mind me asking which pump you went with?

[bobl]

This is the one I'm using. There are a lot of cheap imported ones out there. Don't know how good they are.

GM Genuine Parts 20804130 Power Brake Booster

[Nigel Allen]

My diesel ute (Isuzu) has a compact vaccuum pump on the rear of the alternator. It has worked faultlessly for 25 years. Could be an option...

https://automotivesuperstore.com.au/bosch-0986an0702?utm_source=google&utm_medium=cpc&gad_source=1&gbraid=0AAAAADhr_hXxEMqaA-N6k0ZXyWchI4ix9&gclid=CjwKCAjwtdi_BhACEiwA97y8BIJZLs9T8rqeBybvpqfA W0NhBobeVq8oRhchkSYHPdeTVkIGbaXXyBoC4a8QAvD_BwE

Cheers,

Nige

[CraigS]

I’m open to that.
Do the blocks get wider?
My understanding, from FFR, is the 351 and 408 get wider and require new headers as a result. With my 302, headers are already very close to the drivers foot box.

Sorry, I forgot you already have a 302. Yes you would need different headers and intake to go 408.

[Mike.Bray]

This is the one I'm using. There are a lot of cheap imported ones out there. Don't know how good they are.

GM Genuine Parts 20804130 Power Brake Booster

We all know you cannot use a GM part of a Cobra. Just can't.

[Jeff Kleiner]

From Ford Performance (tech line) on the Z2 (they don’t list that detail) and BP tech support on the 347
Also spoke with FFR today who confirmed that as being the case when the inHg is that low.
I’m told I need 18inHg to feed the brakes on my configuration.
Neither supply close to that. (10-13 inHg)
All three sources said those differences will be noticeable.

Doc,
The Blueprint 347 camshaft has 218 degrees intake and 226 degrees exhaust duration with a 112 LSA. That is not a radical cam. I ran a Trick Flow Stage 1 in my old roadster with 221 intake, 225 exhaust and also a 112 LSA. That's almost identical (actually more intake duration) than what BP puts in their 347s. I used mine with Fox vacuum booster and never experienced loss of assist, even while making several hundred autocross runs that involved lots of quick and repeated brake applications. I've had at least a couple of BP 347s through here for customers that have had vacuum power brakes and have not ever felt that they were lacking proper assist nor have any of the owners expressed that. As far as the Blueprint 347 goes I think you're worrying about a problem that isn't there. The FRPP Boss 363 cam is 232/240 and I can see that one being low on vacuum.

Good luck,
Jeff

[Jeff Kleiner]

We all know you cannot use a GM part of a Cobra. Just can't.

Try telling that to GoDadGo :D

Jeff

[Mike.Bray]

Try telling that to GoDadGo :D

Jeff

That GM vacuum pump would probably lower the value of the car by about 60% if you believe the forum.

[rich grsc]

That's just a wannabe cobra. :rolleyes:

[Doc76]

Thanks Jeff
That BP347 certainly seems to be the “easy button”.

[Doc76]

Doc,
The Blueprint 347 camshaft has 218 degrees intake and 226 degrees exhaust duration with a 112 LSA. That is not a radical cam. I ran a Trick Flow Stage 1 in my old roadster with 221 intake, 225 exhaust and also a 112 LSA. That's almost identical (actually more intake duration) than what BP puts in their 347s. I used mine with Fox vacuum booster and never experienced loss of assist, even while making several hundred autocross runs that involved lots of quick and repeated brake applications. I've had at least a couple of BP 347s through here for customers that have had vacuum power brakes and have not ever felt that they were lacking proper assist nor have any of the owners expressed that. As far as the Blueprint 347 goes I think you're worrying about a problem that isn't there. The FRPP Boss 363 cam is 232/240 and I can see that one being low on vacuum.

Good luck,
Jeff

Thanks Jeff
That BP347 certainly seems to be the “easy button”.