whitehause

I'm not trying to bring up the whole timing issue. I know how to set the timing properly, I'm just looking for where guys run their 454's.
I've got a .30 over 454, 049 oval heads, speed-pro hypers running about 9.5 to 1,Torkker II intake with a Holley 750 carb. It is in my 68 that is still using the original L71 transistor Ign.
I have it set at 12 BTC and about 34 all in, but it still feels sluggish. About how far could I safely bump it and avoid detonation. I really need to watch it with the Hypers in there.

Faster Rat

Could you hear the detonation if it were there? I know I can't on my side exhaust 427 with .030 over forged pistons and a mild Comp Cams 268H, points distributor. I started out at 34 and it too was a little sluggish. Recently tried 38 and it ran like a bat out of hell. Felt like it wanted more. Just put it back at 36 today to be safe and playing around with the idle mixtures. My friend at the local vette shop has a real '67 L88 and told me when he used to drag race it, he ran 42 and it really liked it. Probably had some good race fuel, ya think?

jnb5101

my 72 rat is very similar to your's. my engine guy recommended 36*. i took his advice (been racing since 1955). i'd rather loose a few hp than pay for a new engine. let me re-phrase that-i'd rather loose a few hp that pull that heavy piece of iron out of the car!

roger3

What cam are you running?

Not trying to steal the thread but how much hp and torque are you guys making? I am planning to build a mild 454 for my 76 vette. Any 1/4 mile times?

Roger

Les

Good question- mild is very subjective. Having cam specs would allow for a more accurate answer.

whitehause

I wouldn't be able hear the detonation either ,side pipes as well, that's why I'm looking for some numbers guys have had success with. The cam is a 268H.

midyearvette

are you running a vac. advance??

Faster Rat

I guess both Whitehause and I have the same flat tappet cam. It is only .485 lift and 268 duration, both intake and exhaust, with 110 LSA. Not much more than stock. Guys here will tell you it is "old school" and you should spend the big bucks and get a roller cam. I have stock heads, intake manifold and Q-Jet.

Here is a graph from the engine dyno with an HEI, 3rd pull after break-in:

whitehause

Yep....stock 68 transistor ign with vac advance.

midyearvette

try setting initial at 16 deg and leave the vacuum hose off and plugged....that should give you 38 total...drive the car and see how it feels, i bet it likes it.....

you may be able to run 40-42 total, i see this a lot....try it without the vac advance..only takes a few minutes.....

whitehause

I'll try 16...that's not too much more. It deffinatly wants more, I can feel that it's just not "snappy" to the throttle. More like a truck pulling trailer. It's got the power, pulls well, just doesn't have that nice quick tire chirping response that 400HP should have. I just really want to make sure and stay away from detonation. It's got those hyper pistons in it, and I hear all the horror stories of hyper pistons hand grenading under detonation. How true they are I don't know, but they have me on the cautious side.

I assume your saying leave the vac off for the run as well. If it does respond well, should I hook it back up?

midyearvette

yes, leave the vacuum off, im sure it will respond favorably as bb's like a lot of initial timing that goes away with a vac can at the dig....so, if you are at 12 deg initial, even with the vac can giving another 12 or so and say your initial is over 20 deg at idle, you are still at 12 deg when you use the throttle as vacuum drops...
try the 16-18 initial and you should NOT try it with the vac connected..it will detonate.....low and moderate compression, bb's like a lot of timing at initial and wot...jmo.....

you will have to reset the idle speed maybe....

73, Dark Blue 454

Set the mechanical (vacuum advance disconnected and plugged) to 34-36 degrees all in by 3000 RPM and let the initial fall where it falls, probably around 16~ degrees.

Then reconnect the vacuum advance to a manifold vacuum source, reset the idle speed, and call it good.

Make sure your mechanical weights and springs are able to freely work.

And make sure to run the vacuum advance on the street. It provides better off-idle performance, better cruise performance and gas mileage, and a cooler running engine. At cruise, a typical engine runs best with 50~ degrees or more advance.

Most those that don't run VA don't understand what it does and how it works.

whitehause

I plan to run the Vac advance. I think he was referring to testing the initial advance at 16 deg without inducing an over advanced condition with the can hooked up.( at least I think so) I have read the "all in is the key and don't worry about the initial" school of thought, and I agree, but at 34-35 deg all in, it still feels sluggish.
Do you know off the top of your head what your initial is Dark blue?

Jeff_Keryk

In CA with crappy 92 wannabe octane, I use a vacuum cannister with about 10* advance rated at 2" under idle vacuum. Any more and she pings under low load. Vacuum advance complements mechanical, you have to tune it just like mechanical.

lars

On that engine, bump your timing up about 4 degrees: You want about 16 initial with 35-38 total. If you run into any detonation, slow the centrifugal curve down a little to bring it all in at 3000-3200. If you don't have any detonation issues, bring the curve in as quick as the engine will take it - around 2800 would be good. Run a vacuum advance that only pulls in about 12 degrees (weld up the limit slot to hit this spec). This should run very strong, and will produce best troque and power.

Lars

whitehause

EXELLENT!!
That's exactly the kind of info I was looking for!
Thank you Lars, your a gentleman and a scholar

ajrothm

Yes. Follow Lars advice...

Also, when you say sluggish...do you mean at wot, high RPMs or the initial tip in off idle?

Personally, I would not run more the. 36* total at full load. I have played around with this on the dyno and although our combos are different, you could easily be getting into detonation and not hearing it.

I like a little more initial timing, less centrifugal and much less vac advance...if any at all. You just have to find what works on that particular engine. Also you need to verify the timing you "think" you have is REALLY what you have, especially at high rpms....that centrifugal stuff can over advance or retard timing at high rpms so.....check it high...(within reason....)

Only my dads mild 461", 9.5-1 comp, iron head BB with an old Comp 270h(next size up from yours), we had the distributor curved on a Sun machine and the timing is set at 36*, all in by 2000rpms....initial is around 20* and this car idles, runs perfect. Very responsive, very peppy at all rpms/throttle %. No vacuum advance. No detonation. Been set like this for 20 yrs.

On my BB, it is right at 10.0-1 comp, 049 heads. I run the timing locked out at 32*(no centrifugal weights...so 32* is the initial and total timing). The car runs perfect like this. Any more timing advance then this in 93 oct and the knock sensors on the dyno detected detonation. Matter in fact, I screwed up once and had the timing set at 38* and it melted a head gasket, yet I never heard a ping.

Now I also run a vac advance but I have it limited to 4.5*. That with my 32* locked gives me 36.5* at light cruise and seems to knock a few degrees off my water temps on the highway...any more then 38-39* at light cruise and it pings it's a$$ off.

You just have to play with it scientifically and see what it wants, not what other people tell you it wants...becareful,'don't melt it.

Arthur Dombroskie

What kind of quench do you have? It makes all the difference! Read up on it let me know what you learn

Arthur Dombroskie

Does any body have a pump gas Warrior?