4k With Twins Running Bad

[boosted_gem]

Hey i've got a 4k with a set of sidedraught 40mm dellorto's on it. the motor just seems to keep poping when cold and hot and just runs like a bag of shit. i was just wondering what peoples thoughts are on this. i was thinking of rebuilding the carbies or piss them off and just get a 4 barrel holly.

 

Also the setup of got is basically a rebuilt 4k 300degree cam extractors 2 1/4 inch exhaust the twins when they run right somtimes, elec ignition port and polished head. With all of this do peoples corolla's fell pretty decent i can't rip a doughnut in the dry yet my stock as a rock 1.6 liter gemini can do it easy both have locked diffs and the the corolla just can't do it. Could it be the carbies that are causing the lack of power my old man believes that they are not getting enough fuel.

 

any feedback would be greatly appriciated

 

cheers nathan.

[Redwarf]

A dyno trip is your friend.

 

Dellortos and webers really respond favourable to this. You can screw around with chokes and jetting, but until you know what's actually happening, you're shooting blind.

 

Don't even think about putting a four barrel on. A well set up set of DHLA's will crap on it any day of the week.

[Medicine_Man]

My car had similar problems due to a vacuum leak (on a cold start, it would pop, crackle and backfire). Best take it to a workshop that knows how to tune them too, They have to be balanced or the car runs like shit..

[velociTOY]

Adjust carbs and ignition!

[boosted_gem]

Ok after some thinking i have come up with another idea. that is i have su 1.75" su's sitting at home brand new never used and th albility to purchase an su manifold just wondering whether this would be a better alternative then playing around with getting the dellorto's rebuilt and tuned.

 

any feedback would be much appricated

 

cheers nathan

[Redwarf]

I've had SU's and Webers.

 

Su's are good, however, realistically, once again you'll need a dyno trip to get the most out of them.

 

Why do the Dellortos ned a rebuild? Why not have a quick dyno trip and see what you can get out of them?

 

You won't find a 1.75 SU manifold. You'll get a 1.5" manifold and matchport it. You'll still get more grunt out of Dellortos than SU's.

 

Cheers

 

R

[Corolla_Kid]

I have had both su's and dellortos on my 5k in the last 12 months.

The su's were good but compared to the dellortos they had nothing.

Trust me you will be disappointed going back to su's.

[boosted_gem]

Well if i do decide to go stick with the dellorto's and get tehm tuned on a dyno, you guys recommend anywhere to go and what sort of price i'd be up for i've heard of this place called mammi motors.

 

I'm in melbourne by the way.

 

cheers nathan

[Redwarf]

I understand Mammi to be quite good (Disclaimer; I live in QLD). I think Kangaroosa had his done there(???). I think they are rally boys, so they'll know about Webers/ Dellortos. Budget $2-300 for a start. It all depends on how far out they are and how many runs they have to do. Dyno time ain't cheap.

 

Maybe one of the MEL boys can help on this one?

 

R

[kangaroosa]

Correct. I had my twins tuned at Mammi Motors. The blokes are great and certainly know what they are talking about. They are rally blokes and really love tuning older cars, as its what they grew up with and what they play with most weekends.

They normally do a change-over scheme, where they use parts that they have in stock and take your original parts. This keeps the price down quite considerably.

Dyno time is appoximately $40/hr which is bloody cheap considering most other shops around Melbourne are charging $70-$80/hr.

 

To get my twins tuned from scratch (Balancing,fiddling with jets, mixtures etc) was about $180 from memory. I budgeted for $300 and was nicely surprised when it was under $200.

 

They are a Repco (dealer or stockist) so they have heaps of parts in stock and if they don't have it, they can normally get it the next day. As i found out when my fuel pressure regulator died.

Edited April 18, 2007 by kangaroosa

[boosted_gem]

Thanks for the replies boys i might give mammi motors a call tomorrow and have a talk with them cause the way the car is running at the moment is just giving me the shits. Hopefully they can sort it out as cheap as possible.

 

cheers nathan.

 

just out of curiosity(spelling) did there dyno give out a KW reading aswell

[kangaroosa]

Yes, it reads in Kw. Unfortunately they don't have a printer hooked up, so you can't get a printout though.

Edited April 19, 2007 by kangaroosa

[CorollaNut68]

Just a thought...and I hope it's not whats going on but my 3K started running bad last year, popping and low power, went the whole gamut...new carb, plugs, wires , coil, points, condensor, everything!, finally had the head rebuilt and then discovered my block and pistons were cracked and one lobe on the cam was worn pretty badly. Nightmare!

[OBSCENE]

I have just had the same problem with a 5K running twin webers it had all the same problems!

In this case the problem was a vacum leak through the gasket. An easy way to find a vacum leak is with a squirty bottle of

penetrine or something alike, just spray around soft mounts and inlet gasket while engine is running and listen

for any change in the way its idleing.