[1967Tempest]

My 406 is right around 8.2 SCR. Belt driven superchargers are getting pretty cheap. Was thinking of adding a 6lb job.

Is 8.2 SCR too high?

What is the cheapest route to add boost without having to upgrade EVERYTHING. I realize that I will need a blow through carb, but ignition, heads etc..

3.23 rear
4 speed. Soon to be 5 speed.

Thanks
Dave

[HWYSTR455]

Actually, that's perfect, 8.2. The engine I built for the 'bird is at 7.89, and intercooled I chose 16lbs of boost, which keeps it under the desired DCR for street gas.

With 8.2 SCR, you could run up to 10lbs without an intercooler, like 22lbs with. Obviously, the rest of the build will determine your limits. 6 is no problem with factory parts though.

Without an intercooler, aside from the brackets themselves, adding a procharger or paxton is pretty cake. Making sure your fuel system, ignition, and carb calibration is spot-on is the tough part! (Plenty of help out there for that though!)

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[1967Tempest]

Yeah, it has factory rods and crank.

Do I HAVE to get an ignition like the MSD BTM? OR can it run on HEI.

[BruceWilkie]

Originally Posted by 1967Tempest

Yeah, it has factory rods and crank.

Do I HAVE to get an ignition like the MSD BTM? OR can it run on HEI.

You can keep the HEI and run it with the BTM.

fwiw you can buy a new BorgWarner turbo S475 capable of 500-1000 HP for $650 these days. Its more fabrication though. No problem using stock log manifolds and I know of people who've had no issue using a stock performer intake.

I wouldnt trust untouched stock used rods for any build. A guy was running a turbo'd 400 with forged pistons prepped cast rods with good ARP bolts at around 700 HP but had his rev limiter set at 5000. No issues but he has since stepped up to a 455 with aftermarket rods. Cheap insurance for the money. Turbos are very easy on motors vs NA or other power adders. Largely due to higher exhaust pressures at TDC overlap that basically act like a shock absorber for the rods.

[HWYSTR455]

You can get away with running low boost on a stock engine, shoot, the H-O turbo kits went on the 'weak' 557 blocks and windowed 403 engines and survived. And by the way, think I've heard rumors that the kit from H-O is available again.

HEI is fine, but run a good coil. You want boost retard, or you will be running retarded below X boost levels that would not be optimum. Low boost, you can probably get away with it.

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[1967Tempest]

Yeah, I was always curious about the H-O kit. Seemed easy enough to add a 301 turbo kit to any poncho~!!

[BruceWilkie]

Originally Posted by HWYSTR455

You can get away with running low boost on a stock engine, shoot, the H-O turbo kits went on the 'weak' 557 blocks and windowed 403 engines and survived.
.

Yes but those engines were new or near new. IMO its a crap shoot on a 30-44 year old engine. Maybe a bit less risk as his has obviously been rebuilt at some point. If its still in good shape I still think it quite wise to at least upgrade to forged rods vs cast and forged pistons with a new set of rings. Nothing trick here just stronger parts that will allow for much more power if he decides he wants to turn it up later. Boost IS addicting! It will also be more forgiving on tuning errors or a bad load of fuel or other issue that could possibly cause a detonation issue or an over-rev.

Are you going to help him out if a rod bolt lets go? My 68 Firebird had a Pontiac 350 someone had "rebuilt" some 30k miles before I bought the car. Imagine my surprise when it blew up the bottom end while merging into traffic at about 45mph just before the auto 2-3 shift. well under 3000 rpm. No warning signs. No oil pressure issues. I bought the car from a guy about 70 yrs old who had the car for years. Poor machining of the rod throws, mains had no sign of radius, it had excess crank thrust, and rod bolts nearly fell out when I removed the caps.(finger pressure moved every one of them) It resulted in broken rods crank and block and one damaged piston. Motor was very clean inside

Again, IMO make sure the engine is sound and if your going to open it up that far to inspect it, you might just as well add the insurance of better rods and pistons. Seems foolish otherwise.

[1967Tempest]

All good points. I guess that I should start fresh. I was thinking of boosting the 326 or a 350 for the wagon.

Heavy Car!!! Needs all it has to get his ass moving!!!LOL!!!

