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It’s a 68 350 rocket with #5 heads one of the valve seats was crack so it was welded prior to assembly.
Unfortunately there were some issues with machine shop documents so most of this is just best guesses and there isn’t much money so some of the things I’ve done are not advisable nor too pretty but it is my daily.
It it was bored .30 over and the factory pistons replace with I believe based on guesses and process of elimination keith black cast pistons and I believe they had a dish. From what I know the heads were not shaved and I’m unsure if the block was decked. The cam was swapped and I have no info on that from what I understand it was considered an rv cam.
the intake is an edelbrock 7111 and the heat riser ports are blocked with mondello block off plates. There is an edelbrock steel shim I don’t remember the part number with summit 650cfm carb
the distributor is a msd ready to run with a blaster 2 coil. Plugs are ac Delco gapped to .35 I believe. Mechanical fuel pump I think doing 6psi
good compression in all cylinders. Carbed tuned with a vacuum gauge to 19inches pretty much steady timing set with and dial back timing light to 34 total I believe and I think the msd has 22 centrifugal. So I believe base is 12
my issues.
couple vacuum leaks from intake sealed with rtv for the time being and retuned after.
1. now once at operating temperature not when cool there is I believe a vacuum leak that sounds like a jet taking off I cannot find it anywhere I have used water, propane, carb cleaner and can find nothing everything seems sealed.
Side note related to this if I pull a vacuum line off and leave an open vacuum port on the carb the idle actually picks up. Out of curiosity what does that mean?
2. I have a stutter or stumble or hesitation I’m not sure how to explain it at light throttle until I get up above 2k rpms then everything seems fine and no matter what I’ve done I cannot get it to go away or improve.
side note long shot here but my torque converter is apparently a 1800 stall could what I be feeling be the torque converter?
3. From everything I’ve read it seems I’ve unintentionally lowered the compression. That being said I’ve run 93 octane from shell and 89 from shell both from what I can tell with no issues. Obviously with the issues I’m having my gas mileage is terrible which I hope to eventually improve I get about 10.5 to 11mpg
so since at the moment I’m pinching pennies is it possible to run 87 regular in the car?
4. I need an oil change soon and after look around I’m thinking about rotella t6 full synthetic 15w40 with stp zddp additive does that sound like a good plan?
thanks for all your help sorry for the long clueless post
What carb? If it's a quadrajet, post the number that's stamped vertically on the driver's side of the carb.
1) Where is the leak that you were sealing with RTV? There's a very common problem with Edelbrock intakes needing to be machined right out of the box. Edelbock doesn't manufacture them quite right. What intake gasket was used?
1*) Idle is rich. If adding air makes it run better, then it has too much fuel. My favorite tuning method for idle is to disconnect the PCV host and stick a bolt in it. Get the car idling well, pull the bolt and stick your thumb over the hose. You want to get it to where it runs best when you pull your thumb off a little - like a smallish vacuum leak, which is basically what the PCV is! It should slow down with the bolt in the hose (not enough air = rich), and stumble or die with the bolt out of the hose (way too much air = lean).
2) Accelerator pump is probably shot. WITH THE ENGINE OFF! take off the air cleaner, lean over the carb and give the throttle a 25% nudge. You should see a solid stream of gas spray into the primaries. Try a full throttle rotation to see what it looks like. It should start spraying right away. If it doesn't, then then most likely the accelerator pump is worn out.
2*) That's a good converter for a typical "RV" cam and mild build. That's not what you're feeling.
3) Maybe, maybe not. You would need the part numbers. Surely whoever ordered the pistons at least has a receipt or something?
3*) Give it a try. Just listen real carefully for pinging (sounds like marbles rattling in a can) while lugging up a hill.
4) Stick with non-synthetic for at least 5,000 miles to give the rings time to seat. I just used plain Castrol GTX with good success. I've lost faith in the ZDDP additives.
Ah, all along the top. I've had to cut every Edelbrock small block intake I've bought - usually 0.030" on each intake side works out well. There's lots of opinions on which gaskets to use and which method to install - just search for some threads here.
Also, for the noise, my trick is to take a 3'-ish length length of hose, stick one end in my ear and move the other end around the engine bay. That'll help isolate where a noise is coming from.
the intake gaskets are mondello with a separate valley pan mounted to the block I believe.
unfortunately the short block machining was done a few years back and the parts were ordered by the shop and we can’t find anything in our records beside the final receipt and the shop doesn’t have the records so I can only guess unless I want to tear it apart which I don’t.
