Absolutely.
There are a few here that have questioned whether this is outside what would be considered reasonable for a daily driven vehicle. While I've had experience with this cam in OP's cars, I now have have it installed in my own.
So far, without any real tuning other than adjusting the float level and checking the initial timing, there's 7" of idle vacuum at 850 RPM. Very steady with little notice of the overlap this cam has with a 110 LSA. I should add that the idle mixture has been tuned as well, using a vacuum gauge, tach and a AFR/wideband gauge. The idle smoothness actually surprised me. Considering that the spark lead is very low at 16 degrees, I'm pretty sure that once I dial in the vacuum advance, using full manifold vacuum, that with about 30 degrees of idle timing, another 1" to 2" of vacuum should be realised. As it is, I feel I'm on the edge of the vacuum assisted brakes. Another inch or two of vacuum should remedy that.
So for those that question the driveability issues associated with a cam of this size, un-tuned MPG in mixed driving is already at 18. I would expect highway mileage to be near the mid twenties.
Just in case anyone was wondering...

 

I'd rock it lol. Its all in the tune and what you can live with

 

It's surprisingly liveable.
Even with the carb half baked from my previous build, off-idle response is excellent.
And it's pretty cool to be able to burn the tires up to the top of 3rd gear (without twin turbos...).
The dragstrip, and how it behaves in the 60' will be the real test. That may come in the 1st week of October provided A), I've enough time to build a decent spark curve and ensure my WOT AFRs are OK and B), the weather is decent for the final weekend at the local strip.

 

You'll likey find it will like 26-30 deg at idle and not much advance needed at cruise

 

30 degrees at idle is what my earlier build liked. However it pulled in excess of 12" idle vacuum so the tuning approach will be different.
The cruise advance is what I'm interested in. The 10.4 SCR/8.5 DCR previous engine didn't like 50 degrees of advance at a 75 MPH/ 2700 RPM cruise. This engine is tamer by comparison with 10.2/8.1 CRs. I'm as much interested in 25 MPG on the highway as I am in a low 12 second ET. Or nearly as interested anyway.

 

50 is high. Most heads seem to tolerate 38-40 in real light loads. More load then 35-37 but it all depends

 

Here's a paragraph from Steve Davis' Spark Strategies paper written a few years back. It's what I'm basing my spark curve on.

Also you may have based a cam selection on the basis of minimal negative idle impact. This may have limited your choice of cam to one of say a 280 degrees (advertised). If this was to be paired with a distributor with no vacuum advanced as most competition ones are then rest assured you have probably given away about 10-15 hp. If a vacuum advance is used the ignition timing at idle can be optimized where-as without vacuum advance it cannot. Assuming a realist street engine idle speed a ‘mechanical advance only’ distributor is barley pulling in any advance. What with say 12 degrees of initial and at most 5 degrees mechanical the total timing at idle would be only 17 degrees. In practice we find that a big cammed V8 needs about 50 degrees for best idle along with the lowest idle fuel consumption. I have seen some engines require as much as 55 degrees yet these engines – with cams as big as 260 to 270 degrees at 0.050, would idle tolerably well at 1000 rpm – sometimes less. The same goes for cruise. The vacuum advance can pull in the desired advance which at about 2500 rpm and a quarter throttles can be as much as 50 degrees. Normally an engine with mechanical advance only would have no more then about 25 to 30 degrees max. It does not take a diploma in rocket science to see that cruise fuel consumption is going to be much higher with the timing as much as 25 degrees out!



Depending on how much driving weather is left up here, I may go so far as to bring a hand held vacuum pump into the cabin while I cruise on the highway. I can dial in the best vacuum advance and then build the appropriate curve based on that.
As for the mechanical advance, doesn't seem much has changed in the years I've been at this. The more efficient cylinder heads today require less advance but other than that it seems that starting the advance just off idle, at about 1300 RPM or so and having 34 degrees all in before 3000 is the way to go.
Of course. fine tuning it at the track is what will nail it down. I may book a dyno session as well although that'll only really help the WOT advance curve.
I'll see where that gets me.

