Sorting out 2.7 w/webers and solex cams.

[chiroracer]

Just got engine installed and am sorting out some issues.
minor oil leaks: handled
severe vibration: mostly handled with a flywheel pressure plate balance was 40g. off
sticky advance: jerry woods rebuild and recurve of dizzy.
carb balance: handled.
compression test: all test 175 to 180
Jetting 145main 55 idle 180 air correction and f3 's 34 venturis,this was deemed in the ball park by richard Parr(PMO).



engine still seems like its fighting itself from 3k to 7k I can feel it trying to come alive and Ive had other engines like it and know there is more power available. It just doesnt have that intoxicating rush That I expect.This should be a screamer in a 71,no?


Here are the things I will check next:
Cam timing
fuel pump ,but it is fairly recently rebuild of the stock 911T pump for zeniths.


Could dissimilar cam timing produce this symptom? Steve

[john walker's workshop]

are all the venturi outlets feeding off the nearest emulsion tube well? they can go in backward. maybe ream the idle jets closer to 0.60mm for better low end and either go up to 150 mains or go down to the next size smaller air correctors to pull more fuel from the mains at higher rpm. 3.5# fuel pressure. what is your total advance?

[chiroracer]

Thanks John !total advance is 32 degrees as per jerry woods recomendations for "modern" fuels. the carbs have not been opened since running well on a similar motor,I wanted to check cam timing also because it would be more easily quantifiable ,but I guess I will check the emulsion tubes too ,would I expect to find a chunk in there or should I shoot some carb cleaner through a specific hole? Bruce Anderson states a jetting difference on his "favorite " 2.7 rs pistons but with e cams where he runs a smaller main and air correction jet ,so thats in my thoughts as well.

[RWebb]

got new plug wires?

what CD box?

[chiroracer]

New beru plug wires , cd box is good as far as I know and was working great with old engine even when it was barfing oil past the rings. Thanks Steve

[chiroracer]

I have both 55 and 60 idle jets that I can try .The perceived issue starts at about 3000 are Idle jets still in play at that point? The feeling is that the engine is fighting itself similar to when the carbs are not in balance. The only thing that is stalling me from checking cam timing is the lack of a dial gauge and z block. guess its time.
Any opinions on the cam timing issue ,Could this be a factor? its one thing I havent checked out. S

[RWebb]

take a close look at the progression ports (holes)

the idle jets function a lot higher than you think - but I forget how high

[jpnovak]

Fuel pressure?
Fuel delivery problems at high flow rates? (check gas tank screen and fuel filter)
float levels?

My 2.2E spec engine transitions from idle to main circuit about 3100-3250 depending on throttle position. I think your mains might be too small or clogged. Have you checked the circuits? did you clean and blow out all the passages in the circuit?

If you try a 60 idle jet and the rpm band for the smooth running extends above 3K this helps you pinpoint the lean condition up top. The extra fuel from the idle circuit will help you deliver more fuel to a higher rpm and compensate for whatever problem exists in the main circuit.

I would still verify the secondary venturi and their orientation.

If the engine runs well through the idle circuit I doubt that cam timing is an issue.

You may want to check battery voltage at high rpm. The CDI will be unhappy if you have a voltage drop due to weak battery. The charge time is extended past the dwell time of the CDI.

[chiroracer]

Thanks JP.where would I check battery voltage @ high rpms? At the cd box or on the poles of the battery itself.I just went through all of the connections from the battery when diagnosing a slow cranking problem and finally replaced the starter with a hi torque unit.My battery is a dry cell from its track days until I go back to duals. Steve

[1QuickS]

Are the Webers IDAs, IDAPs or IDTP's. The IDTP's have a leaner transition than the others.

[chiroracer]

Thanks paul. IDA3C's

[911pcars]

What's in the base 2.7 engine? Are pistons CIS, RS or equivalent? Cylinder head vintage? Port size and compression ratio?

Check fuel pressure and volume just to be sure.

Cam timing. I know. This is more involved and perhaps a last resort.

Sherwood

[1QuickS]

Your carbs were off the engine and reinstalled without tuning? I think it would be prudent to check float levels, mixture and idle settings (with drop links disconnected) and then side-to-side balance while activating throttles from someplace like the bell crank at the front of the driver's side intake manifold or by a helper in the driver's seat.

