I am putting together a 383. It will have forged rods and pistons. The pistons will have a 31cc dish as this is for a blown application. I will be using a cam that most of you would say is way too small but the result is that the max RPM will be a bit below 6000. Now for the question, to get the compression I want and minimize the quench zone so there is a reduced chance of detonation, the deck height will be 9.000 and if I use the Impy head gaskets I will have only 0.028" for the quench. I realize that if this were a motor that was reved high this would be a no-no but with the forged internals and low rpm I was thinking that this may just live for a long time. What do you think? This is for my daily driver so I am trying not to build a tempermental motor.

Thanks in Advance
Tim

 

i think detonation is your "real" enemy. what cam? dynamic compression? Static compression?


big cams in blowers isn't a good thing. As rich pointed out a while back-
hopefully he can explain why i again if your really currious. I understand why but i dont think im qualified enough to explain it.

roughtly thoug, charge builds up and then you open the intake... then exhaust. you just want the intake open long enough to get the "charge" in there. any longer and its not really effective.

 

What's the compressed thickness of the gasket you are using?

You decked it .025 then, so you're sitting zero deck correct?

I'm not TOO positive on the LT1's, but the standard Ford gaskets are .041 compressed, so one would deck the block to have the piston .005 out of the hole to have a nice and safe yet tight .036 quench.

I wish I still had the thread on the corral about quench, it was pretty good, I'll see if I can dig it up.

 

I would lose no sleep over a .028 quench height in a forged-bottom-end-motor that's only going to see 6k.

I've run a few thousandths looser quench than that shifting at over 7k and never had any problems. Of course you don't want to flog the motor while cold but that's common sense.

Well, not for your competition. You might be surprised at how large a cam many of the fastest blown street cars are actually running.
There's two philosophies there as with just about everything.

-Mindgame

 

big is a relative word buddy

i was thining 236/244ish as big

 

I think my Cub Cadet as a bigger cam in it than that Trey.

All depends on how much hp you wanna make.

-Mindgame

 

your nuts

although in have only read about "theories" in blowers,
i dont see myself going with bigger than a 224/236 cam in a car i'd intend to s/c.

then again repends on the pully and my goals again. but a high revving blower isn't what i'd want for street anyway..

 

Keeping the LSA wide enough on a blown motor is very important, maybe even more so than the duration. If the LSA is correct, it will prevent you from blowing your boost out the exhaust, even with hefty duration number. Which is why Mindgame is correct in stating that some of the very fastest cars are running big cams with their blowers.

 

One reason I didn't mention my cam was because I knew it would get most of you laughing at how small it is. Mindgame spoke about a 236/244 grind being smaller than the one in his Cub Cadet. Then the one I am going to use is probably too tame for his lawn mower. It is a Comp Xtreme set of lobes that are only 214/224@.050, a 114 degree LSA but with a bunch of lift. I want to blow a lot of air/fuel in and hold it there while it burns and makes power. I will get the power with that cam and a fair amount of boost. Two things to remember. I want a civilized car and I have to pass California smog testing. If it idles like stock all the better. I think there are a few people around here who have made some good power with a blower and cams like this one.

To get that small a quench zone I would be going with a zero deck and Impy head gaskets (compressed thckness is about 0.028"). That would give me right at a 9.0:1 static compression ratio

 

I've ran as tight at .029 with my old solid roller 383, shifting at 7k+, and there was never any signs of the piston contacting the head.

I would suggest running the Fel pro head gaskets because I believe they are better suited to a forced induction setup, and .039 quench is still very good (and what many consider ideal).

BTW, I like your cam choice.