The carb is only like 3 months old and seems to squirt fuel fine also the car doesn’t have a pcv that port is plugged. Thanks for the info about rich it’s strange because the current idle tune provides the highest vacuum level.
The noise Seems based on my ears to be coming from the front passenger corner. Possibly around the carb but I see no signs of leak and I’ve been over all of those areas with propane water and carb cleaner and can’t seem to find a single dang spot.
Truthfully I’m mainly doing this internet troubleshooting because of slight ignorance and lack of time to work on it since it’s my daily I suspect the issue is between the carb and intake and intend to pull them apart to check that they are flat just trying to avoid it for the time being as well as get others opinions
First thing I see is someone used a couple of tubes of RTV on the sides of the intake. You need to correct that first and probably replace the carb to manifold gasket while your there. Chase the vacuum leaks and refresh your tune up, note stock settings are n/a. Make sure the choke is operating correctly. Get rid of that fuel filter, its a fire waiting to happen.
The rtv has to stay to keep the intake from leaking while ugly it does the trick for now. I will likely be taking the carb off as soon as I have time.
what would you recommend for a fuel filter then?
it just got new plugs and wires 2weeks ago at that point I rechecked the timing with the dial back light and I didn’t use stock spec for the plug gap I researched online and originally tried 45 but the motor did not seem to like that
I pulled the carb today no issues with intake or gasket or carb base all were sealed. Interestingly enough the primary throttle shaft was leaking gas on either side when running and happened to be pretty much right where my vacuum noise was so luckily the carb is only 3 months old so summit is sending me a warranty replacement. I also took out the clear fuel filter and leaned out the idle circuit and adjusted the idle accordingly and now when the vacuum port is left open it acts correctly and tries to stumble and die though weirdly enough now my max vacuum is 16 inches whereas before when it was much richer I was at 19 almost 20 inches I believe so I’m not sure why that is especially when the idle circuit is supposed to be tuned to max vacuum from what I’ve read wonder what that means?
Was the fuel level in the sight glasses high (float level too high) causing the fuel leak? Proper timing in conjunction with a/f mixture screw adjustment will raise vacuum. Yes, you adjust the a/f mixture screws after setting timing evenly for the highest vacuum level on the gauge, then I turn them in 1/8 of a turn. They should be turned out approximately the same amount of turns each.
Float level in the sight glasses was half so I lowered to just below half.
I know the throttle shaft was still leaking because I ran the motor to operating tempature prior to removing the carb and it was not leaking after the motor was off but was still wet from the motor running the only reason I missed it is it was hidden behind the electric choke
And I set the timing with a dial back timing light are you saying I should plug the vacuum advance hook up my vacuum gauge and advance or retard the timing for highest vacuum and then adjust the idle mixture screws for highest vacuum at that Point rather than relying on my dial back light?
Wouldn't that risk detonation since my distributor isn’t factory and it won’t be using the mechanical advance at that point?
...are you saying I should plug the vacuum advance hook up my vacuum gauge and advance or retard the timing for highest vacuum and then adjust the idle mixture screws for highest vacuum at that Point rather than relying on my dial back light
No. I believe all Eric was saying was to set your timing as you have, then adjust your A/F mixture screws to the highest vacuum & back each one off 1/8 turn so they are both even.
Found the 2 month old carb was leaking fuel from primary throttle shaft when running and the vacuum leak sound came from that area luckily summit was awesome and warrantied it out so I swapped it retimed the car using vacuum and set mixture with the vacuum gauge the best I could do mainly steady was 17 inches or so and though based on google vacuum gauge troubleshooting it looks like I may have an occasional valve issue so I assume it’s the welded valve seat 😑.
it still has a slight stumble or bog or something on super light throttle between 1500-2000 super annoying but now it has more power and gets up and goes and I believe isn’t running as rich though unfortunately for the idle tune to get max vacuum it required to be a couple turns farther out than out of the box so seems like my motor is a gas hog
and much to my extreme disappointment after driving it a while today my airplane engine noise that signals my vacuum leak has come back so back to the drawing board.
i also discovered my ac belt seems to have too long of a run without an idler pulley because even tensioned tightly it’s kinda flapping around and it also slips and squeals on the dang compressor oh well have to love a project.
i just wish I could get some better gas mileage things killing my wallet with the increase in gas prices.
