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  #16 (permalink)  
Old 04-09-2012, 10:38 AM
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Quote:
Originally Posted by 68HellCo
I've got a HO 350 (stock 350 HP) from a '69 vette with 202 heads quenched, drilled studs, plates, etc. It's got an Edel 600 carb and Holly Street Dominator intake. It's running an MSD and HEI ignition setup. It's got a performance piston kit and original pink rods put back, block bored 30 over, four bolt main, nitrided crank, and mild upgraded cam. All told, machinest said about 400HP. I've got long tube headers and two 2.25 pipes out rear. YES, 2.25 pipes. But it seem like the exhaust out the back is struggling and farting as if too restricted on the way out. When I first ran it, I had it dumping at the axle and it opened up and roared far easier, breathing well. Some of the bend around the rear axle of the exhaust looks like it accordions to 1.75 inches at corners. Should I give up on this exhaust running from the Flowmasters back and go back to the old way and dump to the axle again or is there another way to run it and keep flow? It was rumbling in the cab and loud as hell with it dumping at the axle but I miss the easy roar and quick response, performance. It seems to bog it down. It's fouling a plug a little more charcoal-like than i'd like and I got in and checked the compression on this 5k miles motor and it was 150-160 all around. I was expecting wheelies by now. Thoughts?

Thanks ...
No where near 400 HP with this set up, not near enough carb for that, you'd need 700-750 CFM. I don't think the Holley intake is all that good, this needs an Edlebrock Performer RPM. The 2.02 heads won't get close without a lot of cam. They were good heads in their day but are nearly as obsolete today as 1970's smog heads. To get 400 ponies out of a 350 with Vortec or Fastburn heads takes about 268 degrees at .006 inch and just about .5 inch lift at the valve. This combo I sight is pretty much a no brainer. But the heads and matching intake is the trick. Modern heads L31 Vortec, GMPP Vortec or Fast Burn, aftermarket heads like AFR that say Vortec type chamber is the key. Massively huge valves is sooo yesterday and not very effective. Vortecish heads with 1.94 intakes will blow a prepped set of 69 'vette heads by an easy 30 horses maybe more. You also need to really know what the cam timing and lift is, not some generalized statement that its a such and such cam; plus you need the compression. Another potential for a gross pit-fall is the piston; pistons for the SBC come in standard compression height of 1.56 inch between the pin center and the crown and they come with a rebuilder compression height of 1.54 inch which is used to restore the original crown to deck clearance on blocks that have been zero decked. If the latter piston gets used on a block that wasn't zero decked the compression is way low because now the piston it .040 to .050 inch down the hole rather than the spec .020 to .025. Standard height pistons are often used by hot rodders in zero decked blocks to pump up the compression, but that's another story. Additionally, 400 horses takes 1.6 rockers with that Comp XE268 or equivalent cam. For my money I surely would do this on rebuilt Pink rods. This is the most highly loaded part in the engine, and you're banking the wad you spent that these old critters aren't nearing the end of their fatigue life.

400 horses from a 350 needs an exhaust system of 1-3/4 inch primary pipe, long tube headers that dump into 3 inch collectors through cone reducers to 2-1/2 inch head pipes to 2-1/4 tail pipes. This needs a crossover either an H pipe up by the collector or an X pipe at midbody. I prefer good quality glass packs, just like the low rumble sound and an outlet at the rear. The rear outlet is important from a noise in the cabin standpoint and is an aid to getting the exhaust out of the pipes as there is always a vacuum behind a moving vehicle so dumping the exhaust out there is pretty much a guaranty of less back pressure, anywhere else and you need to test in a wind tunnel to be sure you're not trying to exhaust against higher atmospheric pressure than that found behind or worse into a motion caused ram pressure.

