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helping a club member with his L48 1979, replace plugs, tune up etc.
as we have no testing down here, what emission related crap can we get rid of?
we have already bypassed the thermo switch that goes to the distributer (lt blue/red/brown) and connected the green straight to the carb.
the yellow/white hose that goes to the thermo switch then actuator (E) that's on the exhaust manifold has also been disconnected and the flapper wired open.
I assume that the vac signal pulls it open? Well it did move freely.
have left the purple and orange EGR valve hoses there at the moment.
timing set to all in at 2500-2800 at 35-36* as per Lars papers.
have had to limit the HEI vacuum to 10-12* as it was pulling an extra 22* at idle when reconnected.
getting a slight miss/ping/hesitation under load/wot at around 4000rpm but it stumbles thru, could be fuel, going to up the grade and try again this weekend.
Last edited by riverracer au; May 21, 2021 at 12:19 AM.
Reason: spelling / extra info
I think the heat riser on this is open by default......vacuum closes it. You need to verify this as if it is closed.....almost ALL of the passenger exhaust will have to go through the intake out the other manifold.....bad situation, especially at high RPM.
What port did you run the green vacuum line to? It needs to be run to full manifold vacuum.....not ported.
If you are pulling 22...that is too much with your new timing setting....you can get or make a Lars "stop", get his papers on which can to use to pull 12 degrees, or get an adjustable can from the aftermarket.
helping a club member with his L48 1979, replace plugs, tune up etc.
as we have no testing down here, what emission related crap can we get rid of?
we have already bypassed the thermo switch that goes to the distributer (lt blue/red/brown) and connected the green straight to the carb.
the yellow/white hose that goes to the thermo switch then actuator (E) that's on the exhaust manifold has also been disconnected and the flapper wired open.
I assume that the vac signal pulls it open? Well it did move freely.
have left the purple and orange EGR valve hoses there at the moment.
timing set to all in at 2500-2800 at 35-36* as per Lars papers.
have had to limit the HEI vacuum to 10-12* as it was pulling an extra 22* at idle when reconnected.
getting a slight miss/ping/hesitation under load/wot at around 4000rpm but it stumbles thru, could be fuel, going to up the grade and try again this weekend.
on my 79 l82 manual..
remove
E remove and or replace with spacer EFI
B EGR but leave vacuum to charcoal canister (why not) (remove and block if desired)
assume air pump gone?
plug off the rest...except choke pull off
Last edited by interpon; May 21, 2021 at 10:46 AM.
I think the heat riser on this is open by default......vacuum closes it. You need to verify this as if it is closed
how can i easily check this with out removing the manifold??
if i operate the flapper lever at idle i should be able to hear/feel a difference with exhaust flow/sound, right?
Originally Posted by Jebbysan
What port did you run the green vacuum line to? It needs to be run to full manifold vacuum.....not ported.
manifold, checked with a vac gauge whilst idling
Originally Posted by Jebbysan
If you are pulling 22...that is too much with your new timing setting....you can get or make a Lars "stop", get his papers on which can to use to pull 12 degrees, or get an adjustable can from the aftermarket.
i have his recent papers, that's why i made/tried a limiting plate and attached it to the vac can on the inside of the HEI.
got it down by about half.
the photos will help of what to look at to remove.
how can i easily check this with out removing the manifold??
if i operate the flapper lever at idle i should be able to hear/feel a difference with exhaust flow/sound, right?
manifold, checked with a vac gauge whilst idling
i have his recent papers, that's why i made/tried a limiting plate and attached it to the vac can on the inside of the HEI.
got it down by about half.
the photos will help of what to look at to remove.
things are much simpler on my '72
It defaults to open.....study this photo.....the exhaust push’s it open when free.....just pull the vacuum line or the whole canister and bracket off.....
They make a spacer for this to delete the flap valve.....I recommend it.
The EFE vacuum actuator is spring loaded, so yes the heat riser by default is open when connected via rod to riser.
You will feel some resistance at the riser because of the spring inside the actuator if trying to move the riser when rod is connected.
The EFE TVS vacuum switch is also normally open when engine is cold, vacuum will pass through the TVS vacuum switch to actuator closing the heat riser.
When engine temp reaches operating temperature the TVS switch closes the vacuum path to EFE actuator, EFE TVS switch exhausts vacuum from actuator.
When vacuum exhausts from actuator, because of it's spring return it will open the heat riser.....
You can see in the photo where the finger stops are positioned in both opened & closed positions.
Last edited by bmotojoe; May 21, 2021 at 08:05 PM.
River, as you know I have a 77 over here in Queensland. One day, (back when I was in Wisconsin). I hit a big bump in the road and ALL of my emissions stuff just fell off! (My story and I'm sticking to it).
Anyway, THE biggest thing was loosing the 2 into 1 through a Cat into 2 exhaust. true duel exhaust was HUGE. At least by the butt dyno.
Fairly recent shot of my engine. Note lack of EGR and all those vacuum lines and vacuum switches. The less crap you have, the less crap to go wrong.
1979 Emission delete
