Wesch,
the Zl1 cam is crazy! my car idles at 1250rpm and wont drive below 2000rpm. the start up is critical too. but somewhat solved the problem this morning. I was used to start the engine with hood open. this morning I did it with hood closed , the air chamber foam acting so as air flow restrictor. much better now. but i'll go for a choke carb anyway

 

what a fantastic , beautiful sunday morning!the best Vette ride of my life!-till now...

I was concerned with many car little problems ( choke, exhausts gases...)

started the car in the garage, all windows open . this engine's exhausts are CLEAN ! no bad smell, no smog , nothing

drive out the car for 35 miles or so and did everything I have never did with this car since the purchase ( because of engine's trouble)

winding roads : the car handles almost like a modern car , after all the work to suspensions, steering , alignement , tires pressure , new QA1 shock. simply marvelous. and there's still room for improvements...

engine . oh my god! Kevin 63mako , finally I took it above 6000 rpm in 3 highway pulls through the 4 gear: the engine beautifully screaming above 5000rpm
the speedometer showed 120mph (4.11 rear ) with 245/60/15 ( actual speed should be 5% less than showed).
guys , I have no words to explain. sorry. too much a beautiful experience to explain.
thanks everybody for all the efforts that enabled me to get to such results

p.s. just a little problem. some run on when I shut off the engine and a rubber cap on the carb -sealing the vac adv fitting- was spitted away by back pressure I suppose. could that pressure blow my power valves ?( I have an old holley without blowout protection)

 

Cant help with the problem BUT glad you got her out and wound up! Now we need some in car video of that beast on a few runs up through the gears high rpm changes!!!!

 

Hope the difference between this engine and the previous is apparent now. Shifting above 6000 will keep you in that fat torque curve on the upshift where it will really shine. The carb is tuned for best A/F ratio when warmed up so with the cam, no choke and that tune it will be cranky when cold, Just the nature of the beast. We want in car video!
Happy Easter Aldo. God be with you.

 

A backfire can blow the power valve. Here is a Holley tech link. Tells how to diagnose this. You could back your idle screws out a little to richen up the idle circuit for better cold start but it will then idle rich and load up when warmed up.
http://www.holley.com/data/TechServi...wer_valves.pdf

 

Whether it is my Vette or any one of the Ferrarri race cars I start up. None of them have chokes. So you just pump them a few times and turn on the starter. When it fires you hold the gas pedal down so the motor is running at 2500 rpm for a few minutes until they get up to 80C. Then it is ready to drive.

 

I would be tempted to follow Gkulls advice. Here is a link to holley carb sizing. I don't want to open a can of worms here. There are two schools of thought on this. One side is bigger is better. The other side is enough CFM to supply the engine is all you need. Let's not argue this here. Here is the link. Figure your VE% about 90%. Figure your max RPM at 6500. CI 440. Your 800 is perfectly sized according to holley. We did try a 950 on the dyno with no noticable increase in power. It is stagger jetted and dyno tuned to the engine, performs well at all RPM when warm and it has the manners of an L88 even on startup. One of the compomises of the build specs.
For run on, before you shut the engine down put your foot on the brake and clutch in gear. Let out the clutch just until you feel it start to grab and all play is taken up. Shut the key off immediately and let the clutch out slowly when the rpm drops off to stop the engine. Advanced initial timing might cause this. Again, one of the compromises of the build specs.
http://www.holley.com/data/TechServi...Carburetor.pdf

 

ok , an in car video asap...

I think I'll need soon an higher gearing or ovd. 120mph not enough...the car was so good.can go faster and still be safe

Gkull. I start up the engine exhactly in the way you do

Kevin . I'll check the power valves and possibly go for a new holley with PV blowout protection or just add the PV protection kit to my carb (perfectly tuned and OK for my kind of driving )
http://www.summitracing.com/parts/HLY-125-500/
but what about that run on? checked better : both the rubber plugs on the carb (front and vac adv fitting ) spitted away. reduce a little the timing would help? ( remember the dizzy light springs to get mech advance soon? ). adding 5% toluene avoids any run on, but the engine has no sign of pinging with just premium gas, so i would avoid to use toluene just to get rid of the run on
advises?

 

See last post. Vacuum advance and distributor recurve would help eliminate run on but we beat this horse to death already. A B28 vacuum can and a tuning session would work but again, one of the compromises of the build specs. Babbah did this on almost your exact build with the same distributor with very good results and seems like a great forum member that would probably walk you through it. Both of the recent issues are related to making a race engine build more streetable which I understand.

