Venturi sizing help! Stock 2.0 type 4 with twin 44hpmx

kombi_matt Slammed & Awesome Dubber

76 posts · joined Aug 2011 · 9 May 2012, 8:07 pm

#901016

Not sure if this is the right section to ask this question but....

I have recently got myself a set of twin 44 HPMX's for a very good price.

Pretty sure they have 135 main jets, 36mm venturis, 200 air correctors and F11 emulsions.

I'm thinking this is actually pretty spot on for a 2 litre, though my thinking is its probably more suited for a higer revving (approx 6500rpm) 2 litre.

My dillemma is I am using a stock CJ type 4, with stock hydraulic cam. I think peak power would be around the 4700rpm mark (at a guess) with the stock cam - maybe even lower lol. So my question is what changes do you think I should make to the carbs before bunging them on?

I was thinking of stepping down to either a 32 or 34 venturi, at first, (For better idle and mid range) and possibly F16 emulsions and 190 air correctors.

Obviously capacity is not the issue, but rather low compression and the stock engine. I had the idea of getting some 96mm flat tops to raise the capacity just slightly to 2056cc but more so for the increase the compression ratio.

Any opinions from carb gurus? If it helps, the engine is in my Bay window and uses the stock 091 trans.

I won't be splitting the case, however I am open to converting to solid lifters and some different ratio rockers for a little extra lift.

Help! thanks

vwo60 Veteran Volks Folk

2,036 posts · joined Feb 2007 · 9 May 2012, 9:02 pm

#901041

if they are a copy of the 44IDF the smallest you can get are 32 MM venturies, thats what i would start with, to big and you will not have enough velocity through the carbs, try f11 emulsion tubes.

vassy66T1 Wow ... are U reading this?

2,120 posts · joined Jun 2003 · 9 May 2012, 9:12 pm

#901048

My suggestion is as follows:

32mm venturi (at largest)
Stick with the F11 emulsions
Idles should be either 55 or 60
Main jets are close but most likely rich. I think 130 or maybe even 125
Air correctors are too big IMO. Go for 180 for a start.
Once it is running "okay", a little dyno time or a visit to someone with an air/fuel ratio setup is a great idea.

kombi_matt Slammed & Awesome Dubber

76 posts · joined Aug 2011 · 9 May 2012, 9:21 pm

#901054

Thanks for the help vwo60 and vassy! Much appreciated.

I will step down to the 32mm venturis and keep the F11 emulsions. Thankfully, they have 55 idles in them already so I can leave them in too. I will step the mains down and also change the air correctors.

And yes, some dyno time is on the cards! I just want to do as much as possible by myself first. I bought a carb synchroniser tool off ebay, plus a fuel pressure regulator and guage.

kombi_matt Slammed & Awesome Dubber

76 posts · joined Aug 2011 · 9 May 2012, 9:47 pm

#901066

32 mm venturis are on their way in the mail!

vassy66T1 Wow ... are U reading this?

2,120 posts · joined Jun 2003 · 10 May 2012, 7:42 am

#901108

👍

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 · 10 May 2012, 7:50 am

#901112

HPMX's tend to want a richer setup. I'd go with the smaller venturiis, but wait to rejet after you get it running.

Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

kombi_matt Slammed & Awesome Dubber

76 posts · joined Aug 2011 · 10 May 2012, 10:52 am

#901133

matberry wrote:HPMX's tend to want a richer setup. I'd go with the smaller venturiis, but wait to rejet after you get it running.

Ok cool! I have only ordered the venturis... no extra jets just yet. I would like to get the carbs going well on the stock engine. I don't really want to buy the 96mm kit just yet. I gotta stick to a budget haha! Plus if I can get these carbs running ok without removing the engine all together it will save me some time, money and effort.

kombi_matt Slammed & Awesome Dubber

76 posts · joined Aug 2011 · 10 May 2012, 10:54 am

#901134

This youtube vid is also very very useful for working out the basic initial adjustment before spending all my money on dyno time haha

I'm actually quite impressed with the product support EMPI offers with videos like this. Its quite reassuring. And yes my HPMX's are the newer style ones with the better castings and revised quality control lol....well I hope anyway!

vassy66T1 Wow ... are U reading this?

2,120 posts · joined Jun 2003 · 10 May 2012, 3:37 pm

#901158

I had wondered about the HPMX being a little different.
Thanks for the input Matt.

matberry wrote:HPMX's tend to want a richer setup. I'd go with the smaller venturiis, but wait to rejet after you get it running.