Chevy Nova Forum banner

1 - 20 of 27 Posts

·
Registered
Joined
·
422 Posts
Discussion Starter #1
I'll start here at the beginning.

I bought a brand new Blueprint engine. It is a 355 roller cam, with aluminum head and a holley carb and it dynod from BP with 399HP.
My Engine
Since the day I owned it it felt slow. Its the most HP Ive ever owned but Im positive my families Kia Sorrento would kill it.
Also It gets awful MPG. I have always told myself its slow because it has 3.08 gears and a TH350 (and maybe I bought the wrong torque converter.
The engine really shakes at idle. Today I saw a video of a Nova on facebook that shook like mine. I thought 'good thats normal'. Then I read all the comments and people said not good at all.

I know nothing about carburetors but I do know that people can learn a lot by looking at a spark plug. Attached are 2 plug images from 2 plugs.
IMG_8904.jpg IMG_8905.jpg

Can you all please help me figure out what is wrong and maybe some things I can do to fix? Or just educate me enough that I can tell some local shop my problem. I realize that the plugs shouldnt look like that with chunks on them :)

Thank you all so much. Your helpfulness is SO appreciated!

Ryan
 

·
Premium Member
Joined
·
63 Posts
Looks like lot of fuel was engine dyno with your holley? Check float level air and fuel jets timing to start with
 

·
Registered
Mike - 74 Nova Baltimore, MD
Joined
·
1,494 Posts
Engine looks like it is running too rich. As Danny88 mentioned, checking the float levels... and idle mixture screws is a good place to start.
Is the engine shake minor... or major? With the installed cam specs, your engine should not shake too aggressively.

Need some additional information...
  • Link shows a dressed long block... what intake manifold and carb was installed... please provide details (brand, cfm, vacuum secondaries or double pumper, electric or mechanical choke)?
  • Have you checked for vacuum leaks?
  • Did you install an 8" harmonic balancer?... and also confirm timing marks line up at #1 TDC?
  • What is your initial timing @ idle (with vacuum advance disconnected)?
  • What is you total mechanical timing (with vacuum advance disconnected)?... at what rpm?
  • Engine included an HEI distributor. Is the power wire connected to the BAT terminal of the distributor cap full battery voltage (12-14 volts)?
  • Are you using the distributor's vacuum advance (VA)?... and if so, is the VA connected to a ported vacuum source or a full time/manifold vacuum source?
    • If using a full time vacuum source for the VA, was a VA limiter plate installed to control the amount of vacuum advance?
 

·
Registered
Joined
·
367 Posts
The engine is running rich (too much fuel). But for help, need some more information. What Holley carb, plugs, heads, cam and exhaust? Do you know how to check timing? Have you had any discussion with engine provider?
 

·
Registered
Joined
·
422 Posts
Discussion Starter #6
Great questions. A lot of those I'll have to research. But for now I'll tell you what I know.

  • Its an aluminum intake, not sure the size.
  • I have an electric choke. (never felt like it did its job. No matter how hot it is outside the car stalls 3 times before I can leave the driveway.)
  • Its a Holley carb. Website says 600cfm. Cant find a part number
  • I have a 8" balancer

I dont know if I have any vacuum leaks or what the timing is. I think the distributor has vacuum advance.

I'll have to get the answers to the rest of your questions.

I will say that last night a thought dawned on me. I always have this black soot at the top of my radiator above the coolant level. Its not oil. But it now reminds me of what looks like is on my spark plugs. Thought Id throw that out in case that helps lead to more questions. I did have a coolant pressure system test that was good and I tested for exhaust gases in my radiator and that was good too.
IMG_8907.jpg
 

·
Registered
Joined
·
345 Posts
Your vacuum advance isn't hooked up to manifold vacuum, it's hooked up to "time spark port" on the carb. At idle, your distributor is essentially seeing zero vacuum, which removes a bunch of timing and probably makes the car run like a dog when it's cold at idle (may explain your stalling issue) Moving your vacuum tap for the vacuum advance to below the carburetor/at manifold vacuum will allow your distributor to see full vacuum advance at idle and allow much better idle manners.

Not enough advance at idle will cause the plugs to load up with unburnt fuel & get very sooty, like how you're seeing here.
 

