I just recently got a hold of a b&m 144 for my l69. Ofcourse it has the 416 heads with the 9.5.1 CR. That's a little high for a S/C but I could get by with a 4lb pulley and 92-93 pump gas. I have a set of 350 Heads rebuilt 3 angle valve job, springs installed for a lunati voodoo 60101K cam which I'd also like to use since it's virtually new. I understand that 350 heads drasticly reduce CR which I'm thinking might be good for my engine. I don't have the castings at the moment due to being at work for 5 more days. Probably 882s. Then I could run 6lbs boost maybe 7. Good, bad on this idea?

 

Let's assume the 350 heads are now at a real 74 cc, and you use the Fel-Pro steel shims. This'll put you around 8:1, so 9 psi might be a better idea.
Since it's not too late, get these valves: http://www.competitionproducts.com/S...ductinfo/8435/
then have the shop put a small 30-degree back cut on each and every one of them. Then have the heads 5-angle cut to match, with angles of 15/30/45/60/75. Then take them home, and port the exhaust ports according to this thread: https://www.thirdgen.org/forums/engi...sbc-heads.html
then polish the exhaust ports and the combustion chambers. Have them milled about 0.020", ( not 0.030" because they've probably already been milled about 0.005-0.010" in the last 30= years) and you're ready for boost.
About the cam, I suggest Lunati's 301A4LUN as being a far better match.

 

any idea what machine shop would charge to do this, rough estimate ofcourse.

 

Mostly depends if you need new seats, and the condition of your guides. Even so, this is still a good route to take.

 

ok. thank you.

 

seems as if it would cost as much to have that work done as it would to buy a set of cheap after market heads. would that be a better idea for the money? i'm not looking for anything crazy.

 

The issue here is that with boost, you need good exhaust flow. But none of the cheap iron heads available come with 1.94/1.60" valves. And the cheapest way to get that is to just have a local shop do it to whatever 350 heads you already have, so long as they're not the crack-prone 624 heads.
If you're willing to step up to a 350, then you could use these 180cc heads: http://www.competitionproducts.com/P...fo/223200080A/
They're very good, and $380/pr. bare, but the 2.02" intake valve size won't go with your 305.
If you go with the first plan, I'll type you out what to ask your local shops. If you go with a 350 and these good heads, you'll need forged dished pistons.
Going with a 350 has the other advantage of letting you move up to roller lifters.
With the 350-headed L69 and 9 psi, I'd expect about 350 real horses at the crankshaft. With this new plan, I'd expect 550 real horses at the crank, still on pump premium unleaded.

 

i see. i thought 2.02 valves would work so long as the cam didn't lift above .45 lift or so. i saw a comp cams cam that was .44 int/exh figured it would well with the 350 heads. i input all my

 

data and the cam with that lift showed the best hp/torque curve for a max rpm of 6k at 4psi. that's what got me thinking i could throw those heads on temporarily with that cam for lower c/r until i

 

can buy a gm crate engine for 1600 or a rebuilt l98. just looking to slap something together and make 300 to the rear wheels. the car currently has lt's and full exhaust, 670 holley, and performer rpm

 

intake. the car currently pulls gtps and mustang gts, just looking to hAng with my buddies lt1 car and my other buddies ls1 car. the car currently runs 9.5 in the 8th. figure high/mid 8s with the s/c

 

posting with my phone by the way. only lets me do 200 characters at a time.

 

If you want to put the PT heads on the L69, use either GM 12557236 or Fel-Pro 1044 head gaskets, and either of these cams: http://www.compcams.com/Cam_Specs/Ca...?csid=114&sb=2 or the GM 24502476 cam.
The GM cam is cheaper, but the COMP cam will drive better.
The GM head gaskets are also cheaper, but the gasket bore might be a wee bit small for the chambers of the PT heads, I haven't had both in my hands at the same time to check that.

 

i see. well would the 882s work as is with that 256nx cam? they have new springs, 3 angle valve job, new seals. i could do the home port and polish. get that felpro gasket. any way i could make that work for the time being. it only has to last for about 6 months. concentrating on cosmetics at the moment. did a 84 to 92 gfx swap 3 weeks ago and spent my paint money on this s/c. so the bottom is black primer. just looking to get the s/c on and working with no detonation.

 

Ok, for the 882s, use Fel-Pro 1094 head gaskets, and these valves: http://www.competitionproducts.com/S...ductinfo/8435/ and these springs: http://www.competitionproducts.com/H...uctinfo/98111/ and don't forget new lifters.
For best results, have the shop put a small 30-degree back cut on each and every valve before cutting the heads to match, they should do seat angles of 30/45/60, then a bowl hog of 75 degrees. Then mostly focus on blending the 75 into the port in the exhaust short turns, since they can't do you a 90 degree cut, that's basically what your porting is doing. Then taper the exhaust guide bosses, and lastly polish everything but the intake ports.
That'll give you the best bang for your buck.

 

what's wrong with retaining the valves already in the heads since the seals are new?

 

Changing valves won't hurt the seals, and stock exhaust valves will cost you 20+ cfm that you really need with a blower. These valves aren't that much $, either. And they're lighter, which is a nice bonus.