 

Idk where he got that information but i would take it with a grain of salt and sneak up on it, listening to what the engine says it wants

With modern day combustion chambers, i never seen an engine require more than 40 deg anywhere and never that much at idle

 

Of course, sneaking up on it is a wise tuning approach.
As for where the information comes from, Davis and Performance Distributors are 2nd generation racers. Boat loads of experience to back up their claims and testimonials too. I'm sure you're aware of who they are.
http://performancedistributors.com/about-us/
I suppose to match wits with them would mean getting on a dyno and messing with the timing. I can't think of anyone though that would spend dyno time working out a vacuum advance curve but reasonable results could be gained with the aforementioned vacuum pump and an appropriate stretch of lonely, level highway.
That said, once I'm back in the shop, I'll spend a few days working through some timing curves and see what the engine likes. 30 degrees of idle timing is a no brainer but I'll experiment with more if I can. I'm limited to about 16 degrees out of the vacuum can and can't add much more than 15 initial sue to the mechanical advance being pegged at 18-19 without further distributor modifications. I've maxed out my advance bushing and this engine seems to like 34 WOT timing.

 

I'm running a cam that has numbers pretty close to that cam in my 383 with aluminum heads and it runs much better with the base timing set at 14 degrees, 34 degrees total and vacuum advance connected to manifold vacuum. It idles better, is more responsive and the spark plugs don't try to foul out at idle.

 

I haven't had any time to work on the tune other than to set the max base timing I could without exceeding the max total of 34 I've targeted for now. With 18 mechanical I have in the distributor, that left me with 16 initial. My past experiences have shown that something along the lines of 30 degrees initial is what the engine really likes. Smoother idle with less RPM. Higher idle vacuum and lower idle temps too. Plus the throttle response when cruising around town is better too. The only way to achieve those kinds of numbers is to use full vacuum rather than ported for the vacuum advance. That'll be my tuning task when I get back in a couple of weeks. I have vacuum advance that's adjustable both in amount and the set point. The current idle vacuum is 7" at this elevation. I'll work the curve to have the vacuum advance start around 4" and be all in by 6". That should improve the idle and allow me to work the finer points. My concern is too much advance at highway cruise where, under certain circumstances, could be as much as 50 degrees. That would be a combination of initial (16), max vacuum (16) and max mechanical (18). Its unlikely I would ever drive with that being a possibility but it'll be something to avoid nonetheless.
I'm a big fan of full manifold vacuum and I find a lot of people don't have the necessary hardware to make it work as it should. The ported stuff was the OEMs attempt at reducing emissions in the 70s and its one of those things that have stuck around.

 

That's funny MSgt. I just reread your post and I see you ARE running manifold vacuum as opposed to ported. Seems to me we may have had this conversation a while back when I was commenting on ported vs full vacuum. It may have been when you working through your new engine package.
Glad to hear (again) that it's worked out for you. I'm still surprised at the number of tuners out there that won't accept that this approach is far better in every way from the old smogger days of the 70's and the ported vacuum band-aid approach to improving emmisions.

 

Made the switch yesterday from ported vacuum to full manifold vacuum. While the engine responded by giving another 1-1 1/2" of idle vacuum (at the same RPM after adjustments), I'm at the limits of adjustability of the vacuum can. Vacuum advance starts at 5" and the 16 degrees is all in by 10". Problem is, max idle vacuum at 950 RPM is about 9". That leaves that overlap where the vacuum advance is still coming on at idle. That results in some idle hunting or an overly fast idle speed that takes time to settle down. I've found the best results are to have vacuum advance all in before the idle RPM is reached. I think my options are to either reduce the total vacuum advance available and having the curve all in by about 8". I have Cranes adjustable vacuum advance plate so changes to the total are possible. Either that, or look for a can with greater adjustability.

 

All the data I've read said that we should ideally have all the advance in by 2" below our idle vacuum, so yes, you may have to limit the amount of total vacuum advance and recurve the distributor if you can't find a can that fits the bill. I've been busy with other things lately and haven't done any fine tuning on mine, it seems to 'hunt' a little at idle as well and I'm sure I'm in the same boat as you; so let me know when you find a good part number for a can that does the trick.

 

Yes, 2" below idle vacuum is the target. What I found was, that with the small cam, idle vacuum was about 12". The adjustable can I'm using was maxed out but that resulted in the advance being in by the desired target. That leaves me stuck at the moment although it's still very driveable and I'm guessing we might have another couple of weeks of driving weather up here so there may not be much done in the next while.
Somewhere buried, I have a list of factory vacuum cans and what their set points are. I'll be looking for it over the next couple of days and will post up what I find.
The next step, will be determining the optimum advance for cruise conditions. I'll probably take the hand held vacuum pump into the cabin with me and work the advance while driving. At the moment, with the initial set at 16, vacuum at 16 and whatever portion of the mechanical that's active at about 2500 RPM, total is about 37 degrees. I'm thinking that with my slow mechanical curve, I'm only adding about 5 degrees at that RPM. That'll change for next racing season as I think I'm past the too much compression situation that forced me into a lazy mechanical curve trying to keep the engine from detonation. It's better now but I haven't gone back into the distributor to work on the timing.

