I did not. Opened up my old thread on this motor so we don't fill the OP of this one full of garbage.
https://www.forbbodiesonly.com/moparforum/threads/need-some-engine-advice.225358/page-5
Durability in low deck strokers
- Thread starter TexasRoadRunner68
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k, I thought it may be for your "name"
TexasRoadRunner68
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Yeah, I had a 68 4 speed RR years back when I made the account.
Jeremiah
Well-Known Member
For those with 4.150 stroke low decks and piston slap..were you pistons 2618 or 4032 alloy?
Mine were KB (Icon) pistons. The current model of the same piston is listed as 2618 alloy.
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Did you change your avatar photo ?
What carb are you running instead that you like? I have a 451 with mild cam and run the QF SS 735. It’s jetted up quite a bit and I’ve always wondered about a better carb. Worked Eddy RPM heads. Current tune is yielding dyno at wheels of 523 ft-lb and 391 hp. Very Decent but expected more HP and off idle throttle is not that snappy with my 727.
Jeremiah
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Usually the old school dichromate Holley 750 VS (3310) or DP (4779) are good places to start for a streeter. If it has a big cam, headers etc 850 (4781). For the most part any of the shiny hp carbs qill require transfer slot restrictors, emulsion jet changes and air bleed tuning on top of the normal main jets/power valve / squirter tango. That topic is a can of worms we dont need to open lol.
Thanks. So what is much different between the Holley 750 VS and my QF 735 VS? Both are 750 type starting points and I thought the QF was an improvement. It’s actually got some drawbacks compared to the Holley is what I’m hearing? I’m very new to carb specifics so forgive the lack of knowledge
SlinktRR
Well-Known Member
major advantage of the newer QF or holley clone carburetors compared to something like a 3310 is screw in air bleeds, PVCR's for the metering block versus using drill bits on older dichromate carbs. so in theory its as easy to tune for the street as an edelbrock/carter/QJet carb while not giving up the top end that holleys are known for like the double pumper.
Jeremiah
Well-Known Member
Three things I always have to correct in the shiny carbs:
1) Restrict emulsion passages
2) Move Idle Feed Restrictor to lower hole (below fuel level)
3) Transfer slot restrictors (due to mile long t-slots in the baseplates.
That said, if you are happy with your carb don't think twice about it and continue enjoying the car. Completing the above three steps requires #6, #8, and #10 brass set screws, a wire gauge drill set, a wire gauge pin gauge set, and everything to make and thread the holes. IMO typically the older design of metering block / baseplate has better street manners out of the box. All of the Holley HP's and QF carbs I have owned or worked on were blubbering fat down low and if you jet them to be reasonably lean at cruise they are deadly lean at WOT.
1) Restrict emulsion passages
2) Move Idle Feed Restrictor to lower hole (below fuel level)
3) Transfer slot restrictors (due to mile long t-slots in the baseplates.
That said, if you are happy with your carb don't think twice about it and continue enjoying the car. Completing the above three steps requires #6, #8, and #10 brass set screws, a wire gauge drill set, a wire gauge pin gauge set, and everything to make and thread the holes. IMO typically the older design of metering block / baseplate has better street manners out of the box. All of the Holley HP's and QF carbs I have owned or worked on were blubbering fat down low and if you jet them to be reasonably lean at cruise they are deadly lean at WOT.
Do you know of any good books or articles that explain the tuning of the emulsion part? I have 3 Quick Fuel carbs that have a series of emulsion holes, and I am not sure what they do or how to tune them.
Jeremiah
Well-Known Member
I can steer you to the pertinent info online if the links are still good. There isn't too much theory to my emulsion tuning. I put a 750 holley metering block on my 1050 annular and it had good manners I copied the emulsion package and relocated the idle feed restrictor to the lower hole like the 750 was. As I said above drilling out air bleeds from blanks is an art in itself if you don't have a lathe. If I did not have all of the stuff in the first place I'd be talking to a carb shop about it.
On my carbs, all the holes are already drilled and tapped. I think there are 10 in each metering block, I'll have to check next time I am in the garage. So what exactly does the emulsion circuit do? And by moving the IFR's down lower, that helps to lean out the idle?
Jeremiah
Well-Known Member
The emulsion circuit emulsifies liquid fuel with air coming from the bleeds.
In my experience moving the IFR to below fuel level smooths out the idle and low speed AFR readings and also gives better control of the idle circuit in some applications. I say "some" because I have had a few engines that did not seem to care, however, both of those specimens had big solid roller cams and idle speeds of 1100+ rpm.
In my experience moving the IFR to below fuel level smooths out the idle and low speed AFR readings and also gives better control of the idle circuit in some applications. I say "some" because I have had a few engines that did not seem to care, however, both of those specimens had big solid roller cams and idle speeds of 1100+ rpm.
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