Is that distributor actually a Multi Spark type setup ? If so you need to try a "regular" timing light without the dial back feature and see what you get then. MSD absolutely recommends not using a dial back type light with their Multi Spark ignitions. Also, is the distributor vacuum hooked up to a steady manifold vacuum source ? I have found that most performance engines like full manifold vacuum as compared to ported vacuum. And just to be sure.... you are checking the timing with the vacuum advance disconnected ??
As far as fuel goes, without knowing more detail on your engines internals there is no way to know if the 87 octane will work other than to try it. My Wifes 84 307 runs just fine on 87 Shell but it is not high compression by any means.
As far as oil goes everything I have been told and read says it is better to buy the oil with the correct additive package already in it as compared to buying one oil and putting in a bottle of additive. Rotella is for diesels and has changed significantly in the last few years due to diesel emissions requirements. Buy one of the oils that is designed for older gasoline engines and be done with it.
The msd ready to run distributor says nothing anywhere about issues with dial back timing lights although I’ve bypassed that issue now by timing with the vacuum gauge. I do time it with the vacuum advance disconnected and the vacuum advance is hooked to timed rather than full vacuum.
I just put out a couple dollars of shell 87 in as a test and see so I will find out soon.
Getting the intake to seal can be a challenge. There's lots of opinions on the right way to do it.
No surprise on the carb. Summit keeps those cheap by using generic designs and keeping QA to a minimum.
The A/C belt has a long run so it'll flap a bit no matter what. Note that new belts will stretch, so re-tension a few times. Use a long bar on that one - either a tire iron or a 18" long screwdriver. It can take quite a bit of force.
Couple of things I noticed. One the PCV port on the carb is plugged off. The carb is calibrated for the PCV valve and engine will run rich without it. With that model Summit carb the designated PCV port is located on the front passenger side, the 3/8" port.
Secondly your electric choke is set 2 or 3 notches to the rich side, no good adjust it back to the middle.
Thanks for the opinions on the ac compressor I intend to retention it I also have adjusted the choke but have to lean it a bit more because it’s still rich. Runs fine on shell 87 so that’s nice still have a weird slight bog or stumble from like 1500 to 2000 rpm it’s kinda annoying in low speed situations. As well instead of rotella after further research and not to start an argument about zddp etc. I’m probably gonna use Carquest full synthetic 10w40 also I’m looking to figure out a metal canister fuel filter found a mr gasket at advance though some reviews said the ethanol broke down the glue and filter element and clogged their float and needle causing flooding which is exactly what I’m trying to avoid any good low cost options?
also what all would I need to set up the pcv system rather than breathers I’ve been meaning to.
Any auto parts stores carry a version of this in either 5/16 or 3/8 fuel line. Time your engine with the light instead of the vacuum gauge, first you need to know which stop bushing and springs are in it to set it up correctly. Plain old conventional Valvoline VR1 will run fine in your car, no need for synthetics. For a PCV, just buy the one for your engine, you may have to get a rubber grommet that fits ait and your VC. Connect the hose to the 3/8 fitting on the front of the carb. Tighten the fan belt for the compressor until it stops squealing, it never had an idler pulley from the factory, should not need one now with a later model compressor.
Thanks for all the help I think I’m gonna keep the vacuum timing because it runs way better I know my springs and stop brushing as well as a timing light I couldn’t get it dialed for something reason so I’ll let that ride and thanks for the other recommendations I was just worried about the reviews on those filters I saw about them breaking down with the ethanol in the gas and clogging the needle. I assume with the pcv set up I put the pcv on the passenger side and a breather on the drivers side?
Yea I found a fram metal body fuel filter on amazon so I’m going to grab that with the pcv valve I’m confused about what needs to happen on the drivers side is a breather sufficient or do I need to do it another way because I don’t have a factory air filter. Thanks.
PCV connects from the carb to one valve cover, then the other valve cover has some form of breather to allow fresh air into the engine. The breather you currently have will work.
Anyway to clean it out? It seems to be rather oil soaked. Also what oil weight would you run in Florida where it will pretty much never see lower than 40 degrees and that’s only a few days a year and how do you feel about stp additive
Any ideas on how to retrofit the power door lock relay with something else mine is the old style that seems to be stocked super limited and costs well over 100 my lock side is out.
also I have about I’d say 1/4-1/2 of play side to side in the steering wheel before the wheels move the intermediate steering shaft was apparently replaced in the past and the steering gear was supposedly adjusted. The entire front suspension has been replaced with moog replacements so I know that’s not the issue any ideas?
and still wondering about that dang little stumble and hesitation around 1500-2000 almost seems like a terrible misfire or dead cylinder it’s hard to explain.