[chiroracer]

Sorry if I didnt mention paul but the carbs WERE balanced by a master(not me) after install but we werent able to asess jetting or upper end function due to the distributor problem that has been rebuilt and recurved since by jerry woods. My plan today is to try a couple different jet sets to see if it is a lean condition in the mid range I have I think some 155s so if that wakes it up somewhere then I will probably look at smaller air correction jets as well.Am I correct in assuming that this will fatten the midrange a bit? Steve

[chiroracer]

Oh, RS Pand Cs at 8.5;1 but it seems to have more on cranking ie I cant crank it by hand for ex. so maybe more. the ports are 38 resulting in a step from my manifolds 36mm which I hear is OK ,my musing is that maybe this is more of a beast than first assumed ,I got it in a parts trade with someone I have traded with before and I am still awaiting a build sheet of some type.(the price was right and the compression tested great).This was purchased on a lark to be my cruiser engine looking ,to the passive observer like the stock T motor, coupled with ac pump (factory air) and a stock ratio box. I am in the process albeit a long one of building a 2.2 mfi S spec motor on an alum. case for POC racing class HP with airport gears and an lsd. Im off to try some jets! thanks for the suggestions and Ill update in a bit. Steve

[Grady Clay]

Here is what John is talking about:




If any auxiliary venturi is in backward, that cylinder won’t work.
Just look down the throat and the outlet should be on the side from the air correction jet.

I agree with possible fuel flow issues.
Do you have a circulating fuel system or ‘dead head’?
Take a long fuel line from the carb inlets and return it to the gas filler on the fender.
Let it circulate for a while (5 min?)
Measure the flow rate into a calibrated container.
Should be about 2 liters per minute free-flow. (Spec minimum for the 911T Bosch pump is 80 liters per hour at operating pressure 0.2 - 0.3 bar.)
The pump is a little voltage dependent (12.0 vs. 13.5 V).

If you have a fuel pressure gauge at the carburetors, restrict the return flow to get 3.5 psi at the carbs and then measure the flow.

Make sure your N&S don’t leak, filling a cylinder, hydraulic locking the engine.

When you time the engine at 6000 rpm, does the advance follow the rpm or is it still sticking?
Confirm the advance curve with your timing light.
What is the battery voltage when you rev it?

I agree, check the valve clearance and cam timing.

No rodent nests in the exhaust?
If in doubt, try another muffler.

No rag in the air filter?
Do you get full throttle?

With the sparkplugs out, the engine turns freely with a wrench and starter?

What is the CR?
Do you have fresh 100 octane fuel for brake-in and testing?

Don’t be afraid of trying a lot larger main jets as a test.
Just be aware that it will soot-up the plugs.

What sparkplugs?

Does it perform better or worse hot or cold?


Best,
Grady

[chiroracer]

Thanks Grady! thanks for the practical on fuel flow and the venturi pics ,I will check that out today.it is supposed to have RS 8;5 to 1s plugs are new ngk bp7es or b7es whichever is the reccomended plug for the S. engine turns freely without plugs. hot or cold not much difference . Steve

[larrym]

I have a similar issue - same basic setup - cams calimed to be solex regrind, but not behaving that way

see my post

odd 2.7 engine torque curve on dyno

[chiroracer]

Hey folks some new info.
fuel flow and pressure: good!
secondary venturis: correct orientation!
Jet size check: the 155s are installed already

Removed airbox and ran it around the block! seemed to wake up a bit!! Id like to run the stock airbox on this motor combo ,should I look at running a modified snorkel? It has a K+N element btw.could this mean its a little rich? I have smaller mains that I can try.
Next check is battery voltage @ rpms and Valve adj. and cam timing when I get a z block and the specs for solex cams( i hope after reading the link of the last poster). Steve

[911pcars]

Not sure this was on the previous checklist:

With engine OFF, confirm WOT when gas pedal is fully depressed.

Unless there's a shop rag stuffed in the snorkel or the exhaust pipe, don't think the factory air cleaner housing is creating a restriction.

Sherwood