[ta man]

Have you adjusted your carb tuning ?

[AdamIsAdam]

I have not touched it yet. It's a brand new Cliff carb that I put on last Fall. I'll write him about the surge to see what he suggests. I can make it go away with timing, but is it timing or is it running lean at a steady 3,000 RPM on the highway?

[PontGuy]

What year is the carb and does it have APT adjustment? If it is a later carb then you can easily see if adjusting the APT to richen the cruise mix helps. FWIW both of my cars have Cliff-built carbs and both have wideband meters, and the cruise A/F was spot on as he set them up. So it shouldn't be a lean surge but then again anything is possible.

Its been a long time since I had one of those adjustable crane vacuum cans, but I seem to remember that adjusting it changes the base timing as well as the advance? If so then you would need to disconnect it and re-set the base timing after you make an adjustment. The idea is to keep the timing curve without vacuum in the sweet spot for max power, and then add in as much vacuum advance as it will take without pinging or surging.

Yes running cooler definitely helps maintain oil pressure. 205 deg won't hurt the engine but most of us aim for 180-190 as optimum.

[AdamIsAdam]

I don't recall the carb year. It's electric choke and I do believe he said it would be a later model carb. It was built to my car's complete specs and I expect it's spot on based on my conversations with him before and after the build - and how it runs. Playing with the timing seems to be doing more to help/hurt my surge issues and temp + oil PSI issues.

yes, you are correct that as I adjust the crane vacuum advance, I have to go back and readjust the initial timing. The car likes 12*.

[78w72]

as for timing... suntuned HATES the adjustable vac adv canisters, stick with a stock one of known advance. i suggest contacting him or cliff for advice on that.

also the vac advance should almost always be connected to a ported vac source, not manifold. that is most likely whats causing the surging, cliff almost always says use ported vac from the carb, above the base plate, you should have a couple unused ports for that.

also agree to try & get the engine running cooler, 200+ is not too hot to cause damage but definitely doesnt need to be that high, not sure what t-stat you have or what the rest of teh cooling system is, but a 180 t-stat is best in most street cars & if you can lower the temps 15-20* it should help the pressure.

i think 20/50 is too thick for a street engine, 10/30 may be on the thin side... why not try a good 10/40 conventional oil or maybe a 15/40 diesel oil like delo 400 or rotella-t? might increase the pressure a bit, & with reduced temps you should be fine.

change the timing to ported & swap back out to a factory vac advance, then set timing based on the dist curve & known base & vac adv numbers. contact suntuned, he can provide a good vac adv canister based on your engines specs. if the dist wasnt re-curved, that will be a big help.

good luck

[HWYSTR455]

Scope creep. You should really start a new thread for tuning, think the oil psi thing has been resolved.

As for manifold vs ported, you are going to get a lot of opinions there, but my personal experience has always to run full time/manifold. The exception is when you have a radical cam, and make little vacuum at idle. Just to say though, manifold/full time does help idle temps.

There is some true about the adjustable vacuum cans, since the adjustment isn't linear, like, a 1/2 turn may give you X, but the next half turn can give you XXX. You can still get reasonable results with them though, and they seem to work well for me.

Surge at 3k RPM would have nothing to do with where your vacuum can is hooked by the way.

This statement confuses me: 'So I have initial set to 12* and added 24* with the adjustable unit using MVA.' . A vacuum can isn't adjustable for the amount of advance it adds, that is a static value, and the adjustment is when it starts opening, like at a particular amount of vacuum. In order to limit the amount of timing it adds, you have to have a limiter. The crane units come with a cam that can be adjusted to control the amount of timing the can adds. Is that installed?

Remember, the can is just a diaphragm with a spring, and the adjustment controls the tension on that spring.

Just to say, the adjustable can has a range of 9.5 turns out (CCW) from the bottoming point (CW), and if you exceed the 9.5 turns, the adjustment screw pops out, and it's a biotch to get it started again. Most of the time it falls out, and you need to buy a new can. So turn it all the way in (CW), and if it doesn't bottom, it's fallen out, and it's junk and needs to be replaced.