Also so how do you check for a valve issue? based on the internet if on my vacuum gauge it’s steady with small drops it’s a valve issue?
Any ideas on how to retrofit the power door lock relay with something else mine is the old style that seems to be stocked super limited and costs well over 100 my lock side is out.
also I have about I’d say 1/4-1/2 of play side to side in the steering wheel before the wheels move the intermediate steering shaft was apparently replaced in the past and the steering gear was supposedly adjusted. The entire front suspension has been replaced with moog replacements so I know that’s not the issue any ideas?
There is going to be some play, normal for a recirculating ball system.
and still wondering about that dang little stumble and hesitation around 1500-2000 almost seems like a terrible misfire or dead cylinder it’s hard to explain.
Check your accelerator pump, ensure that you get 2 good streams of fuel as soon as you start to move the throttle.
Also so how do you check for a valve issue? based on the internet if on my vacuum gauge it’s steady with small drops it’s a valve issue?
Thanks for for the help.
Small needle movements could be as simple as a carb adjustment.
That much play is standard wow I guess I’m just spoiled with more modern tight steering. What symptoms would the steering gear or rag joint going out show?
The accelerator pump is fine and I’ve had the issue with 3 different carbs and multiple other changes so I’m not quite sure what exactly is causing it.
Well the needle jump is weirdly consistent but I can’t figure out the pattern or may be too lazy it’s like it will be steady for a few revolutions then drop and come back then steady for a different amount of revolutions drop etc. idle does that some times too. I only ask valves because I saw that online and I know one of the valve seats was cracked and had to be welded.
That much play is standard wow I guess I’m just spoiled with more modern tight steering. What symptoms would the steering gear or rag joint going out show?
Rattling, excessive play, vibrations.
The accelerator pump is fine and I’ve had the issue with 3 different carbs and multiple other changes so I’m not quite sure what exactly is causing it.
Timing, use a light not the vacuum gauge.
Well the needle jump is weirdly consistent but I can’t figure out the pattern or may be too lazy it’s like it will be steady for a few revolutions then drop and come back then steady for a different amount of revolutions drop etc. idle does that some times too. I only ask valves because I saw that online and I know one of the valve seats was cracked and had to be welded.
A valve seat or valve issue would be very consistent and show up as a miss, backfire out the exhaust or intake depending on how bad or which type of valve.
Can’t figure out for the life of me how I managed it but most of my issues were my fault from what I can tell somehow I was at 30 degrees base timing so I have since backed that off to 15 and may still back it off to 12 then I’ll have to change my advance stop bushing to get more mechanical advance and adjust my timing curve. Since doing that I’ve been able to take a lot of fuel out of my idle I also finally added my pcv valve. I’m thinking about sea foaming the vacuum line and the oil before my oil change. And then I likely need to relocate the new fuel filter because it seems like it’s getting hot and possibly evaporating fuel or something because the car randomly acts like it’s running low on gas at idle so I figure either the fuel is getting hot running into the carb or the fuel pump is going out. Unfortunately after my tuning I’ve done something wrong because I have to give it quite a bit of gas and it’s hard to start so I’ll have to figure that out.
Learning from my mistakes one step at a time.
How reliable are are the rally pack gauges are the usually correct?
how would I know what the correct fast idle and curb idle is for my motor?
Unfortunately with my changes the motor runs better but the vacuum has dropped quite a bit from 20 to 15ish
also so is it worth it to change the rear gears in my factory 7.5 and beef it up or do I need to drop the cash for an 8.5?
I also want to make sure the drive shaft from the 3.8 won’t have any problems if I keep the 7.5 the car likely isn’t making too much power and I never run slicks just Michelin defenders I also never take it to the track.
This is car is supposed to be a fun daily and try and save as much gas as I can with it being a carbed v8
i still I’ll have to adjust my accessories unfortunately the alternator is just slightly off causing it to chew the belt a little and the ac compressor I still have to tension more so the belt stops slipping.
Anyone know now how to modify the bracket for the Quadra jet ac solenoid so I don’t have to drop a fortune for the Holley version to keep my idle with the ac?
May 5th, 2019, 11:32 AM
