[69-CHVL]

Not a happy camper here folks. My car slowed down! Somethings amiss in a big way. 1st run I missed a shift and over-rev'd the motor. I thought that's what did me in initially. Ran again twice, track was crowded. Best:

1.8, 8.142/86-12.5/113

This is not good. Last years combo ran 1.8, 7.8/89-12.1/115. This is with 770 Avenger, GMPP heads/intake with 5 bent valves and leakdowns as high as 60%!!!!!

Only changes this year were to AFR 305cnc's, little more compression, Air-Gap, 950HP. Same bottom end.

Did compression test - 190 all around. Leakdown 8-10% all around on a COLD motor.

Only thing I can think of is the carb. If you remember I tapped both sides of the intake to run the PCV. Is it possible that this creates a lean condition b/c this carb wasn't designed/calibrated for a PCV? It seems like the motor was struggling to get to 5000rpms, but I was kinda watching the track and focusing on shifts so I didnt really keep an eye on the tach. I had the wideband going, although I dont have the rpm converter, looks like the AFR's were in the 13-14 range, which I know cant be good. Doesnt the PCV become inactive during WOT?

Shoulda brought another carb with me to test - I just thought that this one was the one to run.

Any suggestions? At least I didnt bend any valves! Motor runs great otherwise.

 

[CDN SS]

..... I doubt the pcv has anything to do with it .......no vacuum at WOT .struggling to get to 5000 ...sounds like fuel pressure do I recall you were the one tuning carb for clean idle etcetc are you still running a PV in sec ?? Are your floats et 25% into the sight window and jet extension in rear jetting around 76/86 with no rear pv ..... IMo the 950 is a good carb for your motor when properly set up on dyno with approx 600hp my stock 950hp only gave 1 hg of vacuum at wot now Patrick maasaged it and is very strong to 7k

 

[69-CHVL]

950HP has 76/78 jets front and rear PV's. Floats are set to just a trickle out the window, Carter 120 GPH mech pump, 7.5 psi. So only mod to the carb is 2 sizer leaner in the primaries.

 

[Teufelhunden]

I am glad to see you back at the track. From my point of view... patience. Your first time back out, you have heaped some lofty expectations upon yourself. It just needs your time and tuning.
I have seen where someone is expecting something and actually overdrives the car. We with three pedals must drive the car to what it can do and not what we think it will do.
So with that said, take a step back, relax, the car will run in the 11s. Focus on your 60' and the rest will fall into place.
Of course this is only my opinion. But for the most part, I know what your car can and is going to run. You do too. Dont make it do it, let it do it.

 

[69-CHVL]

Thanks Jeff. But MPH dont lie. I was expecting to run about a second quicker, and about +5 mph with the new heads and valves that actually seal. My '60 were pretty identical, so I was at least consistent.

 

[Ron454]

Throttle not opening all the way?

 

[mr 4 speed]

Wanna race?

Vince,I think its this funky weather..compare the conditions last out with your latest..
Least you got out and had some fun even though it wasn't up to your expectations..
you are going from 86 MPH in the 1/8 to 113 MPH in the 1/4...not a bad pick up
I would try the other carb for ha ha's

 

[69-CHVL]

Throttle not opening all the way?

That was my intiall thought but it was ok

Wanna race?
Vince,I think its this funky weather..compare the conditions last out with your latest..
Least you got out and had some fun even though it wasn't up to your expectations..
you are going from 86 MPH in the 1/8 to 113 MPH in the 1/4...not a bad pick up
I would try the other carb for ha ha's

Now would be the time to go after me! Honestly, anytime you can make it back from the track under your own power it was a good day :thumbsup:, that I'm cool about. But weather or not, I'm slow . My 454HO would give me a run for the money right now.

 

[M.Maner]

..... I doubt the pcv has anything to do with it .......no vacuum at WOT .

While I can't say that this is the problem or not,the pcv valve allows the maximum amount of airflow during WOT. You have made several changes and done them all at the same time. You will have to sort thru several different things to move the tune up back toward correct. I would consider reducing the total timing to something safe and then work on jetting. Once you feel like you have the jetting close then start bringing the timing back in.
Mike

 

[Dave427]

I wish I lived closer thats dis-hearting. I love test & tuning. Are you spinning real bad?