Best way to test what the total amount of advance a can adds, hook up a vacuum pump with a timing light hooked up and suck the can down, watching the timing mark. That will tell you total advance a can adds.

Vacuum is the last adjustment you make when doing a timing curve. Initial, total, and rate are the 3 items you adjust before you even hook the can up, and generally in that order. Initial is obvious how you adjust that, total is by limiting travel or by the center cam and weights, rate is by the springs.

Plot your curve. Use a piece of graph paper, on the left do degrees, on the bottom, do RPM, and go in 500 RPM increments. With a dial back light, step the RPM in 500 increments, and write down the advance, all the way up to 4500 RPM or so. That's your baseline. That should be done with the vacuum can disconnected. All adjustments should be made to initial, mechanical, and springs with the can disconnected.

Oil weight depends greatly on engine clearances, wider clearances require heavier oil, and the general indication is seen by oil psi. If you're getting 15-20 at idle hot with 20-50, then run 20-50. You don't really want anything lower than that.

.

[AdamIsAdam]

Originally Posted by HWYSTR455

Scope creep.

I had to look that one up!

You should really start a new thread for tuning, think the oil psi thing has been resolved.

Will do. I know it will open up a can of worms, so I'll get my facts straight and work out a few things before I do this.

Surge at 3k RPM would have nothing to do with where your vacuum can is hooked by the way.

What causes surge at 3k cruising? I can get it to almost go away by just backing out the adjusting screw on the crane vacuum unit.

This statement confuses me: 'So I have initial set to 12* and added 24* with the adjustable unit using MVA.' . A vacuum can isn't adjustable for the amount of advance it adds, that is a static value, and the adjustment is when it starts opening, like at a particular amount of vacuum. In order to limit the amount of timing it adds, you have to have a limiter. The crane units come with a cam that can be adjusted to control the amount of timing the can adds. Is that installed?

Yes, I have the notch plate/adjustment cam. I used that to get the timing from 12* to 36* at idle since 36* is my car's sweet spot. then I was using the adjustment spring to fine tune that. I guess what I'm doing is fine tuning how much vacuum advance is coming in at idle and part throttle because as I turn it, I brought the initial timing (with vacuum advance connected) from 36* all the way down to 20* in order to get rid of the bad surge and also the slight part throttle ping. However, the engine really runs best and is most responsive at 36* at idle with MVA connected. Only down side is that surge.

Just to say, the adjustable can has a range of 9.5 turns out (CCW) from the bottoming point (CW), and if you exceed the 9.5 turns, the adjustment screw pops out, and it's a biotch to get it started again. Most of the time it falls out, and you need to buy a new can. So turn it all the way in (CW), and if it doesn't bottom, it's fallen out, and it's junk and needs to be replaced.

I think I've turned it more than 9.5 turns CCW already I'll close it (CW) and start again. I've read that about the screw coming out.

Best way to test what the total amount of advance a can adds, hook up a vacuum pump with a timing light hooked up and suck the can down, watching the timing mark. That will tell you total advance a can adds.

I don't have a vacuum pump. But I know that the notch plate/cam on the Crane gives 2* for every notch. It seems pretty straightforward and easy to get my initial timing connected to 36* at idle.

Vacuum is the last adjustment you make when doing a timing curve. Initial, total, and rate are the 3 items you adjust before you even hook the can up, and generally in that order. Initial is obvious how you adjust that, total is by limiting travel or by the center cam and weights, rate is by the springs.

My timing curve has been checked by Richie as being good. It's 12* initial, 32* total at 2,800 RPM and about 20* at 1,800.

[nytrainer]

Maybe I'm reading this wrong Adam but it seems you are calculating/adjusting total timing using vacuum advance? Initial and mechanical advance combined (with no vacuum advance factored in at all) will give you your total advance (for ex. 34* total with 12*initial & 22*mechanical). Springs will dictate how soon/fast in the rpm range the mechanical advance comes in (you should be OK as Richie said curve was good). The vacuum canister will further advance the timing at cruise with high vacuum signal or idle when connected to MVA as you have. This will help with engine cooling at idle and cruise (benefit to oil pressure too). The need for the adjustable vacuum canister is to compensate for your cam's profile that gives you a lower max. vacuum than stock type cams. Your lower max vacuum signal may not be high enough to actuate a stock vacuum canister.
Maybe you do have a handle on this concept and I read it wrong but just trying to help.