I rather think you mechanic is suffering from mid last century inflated power numbers that everybody had back then. In those days the camshaft and compression were the weapons of choice to make power, which they did at the cost of a lot of fuel. Today the game is in the cylinder head and fuel delivery this is driven by the unleaded fuel which prevents designers from just doing the simple though inefficient things to get power. Today's 'vette's will have the best of 1969 for breakfast and deliver nearly 30 mpg doing it. You can't get there with a GEN I, 350 but Vortec type heads, RPM intake and a 750 Holley will at least start to close the power gap. Wheelies ain't gonna happen at 400 horses.

Bogie

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  #17 (permalink)  
Old 04-09-2012, 07:45 PM
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Thanks Dogwater for the quick fix on the exhaust. And thanks Bogie for the the in-depth info. I know the machinist zero decked the block and built it with some particular pistons for that. As well, rolling rockers of 1.6 and drilled studs and plates. The cam had these specs:
http://www.enginepro.com/downloads/EPCatalogCams.pdf
MC1730 HYD 2 204 214 278 288 .420 .433 107 117 1500-4000 SMOOTH 817 B
His partner redid the 2.02 heads to match what he was up to. I wanted to make the best of the heads I had rather than fork out for some others. I suppose I'm doomed and should just go out and buy a brand new 500HP car and skip all this nonsense going into my 68 ElCo. Sometimes I wonder why I keep at this. Thanks for the advice, wisdom.
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  #18 (permalink)  
Old 04-10-2012, 02:54 PM
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Keep in mind that your 350 hp in 1969 was gross HP. By today's standards, it probably made 275-290 SAE net HP at best. Stock performance heads in 1969 are also usually pretty pathetic by today's standards.

I think you're probably 300-325 net HP at best when tuned properly.
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Old 04-10-2012, 04:09 PM
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Thanks for the group beat down on my machine shop's specs. I'm selling all my Chevys and buying a Shelby (new) that won't require wrenching or cussing. Been good knowing you all...
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  #20 (permalink)  
Old 04-10-2012, 05:13 PM
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Seriously? Whatever. Your machine shop did nothing but rebuild your engine. They put hopelessly outclassed cylinder heads on it, and stuffed it with a very mild camshaft. You would know that if you did a forum search on here and read what it takes to make 400 HP, let alone 450 HP.

For that matter, what made you think it was a 350 HP Vette engine? Does the engine serial # end in HW? If not, it's a 300 HP Vette motor?

You fell victim to the two things. One, the myth of the fabulous all-powerful Vette motor. Don't feel bad, people have fell for that one for decades. The other thing you fell for is thinking 450 HP engines fall out of trees. Have you looked at the specs of the GM LS3 engine in 2012 Vettes? That puts out 430 HP (SAE NET) and has direct port sequential fuel injection, heads that flow a tornado's worth of air, computer controls to make sure it runs in perfect tune, etc, etc, etc. What your shop did is nothing close. Reality check time.
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Old 04-10-2012, 05:50 PM
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Yea, somewhat. I've spent a couPle years on several projects that could all get toasted by some modern road warfare easy. So why bother anymore? I mean do I want to spend the next several years under a car or enjoying some real fun?
You are perhaps correct. I think the stamp on the block indicated as much. Kinda over it though
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Old 04-10-2012, 06:31 PM
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Quote:
Originally Posted by curtis73
Keep in mind that your 350 hp in 1969 was gross HP. By today's standards, it probably made 275-290 SAE net HP at best. Stock performance heads in 1969 are also usually pretty pathetic by today's standards.

I think you're probably 300-325 net HP at best when tuned properly.




No argument on what you posted but a definition for the gentleman should be included!

Gross hp: is measured fly wheel hp ( with no alternator, air conditioning or any add on's! robbing any power!

Net hp: is measured fly wheel hp with alternator, air conditioning,power steering and all accessories on the engine, robbing power!

rear wheel hp: is measured at the rear wheels with all the hp robbing accessories on and working, pluss the hp robbing trans, drive shaft, rear end, axles, brake drag, wheel & tire drag all robbing hp!!


