Hot Rod Forum banner

41 - 51 of 51 Posts

·
Registered
Joined
·
54 Posts
Discussion Starter · #41 ·
I am almost back to what the carb came with , (68 primary , 31 ifr's , 65 power valve , 74 secondary jets) and now I am at , (66 primary , back to 31 ifr's , 75 power valve , 72 secondary jets).
 

·
More for Less Racer
Joined
·
20,095 Posts
I did not check top dead center, its a gm sp/357 crate engine with all the timing marks on the balancer. Think I need to? It seems to like the more timing I give it so far.
Doesn't matter where a motor comes from, true TDC needs to be verified or you'll never know if a mistake was made on assembly of he pointer or balancer. If you check it then it can be eliminated as a possible issue.

I think you're just fine with the current timing set-up and wouldn't reduce the initial. might be better with ported vacuum, as this will help with rpm drop when place in gear not being as much of a drop, but still give you the vacuum advance at cruise speeds. If you don't have any trouble with rpm drop in gearon full vacuum, then leave it that way.

From where you are at right now I think I'd try a .032-.034" IFR. Sounds like transition circuit is just too lean.

I don't know if it is the case, but you mention this carb is the Quickfuel version of the Holley Slayer....I wonder if it has some of the same problems that have been popping up about the Avenger carbs. You might read this and see if it helps:
https://www.hotrodders.com/forum/holley-670-vs-street-avenger-hesitation-fix-507033.html
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #44 ·
Had to out of town again , but back to tuning. I swapped the quick fuel primary metering block out with a 670 avenger block for fun and it seems to be much better, not perfect but way better all around. I was reading about the t-slots on the quick fuel carbs being to wide so I went and got a new 600 holley street warrior to check it out and the t-slots are way smaller so I was wondering if I could use the holley base plate on the quick fuel main body? I was going to get a brawler 600 but I think they are the same as what I have, (mine is just an off road slayer),anyway what do you guys think of a base plate swap?

Also on the quick fuel it has idle holes on the secondary side where as the holley base plate does not, whats up with that?

just trying to learn these holleys
 

·
Registered
Joined
·
4,147 Posts
The reason the quick fuel base plate on the secondary side has same size idle discharge ports like the front is because all of there carbs have a four corner idle base plate but on the slayer carbs they just set them up as a two corner idle but you can make it a four corner idle just by taking off the secondary metering plate and then changing the secondary idle air bleeds to be the same size as the front and then also put the same size idle feed restrictor in the secondary metering block to be the same as the front as with a four corner idle carb the secondary side needs to be square and the same as the front or things just won't be correct as it can be for the tune. Also the secondary metering block has to have idle mixture screws ability on them.

Yes you can use the holley base plate from a street avenger on the quick fuel carb just make sure your secondary idle air bleeds are what they were out of the box as with a carb setup as a two corner idle the holley base plate has a channel that allows the secondary fuel to be shared with the front so things don't get stale in the rear since the secondary side is not used much while driving. The quick fuel 4 corner idle base plates don't share with the front and that is one reason why they have the idle discharge port that is identical like the front and I actually have been reading about the billet or cast quick fuel base plates having wider transfer slots but in my experience it has never caused me any issues with many different builds with cams from mild to wild etc.

The street avenger metering block if it has not been messed with has a .028 ifr size out of box and a .046 power valve channel restrictor size hole. Also on your secondary metering plate it has most likely a .039 ifr size which will make for a really fat idle and pretty rich for that cam you have and I do think the secondary idle air bleeds are .039 unless they changed them. I had a quick fuel 600 slayer once on a 350 with a lunati voodoo hydraulic roller cam which was 272/276 219/[email protected] 515/530 lift with a 112 lsa and my quick fuel carb was pig rich on the idle that I could only go half a turn out on the mixture screws as anything more it would foul my plugs and I had an off idle stumble with the pink pump cam. I took the primary metering block and went down from the .033 out of box ifr down to a .031 and then I ditched the secondary metering plate and installed a holley secondary metering block that came off of a 670 street avenger that was only a two corner idle so the block has no idle mixture screws and it has a .031 ifr size. I then installed a orange pump cam and that made my idle perfect as I could get it outside of using an o2 gauge and I then could get my idle mixture screws to about a full turn plus out.