 

Before you go to all that trouble I would like to ask what is your procedure for start up?

 

[QUOTE=63mako;1573648459]

For run on, before you shut the engine down put your foot on the brake and clutch in gear. Let out the clutch just until you feel it start to grab and all play is taken up. Shut the key off immediately and let the clutch out slowly when the rpm drops off to stop the engine. Advanced initial timing might cause this.
QUOTE]

i'll do that . no problem. will not touch the mech adv springs

 

I will have to say I have never had a choke on any Holly I have run. And this procedure has worked in all of them. But it will take a bit of trial and error on your part.

When engine is cold I pump the peddle to the floor twice then hold the throttle peddle down about 1/4 of the way but this is just off the top of my head as it is all feel. Then turn key on and start the engine.

You may get away with 1 pump but I think 2 or 3 would get you there but start with only 2.

 

Hi

120mph not enough..

Aldo, I was under the impression that every European country except for Germany has drastic speed limits on highways. Like 120 KMH ( about 80 MPH ).

Where are you driving this 120 + MPH ?

Would love to try your car out for comparison.

Happy Easter. Günther

 

80C???? I wonder what that is in Kelvin? Gkull, you are so international. Like 007. Shaken and stirred.
Bee Jay

 

On my race motor with a Holley DP with removed choke housing, I just installed my LT-1 idle stop soleniod to a dash mounted switch to make a high idle circuit for warm-ups. Works like a charm and I can do other things while Vette is warming up.

 

yes the speed limit is just 80mph here, but with my car is just a matter of few seconds and less than 1/2 mile to go to 120mph ( I think it's a 13sec car or so).
i get into the highway ( a kind a of hiway, actually) , go through the 4 gears then i let off the gas and back to lower speed. I just check that few or no cars are there when i get into the highway.
i will post a video to show
"the problem" is that when I drive on "non hiway " roads here, it's anyway so easy to go to 80-100mph on the straights in a heartbeat: and this is somewhat more dangerous.
btw I do this only if there are no cars on the road, often, and pay lot of attention to asphalt condition (asphalt grain and imperfections).
Wesch, you're welcome to drive my car, just buy the gas! this is a no MPG car when driven hard or so

 

Hi

I guess best is you come over to Luxemburg , may be the first W/E in July to our Roadrunners meeting and we try your car across the boarder in Germany. Only 50 KM away, there is no highway limit and we can try it a bit longer to it's limits, legally.

Fuel is also a touch cheaper over here.

Have fun and watch out.

Rgds. Günther

 

Hi

80C???? I wonder what that is in Kelvin?

Took the allknowing internet as aid:

80 C = 353 K = 176 F

Why do you want this in Kelvin ? I thought Fahrenheit are the USA standart.

Rgds. Günther

 

Yes, Fahrenheit is most common temp scale here is US, but a lot of road racing cars over here still have Celsius gauges. I don't use Kelvin for anything but lighting...

 

UPDATE.

new carburetor

I had recently a good deal on this Holley refurbished 0-9380 850 annular booster carb. It's the carb that i wanted on this engine since the time it was still at the shop but not enough $$$ left that time, so we completed the dyno tuning with a 800 DP.

It took me a while ( not that much at the end...) to have the new carb dialed in and above all lot of brainstorming with Jim ( 427Hotrod via PM . Thanks Jim)

I had a nice ride today and YES , the annular boosters work great at low speed and light throttle with my ZL1 radical cam ( duration @ .050 262/272 ). Now I can enjoy a little more round town rides , even if the cam is barely streetable anyway. But MUCH MUCH better now.
Under acceleration ,steady throttle hill climbing etc the carb works great so i think i'm not far from the optimal tuning of the previous carb ( dyno tuned). The spark plugs are now clean as those with the 800DP. I kept the stock jetting ( 78/78) using power valves both at prim and sec . My idle vacuum is 6" HG , I used 5" PV at prim , 4.5" PV at sec. WOT not yet tried but I'm seldom there...

the idle is fine and better than with previous carb. But It took a lot of job and can be still made better. Actually the idle A/F screws are a bit "strange" : I have 2 3/4 turns out at prim and 2 turns out at sec. My engine wants a lot of gas ( Idle is 1150-1200 rpm ) and spark plugs looks anyway clean , almost lean. I read instead that very often there's the opposite problem with radical cams at idle, very rich , fouling plugs etc... that's not my situation

Aldo