400 Small Block Build. 500+ HP

[502ci]

Bummer you are going slightly slower. As much as I would think your problem might be your tiny stock fuel line your mph is matching your ET correctly. Still I would upgrade it like you mentioned.

 

 

[TN454Monte]

LOL...Just an observation....But only a dude born with drag racing in his blood can write a post after ripping off multiple 12 second passes and one sub 12 second pass and call it "Not good".

 

Hang in there you'll work the bugs out...!!

[Winston Wolf]

This miss on the top end is getting the best of me. Check out this video of before and after. I need to get it fixed. I looked at logs and was trapping at the same RPM's. It has to be something in the ignition system???

 

 

 

 

Also look at my dyno sheets. I knew I wasn't hearing things on that dyno... Notice how at that exact point the power drops off like a lead weight, and how it acts goofy. But if you look at the data logs I posted above, my fuel mixture doesn't go way rich, like it should if you were floating the valves.

 

 

I am running a stock distributor with a Mallory E spark conversion (photo optic led trigger) in place of the points to a MSD 6AL box with Blaster 2 coil. I use no vaccum advance and it has been recurved to be all in by around 2500. I did install a new cap and rotor with the head upgrade, Accel high perf stock replacement. I also installed new MSD plug wires.

 

I pulled the cap and it does not seem to have any arcing marks or look bad to the eye. Could it be a coil issue? Perhaps the distributor is worn out? Mallory ignition module?

[Heckeng]

I think you have several issues compounding here.

 

Timing is the first problem, you are leaving lots on the table with it at 34 max. I say try 38 degrees.

 

Next is debatebly the carb. The size should definitely support what you are trying to do, but I think there may be some tuning issues yet to find. This engine should in no way drop off below 6500 rpms.

 

I think the fuel line will be a problem for you eventually, so it wouldn't hurt you to change that just in case. I would recommend the Summit aluminum hard line. Take your time and you can run it from front to back and if you are careful, then you can have either 3/8 or 1/2 hard line which would be excellent.

 

A 3500 converter should be excellent. What is it actually flashing to off the line?

 

I have heard of the Mallory optic sensors causing problems sometimes due to dust covering the sensor, but I doubt it would only be an issue at high rpms.

 

Everything could be explained by a cam timing issue but I know you degreed things in. If the cam was too far advanced, your low end would be emphasized and the upper end would fall off.

 

I think the intake is likely ok. How about the gaskets for the intake and the exhaust? Do they overlap into the port more than they should causing restricted flow?

 

I don't think any extra lift going from 1.5 to 1.6 rockers will solve anything.

 

The miss was there with BOTH engine? If that is the case, it would almost certainly be ignition or gasket issues since those would likely be the only same items.

 

I hate problems like this, they are so hard to find!

[Winston Wolf]

I think you have several issues compounding here.

 

Timing is the first problem, you are leaving lots on the table with it at 34 max. I say try 38 degrees. I did test it out at the strip and found the best times at 37-38 degrees, so that is solved

 

Next is debatebly the carb. The size should definitely support what you are trying to do, but I think there may be some tuning issues yet to find. This engine should in no way drop off below 6500 rpms.

I've done everything I can to this Thunder AVS, I think I'm going to order a custom Holley DP

I think the fuel line will be a problem for you eventually, so it wouldn't hurt you to change that just in case. I would recommend the Summit aluminum hard line. Take your time and you can run it from front to back and if you are careful, then you can have either 3/8 or 1/2 hard line which would be excellent.

 

I am going to change out the lines and the fuel pump asap. I was thinking about 3/8 line from these guys Inline Tube I have Stainless brake lines from them and they were very nice.

 

A 3500 converter should be excellent. What is it actually flashing to off the line? It's tough to say, but looking at the logs, it foot brakes to 2500 no problem and it starts to get tight around 4200

 

I have heard of the Mallory optic sensors causing problems sometimes due to dust covering the sensor, but I doubt it would only be an issue at high rpms.

I agree

 

Everything could be explained by a cam timing issue but I know you degreed things in. If the cam was too far advanced, your low end would be emphasized and the upper end would fall off.

I think I'm going to re-check it when I change out the intake.

 

I think the intake is likely ok. How about the gaskets for the intake and the exhaust? Do they overlap into the port more than they should causing restricted flow? I used the gaskets AFR told me to and they seemed fine. I think I'm going to switch to an Air Gap intake and port match it to the heads, just to be safe.