But every engine is different on what it needs but you got to make sure your timing is good for what your engine needs. I don't ever like the metering plates even the quick fuel ones that take jets and I always replace them with a metering block as for me they always are better for performance and working wise but that is my two cents.
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #46 ·
Thanks for the info. eric , I have a 670 street avenger and a 600 street warrior I can play with. I might try the base plate swap just to see what it does and then try the rear 670 block as well. What the deal with the secondary side for idle on a two corner carb? does it feed fuel at idle as well?

My card for the quick fuel has 33 for the air bleeds for the rear. Also I see that the quick fuel has three emulsion holes in the block and the holley block has two, I have my float levels a bit low, (for off road use) and maybe that is messing up my tuning with a three hole block, works pretty good with the 670 two hole block though. Maybe I will have to raise the float levels back up to mid window, they are at the very bottom now.
 

·
Registered
Joined
·
4,147 Posts
The holley metering blocks actually have three emulsion holes its the bottom one is kind of hidden by the idle feed restrictor if its at the bottom location but it does have three its just the quick fuel blocks are somewhat different then then the old holley metering blocks but actually do the same thing and its a long post there and I won't get into all that and bore you to death but as far as the 670 street avenger and street warrior goes look at the base plate as they both should be 1 9/16 butterfly size and may be slightly different or look the same but the main body of both the street warrior and the 670 street avenger are the exact same body just a different part number stamped on the tower.

Now on the 2 corner idle carb of a holley not quick fuel on the holley base plate there is a channel that goes from the front to the back and what that does is allow the secondary side of the fuel to be shared with the front and the secondary side of the holley base plate actually does have idle discharge ports like the front but they are so tiny you really have to look really close.

On the quick fuel base plates because they are all four corner idle made from the factory they do not have a channel going from the front to the rear of the base plate because of it being made for a four corner idle and on the four corner idle you have to keep the rear separate from the front and its kind of like having two 2 barrel carbs sitting on your intake as the front is totally separate from the rear and neither side share anything with fuel thus the 4 idle mixture screws. On the quick fuel base plate there will be the holes made into it on the rear that is identical to the front for the most part and also that is why the rear has the same size idle discharge ports like the front as its setup to adjust juts like the front.

The thing on the quick fuel carbs that have the secondary metering plate instead of the rear metering block with the idle mixture screws all they do is put way smaller idle air bleeds on the rear to enrichen the rear mixture and also the metering plate does have a idle feed restrictor size that is way more bigger then the front out of the box from quick fuel and its basically unadjustable to a certain degree unless you change the secondary idle air bleeds to lean out the secondary side but outside of using an o2 gauge and also knowing a lot of about how a carb works and and also with a some good knowledge and experience trying to adjust the secondary side on the quick fuel carb with the secondary metering plate which you can change the jets but on the metering plate itself they don't have the removable idle feed restrictors in the metering plate and its a fixed size and its already pretty big as I measured mine and its .039 and that is really big for a idle feed restrictor size but there carbs are more calibrated richer then compared to a holley street avenger which is setup a lot leaner. Also I would recommend you not put the holley base plate on the quick fuel main body as it might not work quite right but I can't say for certain but the quick fuel base plate can work on the street warrior or street avenger towers as I currently have a quick fuel base plate on my holley 650 main body which is the same as your street warrior main body.

The backside of the holley tower also is not machined with the holes necessary to have it as a four corner idle as the front does and that is also why the holley base plate has the channel made into the base plate so the secondary fuel side shares with the front. The quick fuel main body does have the holes in the rear of the main body already on the slayer carbs even though they come as a 2 corner idle they are already machined to be a 4 corner idle with a few changes like I stated in a previous post.

Hope I have not confused you any.
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #48 ·
Thanks again eric,I am just trying to learn holleys , so they do feed fuel at idle through the rear? Why I ask is when I lowered my float level in the rear bowl while running my idle came up a bit. Anyway I want to get this new engine running perfect and I have three holley carbs to play with.This is a k-5 blazer so for off road I want to stay with side hung floats. I think my timing is close with vortec heads,(its at 22 initial and the hei is locked at 33 total, all in at 2800 rpm), (seems to like it there) at 5.500ft elevation with another 6 degree's with the vac can on full manifold vacuum.

I think its really close , 670 block , 70 iab , orange pump cam, I think the primary jets are 66,just not perfect , fat at idle , little lean spot and popping just at light throttle off of cruise and seems a bit slow all around , but maybe that's all I can get out of it in a big k-5.

For a 357 horse engine from gm it really does not pull much harder than my old worn out 400 that I took out, (2 quarts of oil every 500 miles).

Thanks again, I am going to play with these carbs and see what happens, and mess with some more timing as well until I get it right.
 