[HWYSTR455]

Well, no pain no gain, right? I've run factory rods many, many times, in high hp configs, and as long as they're prep'd right, they're good to 500 or so ftlbs. Age has nothing to do with it, unless it's like a million years old! Heh-heh! Heat cycling tends to make them stronger actually. Factory cranks, same thing, and for the longest time, the factory rods and cranks were the only thing available. Didn't see anything about cast pistons, but newer cast pistons are way better than cast pistons in the day.

I remember B&M made a 188 blower and many were tossing those on new cars in the 70s. Yeah, they'd turn them up, and many cast pistons let ring lands go. Still, if using a cast piston of today, bet that wouldn't have been a problem at all.

Your 350 example is a poor one, since it wouldn't have mattered if it had the best rods, pistons, etc in the world, it would have still let go from poor machine work and assembly, so not sure how that applies here.

Didn't think he planned on opening it up, which is why he had low boost in mind. Simply 'adding the insurance' or rods & pistons isn't like slapping them in there, would end up like your 350 that way. Turns into a full build at that point, defeating the purpose of a simple bolt on.

Honestly, to get first hand info, call Procharger or Paxton, see what they say. Obviously they can't take every factor into account, but they certainly have a sea of examples to pull best-case scenarios from.

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[1967Tempest]

That is true. I will call them. I think both of you make good points. Yes stock stuff will take some boost and be ok, AND boost is addictive.

So Sure 6LBs is great. but then an underdrive pulley can get me 10. Then what? I guess I will prep the engine for boost on build.

[HWYSTR455]

Originally Posted by 1967Tempest

.... I guess I will prep the engine for boost on build.

That obviously is the best approach, and what Bruce was trying to point out. I was just trying to say that for a simple bolt-on kit, you can get away with, though there are obvious risks.

If you're building, you still have limits. Factory blocks and a little padding, 700 ft lbs is about it (650-750hp). And that's with all the 'tricks'. (partial fill, billet caps, stud everything, etc). If you plan on going 10 psi or more, chose the piston wisely. Ross makes anything, and they actually have a nice off the shelf boost piston for pontiacs on a 680 rod. (Ring land is lower, thicker crown).

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[BruceWilkie]

Originally Posted by HWYSTR455

That obviously is the best approach, and what Bruce was trying to point out. I was just trying to say that for a simple bolt-on kit, you can get away with, though there are obvious risks.

If you're building, you still have limits. Factory blocks and a little padding, 700 ft lbs is about it (650-750hp). And that's with all the 'tricks'. (partial fill, billet caps, stud everything, etc). If you plan on going 10 psi or more, chose the piston wisely. Ross makes anything, and they actually have a nice off the shelf boost piston for pontiacs on a 680 rod. (Ring land is lower, thicker crown).

.

I'll add that a turbo build can hold up better. Part of the reason for that is the cushioning effect of exhaust pressure against the piston. Second reason is you dont need high rpm to make huge amounts of power. Belt driven blowers also introduce stresses on the nose of the crank especially as boost is increased putting loads where they dont normally exist. NA motors need to turn high rpm to make big power and that stress is the horsepower limits we see there.

Turbo69bird runs a studded 2 bolt 455 with cast crank, a good set of H-beams, forged pistons stock 6H heads and a T88 turbo. 9 second car, pump gas and for several years a regular old performer intake and blow-thru 850 carb. He has done a bit of home porting and switched over to Accel EFI and on baseline tune about the same mph as before. There are quicker combos out there running far faster at same or higher weight living fine on a stock block based foundation. MartyP was over 1600 hp for 3 seasons with a very well prepped 67 400 block. (Not suggesting you attempt that but its been done)

BTW my point on my 350 was just because something was rebuilt and seemed fresh and problem free didnt mean that everything was ok. Learned long before that that if you are going to step up significantly from where you have been its a wise idea to make sure what you have is up to the new tasks it will see.

[bryansMtngto]

turbos and blower both make good power. I think turbos take more initial work to get installed. With the pipe work and re routing. at lower boost dont think either really puts more stress then the other. 6-71's have come down in price and there's a few out there. Still love the look of a roots blower sticking thru the hood. You can definitly do a small turbo cheaper thou still then a blower unless oyu get into all stainless piping and such. I ran a Dyer's on a 350 Chevy back in the 80's what a blast. Which ever way you go. I would definitly consider redoing the bottom end atleast, with Either Eagle or Ohio crankshaft kit. I really dont trust the stock rods at all. JMO