Dave

 

[69-CHVL]

Oddly enough I was getting some pinging, so I disconnected the vac advance. Timing was at 36*. Jetting is almost factory.

Kinda all making sense now...struggling to 5000+, pinging, AFR readings in the 14's....

Looks like I was LEAN!

 

[M.Maner]

Vince keep in mind your vacuum advance should not have been a factor as it drops out as soon as you go WOT. Did you say you tapped the intake for two PCV valves?
Mike

 

[69-CHVL]

Mike, good point, but the can I'm running is deployed at like 2", possible that there was still some vacuum present before the motor got to full WOT?

 

[wildman926]

950HP has 76/78 jets front and rear PV's. Floats are set to just a trickle out the window, Carter 120 GPH mech pump, 7.5 psi. So only mod to the carb is 2 sizer leaner in the primaries.

I would bet on your fuel delivery.

3/8" line with a 120 gph pump won't feed it anymore.

Mike, good point, but the can I'm running is deployed at like 2", possible that there was still some vacuum present before the motor got to full WOT?

Isn't that HP950 only a 750 cfm? Could go back and try your 870 instead.

 

[JIM]

I'm pissed that you went to the track and didn't invite me! Serves you right.
Your incrementals looked whacked for a stick car. Looks like you pull harder in the second half and the 1st half it is a slug. (<< no offense) That to me would rule out fuel delivery. Got a fuel pressure gauge in there?

Example. Your 8.142 in the 1/8th should have gotten you a 12.70 in the 1/4. You ran a 12.5
Your 86 MPH in the 1/8th should have gotten you to about 111 MPH in the 1/4. You ran 113.
Seems like the car is better on the top end. Something is definitely wrong here. Your ARF headed combo should be running much better than that. Either something is way out of tune or you are taking a nap between shifts. Got any videos of the runs?

 

[GRN69CHV]

Unless a stick car hits the fuek curve different, I ran the same Carter 120GPH to 11.67/117.43 last fall. My first thought was fuel pump. Now, is possible that the fuel pump is going into float? Possibly the spring is now weak? Vince, I have a new 172 here, just need to get the correct 10AN & 8AN adapter fittings or maybe tap the ports for 3/8NPT.

 

[mr 4 speed]

I doubt its the pump. Gene's 427 has gone 118.75 MPH with a stock AC Delco pump

 

[69-CHVL]

I'm pissed that you went to the track and didn't invite me! Serves you right.
Your incrementals looked whacked for a stick car. Looks like you pull harder in the second half and the 1st half it is a slug. (<< no offense) That to me would rule out fuel delivery. Got a fuel pressure gauge in there?

Example. Your 8.142 in the 1/8th should have gotten you a 12.70 in the 1/4. You ran a 12.5
Your 86 MPH in the 1/8th should have gotten you to about 111 MPH in the 1/4. You ran 113.
Seems like the car is better on the top end. Something is definitely wrong here. Your ARF headed combo should be running much better than that. Either something is way out of tune or you are taking a nap between shifts. Got any videos of the runs?

Sorry Jim, it was a last minute thing...just got up and left b/c I'm going to be tied up for the next couple of months.

The car is a slug, no offense taken, no vids either. Even If I shifted slow, I still should be MPH'ing much better. I dont have a fuel pressure guage here handly but can get one. I have one of those carb mounted ones though and it shows 7.5 at idle.

I have the lighweight hollow bronze tip fuel pump pushrod..doubt I'm floating anything at these rpm levels. I also figure theres guys ALOT faster than me running 3/8 line, so I'm not ready to attack that yet.

 

[Mike]

Isn't that HP950 only a 750 cfm?

More like 830.
That HR cam seems off for those heads.

 

[M.Maner]

Mike, good point, but the can I'm running is deployed at like 2", possible that there was still some vacuum present before the motor got to full WOT?

I would think that possible. You may need to change that up a little.
Mike