 

I don't think any extra lift going from 1.5 to 1.6 rockers will solve anything. With the strong exhaust flow of these heads, I do think there may be something to gain there. I don't think it's my main issue, but it might give me a few ponies.

 

The miss was there with BOTH engine? If that is the case, it would almost certainly be ignition or gasket issues since those would likely be the only same items.

 

I hate problems like this, they are so hard to find!

[Winston Wolf]

I just went and checked. I already have 3/8" fuel line.

 

I was thinking of ditching my electric fuel pump and going to either the Edelbrock Performer RPM Street pump or the Carter high volume (but the Carter only has 1/4" ports...)

[Sam (Bones)]

you said you had to advance your cam 4 1/2 degrees keeps sticking in the back of my mind, that sure would hurt the big end

[Winston Wolf]

you said you had to advance your cam 4 1/2 degrees keeps sticking in the back of my mind, that sure would hurt the big end

 

Trust me, I'm losing sleep over this, and I'm triple checking it again when I swap intakes for my own piece of mind. But what I actually had to do was retard the cam, it was advanced. I know for a fact the dot is turned to the right, which by the timing gears instructions I just re-read is retarding the cam. So even if I would have messed it up, it should have helped me on the top end.

 

Hex Adjust Instructions

 

I just went out to the garage and starred at my degree wheel for a bit, trying to remember degreeing the cam. I remember the cam card called out for the the intake to come in at 18.5 deg at .050. It came in early at 22 or 22.5 I'm 99.5% sure it's right. I think all the talk about not making the power it should is making me crazy second guessing myself.

[Heckeng]

Are you sure you didn't actually advance the cam another 4 degrees instead of retarding it? Most performance cams now have 4 degrees of advance ground into them from the factory, it could have been intentional.

 

 

Also look at my dyno sheets. I knew I wasn't hearing things on that dyno... Notice how at that exact point the power drops off like a lead weight, and how it acts goofy. But if you look at the data logs I posted above, my fuel mixture doesn't go way rich, like it should if you were floating the valves.

 

On an engine miss or valve float, the A/F ratio will actually show as a lean spike on the meter because the O2 sensor simply measures the leftover oxygen in the exhaust. If a cylinder doesn't fire, even though there is unburnt gas in it that you would think would show rich, there is also extra O2 that didn't burn, so it shows as a lean spike. it does look like you have some lean spikes going on near your 6200 rpm mark or just after it. Actually looking at it more, it appears that your carb goes lean on the gear changes when the rpm drops to around 5k. That carb is all over the place.

 

Since you are handy with the wideband meter, you don't necessarily have to get a fancy carb. I would get a good ole Holley 750dp with the contoured base which will have adjustable air bleeds, and get a set of adjustable metering blocks like they stick on the ultra HPs. BLP makes them ,and I have bought a pair, they are really nice. Then you can adjust everything just how you need.

[Mike 57]

Winston, I have been thinking about you cam timing since I read your dyno sheets.

When I install my cams I degree them off the intake center line. I hate doing it by intake opens at this closes at that. I check it at center line If it is 106 or whatever, I mark .050 before max lift and .050 after max lift. and find out where the center line is and adjust from there. Lunati cams are pretty much right on and 4.5 degrees is quite a bunch. With your new setup I would have thought that you would have lost a little of the bottom, but it seemed to pick up

Never cared for the optical pickup, way too ozone from hot spark.

I like AFB and AVS carbs for street but I think you are leaving a lot at the track.

Change one thing at a time, see what corrects your miss issue and what betters your times.

[CrazyDavey]

Hey Justin...

 

You've got great parts, you just have to give them all the support they need. Agreeing with Mike Lumati's are pretty straight up and I would only put in maybe 2 degrees advance.

 

The Airgap is a great idea, go with that...

 

As Scott says a box 750dp would probably work okay..I know you've talked to Patrick and I would still think about going with that..he does all the tinkering for you, one less thing to wonder if it's right or not..it will be...

 

I think you're in the ballpark with 37 degrees...

 

get rid of the modified distributor and put in a good MSD Ready To Run or if you really want to get serious a MSD crank trigger system with a Digital 6...