 

is the machine shop work difficult. the cutting of the valves and matching the heads? i have a buddy who works in one. they don't particularly do car heads but if we knew how we could probably do it. his dad owns the shop.

 

I understand the appeal of free machine work, it's why I became a machinist, but forget trying to do it without the correct equipment. Just find an automotive machine shop. You'll rest easy knowing the work was done right by experienced specialists.

 

Alright, thank you for the tips and help.

 

On the cheap, I think your original plan is a good one. Getting the compression down low is really job one with a roots blower. Detonation is the enemy and the best way to avoid it is to drastically reduce cylinder pressure.

Are the -882 heads ideal? No, they are obviously limited in flow (probably not much better than your current -416s), but they do achieve a sizable drop in compression. I calculate just shy of 8:1, with all else held constant.

The stock L69 cam is actually a decent choice for a blower. Really wide LSA and enough duration to get the job done in the sub-5500 RPM range. Maybe just put on some 1.6 rockers and call it a day.

Forget throwing any real money into the -882s. Clean up any sharp edges in the combustion chamber to ward off detonation and bolt them on. Not that a bigger exhaust valve, port work and seat work won't help, but they just aren't worth the expense in my opinion. Certainly nobody will pay a nickel more for them with the work than without when you go to sell them later.

300HP is very achievable with just the head swap and the blower (using the stock supplied pulleys). Plus MOUNTAINS of torque that will make it feel like even more than that out on the street. On a little 305 it should be pushing over 7 PSI even with the stock pulleys. But with an ~8:1 compression ratio it shouldn't be a problem.

My mild 383 blower engine in my Malibu has undergone some significant changes over the years (mostly due to me blowing it up multiple times). What I've learned is that low compression doesn't cost you any power with a roots blower. I've gone from 9.2:1 down to 8:1 and never lost any power, only improved detonation resistance. Roots setups just don't lose power to low compression the way a N/A combo does.

 

Ok, finally home. Checked the heads out, they are in fact 882's. So After reviewing, i'd make more hp with the 882's 8-9lbs of boost be less detonation prone and probably be able to achieve more timing, than my 416's under 4-5lbs boost. Correct?

 

In general, yes. More boost is going to have a larger effect on power output that a point or two of compression.

 

Went to buy my gasket set. We couldn't locate the felpro 1044 head gasket you spoke of at advance. So we just assumed using the 350 heads i'd need a 350 head gasket set. Was this a correct assumption or do I need to go back and get a 305 set? Also, I bough a holley mechanical fuel pump to replace my stock one. It does 80 ghp at 7.5psi. Holley says you need one capable of producing a constant 5 psi. I'm assuming this pump is alright for my setup. The S/c should make about 9psi on my 305 according to the pulley formulas I looked up.

 

Yes, match the head gaskets to the cylinder heads. On the cheap I have found that a set of GMPP .028" composite head gaskets works just fine. I use them on my mild supercharged 383. The price is right, too- about $32 for a pair through Scoggin Dickey.

Even a stock pump in good working condition should be adequate for what you are doing. The Holley pump should work fine, too.

 

Ok, well I got the Felpro full 350 gasket set from Advance and the holley pump to be on the safe side. $110 total.

 

So far so good. 416s are off and laying on a tarp. I'll be putting the 350 882s on tomorrow along with the S/C. I'll let you know how it goes.

 

Should look approximately like this when you're done:



That's as first installed in my Malibu before cleaning up the wire routing and things like that. I also use a QJet carb on top of mine, not a Holley. That picture is probably 7 years old and several engine combinations ago for me.

If you are using a 142/144 style blower DO NOT OVER-TIGHTEN THE BIG BOLTS THAT HOLD THE BLOWER TO THE LOWER INTAKE!!! There are dire warnings against this in the instructions and you damned well better believe them! They are FOR REAL. Despite the huge size of the bolts you want to tighten them ONLY "SCREWDRIVER TIGHT." And I mean that literally- use a screwdriver handle to tighten them, not a ratchet handle. Over-tightening won't hurt anything when the parts are cold. But once things get hot and you lay into it a few times you can EASILY have lobe-to-case contact if you over-tighten (instantly destroying the blower). Believe me, it's nightmarishly touchy. The good news is that the big retaining bolts will NEVER back off even the slightenst bit from where you set them, so don't think you need any more torque than is necessary to retain the blower and seal the gasket underneath it.

Just a little friendly advice from someone who has been there and done that already.

Once you get it runnign and dial it in close enough to have some fun you will absolutely pee you pants when you lay through on it the first time. These little mini-blowers are an absolute hoot to drive on the street. It feels like nothing has changed under the hood until you get past about 3/4 throttle. Only then will you hear the blower whine, see actual positive boost and reach for fresh underwear. You won't need a dyno to know it's making a ton more power than before. It's just kind of "hidden" until you dig deep in the throttle.

 

Well, I'm at a stand still. I have everything back together, but my fan switch and temp guage plugs are to small for the 350 heads and I don't get paid till tomorrow. I also need a couple bolts and hose clamps. Sigh, it's always the little things that snag you up.

 

Moved the rest of this thread to the power add forum with pics. https://www.thirdgen.org/forums/powe...b-m-144-a.html