 

Did a little digging this morning. Found an article on vacuum advance and with it a list of GM's vacuum can specs. Looks like I've found what I was looking for.
Echlin's VC-1810. Advance starts at 3-5" and 16 degrees is all in by 8". Should be just about perfect.
Problem is, not available in Canada. Need a U.S. based/NAPA/Autozone/etc.

http://www.crankshaftcoalition.com/w...ance_Specs.pdf

 

^^ Thanks, I'd seen this list before, but for the life of me I couldn't remember where.

 

The plot thickens.
Seems this part, the elusive "B28" stamped vacuum advance canister, available under any number of PN's, hasn't been manufactured for years and stock from the usual sources is all but gone.
Need one. Gotta find one.

 

Found a B28 can is sold under the Airtex brand name. PN 4V1053.
Rock Auto still had inventory. They cross-reference this valve with several others and they all match the PNs given for the B28 can. I have two on order.

 

As for the original question regarding streetability: My recent road trip yielded fuel consumption just slightly better than 20.5 MPG (U.S.). That would be a personal best in the economy game. All highway cruise: 75 MPH, 2600 RPM, 13-14" of vacuum, AFR high 15's. That was about a 250 mile sample of super highway.

 

Not bad at all and thanks for the info on the vacuum can.

 

Once the can is in and installed I'll post on results and comparisons. Probably a couple of weeks. Here's hoping we're not buried in snow before then. It's coming...

 

I have this cam in my stroker 408. I could DD this cam no problem, its quite reasonable.

 

Yes, I can imagine it being even more reasonable with the additional cubes.
I am noticing problems with the power brakes though. At it's lowest idle, with the current vacuum advance arrangement, vacuum is at or below 7". That's problematic as the brakes start to get a very low pedal and very little assist.
Once I get the timing fully sorted out, I expect idle vacuum to be a couple of inches stronger and that may alleviate the braking problem.

 

Slowly getting dialed in.
I picked up a B28 vacuum advance canister. With that can, vacuum starts to pull in advance at about 4". The full 16 degrees is deployed by about 8". At the moment, that allows for 32 degrees of total idle timing. Idle RPM is 850 RPM and idle vacuum is a rock steady 9". There's more in there too. I'd like to restrict the available mechanical advance in the distributor. Currently I'm running the largest limiting bushing but I still have 18 degrees available. I'd like to limit that to 16 or even 14 degrees, and add the extra to the initial timing. That should perk up the idle a noticeable amount. I just have to work out a way to limit the advance.

 

Hey Skinny, on a totally unrelated topic, I'd like to see a pic of your Hurst Dual Gate shifter set up. I'm going to be installing a new shifter soon and while i'm leaning towards the B&M mega shifter, the Hurst Dual Gate is a contender.

 

Anything in particular you want to see? Being buried under the shifter plate and centre console hides the shifter itself.
By the way, where did you find one? My understanding is they are becoming difficult to locate.

 

Just wanting to see how it looks installed in the console. I haven't bought a new shifter yet, but Summit sells the B&M for the third gens; not sure about the Hurst.

 

You may not have heard of Lars grimsud but his a tuning expert and he developed a advance stop for the vacuum advance. Mostly because of low octane fuels we have today the older canisters added to much advance compared to what we need today. Now his device I believe is for the vacuum canister advance slot. But you should contact him and see what he suggests for limiting the mechanical advance only.

Email him at: V8FastCars@msn.com

Hope this can help.

 

I am familiar with Lars Grimsud. It was one of his papers that provided the part number for the vacuum advance unit I'm using now.

http://www.crankshaftcoalition.com/w...ance_Specs.pdf

As for the limiter, up until I installed this B28 can (which has the ideal spec), I had been using Cranes adjustable kit.

https://www.summitracing.com/parts/crn-99600-1

The amount of advance is controlled by the serrated disc. Set point is via the can itself. I found there wasn't enough adjustment provided by the set screw in the canister. It worked very well with the previous cam (XR276HR and another similar custom grind) that produced 11-12" of idle vacuum.
Limiting the mechanical advance, in the case of my MSD distributor, is accomplished by various sized bushings that limit the advance plates travel. Problem is, with the largest bushing already installed, I have more advance than I care to. Traditionally, at this point it's necessary to weld up the advance slot the appropriate amount.
Perhaps Mr. Grimsud has a different approach though. Thanks for the e-mail.

 

E-mail sent.

 

I believe this is the approach I'd take on it.

 

This will have to wait now. New developments have changed the order of operations.

https://www.thirdgen.org/forums/tran...goes-bang.html