 

I think the carb and distributor will take out that miss (or is it more like a pop?). I know you are up to speed on the data info and I'm not minimizing that but once you get to the Holley you will be able to play with jetting at the track much easier.

 

The sound doesn't sound like valve float, I'll go with ignition or a lean pop....I know..I know..the AFR....still I'm just sayin'...

[Winston Wolf]

Well Dave, I have to laugh at your post. This is following my to my nightly dreams, I just couldn't take it anymore. Today I threw the book at it....

 

Ordered new fuel pump.

RPM Air Gap intake that I will be porting to match the AFR heads.

1" open spacer to try at the track for the top end.

New coil

New MSD ready to run E-Curve dist that I am going to wire so I can run it on the 6al box and off (that way I can eliminate any suspect box issues)

1.6 rockers for the intakes.

and........the grand finale...the Prosystems Double Pumper carb.

 

If this doesn't work now, I'll be jumping on my Harley, headed west to throw this carb you talked me into at your mailbox.

 

 

[CrazyDavey]

Well Dave, I have to laugh at your post. This is following my to my nightly dreams, I just couldn't take it anymore. Today I threw the book at it....

 

Ordered new fuel pump.

RPM Air Gap intake that I will be porting to match the AFR heads.

1" open spacer to try at the track for the top end.

New coil

New MSD ready to run E-Curve dist that I am going to wire so I can run it on the 6al box and off (that way I can eliminate any suspect box issues)

1.6 rockers for the intakes.

and........the grand finale...the Prosystems Double Pumper carb.

 

If this doesn't work now, I'll be jumping on my Harley, headed west to throw this carb you talked me into at your mailbox.

 

 

..can't we blame this on the chevelle forum??? they all love to put Prosystems in their signatures....

 

seriouly, you sound like me...the hell with it..click on the drop down and click on Summit racing!!

 

if that doesn't work then we'll have to blame the engine builder!! The miss or pop itself isn't slowing you down much but it's a signal that something else isn't quite right yet so your potential is good Justin. You know it's all about combo so I think these pieces are going to help that.

 

I spent my whole PSCA meet this weekend under the car changing starters! Went through 3 of China's finest, got in 2 passes and then said screw it. Kept blowing the ends off of them, the rice paper just couldn't handle it. That's all you can get on a weekend at Pep Boys....

 

I'm throwing a new book at mine too. Heads, cam, intake........I have a giant AFR box sitting on the living room floor...if this doesn't work Chris Straub isn't going to like my post ...Dave

[Heckeng]

if this doesn't work Chris Straub isn't going to like my post...Dave

 

I hope the if the opposite is true, he'll see a post that he DOES like!

 

I bet that distributor cleans up the miss issue. I'm still curious on the cam degreeing--that may be the rest of the issue!

 

Then hopefully you have a full striped [censored] ape in the engine compartment Winston!

[Winston Wolf]

and for all the nay-sayers out there about my intake of choice, I just scored a used Victor Jr off of Craigslist that I will be porting to test at the strip against my RPM.....

 

I will run whatever is better at the strip.

 

Now I'm debating on just porting my regular Performer RPM and cutting down the plenum like the Air Gap, then sending the Air Gap back...... I don't want to hack up a $200+ manifold to sit on the shelf if I end up sticking with the Victor in the long run.....

 

Thoughts?

[Chevyss]

Non-strip weekend for me. Same problem Davey. Got the car on Thursday and I was all primed and ready to go to the Friday night test-and-tune. Got out to the car and the starter sounded like a box of rocks. Knocked all the teeth off the flywheel. Now that they have finally figured out what the trans problems were, now they're trying to figure out the starter issue. Murphy's Law

[CrazyDavey]

and for all the nay-sayers out there about my intake of choice, I just scored a used Victor Jr off of Craigslist that I will be porting to test at the strip against my RPM.....

 

I will run whatever is better at the strip.

 

Now I'm debating on just porting my regular Performer RPM and cutting down the plenum like the Air Gap, then sending the Air Gap back...... I don't want to hack up a $200+ manifold to sit on the shelf if I end up sticking with the Victor in the long run.....

 

Thoughts?

 

Justin, that will be interesting. The problem usually is that there are so many other variables (track conditions, weather etc) and the difference is so small that getting a real good A/B is hard. I think the Vic will work good if you're just concerned about track. The RPM's just have a better split personality for street and strip.

