The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 07-24-2017, 11:52 PM   #1
KyleSeal
Senior Member
 
KyleSeal's Avatar
 
Join Date: Mar 2014
Location: Toano, VA
Posts: 799
Engine dying with brakes issue

I have a K30 with a big cammed 454, 4 speed, with hydroboost brakes. Lately Ive been having some issues. When I give partial brake, like coming up to a stop light while in neutral, the whole truck will shake some and then the idle will drop to about 1500 and virtually drop all the way down to 200 rpm like its going to die. I am still able to keep it going by giving some gas but this has become an issue because it makes the truck impossible in traffic.

All fluids are topped off, could there be air in the system? I heard theres a diaphragm in the hydroboost system that tends to stick, causing something like this.

Does anyone have any pictures of the hydroboost system showing where such diaphragm is?

Another part to this issue is that the motor will try and die when turning the wheel while sitting still. Like it kills it. I know it puts some strain on the system but I dont feel that much strain is coming from a single turn of the wheel.


454, 4 speed, 6 inch lift with 35s.
__________________
"Sometimes I do serve as a good bad example. Glad to be of service."

My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809
KyleSeal is offline   Reply With Quote
Old 07-25-2017, 07:05 AM   #2
homemade87
Registered User
 
Join Date: Apr 2010
Location: Guntersville Alabama
Posts: 1,073
Re: Engine dying with brakes issue

From the sounds of it especially when sitting still and turning the wheel and it drags it down , my guess you need some more tuning on the engine . With that big cam the vacuum is low along with timing and air fuel ratio . Just idling on its own with no drag it may be fine . The hydo system puts a load on it .

Same thing happens to automatics when you drop it into a gear . The rpm will drop to much when the tune is off .

Take a look at your timing and carb setting . The engine is more sensitive at idle ( low rpm ) . Once your tune is closer you problem will be helped alot . Also the big cam may require more rpm at idle as well .
homemade87 is offline   Reply With Quote
Old 07-25-2017, 05:26 PM   #3
wilkin250r
Registered User
 
wilkin250r's Avatar
 
Join Date: Sep 2010
Location: Lake Tahoe, Nevada
Posts: 755
Re: Engine dying with brakes issue

I can't fix your problem, but I may be able to help identify it. Let's look at this logically.

I don't have a hydroboost, but from what I understand, they're powered by pressure from the power steering pump rather than engine vacuum. When you're brakes are applied, your engine almost dies.

Also, the engine starts to die when you turn the wheel standing still.

BOTH of those issues involve the power steering pump, yes?

It's starting to sound like you either have a general engine problem (vacuum leak, carb settings, ect ect) OR your problem is somehow centered around the power steering pump.
__________________
I know a little about cars, but if you have a question about electricity or sport quads, I'm your man!!!
wilkin250r is offline   Reply With Quote
Old 07-26-2017, 12:32 AM   #4
KyleSeal
Senior Member
 
KyleSeal's Avatar
 
Join Date: Mar 2014
Location: Toano, VA
Posts: 799
Re: Engine dying with brakes issue

I dont believe I have a vacuum leak because I covered the carb with my hands and the engine died instead of revving back up. I suppose next I will move onto getting it better tuned and timed.
__________________
"Sometimes I do serve as a good bad example. Glad to be of service."

My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809
KyleSeal is offline   Reply With Quote
Old 08-07-2017, 04:50 AM   #5
Super_Dave
Registered User
 
Super_Dave's Avatar
 
Join Date: Jul 2014
Location: Sherwood, Oregon
Posts: 974
Re: Engine dying with brakes issue

Same thing happened to me. My new Summit HEI Dist went south. Bought another one from another supplier and problem went away.
__________________
--Project BABA YAGA!... http://67-72chevytrucks.com/vboard/s...d.php?t=655783
--Project BABA YAGA!... http://67-72chevytrucks.com/vboard/s...ghlight=Belair


"Life is tough - wear a cup!"
"Old Enough to Know Better - Too Young to Resist"
"Junk is something you will need three weeks after you throw it away."
Super_Dave is offline   Reply With Quote
Reply

Bookmarks

Tags
454, big block, brakes, hydroboost

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 08:39 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com