Head TQ guidelines - This right Ted?

[kinger]

Thanks guys, I appreciate it!!

We should sticky the updated version be a great help to everyone!

 

[Ted Jannetty]

I love boost way more than nitrous oxide, because after helping boost 2000 Harleys when I was involved with Aerodyne I'm still amazed at how stock parts keep up with big boosted HP, as long as deto is avoided.

According to Corky Bell (HP books "Maximum Boost") if you double a stock engine's HP with turbo boost you only increase peak combustion chamber pressure by 20%. But at 90 degrees ATC the turbo adds 100ish% to stock pressure so the huge boost in torque is mostly from the added pressure well beyond 15 degrees ATC.

But if you experience detonation from poor gas or poor tuning that peak combustion chamber pressure will occur way before 15 deg ATC instead of 20% increase perhaps 5x increase worst case?

So if you have good tuning, good gas stock cylinder studs are adequate and in my opinion even better for boosted engines. Justin Fuller has made 450 HP with stock studs on my dyno, tuned perfectly, no need for any added strength there. Plus stock studs will stretch appropriately as the aluminum head grows, maintaining even pressure on headgasket seal. Unyielding monster studs will not stretch as cylinder grows with normal heat, and that cylinder will grow regardless of wether it has stock studs or 1" diameter studs. So growing stock studs increase clamping pressure as they stretch, and the monster studs stretch very little so head sealing surface distortion is likely.

Then if you detonate from bad gas or bad tuning the BEST thing to happen is head gasket blown. The headgasket acts like a safety relief valve. If you detonate someting WILL give. Piston, block, cylinder head, nothing will contain detonation for extended periods.

Excellent follow up Jim, I couldn't agree more.

Ted.

 

[dynotechjim]

My pal and Adirondack Shootout partner George Taylor worked with me when we were doing Aerodyne turbos for Harleys. George had a 80" DynaGlide stock pistons stock studs stock fiber headgaskets he made 160hp Rear Wheel dynojet, stock was 50hp (3 times stock HP). But no deto due to smart george spending only a few seconds at a time at that HP on pump gas. For six second dyno runs race gas only and all was well for several years of that sort of abuse. No problems.

But many other turbo harley guys had deto issues at 90 HP. Turbo Baggers with loud radios and riders wearing those goofy beany helmets made hearing the clicks of deto impossible. So headgaskets would blow from deto, and too often they would replace the stock fiber gaskets with copper gaskets. So next instead of blowing the headgasket the studs would pull the threads out of the crankcases. And pistons would break sending chunks of aluminum through the turbo. So instead of a $100 headgasket replacement they had a $4000 case, piston and turbo replacement.

Deto will wreck everything if it needs to to get that monstrous pressure out of the combustion chamber as it tries to drive the piston back down the bore as the peak pressure of deto arrives WAY BEFORE top dead center.

And you guys buying race gas in supposedly sealed 5 gallon cans beware. Three weeks ago Glenn Hall came to tune a F1200 Boondocker turbo for a Michigan customer. We began tuning with Glenn's own nitrogen pressurized race gas, all was dandy, then the owner came with 10 gallons of turbo gas he bought from a large VP distributor in Detroit. A few runs after pouring in the new supposedly 116 octane gas problems arose. Surging on the dyno as we approached 300 HP, blew a headgasket (oring) from deto. Glenn replaced that Oring and we switched back to Glenn's racegas and all was dandy, tuned another 50.

That $10 rubber oring surely saved the engine/ turbo from severe damage.

Now I have copper tubing we bolt to the engine connected to earphones and that deto is loud and scary sounding to the guy listening. From now on all turbo and nitrous engine dynod here will be listened to by the owner/ tuner.