[AdamIsAdam]

Originally Posted by nytrainer

Maybe I'm reading this wrong Adam but it seems you are calculating/adjusting total timing using vacuum advance? Initial and mechanical advance combined (with no vacuum advance factored in at all) will give you your total advance (for ex. 34* total with 12*initial & 22*mechanical). Springs will dictate how soon/fast in the rpm range the mechanical advance comes in (you should be OK as Richie said curve was good). The vacuum canister will further advance the timing at cruise with high vacuum signal or idle when connected to MVA as you have. This will help with engine cooling at idle and cruise (benefit to oil pressure too). The need for the adjustable vacuum canister is to compensate for your cam's profile that gives you a lower max. vacuum than stock type cams. Your lower max vacuum signal may not be high enough to actuate a stock vacuum canister.
Maybe you do have a handle on this concept and I read it wrong but just trying to help.

Maybe I wrote it wrong, but I do understand that the vacuum advance doesn't come into the total advance formula. These figures were all taken with the vacuum advance disconnected: 12* initial, 32* total at 2,800 RPM and about 20* at 1,800.

When I said that it idles at 12* initial, then I got it up to 36* by connecting the Crane advance, that was all at idle. The car likes to idle at 36*. That means that part throttle cruising maybe be as much as 58* or so. They say 54-56* is ideal for efficiency on the higway (that's mechanical + vacuum at part throttle like highway cruising at 3,000 PRM.) Maybe 58* is too much and giving me the surge. I'll go back and double check my Crane notch plate limiter and start that process again.

[jonmachota78]

Originally Posted by HWYSTR455

Scope creep. You should really start a new thread for tuning, think the oil psi thing has been resolved.

As for manifold vs ported, you are going to get a lot of opinions there, but my personal experience has always to run full time/manifold. The exception is when you have a radical cam, and make little vacuum at idle. Just to say though, manifold/full time does help idle temps.

There is some true about the adjustable vacuum cans, since the adjustment isn't linear, like, a 1/2 turn may give you X, but the next half turn can give you XXX. You can still get reasonable results with them though, and they seem to work well for me.

Surge at 3k RPM would have nothing to do with where your vacuum can is hooked by the way.

This statement confuses me: 'So I have initial set to 12* and added 24* with the adjustable unit using MVA.' . A vacuum can isn't adjustable for thehwysta of advance it adds, that is a static value, and the adjustment is when it starts opening, like at a particular amount of vacuum. In order to limit the amount of timing it adds, you have to have a limiter. The crane units come with a cam that can be adjusted to control the amount of timing the can adds. Is that installed?

Remember, the can is just a diaphragm with a spring, and the adjustment controls the tension on that spring.

Just to say, the adjustable can has a range of 9.5 turns out (CCW) from the bottoming point (CW), and if you exceed the 9.5 turns, the adjustment screw pops out, and it's a biotch to get it started again. Most of the time it falls out, and you need to buy a new can. So turn it all the way in (CW), and if it doesn't bottom, it's fallen out, and it's junk and needs to be replaced.

Best way to test what the total amount of advance a can adds, hook up a vacuum pump with a timing light hooked up and suck the can down, watching the timing mark. That will tell you total advance a can adds.

Vacuum is the last adjustment you make when doing a timing curve. Initial, total, and rate are the 3 items you adjust before you even hook the can up, and generally in that order. Initial is obvious how you adjust that, total is by limiting travel or by the center cam and weights, rate is by the springs.

Plot your curve. Use a piece of graph paper, on the left do degrees, on the bottom, do RPM, and go in 500 RPM increments. With a dial back light, step the RPM in 500 increments, and write down the advance, all the way up to 4500 RPM or so. That's your baseline. That should be done with the vacuum can disconnected. All adjustments should be made to initial, mechanical, and springs with the can disconnected.

