[KevinL]

I hurt a head gasket recently and would like a ballpark timing recommendation at my high boost level of 30 plus lbs boost. I use a MSD 7531 to control timing. My present timing curve starts at 31* with zero boost and retards to 20* at 30 lbs and above. Car made excellent power for 10 runs then cylinder compression found it's way into the cooling system. I've actually tried 17* total timing at 30lbs boost and car ran the same numbers as it did with 20*. I've always thought 17* total was to little timing but maybe not with my combo.
Combo is SBF 337 with TEA TW-R heads. Air/water intercooler, and 118 octane race gas. Compression ratio is 9.0, with a Jay Allen custom solid roller blower cam. Car traps at 176-179 mph. 90 Mustang 3050 lbs. I use Felpro 1133 MLS head gaskets and ARP studs on my A-4 Ford block. Airfuel ratio is 11.8 and I use 150 lb injectors at 80 percent duty cycle. Datalogged air temps start at 75 and rise to 120 by end of run. Any advice on timing would be helpful.

 

[blownstang01]

First off I will admit that I don't have experience with your combo but, I think you answered your own question...If it MPH's the same with 17 degrees as it does with 20, then run 17 and save parts.
On my set-up, I run 26 lbs. Iat's at 110 max , 11.6 AFR and 16 degrees total and never hurt a head gasket or even a plug.

 

[KevinL]

Anybody else?

 

[xpndbl3]

you ALWAYS want to run the least amount of timing to get the best mph at the track.

 

[BCCOUPE]

I was running 26* with 28-30lbs and a YSI a couple of year's ago. It was also a 337 and pretty close to the same combo. Which last year I had the same motor and a F1R, PT3000 A2W but on the run that killed the motor it made 28.50lbs of boost with 22.50* of timming. Im not saying that's what killed the motor cause it had other issues after I let a local engine builder freshen it. But Im running a 363ci motor now with a set of TEA 255 Hi port's and started the year out with that same F1R but I just swapped over to a F2 last week and havent ran it yet so Im kind of currious to see what kind of answer's you get with your question. But Ive got a question for you and that is what pully configuration are you running to make 34lbs of boost???
Thanks
BC

 

[KevinL]

I'm running a 73 tooth lower and a 48t blower pulley. I also rev the motor to 84-8500 rpm. I have also just discovered that it was a mechanical issue not a timing issue which caused my head to lift in one particular place.

 

[AJ Powell]

how big is the combustion chamber? And what do plugs look like I had a motor that loved to be 11.9 a/f but my new motor likes to be around 11:0. Every combo is different that is why all the data loggers in the world are awesome but the right way to tune a car is to read plugs!

 

[dennysavage]

you ALWAYS want to run the least amount of timing to get the best mph at the track.

WOW... Really? Care to explain that?

 

[bottlefed1]

I am no expert on centrifugal blower setups at all but if 34lbs of boost is high and you feel you are developing high cylinder pressures with normal timing here is something to ponder.

If you do not have enough exhaust side flow for whatever reason you will " stack boost" and build both high boost and high cylinder pressure. If you have the problem on the intake side you will see the high boost but not the cylinder pressure deal just food for thought. Its should be easy enough to look at just tighten your exhaust vavle lash to advance the exhaust event and see if the pressure comes down and the car picks up.

I agree 100% with the minimal timing deal. I have worked on both nitrous and blown alky cars and in my experience unless you are in a class where every last HP needs to be used both blown and nitrous cars have a point of diminished returns on timing where the last few degrees make very little difference in HP but cost big money in parts. Nitrous motors detonate and ruin pistons blown alky motors squash bearings short order and if left alone turn to wrist pins, rods, blocks<>dance the maincaps, and pistons shortly thereafter.

Richard Gavle

 

[procharged]

depends on how big the heads are and what they flow but I say 25 degrees.

 

[BBF]

You hurting it doesn't mean detonation... First of all I would not use the 7531 to control timing with boost reference using EFI just use it for gear retard. I run 25 degrees with 38 psi on C-16. Head torque should be about 120 long bolts and 110 short with moly in 20lb spreads. You could have stretched studs, block/heads need decked etc. I'm not sure if the A4 is even as thick as R block in the deck I know it's not in the bores.

 

[KevinL]

I don't really think timing was the problem with my engine. A small piece of cylinder wall actually broke off at the very top of # 2 cylinder. The block had previously been o-ringed but I had switched from copper gaskets to MLS gaskets. When I made the switch I simply removed the stainless wires and left the empty groove in the block and put the MLS gasket on. It ran fine like that for the past year. Recently, I changed heads, pulleys and changed shift points to around 8400 rpm. I was trying to max out my combo. I went from previous max boost of 27-28 lbs to 34 lbs. The piece of metal that broke off formed a wall between the now empty o-ring groove and the cylinder. Motor has been drag raced since 1997 and freshened twice. BTW head torque was 120 long/115 short. All spark plugs looked great. Block bore is 4.040.

 

[turbogt]

You hurting it doesn't mean detonation... First of all I would not use the 7531 to control timing with boost reference using EFI just use it for gear retard. I run 25 degrees with 38 psi on C-16. Head torque should be about 120 long bolts and 110 short with moly in 20lb spreads. You could have stretched studs, block/heads need decked etc. I'm not sure if the A4 is even as thick as R block in the deck I know it's not in the bores.

good info.. care to talk more about your combo? IE power adder, car weight, mph, etc... are u running the 1/2" arp head studs and using those torque figures? I have them on my r302 afr185 head motor and they are all torqued to 100lbs but i would like more if i could

 

[joemondo]

I also have old school A-4 block, o-ringed deck I use fel pro 933pt1 head gaskets. I run 28 degrees timing at wot. my blower is xx trim with 73 28 pulley. so far i have not lifted a gasket, with c 16 . How do you no how much more timeing you can throw at it , if the car is still picking up mph?

 

[morris]

how big is the combustion chamber? And what do plugs look like I had a motor that loved to be 11.9 a/f but my new motor likes to be around 11:0. Every combo is different that is why all the data loggers in the world are awesome but the right way to tune a car is to read plugs!

X2

Read plugs, run as much or as little timing as the engine wants. Increase fuel when adding timing.

 

[AJ Powell]

Steve you know the problem is that most guys do not know how to read plugs and rely soley on what the data logger says! For the life of me I don't know why people don't learn how, the internet has a lot of helpful info and everyone has it just use it!

 

[morris]

Steve you know the problem is that most guys do not know how to read plugs and rely soley on what the data logger says! For the life of me I don't know why people don't learn how, the internet has a lot of helpful info and everyone has it just use it!

Yep.
I don't even argue the timing issue with people anymore. The plug will tell you all, timing, fuel, everything.

 

[67AfroMaro]

Yep.
I don't even argue the timing issue with people anymore. The plug will tell you all, timing, fuel, everything.

Help me out... for N20, I can read plugs just fine but the timing is fixed so that it is either this on motor or that on the jug...

With the blower, you run a curve based on boost. Won't the plugs tell me that my timing was OK towards the end of the run? What about as I'm ramping it out as boost is ramping up?

 

[BBF]

Yep.
I don't even argue the timing issue with people anymore. The plug will tell you all, timing, fuel, everything.

I cut the threads off plug to read A/F... Timing can be seen on the strap... Most people are stuck on the 02 wideband as this can be off too....Most big power adder motors I've ever built will set between 20-25 degrees on good fuel so there is no big secret where to start just start conservative and read the plugs....

 

[BCCOUPE]

Any update on what you found?