·
Registered
Joined
·
4,147 Posts
There are two things that make the idle circuit calibration on the holley style carbs. The idle air bleeds and then the idle feed restrictors in the metering blocks or metering plate and they are a specific size and on air bleeds when changing them they are the opposite of changing jets. When you change air bleeds and go bigger it leans out the calibration as it allows more air in and if you go smaller then it makes less air pass and will make the calibration richer.

On the idle feed restrictors they are just like changing jets the bigger you go the richer it makes the calibration and the smaller you go the more leaner it becomes. Now the thing on changing air bleeds you have to go up or down .04 size difference at a time to get a change in the fuel curve and its a bit tricky messing with air bleeds without an o2 gauge but even with that its a little bit tricky to mess with air bleeds and 99 percent of the time what they are out of box I just leave them be and change idle feed restrictors in the metering blocks as changing them just .01 in size up or down makes a double percentage change in the fuel curve but I don't know the math and won't get into that but to make it easy you go up or down .02 size difference on the idle feed restrictors at a time to get a big enough change but tuning with the idle feed restrictors takes a little bit of experience and also time and knowledge and knowing how each circuit of the carb must transition from one circuit to the next without having any stumbles or having it to rich or to lean etc and also make sure the settings are all good and the best for what the engine can use.

The idle circuit is in full effect in park and also off idle on the transition circuit clear up to about 40 mph give or take a little and to about 2000 rpm or a hair higher before the main circuit starts to kick in and that is where the jets come into play and then when enough air is coming through the carb and causes enough velocity it will then start to pull fuel through the boosters at higher engine speeds like being on the highway.

You also want to make sure your not showing to much transfer slot on the primary idle or in situations with really big camshafts on the secondary side but yours is nowhere near big enough to need the secondary side transfer slots showing. You want to keep the primary idle transfer slot square and have it about no less then .020 and have it no more then .040 open or the carb will be allowing so much more air through the primary butterflies that it will be pulling fuel more from the transfer slot vs the idle discharge port and it will make your idle pig rich also.

The transfer slot has to be within the right range along with the metering blocks to have the right idle feed restrictor size so the idle is not to rich or to lean and you also have to have the pump shot and shooter size to be giving the best shot possible without it being to much or to little and that takes a little bit of experience as well and trial and error to get all three of those things to all work hand in hand and transition smoothly from opening and closing the throttle in all sort of driving conditions.

On tuning the pump shot you want to go about three sizes up or down on the shooters to get any change and on the shooters the bigger the number the bigger the initial shot will be given but will happen over less duration of throttle opening as to where the smaller the shooter size then the lesser of initial shot it will give but will give a longer duration of a shot during throttle opening. On the pump cams like the pink one for example it gives a smaller and longer travel of duration of throttle opening vs the orange pump cam which will give more duration starting off but has less duration over the throttle opening thus it has a quicker profile vs the pink cam.

Below is a link you might want to check out and familiar yourself with the different circuits on the holley and gain some more knowledge.



Carburetor Tuning the Scientific Way

https://www.hotrod.com/articles/tuning-holley-carb-made-easy/
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #50 ·
Thanks again eric, On the t-slots I was having trouble with them at .020, (to low idle) so I marked the curb idle screw and at 3/4 turn more with the secondary's opened a bit,(1/4 passed closed) , it seems to get enough idle speed in gear. The 670 block seems to idle much smoother than the quick fuel block , with the same ifr's, maybe because the ifr's are down low?

I have 7 to 9psi fuel pressure ,(needle bouncing) with my mechanical fuel pump and the needles and seats seem to be holding, I may have to get a regulator.

Thanks again for the info. I am having fun figuring out all these different holley carbs
 

·
Registered
Joined
·
4,147 Posts
Your quick fuel metering block has a .033 size idle feed restrictor most likely as most of them out of the box has that size and on your holley primary street avenger block its most likely .028 on the idle feed restrictor and that will make a big difference in change and make your idle circuit leaner quite a bit so that is most likely the reason your engine is idling smoother as your engine would not need an overly rich mixture as your combo is not that radical by any means.

There is a debate on the idle feed restrictor location with it being at the top vs the bottom of the metering block if that is what your talking about it being lower but I don't know for sure if that is what you mean. I won't get into that part as I have read on that and there is a lot of stuff about the best location part and for me on my end its never made any difference if the ifr was up high on the metering block like most of them are nowadays vs the lower area on the older holley carbs I have.
 
41 - 51 of 51 Posts
Top