Oil weight depends greatly on engine clearances, wider clearances require heavier oil, and the general indication is seen by oil psi. If you're getting 15-20 at idle hot with 20-50, then run 20-50. You don't really want anything lower than that.

.

Great write up hwystr. I've always had better luck with manifold vacuum too. The only issue i see is this quote
"Remember, the can is just a diaphragm with a spring, and the adjustment controls the tension on that spring."

I'm sure not all vac advance cans are created equal, I run one and the adjustment controls the amount of advance rather than the rate. For example mine is currently set to limit at 8deg. My initial is at 10 deg so at idle with manifold vac I'm at 18 degrees. I wish I could adjust the rate and make it pull the advance out sooner when the throttle is depressed. This is where suntuned likes the factory cans because he know which ones to use that have the spring rates desirable for performance apps.

[78w72]

hopefully cliff will chime in on the ported vs manifold vac issue, or maybe on your new thread. but im my personal experience, on a very mild cam 400 in a 78 4 spd t/a, the manifold vac was terrible, it adds timing at idle & caused pretty bad surging & bucking at cruise speeds, more so at street mph/rpm as opposed to highway speeds/rpms. cruising at 35-45mph & about 2000-2250, the engine would buck & surge & just not run smoothly from idle to the above mentioned cruise rpms. after lots of research & asking cliff what the best way to go is, i got an overwhelming majority saying ported was the best source for vac adv. why would you want full vac on the vac adv canister at idle & just off idle? having a gradual amount of vac come on as the throttle opens seems to run best on all my street cars, from a stock 301 turbo, to a mild 9.5:1 .480 lift cam 406, to my recent 10.7:1 alum head OF roller cam 467 stroker... all run best with ported vac & a known # vac adv. i wanted to try the adjustable canister but suntuned convinced me out of that with a great explanation as to why. i will leave those explanations on ported vs manifoold & adjustable vac adv to cliff & suntuned on your new thread.

as for oil, yes it depends on clearances but, most "street" engines are built within a certain range of clearances to allow for longevity of a street driven car, this isnt a race only engine or clearances, its a very common street pontiac engine... 20/50 is too thick IMO, especially if the car sees cooler weather in srping & fall of NY. my engine builder says 10/30 is fine for normal street use, unless its raced hard or built more towards a race type clearance, then maybe 10/40, but either 10/30 or 40 is perfectly fine. thicker oil just causes more drag on the internals, robs horsepower & doesnt flow when cool/cold. its a fine line between psi & flow. in your climate for a street car, go with 10/40 or maybe 15/40 if you want a little better psi. but cold starts with 15/40 & 20/50 at 40-50* & below will be doing more harm than good.

thats my 2 cents based on other experts suggestions... but as stated above, you will get all kinds of "opinions" on almost every subject when it comes to engines & cars. & usually going with what people who do this for a living suggest is the best option.

[STEELCITYFIREBIRD]

I do believe that is a 1975 block.
Casting #?

http://s300.photobucket.com/user/ada...53522.jpg.html

If your changing your initial timing, or if you haven't done it in a while.
First reset your idle screws, for max rpm/vacuum,then +1/4. (my method, others feel free to chime in)

My thoughts on the surge, it's going lean,add more fuel or less vacuum advance.

[AdamIsAdam]

Originally Posted by STEELCITYFIREBIRD

I do believe that is a 1975 block.
Casting #?

http://s300.photobucket.com/user/ada...53522.jpg.html

It's a '66 built block that was installed in a 67 pontiac 400 with 350hp and manual tranny according to the codes.



http://www.wallaceracing.com/engine.htm

[HWYSTR455]

78w72 - Sorry if I came across wrong, wasn't meaning anything insulting.

Yeah, I can take a swing at it Adam, but it's still speculation to some point, so please take with a grain of salt.

The surge, a few things can cause it, but yes, a vacuum can setting might cause that. My comment was regarding the fact of if it was ported or not, since at that point, the throttle blades are open, so it would be seeing the same amount of vacuum regardless. If your getting 18 degrees of advance from the can at idle, that's a lot, wasn't even sure those cans could provide that much. I thought they only did like 14-16 degrees, but not sure. You throw 36 degrees at it at idle, then something else is off, like I'm thinking carb. I would also check for vacuum leaks.

