John Swift

Hello All,
I have been working at getting my stroker timed PROPERLY! I have had a couple working with me to accomplish this through private message etc. I have it set to Jegs specs, and am pursing a a chassis dyno shop! If this is not possible then I will time the curve myself. I have been reading and digging info the subject so I can be informed. I lost track of the number of posts and articles, some extremely informative. I've read. THIS however is NOT my issue right now...

The subject seems to more of an argument then any decisive answer, and maybe there is NO cast in stone answer. I have read many, many pros, AND cons.. Maybe with my particular setup I could get something more definitive. I have a 383 stroker, 420 HP 450TQ, .MSD distributor, Edelbrock 750cfm, Cam is ground best for mid-range, and I'm running Turbo 400 with 4:10 rear end, on 17" tires. I bought the vette after the engine was installed.
I was looking through all the paperwork I received with the car....and.....
I just ran across the "Blueprint Installation Procedure" manual. Under the timing and start-up ..At the bottom after explaining the procedure..it say's in big bold letters.. "A vacuum advance should not be needed or used on BluePrint Engines".
It has an adjustable VA already and it was ported when I received the car, but I have since connected it to the manifold. When I received it it was ported, so I changed it...
Any thoughts from you pros.......??????? Or not pros..
Here is a link if anyone is interested. I also can screen shot full directions, in case anyone thinks I am taking out of context!
https://www.jegs.com/i/Blueprint-Eng...4CTC1/10002/-1

bobs77vet

vacuum advance is controlled by vacuum.....big cams sometimes produce so little vacuum you have to get vacumm advances that have the diaphragm set up for low vacuum.

many race engines only use mechanical advance. mostly people switch between ported or unported and stay with the one that runs the best....make sure you have the right vacuum diaphragm that pulls vacuum at the right spot. I had one that started pulling at 7" and was all the way in at like 9".

sounds like its just a final tuning decision and some playing around will get you there.
you need to know the specs of your vacuum can.....you can test it your self with a mity vac

cooper9811

Vacuum advance is not necessary - and keep in mind that Jegs is essentially a race shop - That is their bread and butter. AS stated above, the vacuum advance is usually not used on the strip.

Vacuum advance is a way to modulate your timing advance based on engine load. It is most useful in street driving situations. Properly set up, it should provide some additional economy on the street, and has no penalty at WOT. It can't hurt to run it.

resdoggie

As mentioned, the engine is sold for race applications and hence the way it should be setup in the instructions. Also note they recommend a 160*. A 180* should be used for non-emission, street application. If your main purpose for this engine is street, you should use a vacuum advance.

lars

See my article and comments about this subject in this recent post:

https://www.corvetteforum.com/forums...972-454-a.html

Lars

John Swift

I'm sorry Mike, A 160*, or 180* what? Must have missed that.

MelWff

page 7 states install a 160 degree thermostat, resdoggie is telling you to use a 180 degree thermostat for street applications.

John Swift

Ohhhhhhh !!!! Thermostat Got it!! Thank you Mel. Just wasn't following, sorry!

DUB

All I will say again is put it on a chassis dyno and get it tuned. I can not say that enough. Especially if you have access to a shop that has one.

This will take all of the guess work out of it and you can see what the engine is doing.

UNLESS you like to spend time trying to fix 'whatever it is' and you do not even know if that is what needs to be done.

DUB

John Swift

DUB,
I AM in the process of finding a place to chassis dyno the car. In the meantime, I'm just trying to LEARN, and asking questions, in my humble opinion.is the only way to do that other than reading etc. I also had a 1/2 hour conversation with Jegs this morning.. very informative!
.I didn't mean to offend you! My apologizes if I did!

DUB

By no means are your offending me.

I understand you are wanting to learn about what you are working on. I get that. But in doing so...I was just trying to keep you from spending a lot of time doing 'this and that' so when you DID go to a chassis dyno. All of your hard work was then changed and none of it applied to how the engine needed to be adjusted to run correctly.

Now...on the other hand..ALL of your hard work could result in an engine that DOES NOT need to be touched and it was tuned to prefect specs also.

THAT is all I was trying to do is save you a bunch of time wrenching on your engine.

I am sorry but I am thinking of it to something like this.

If you were having a black walnut table made and you go the wood in planks so they can be glued together....and you sanded on them and got them to what you felt was good enough so the wood shop could join them together and begin building your table.

And you took the wood to the wood shop and they immediately ran their hand across them and then put them through the planer. All of your hard work of sanding was a waste of time because the boards needed to be much flatter and better than what you had so you can get a table to the level of perfection that this wood shop can deliver to you.

I won't interrupt your thread any longer if you want work on your car and learn on it. Sorry.

DUB

bobs77vet

read this and all of Lars published information....it will help fill in the gaps

John Swift

DUB,
I do not want you to stop interrupting ANY of my threads!! I want your input on everything related to my car, that's why I came to you privately to begin with. I very much value your knowledge, experience, and expertise. Perhaps clarity is not my strong point. I switched gears, so to speak, and started this thread after I read Jeg's instructions to NOT run vacuum advance, to get consensus from other's of similar setup's, if they were running it or not.
I attempted to make it clear that I am no longer wrenching on the engine, just input to who may or may not run vacuum, and why. I had the engine at Jegs recommended timing a number of days ago already, and after you suggested a chassis dyno, which I totally agreed with, I haven't put a wrench on since and have no intent to.
I perfectly understand your analogy, and it makes perfect sense! Truth be told, I am not allowed to be employed, and hence on disability for reasons I explained to you. I have nothing but time to wrench, however, I still don't want to spin my wheels on something that undoubtedly will get changed!
Hopefully you will remain my mentor, so to speak !! You owe NO apologizes. If anyone does, it would be me!
ON a side note... I did find a chassis dyno place close to me. $80.00/hr, and recommend two pulls, not sure why two, but that's what I will do.

John Swift

Thank Bob and Lars for that link! It was very helpful!
I also found this to be helpful as well. I found it simple, but informative!
I'm sharing the link, so that other's with similar questions, may find helpful as well.
Thanks

http://www.gofastforless.com/ignition/advance.htm

Mike Stansbury

with my advance hook to full vaccum my idle goes way up and comes down very slow

lars

You have a mis-matched vacuum advance that does not meet the 2-inch rule. Have you read my papers? E-mail me if you need a copy.

Lars
V8FastCars@msn.com

Mike Stansbury

Yes I have, but both of my vacuum ports on my Edelbrock carb have vacumm at idle is that normal

jim-81

For what it's worth, I was told the same thing by BP and it runs great. I think I have the same engine (383, 10:1, 430HP). Thing runs like a beast!

jim-81

'John Smith' - I'm curious now, what did you end up doing? Vacuum advance or no?

lars

If you have manifold vacuum on the ported vacuum port, it means that your throttle blade opening at idle is so excessive that the ported vacuum port in the throttle bore is being partially uncovered and exposed. This is providing "partial manifold vacuum," and if you use that vacuum source, it explains your issue. The excessive throttle opening is usually caused by inadequate timing.

Lars