Supercharger with 9:5.1 compression!?

[Greeno42]

Seems like everyone is just not liking the iron heads and hyper pistons. These kits can be put on stock 302's and they certainly don't have those components.[ATTACH]87420[/ATTACH. ] but I do realize mine is already doubled the output from stock. Anyone run boost with hyper pistons?
Picture of my 1983 T-top GT. Hope it loads

[Ltngdrvr]

Seems like everyone is just not liking the iron heads and hyper pistons. These kits can be put on stock 302's and they certainly don't have those components.[ATTACH]87420[/ATTACH. ] but I do realize mine is already doubled the output from stock. Anyone run boost with hyper pistons?
Picture of my 1983 T-top GT. Hope it loads

And if they get run in a detonation situation then they are likely to break a piston. And of course, the 85-92 motors have forged pistons.

And 10 pounds of non-intercooled boost on a iron headed cast piston motor is begging for piston damaging detonation with the slightest miscue of the a/f ratio or ignition.

But, hey, it's your car, you go ahead and do it if that is what you think is best, even though you came here and asked what everyone else's advice was.

So, when you strap the blower on and go out and hammer it and the motor gets hurt, you can't say you weren't warned.

[Greeno42]

Thanks

[Ourobos]

I had a 331 at 10.5:1 compression, ran 92 octane, and 13 psi, made 576 rwhp. I set timing at 10 degrees base, and added time on the dyno until it didn't help. Can't remember how much total timing it finally held.

A lot of the big racers run very high compression with forced induction, it's all in the tune.

[xctasy]

I'm with the ec on this one. For three rasons. Here's why.


1. The Windsor base is a very sound one


Ford kept the Windsor engine in production beyound the Boss headed Windsor, Cleveland/351m/400 engines for one good reason...canted valve engines detonate.


The Windsors chamber (including aftermarket Windsor design variation heads in iron or alloy) don't detonate easily..it has a large threashold before incipient detonation sets in. As such, a Windsor 5.0 will take a lot of abuse. Ford found this in the PROCO days when researching with Honda the best cylinder heads and induction systems. The Windsor style head is seen on the 82 onwards 3.8 and the 1983 onwards non cross flow non canted valve head on the 2.3 HSC/HSO/2.5 ohv in line fours because its got better detonation resistance compared to the canted valve heads. Its a case of Detriot getting the data back, and ditiching the technically supperior, but operationally inferior prospect. In a race engine, the Canted valve head indeed makes much more power, but its like a pent roof twin cam head, its got no leed up defore casatrophic failure. You have cylinder wall, block, bearin and rod problems with Boss head Windsor and Cleveland engines that don't exist with the Windsor headed windsor engines. Detonation causes it all, and you have to peal back timing or go to a better block, conrod, oil delievery and con rod and crank material to hold it all together.


This makes the 289 and 302W are one of the most friendly to detonation engines ever. Only the Chevy LS engines are better, due to there Windsor 351 deck height, longer rods, better mixture motion, and construction, they are a lot nicer to boost. But there is not a huge amount in it if you use the aftermarket Windsor parts.

From memory, forged pistons on a 4" bore engine run 100 degrees centigrade lower temperatures on 1 hp per cube engines, alloy heads allow an extra point of compression before detonation onset, in some instances where mixture motion is high, 3 points up from a nominal 9.3:1 pump super diet engine. That's where there is a clear performance advantage with the 85 to 93 engines and aftermarket heads.



2. The supercharger isn't the type that makes detonation.

The type of supercharger governs the level of boost. Prochargers are very compression friendly, they are an inferior off idle boost provider. So to are the modern b&m 144...it may be efficent, but it failes to make boost, and is is not an efficent supercharger for making bg power. Since it doesn't work like most Rootes 3, 4 or 6/71's or 4/53 or 6/53's, and is more like the V 6/71...also an inferior boost pump to the 6/71 not because of its small volume per revolution, but inferior clearances and design. If the boost growth produced is more moderate than a classic GMC superchargers boost, it makes more moderate heat, and it won't detonate as much as the much more aggressive GMC cast off blowers do.


So the old rule applies for GMC blowers, which pressure in psi per degrees of temparture added, a very bad, and more inefficent than just about any other blower like M series Eatons, Lysolm, Screw or Paxton style, but they flow a massive amout of cubic inches per rev, and even on 6.5:1 compression, will trump any of the more modern blowers if they are big enough. Modern blowers don't need the compression dropped as much.


3. When detonation occurs, you have to wind back the ignition timing.I f its still iron had and cast piston at 9.5:1, then you have to use Miller Process bleed off style cam duration to reduce cold cranking pressure enough protect the engine, and that requires a specific camshaft with a dual pattern event to control bemp. In essance, the peak power on a reduced ignition advance engine set up to keep out of detonation will be a lot lower than an optimised engine with out a supercharger.