 

I think overall the Airgap is just a bit better than the standard RPM (there are subtle differences plus the cooling) but yeah, wack on the old one first. If you end up liking that I would put the Airgap on, if not then send it back...JMO

[CrazyDavey]

knocked all the teeth off???? man Royce, that's hard to do!! I blew up 3 starters at Fontana this weekend, kept blowing the nose off the chinese junk. Last one was in the staging lanes getting ready to go up for my first competition...

 

Motor and trans is coming out tomorrow, I'll be adding a SFI flexplate and a billet starter....

 

we're probably going to run Red's car on the 5th.....

[Winston Wolf]

Well, ripped the engine apart again last night. Here is where the cam was:

 

 

 

As I remembered, I had to retard it a few degrees to get it installed correctly. It was dead on with the cam card.

 

 

I pulled the cam anyways, to look it over, all looks good.

re-degreed it and triple checked everything. Put the 1.6 rockers on the intakes tonight and set all the valves. I did have to slightly clearance 3 of them as they were hitting the valve keepers, which surprised me a bit.

 

Now trying to make a decision on which intake to start with. I have the RPM, Air Gap, and Victor sitting in the garage. Porting is a bit of work, so I'd like to get it right the first time if possible. I set the Air Gap on the engine, and it does look like a nice piece, I'm really leaning toward it at this point. I grabbed the Victor for 75 bucks, so I don't really care if I use it or not.

 

Here is a shot of the RPM that cam off and the Victor JR. The Victor needs some cleaning up, the casting has some crap in it. Notice how much smaller the ports are than the 1206 gasket that the AFR's need. I think just a port match will really help this thing breath....

 

 

 

[wallaby]

Sometimes that stuff is hard to figure out: The heads might have big ports, but does the engine want them that big? I know with the BB chevy the rectangular ports are the big ones, but they are often not the best choice.

As for the port matching, there isn't a lot to be gained in flow numbers, but getting rid of that ledge will reduce the turbulence there. I personaly wouldn't go crazy and try enlarging the entire runner...I'd only do what was needed to get a smooth transition.

I'm trying to remember where I saw it, but there was a specific instruction with an intake I bought that adressed that difference in port size, and they said that was intentional for port velocity and don't try to second-guess their design by trying to "fix" it.

 

Geez, I hope it all comes together for ya.

 

 

[Sam (Bones)]

it's been proven time and time again that port matching only gains very, very small amounts, unless you are building an "all out" race engine....it's hardly worth the time

 

but that's only my opinion

[Winston Wolf]

Well, got the engine back together finally. Ran it briefly to get the timing set and make sure everything was correct after installing the new distributor, coil, intake, and fuel pump.

 

Here you can see some of the work in progress of the intake. The 1206 intake gasket and the AFR heads are much larger than the 1205 stuff from the old combo. I decided to go with the RPM Air Gap intake. The intake work took probably 3-4 hours. I basically port matched it and worked the runners in as far as I could (maybe 2 inches with the die grinder and rotary tool. Smoothed out the transitions. There was actually alot of work there. I didn't do much on the plenum, just smoothed out the divider a bit.

 

 

Here is the notching on the frame I had to do to get the Carter pump to fit. I wasn't too crazy about doing it, but oh well....

 

 

I actually had to rotate the pump body to a point in between where it was made to be. It had the holes, but they were not tapped. I ran a M5x.8 tap through and got it in the right spot. I'm changing out this tubing for some other line, but I wanted to get things going last night.

 

 

 

 

 

 

[Winston Wolf]

 

New MSD Digital E-Curve distributor. Really slick. Timing curve is very, very smooth on the light. I am excited about it. Right now I have it set up with a 15 deg "mechanical" advance that is all in by 2500 RPMs and I'm going to try and run a vaccum advance this time, with a 10 degree advance all out by 4" of vaccum. There is a port for the vacuum advance on the bottom of the dist. Really looks clean without the canister.

 

 

 

New carb should be here on Friday. I'll get that in right away and am planning on the Muscle Car only drag races this weekend to see if all this work payed off.

[monte70car]

The digital e-cruve is nice I'va had my for a few years. It took a while to get the right settings for my motor, just keep up with the book in case you want to change the settings.

[Jared Richey]

I'm anxious to hear the results!

 

Good luck, and I think you'll be very happy with your pro-systems carb.