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what upgrades would u make to a 3.4l block if any by ttt123
Started on: 01-16-2014 05:53 PM
Replies: 97 (1543 views)
Last post by: JCircs on 02-04-2014 05:00 AM
RobertGT
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Report this Post01-24-2014 01:56 PM Click Here to See the Profile for RobertGTSend a Private Message to RobertGTEdit/Delete MessageReply w/QuoteDirect Link to This Post
But he was specifically talking about having boost at idle. If there is boost, the BOV is closed. That's how they are designed.
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AL87
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Report this Post01-24-2014 05:42 PM Click Here to See the Profile for AL87Click Here to Email AL87Send a Private Message to AL87Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by RobertGT:

But he was specifically talking about having boost at idle. If there is boost, the BOV is closed. That's how they are designed.


hmm. how come no one ever recommends a 272 to anyone building a 2.8?
it would just be common sense to do so, reading on this thread and finding out that even if it were turboed that it would still work.
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bcampbell
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Report this Post01-24-2014 06:02 PM Click Here to See the Profile for bcampbellClick Here to Email bcampbellSend a Private Message to bcampbellEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by RobertGT:

But he was specifically talking about having boost at idle. If there is boost, the BOV is closed. That's how they are designed.


I was explaining how it's not possible to have boost in the plenum at idle. It is theoretically possible to have boost in the charge pipe at idle; however if that were the case then the BOV would be opened.

A cam with a lot of overlap can be less desirable for boost because you can lose some of the charge straight out the exhaust. I don't know if the 272 has enough overlap to cause this to happen.
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RobertGT
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Report this Post01-27-2014 04:24 PM Click Here to See the Profile for RobertGTSend a Private Message to RobertGTEdit/Delete MessageReply w/QuoteDirect Link to This Post
And how would you have pressure before the throttle plate when the BOV is wide open?
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Custom2M4
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Report this Post01-27-2014 07:02 PM Click Here to See the Profile for Custom2M4Click Here to Email Custom2M4Send a Private Message to Custom2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by bcampbell:


I was explaining how it's not possible to have boost in the plenum at idle. It is theoretically possible to have boost in the charge pipe at idle; however if that were the case then the BOV would be opened.

A cam with a lot of overlap can be less desirable for boost because you can lose some of the charge straight out the exhaust. I don't know if the 272 has enough overlap to cause this to happen.


The bov works off crankcase vacuum. Vacuum, When the throttle plate is closed, and no boost is introduced to correct the vacuum.. The vacuum will suck the plunger on the bov, and boost on the charge pipe together will be enough to overpower the bov spring and slightly open. When the throttle plate is open and the motor is under boost, the engine vacuum turns to pressure and forces the bov closed. If the engine was building boost at idle, then it would be forcing the bov closed, and the pressure in the charge pipe would be fighting it... Ie; not going to happen.

With out a blow off valve or diverter valve, your pressure would backtrack and fight the turbo causing a compressor surge.

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hnthomps
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Report this Post01-30-2014 09:54 PM Click Here to See the Profile for hnthompsClick Here to Email hnthompsSend a Private Message to hnthompsEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by AL87:


Its because there are two guys using a 272 cam with a turbo. a 272 cam has valve overlap to help the 60* motors make more power at the higher rpm, because as we all know no matter what between a 2.8 and 3.4 they both fall flat on thier face after 5500rpm since the intake is so restrictive. BUT they are also using a turbo.

so I was wondering how the motors run at idle with the turbo, thinking that if they dont create any boost at idle would be understandable, because im imagining that if the turbo was making pressure, it would interfere with the idle since the cam has overlap.


My idle speed on the turbo 3.4 with 272 cam is 950-1000 RPM with a Getrag 282 transmission. The boost gauge is mechanical and likely not very accurate. There is some light boost shown at idle but that could easily be a gauge error.

Nelson
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Custom2M4
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Report this Post01-30-2014 11:05 PM Click Here to See the Profile for Custom2M4Click Here to Email Custom2M4Send a Private Message to Custom2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by hnthomps:


My idle speed on the turbo 3.4 with 272 cam is 950-1000 RPM with a Getrag 282 transmission. The boost gauge is mechanical and likely not very accurate. There is some light boost shown at idle but that could easily be a gauge error.

Nelson


Mechanical gauges are very accurate, but it would have to be a higher quality model... If your boost line was run correctly, without any leaks. Your gauge starts at -30 psi to 30 psi, and is sitting at 0 on idle?
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RobertGT
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Report this Post01-31-2014 02:02 AM Click Here to See the Profile for RobertGTSend a Private Message to RobertGTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Negative psi?

His boost gauge reference line isn't run correctly. He's likely referencing before the throttle plate, where a gauge hovering around 0 would be pretty likely.
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jb1
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Report this Post01-31-2014 03:21 AM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by RobertGT:

Negative psi?


Vacuum

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ttt123
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Report this Post01-31-2014 08:35 AM Click Here to See the Profile for ttt123Click Here to Email ttt123Send a Private Message to ttt123Edit/Delete MessageReply w/QuoteDirect Link to This Post
So from the last two pages of this thread.. I'm going to invest in a BOV for the best mods to a 3.4l motor lololol sorry just a little humorous sarcasm

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RobertGT
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Report this Post01-31-2014 12:19 PM Click Here to See the Profile for RobertGTSend a Private Message to RobertGTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by jb1:

Vacuum


Which is not measured or expressed in terms of negative psi.
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Report this Post01-31-2014 04:25 PM Click Here to See the Profile for ericjon262Send a Private Message to ericjon262Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by RobertGT:


Which is not measured or expressed in terms of negative psi.


it makes no difference, it can be expressed either way, as long as you're not dealing in absolute pressure.
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Custom2M4
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Report this Post01-31-2014 06:05 PM Click Here to See the Profile for Custom2M4Click Here to Email Custom2M4Send a Private Message to Custom2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by RobertGT:


Which is not measured or expressed in terms of negative psi.


It was easier to explain, then 0-30 psi vacuum to the left of zero, 0-30 psi boost to the right. Everyone seems to understand it left of zero is negative, but thank you for your correction.
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carbon
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Report this Post02-03-2014 12:03 PM Click Here to See the Profile for carbonSend a Private Message to carbonEdit/Delete MessageReply w/QuoteDirect Link to This Post


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JCircs
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Report this Post02-03-2014 01:53 PM Click Here to See the Profile for JCircsClick Here to Email JCircsSend a Private Message to JCircsEdit/Delete MessageReply w/QuoteDirect Link to This Post
How much (negative psi) vacuum should a 3.4 with a 272 cam have at idle?
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RobertGT
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Report this Post02-03-2014 10:35 PM Click Here to See the Profile for RobertGTSend a Private Message to RobertGTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I already answered that, probably somewhere around 10-11 in-Hg. That's inches of Mercury, the standard unit of measurement for vacuum in internal combustion engines. That's what my 3.4 DOHC pulls at least. It won't be the same, but it'll be close.
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Blacktree
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Report this Post02-03-2014 11:32 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by JCircs:How much (negative psi) vacuum should a 3.4 with a 272 cam have at idle?

My 3.4 V6 has a camshaft from another mfgr that's roughly equivalent to the Crane H272. My engine produces about 12-13" Hg at idle.
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JCircs
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Report this Post02-04-2014 05:00 AM Click Here to See the Profile for JCircsClick Here to Email JCircsSend a Private Message to JCircsEdit/Delete MessageReply w/QuoteDirect Link to This Post
So at 9.5 to 10.5 at idle I guess I'm in the right area, I thought it was a little low but couldn't find any vacuum leaks.
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