·
Registered
Mike - 74 Nova Baltimore, MD
Joined
·
1,494 Posts
Moving your vacuum tap for the vacuum advance to below the carburetor/at manifold vacuum will allow your distributor to see full vacuum advance at idle and allow much better idle manners.
I agree with the above statement... but in doing so (moving VA to full time manifold vacuum) you need to also know how much advance the VA can is providing. Most aftermarket adjustable VA cans can produce 20+ degrees of crank advance at full pull. If you set your initial mechanical timing to 15°, you could have 35° (or more) initial timing once you connect the VA can to a full time vacuum source.
And there is cruising that will also come into play. Without a VA limiter plate, you might experience pinging during light throttle... or engine surging during highway cruising from too much advance being produced from the VA can. Sure, you could increase the resistance of an adjustable VA can to help solve this... but then you might not be getting full pull from the VA at idle (makes for an irregular idle RPM due to the VA arm movement... especially with a larger cam profile).

The best way to control how much advance the VA can is providing at full pull is to add a VA limiter/stop plate to limit the VA can to about 10°- 12° of advance at the crank. An easy may to limit the amount of VA for an HEI distributor is to install a MSD VA limiter plate (part #84281). Below is a photo of the MSD limiter plate (red arrow) that I installed on my HEI to limit the VA to add 11° of advance at full pull.
408925
 

·
Registered
Joined
·
422 Posts
Discussion Starter #10
I found this nipple below the carb. Would this be manifold vacuum? And do I just cap off that other one or should it have a line running somewhere else. Im so glad we've already found a problem.
IMG_8912.jpg
 

·
Registered
Mike - 74 Nova Baltimore, MD
Joined
·
1,494 Posts
I found this nipple below the carb. Would this be manifold vacuum?
Yes.
And do I just cap off that other one or should it have a line running somewhere else.
You would just cap off the unused one.

.... but as I mentioned in post #9, there are a few more things to look at when connecting the VA to manifold vacuum.
 

·
Registered
Joined
·
422 Posts
Discussion Starter #12
I think I may be unqualified to trouble shoot this. I dont know enough about vacuum advance or timing to feel comfortable changing anything. I really do appreciate the info and I will have to pass it along to someone local. One thing I did notice was when I pull the throttle and look down the carb it looks like a super soaker. Dumping fuel. But I dont have enough exp to know if thats a lot, little, or normal.

I dont want to do any (more) damage to my engine by my ignorance. :( I will just take it somewhere.
 

·
Registered
Mike - 74 Nova Baltimore, MD
Joined
·
1,494 Posts
Below are the recommendations you should seek from someone who is qualified/experienced to work on this engine.
First... Confirm full battery voltage is being supplied by the power wire that is connected to the BAT terminal on the distributor cap, and then make sure the carb's float levels are adjusted correctly.

SET (in this order):
  • Initial timing @ idle (no VA) = 14°
  • Total mechanical timing all in at 3200-3400 rpm (no VA) = 36°
  • Install a VA limiter plate to limit advance to about 12° (at the crank) and connect VA canister to a full time/manifold vacuum source.
  • Adjust/set carb's idle mixture screws to obtain the best/highest vacuum level at idle.
Good luck!
 

·
Registered
Joined
·
486 Posts
Three or four things to note after looking at the pics and reading your responses.

#1....it was mentioned to verify you have 12V to the distributor power connection, you mentioned in your next post you had verified 12v to the choke....which wasn't the question/issue asked about. .
The reason this was asked is the original Nova power feed wire to the coil was a resistance wire, made to drop the running voltage to the points ignition to around 8-9 volts, so that it wouldn't quickly burn the points in the distributor.
When converted to HEI ignition, you must either remove and replace this resistance wire from the bulkhead connector at the firewall backside of the fuse panel with a frsh non-resister wire, or run a new bypass wire from inside off the fuse panel ignition hot tab to the HEI.
When run off just 8-9 volts, the HEI trigger module will not behave properly, be weak on spark, and foul up the plugs along with poor power from the engine.
1968-1971 I believe the original resister wire will be a white/orange/purple striped wire or white/red/black striped. May start out Pink or Pink/black at the firewall and splice to the three color midway to the distributor.
1972 it is a pink/black striped wire, and I believe '73-74 are the same. First car that came with HEI stock was 1975

This can fool you on just a test light, since it will show 12v with the engine not running but key switched on...it doesn't reduce voltage until power is being drawn through the running distributor.
if you can't test and want to just foolpproof it, run a new wire from the fuse panel inside to the distributor.

#2....that PVC connection into the valve cover....if that aftermarket valvecover isn't well baffled like a stock cover is, it will suck oil pretty badly, which is another possible reason why your plugs look both oil and gas fouled.

#3...yes, move the vacuum advance to the nipple you indicated with the screwdriver, and move the nipple cap to the one on the side of the metering block.

#4...choke is adjustable...you loosen those three screws holding the retainer ring around the black choke housing , and rotate the black housing clockwise makes it richer/choked tighter so chake stays on longer...counterclockwise makes it leaner/choked looser and it releases off chokle sooner. Those little cast-in hash lines on the top of the aluminum part of the choke housing are there to help reference your adjustments.

