So I'm in the process of building a 393ci windsor, and aiming for 8-10lbs of boost with a blower, and carbs. This is my first gas engine turbo build. The motor is a 4.030" bore, 3.85" stroke, 20cc dish pistons, .015" from the deck surface, and 60cc heads. I'm looking to run 91 octane, but e85 would be okay too, only downfall is it's not as readily available, and concerns on the actual ethanol percentage/octane rating. I'm trying to pick out a headgasket, a 0.027" headgasket gives me just under a 10:1, and a 0.047" 9.6:1.

Now this is a project car, so the blower will be a while, so was just going to run a xe285h camshaft, until I can purchase a cam and blower. So my issue here is what headgasket should I go with? I'm leaning towards the 9.6:1, but the higher compression ratio would be nicer.

And since I'm already asking questions, any cam recommendations when I do get a blower? Or any manufacturer recommendation for a custom cam?

 

Very minimal gains to be seen with that small cr change, so for me it's a fuel choice.... On just 91 I personally would want it more near 9:1, but with the e85 go for 10:1.

 

Whats the vehicle weight and your altitude? If its a lighter vehicle and your near sea level I agree with Mnlx: doesn't matter much.

 

Ok, so E85 and 10:1 w/ 10lbs of boost, I'm happy with that. The car is around 3,000 lbs., and I'm about 1100 ft above sea level.

 

Welcome to the forum.

Welcome to the forum. So are you putting a turbo on or a blower? A custom turbo cam and a custom blower cam can be different.If turbo single or twin.Multiple carbs make things a more difficult to tune.

 

The plan was originally two carbs and a blower, just for the "cool factor". But after some more research i'm leaning towards centrifugal supercharger and one carb, with a intercooler, as my cr is pretty high, and the whole heat factor. Again this is my first forced induction motor, so I should start of easy, while I'd prefer a blower, a centrifugal supercharger seems more practical.

 

Ok cool If that’s what your comfortable with. Self contained units can further simplify things since you don’t need to add oil lines to it but you are supposed to change the oil around 3000 miles or so. If your buying the supercharger setup new the belt upgrade going from standard to like a 10 rib can cost some money if you need that due to belt slippage. If it’s gilmer drive than it shouldn’t have a problem with slippage. Turbos make more power because they don’t have parasitic losses like a supercharger . If you regulate your boost at 10psi with a wastegate added to the piping and run a let’s say 16lb pulley it will spin the centri a lot quicker and get more power just don’t go over the max supercharger rpm of the unit.

 

If you're on board with e85, there's really no reason not to go blower if that's what you really want. The turbo or centri will make power more efficiently, but e85 thtough a carb is a darn good intercooler.

 

I suppose it's all going to depend on the cost in the long run, what I can find used and what not. I'm just setting the car up for forced induction, just finishing up the motor and transmission, and will have to do some rear suspension work before I go slapping a blower/centrifugal on it. I'm worried that my deck surface might not be smooth enough for an MLS gasket now, I found a .039 composite gasket, so 9.8 cr, think I'm going to use that instead, unless you have a better opinion. I will add a link to photos of my deck surface, but there are some scratches on it that I can catch my finger on, not right next to a coolant/oil port, but I really don't want to have any problems with it. I should have had the deck resurfaced,but didn't even think of surface finish, just that it was flat. No scotchbrite pads were used on it, just a razor blade, brake clean, and a hot tank. It was originally a graphite head gasket. I've had mixed opinions on whether or not to use an MLS gasket, so let me know what you think.

 

I prefer a paper gasket for a street car, but thats me. I's rather replace the head gasket then the pistons.

 

On most supercharged applications Turbo and a blower. I would run no higher than 8:1 with a dishes piston and a set of Fel Pro "O - ringed head gaskets. with the rest of valve train to match.

 

There is no reason to run compression that low. Good tuning and higher compression is going to be a lot more responsive off boost, more fuel efficient and make more power. Low CR should be reserved for extremely high boost applications and people who are unable to tune, its a relic from poor fuel quality. Even the OEM are doing it this way.

Ford Ecoboost 3.5l 10.5:1 22PSI
GM LS (You know the engine everyone is boosting to the moon) The lowest CR in gen 3 is the LQ4 at 9.4:1

 

Afraid not .I have done my research and built and driven supercharged vehicles. And with todays fuel you will have detonation issues otherwise.

 

LOL.
Fake news.

 

Nice, good job on your research. How about you go build something and stop running your mouth. Then when you actually have experience and wisdom rather than some bullshit you read on the internet that is leftover from the 70's come back and make another post. Stop spreading bad, dated info.

 

Thats rude just because I have a different opinion than you.

 

... What? 8:1 and O ringed heads. The hell? You trying to run 30 lbs of boost? This is 8-10lbs on E-85.

Oddly enough, I'm the one asking the questions here, but I think you need to be the one asking them, and doing some more research.

 

I agree with them. Fastspec2 and Ben know what they are talking about.

 

Zspoiler - CONGRATULATIONS : You are CORRECT - more so ,on the compression being LOWER - than these tinker toy 4-banger BJ queens ,thinking they know something about forced induction .
Heres a bit of INFORMATION for you girls that toot 'More Compression with Boost' ...
FACT - a top fuel nitro supercharged engine runs 6.5:1 Compression & while my Vette you see in my photo runs higher than that with 15# through a ProCharger - for just over 1000 H.P. @ the crankshaft - if I wanted more ,Id go lower compression & spin a larger blower for more PSI ... Class is over !

 

Lol... you're seriously comparing a top fuel, nitro burning engine, a procharged engine, and a pd charged engine on low boost, and think they should be built the same? Low compression for all but max effort forced induction engines went away with good ign and fuel management... welcome to the 21st century.