how timing effects my engine.

[Jim Comet]

How timing effects my engine or more importantly doesn't effect the cars performance. As many know I have a BP built 416 with his pro port heads, 850 dp, 12.2 to one compression and his baby roller solid cam (265/272@.050 .540/.525 lift) that made 600hp on Jays dyno. My car is a 3500lb 66 Comet with 4.11 gear, 5000 stall and 28 inch slicks. The car runs great 10.75-10.90 @122 in the quarter. My question is, I have changed the timing from 26deg to 32deg trying to either get closer to 10.50 or 11.0 for index racing at my local track. No matter where the timing is, the ET doesn't change. At least until I tried 25deg and had a bog off the line. What are your opinions on why the timing changes do not move the ET? Could it be the efficient combustion chamber? I think my next try will be a throttle stop. Next year I am going to try 29 inch slicks and see what happens. Also no matter what the timing, my 60 FT times are 1.47-1.49. Any thoughts would be appreciated. Thanks, Jim

[cammerfe]

More timing than the layout of your combustion chamber needs will simply not make more power. When I say 'layout' I mean the entirety---the space and shape in the head, the surface of the piston, the locations and sizes of the valves, the placement of the plug, et al.

On the other hand, less timing than is needed will surely make a difference, as you have discovered.

KS

[frnkeore]

Do you know or remember any timing figures when it was on Jay's dyno?

[blykins]

I see instances on the dyno all the time where timing changes really don't make a difference.   For instance, I may set an engine at 36°, make a pull, read a plug and see that I can take timing out, then do that and not see a change in horsepower.  Making a timing change doesn't always mean the engine or car will respond. 

[Barry_R]

Similar deal here.  Some combinations are just insensitive to timing, while others are very reactive.  On some tests I have seen engines where advancing the timing will improve the A/F ratio numbers, making the engine more efficient without significantly changing power.  So changing the timing made the engine "better", just not better using the measurement metric we like as hot rodders.

[My427stang]

How did the trap speed change with timing?

[Jim Comet]

All my trap speeds were 121-123 through all 15 runs over three day weekend. Sounds like my  best bet may be a throttle stop and adjust it for the 11.0 class. Jim

[blykins]

Throttle stops can be a little tricky.  Some of my guys use adjustable carb spacers.  They act as an adjustable restrictor.  You can slow down easily if you need to, no need to adjust driving style.  One of my guys can run a 6.90 but regularly runs in a 7.50 class with one.  Holds it flat on the floor and drives like normal.

If you want to go a little quicker and aim for running a 10.50 class, I would suggest some different cylinder heads or camshaft.  If you're running a 10.80 and want to run a 10.50, you're gonna have to pick up about 60 hp. 

[cjshaker]

If you want to go a little quicker and aim for running a 10.50 class, I would suggest some different cylinder heads or camshaft.

So what heads are you suggesting would suddenly pick up ET over Blair's Pro Ports?

Jim, to slow down a bit, Mr. Fotti would simply limit his throttle, and/or add a little ballast to the car. It seemed to work pretty well for him.

[My427stang]

Just a WAG here, but to get into the 10.50s I think you need to get the 60 ft down. Might need some gear depending where you are on the big end, maybe a different converter, maybe not launch it on the converter, come out a little lower rpm to use the torque multiplication? 

Just bench racing, if you have tried it all, pat me on my head and send me to get everyone a hamburger

[blykins]

If you want to go a little quicker and aim for running a 10.50 class, I would suggest some different cylinder heads or camshaft.

So what heads are you suggesting would suddenly pick up ET over Blair's Pro Ports?

Jim, to slow down a bit, Mr. Fotti would simply limit his throttle, and/or add a little ballast to the car. It seemed to work pretty well for him.

I will back up and clarify my statement.  I think a head/cam upgrade would pick him up, but I don't think he's going to get a 10.50 with *just* a head/cam upgrade.  Dropping .3 would take around 60 hp, but I don't think he's going to make that up with just the engine alone.  I think it would take a head/cam upgrade, along with maybe some converter/chassis/weight work to make up the difference. 

As far as a head upgrade, I would try some ported TFS heads and a camshaft to match, or even have Blair go back into the heads that Jim has. 

Adding ballast would certainly be another way to slow the car down consistently.  Several ways to get to that point. 

[DEANs427]

when I was running index with my 289 66 fairlane I had a 12.50 setup with a 780 carb, open headers and no added weight on good air days, if bad air, I went with my 13.00 set up, 650 carb, mufflers, and added weight as necessary to get dialed in. never changed timing. worked well for me for years.

[475fetoploader]

Do you happen to have a different torque converter to try?  I’m wondering what the rpm is through the lights also?

[Joe-JDC]

Your 4:11 gear is not  your friend with 3500# car.  Try a 4.44, or 4.57.  Joe-JDC

[Falcon67]

Throttle stops can be a little tricky.  Some of my guys use adjustable carb spacers.  They act as an adjustable restrictor.  You can slow down easily if you need to, no need to adjust driving style.  One of my guys can run a 6.90 but regularly runs in a 7.50 class with one.  Holds it flat on the floor and drives like normal.

There is a trick some use with throttle stops that is hinted at here - setting the stop to be ON for the entire run.  Some are finding more consistency by having the stop just be set to partially close and stay there.  Like the adjustable restrictor.  Should be able to quickly build a database of stop settings vs air conditions for running against an index. 

I know a lot of the X.90 classes use stops, same reason as some bracket racers.  Some of the fast bracket dragsters (and at least one fairly fast big door car that dials 7.0x in Super Pro) use the stop to make a big run at the stripe to make it hard to judge.  8.90 Super Comp running 180+ - yea, that's what.  Top Dragster people use them to not get DQ'd for running quicker than 6.10 at 220+ MPH LOL.