So when you crack the throttle, say like giving it 1/4 throttle or more, vacuum drops, so it's going to immediately pull 18 degrees of advance out. Hook a vacuum gauge up and hold it at 3k rpm, and watch the needle. If it's swinging around, then the advance is prob an issue/cause.

It would be better to get more advance at idle with initial, would be more stable, especially in transitions. But to do a lot of advance at idle you would need a mini starter. As an example, my driver was setup with 16 initial, 16 mechanical, and 10-12 vacuum. All mechanical was in by 2800. I tried more advance before, since everyone said e-heads like a lot of lead, but mine didn't, ran best that way. As another example, many new cars with EFI run 20-22 degrees initial. The iron head 442 I have likes 16 initial too.

Like I said, on the can, if you turn it all the way in and it bottoms, like stops turning, then the screw didn't fall out.

You can get a cheap hand pump at the auto parts store for like $25, good tool to have. Think I have an Actron one.

36 at idle is too much by the way, something is going on there. I would verify the timing mark on the balancer for starters, recheck your idle mix screws and idle speed, with the vacuum can disconnected.

The curve sounds close, but, if you run more initial, you will have to limit total more. Think you just need to spend a little more time dialing it in for your combo, like I said, you're close.

.

[78w72]

Originally Posted by HWYSTR455

78w72 - Sorry if I came across wrong, wasn't meaning anything insulting.

wasnt taken that way at all, & my comments weren't intended that way. just saying what i found on my cars & what i was instructed to do by the guys i paid to do the work on my carb & dist. i dont claim to know the facts behind it. each person will have different results i guess.

luckily i never had cooling issues to make me have to stick to MAV, also never had an adjustable vac adv to try & dial in. when my 78 t/a's engine was rebuilt & dialing it in, it surged & bucked a bit at the speed/rpm i mentioned, going to ported vac stopped it 100% & it seemed to cruise, idle & just run better. stopped the minor bucking 100%. i did remove all the emissions & TVS related vac lines & hook the vac adv directly to a ported source on the carb. my understanding of ported vac is to not have constant & full vac on the vac adv at idle, rather have it come in gradually off idle & at light throttle/load situations with higher vac, where its most beneficial.

i think ported vs manifold vac is like oil debates, the threads could go on & on & usually do. use what works best for you is all that matters.

[HWYSTR455]

Flip the block over and post a pic of the main webbing, that will be the give away, if they are undercut or not.

.

[STEELCITYFIREBIRD]

Originally Posted by HWYSTR455

Flip the block over and post a pic of the main webbing, that will be the give away, if they are undercut or not.

.

I think it's in the car.

[HWYSTR455]

Originally Posted by STEELCITYFIREBIRD

I think it's in the car.

That would make it difficult to flip over then.


.

[AdamIsAdam]

Thanks. Yes, let's not start a ported v manifold discussion here. Been there, done that. I know Cliff's opinions and I've read all the books too. But the bottom line on that subject is that your engine is the bottom line. I've tried both on my car and it likes MVA better. But I'll try ported again - I'm open minded.

Same goes for oil weight. I went to Amsoil 20W50 since it flows as good or better than 10W30 dino when cold. It did leak a bit more. But I took the amsoil out and trashed it, probably unnecessarily, and put in 20W50 dino since I was seeing low PSI. I'll change this again before winter to lighter weight oil.

But for now, I think I've deduced that my oil PSI issue is ok. That I need to get timing in order which will keep temp in order which will keep PSI in order.

So, if HWYSTR455 wants to answer my questions above on this thread, great. If not, I'll start a new thread on timing. Hopefully this thread will help others in the future as will the timing thread I'm about to create.

As usual, the members here have been great to me by sharing their info. And for that, I'm very grateful.

THANKS!

[grivera]

Glad to see you're making progress and sorting things out. The engine type number should be by the distributor hole- at least it's that way on the 69 and 73 blocks I have...