You can go to Holleys web site, look up the new sales listing for that carb List number, and down below the specs is a spot to click and download the installation PDF for the carb....it details the choke tension and choke high idle speed adjustment, and all the other adjustments for the carb.
 

·
Registered
Joined
·
422 Posts
Discussion Starter #15
Three or four things to note after looking at the pics and reading your responses.

#1....it was mentioned to verify you have 12V to the distributor power connection, you mentioned in your next post you had verified 12v to the choke....which wasn't the question/issue asked about. .
The reason this was asked is the original Nova power feed wire to the coil was a resistance wire, made to drop the running voltage to the points ignition to around 8-9 volts, so that it wouldn't quickly burn the points in the distributor.
When converted to HEI ignition, you must either remove and replace this resistance wire from the bulkhead connector at the firewall backside of the fuse panel with a frsh non-resister wire, or run a new bypass wire from inside off the fuse panel ignition hot tab to the HEI.
When run off just 8-9 volts, the HEI trigger module will not behave properly, be weak on spark, and foul up the plugs along with poor power from the engine.
1968-1971 I believe the original resister wire will be a white/orange/purple striped wire or white/red/black striped. May start out Pink or Pink/black at the firewall and splice to the three color midway to the distributor.
1972 it is a pink/black striped wire, and I believe '73-74 are the same. First car that came with HEI stock was 1975

This can fool you on just a test light, since it will show 12v with the engine not running but key switched on...it doesn't reduce voltage until power is being drawn through the running distributor.
if you can't test and want to just foolpproof it, run a new wire from the fuse panel inside to the distributor.

#2....that PVC connection into the valve cover....if that aftermarket valvecover isn't well baffled like a stock cover is, it will suck oil pretty badly, which is another possible reason why your plugs look both oil and gas fouled.

#3...yes, move the vacuum advance to the nipple you indicated with the screwdriver, and move the nipple cap to the one on the side of the metering block.

#4...choke is adjustable...you loosen those three screws holding the retainer ring around the black choke housing , and rotate the black housing clockwise makes it richer/choked tighter so chake stays on longer...counterclockwise makes it leaner/choked looser and it releases off chokle sooner. Those little cast-in hash lines on the top of the aluminum part of the choke housing are there to help reference your adjustments.

You can go to Holleys web site, look up the new sales listing for that carb List number, and down below the specs is a spot to click and download the installation PDF for the carb....it details the choke tension and choke high idle speed adjustment, and all the other adjustments for the carb.

1. I just went out in the garage and peeled back a bit of the pink/black wires insulation going to the BAT plug on the HEI. With the car running I got 12.2 V. Bummed cause that would have been good to find something so clear cut.

2. The holley site says both covers are internally baffled. I dont know if they are well designed or not. But they are there.

3. I better learn more about the timing I guess before I move move that hose. If I could just swap it and see if it ran different with no harm I would. But Im guessing with possible pinging being on the line I better not yet.

4. I will turn that counter clockwise a bit to see if it idles better on first start.
 

·
Registered
Joined
·
367 Posts
Setting the electric choke is fairly easy. If you want to try, watch this video.

If you set it, you can verify by. Before you crank car for the first time in the day remove the air cleaner. Choke (flapper on the front top) should be closed. Turn key on, don't crank car. After a few minutes the flapper should open all the way. Turn key off and after few minutes, flapper should close. Now crank the car. Idle should be at fast idle (little high). After a few minutes blip the throttle and car should idle down to around 900. If it's an automatic, idle should be around 700 when placed in gear.

Do you have or have access to a timing light. If yes, timing is not that hard to check.
 

·
Registered
Joined
·
422 Posts
Discussion Starter #17
Just want to say thank you all for your advice and trouble shooting help. Ive compiled all your thoughts and will be delivering that to my shop this afternoon when I drop my car off. I'll let you know what they come up with and how it runs. Fingers crossed she runs like a top when I get it back
 

·
Registered
69 Nova, 454 BBC, TKO
Joined
·
61 Posts
What does that mean? Im not sure I understand
I think that is an autocorrect mistake, what I think he is saying it to get rid of the PCV valve altogether. Proper PCV is good for environment but also for you engine. Some reading on PCV (promo article for their adjustable on but anyways) article

You can always have an oil separator/catch can in the PCV circuit, which is nice have for anyone with a PCV circuit.

Btw what is with the IronSwede nickname? Myself I was born and raised in Stockholm. 🇸🇪
 
1 - 20 of 27 Posts
Top