So you can have 400 fly wheel hp ,325 net hp and 280 rear wheel hp. depends whos stating it and how hes figuring it ! Save some of your pocket money, put it on a rear wheel dino and start reducing the hp draining parasitic accessories and drag on the engine!!! just the fan alone can be worth up to 15 hp, change to electric water pump can be over 20 hp, no drag rear disks 10hp, 25 ohm per foot plug wires 10 hp over 300 ohm per foot, copper core plugs 5hp over resistor, etc, etc

Jester
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  #23 (permalink)  
Old 04-10-2012, 07:09 PM
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First time I've felt fortunate to have no power steering
and no a/c. Sounds like my el camino and chevelle are both
gutless heaps. Since I'm debating quitting all this nonsense and
getting some real power. A turbocharged Shelby 500 GT -- these are 500 HP. This is net, right? A/C (finally!) power steering all that ...
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  #24 (permalink)  
Old 04-10-2012, 07:54 PM
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Quote:
Originally Posted by spokes101
It was rumbling in the cab and loud as hell with it dumping at the axle but I miss the easy roar and quick response, performance. It seems to bog it down. It's fouling a plug a little more charcoal-like than i'd like and I got in and checked the compression on this 5k miles motor and it was 150-160 all around.
What the hell are you trying to say here?
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Old 04-11-2012, 05:41 AM
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Quote:
Originally Posted by 68HellCo
First time I've felt fortunate to have no power steering
and no a/c. Sounds like my el camino and chevelle are both
gutless heaps. Since I'm debating quitting all this nonsense and
getting some real power. A turbocharged Shelby 500 GT -- these are 500 HP. This is net, right? A/C (finally!) power steering all that ...
Hey now why would you want to go and do that. You know real muscle cars have push rods and boost is for diesels! Don't be mad that 40 years old engine parts especially the heads leave a lot to be desired. Get some good heads and it will be like night and day.
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  #26 (permalink)  
Old 04-11-2012, 07:51 AM
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Shelby GT500's are blown not turboed. The new one(2013) is going to be a 650hp/202mph monster.
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  #27 (permalink)  
Old 04-11-2012, 09:38 AM
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The man that built the engine said 400hp. Make him prove it, or fix it.
If it we me, I'd put a 2009 Corvette in in there.
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Old 04-11-2012, 09:58 AM
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Quote:
Originally Posted by painted jester
No argument on what you posted but a definition for the gentleman should be included!

Gross hp: is measured fly wheel hp ( with no alternator, air conditioning or any add on's! robbing any power!

Net hp: is measured fly wheel hp with alternator, air conditioning,power steering and all accessories on the engine, robbing power!

rear wheel hp: is measured at the rear wheels with all the hp robbing accessories on and working, pluss the hp robbing trans, drive shaft, rear end, axles, brake drag, wheel & tire drag all robbing hp!!


So you can have 400 fly wheel hp ,325 net hp and 280 rear wheel hp. depends whos stating it and how hes figuring it ! Save some of your pocket money, put it on a rear wheel dino and start reducing the hp draining parasitic accessories and drag on the engine!!! just the fan alone can be worth up to 15 hp, change to electric water pump can be over 20 hp, no drag rear disks 10hp, 25 ohm per foot plug wires 10 hp over 300 ohm per foot, copper core plugs 5hp over resistor, etc, etc

Jester
X2, horsepower is all in the rules of the test. Four hundred horses from a 350 is easy to do on a dyno testing for gross power. It's a lot harder to get when installed.

Bogie
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  #29 (permalink)  
Old 04-11-2012, 10:31 AM
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I wonder what the horsepower per dollar is on that Shelby GT500 versus what you got and what it could/should be.
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Old 04-11-2012, 09:46 PM
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Quote:
Originally Posted by RippinRon
Hey now why would you want to go and do that. You know real muscle cars have push rods and boost is for diesels! Don't be mad that 40 years old engine parts especially the heads leave a lot to be desired. Get some good heads and it will be like night and day.
I hear it, ha. Maybe I'm getting tired and cranky from crappy results. And endless motor and tranny swaps. Sometimes it sounds better to hang it up. But assuming this setup is roadkill, what non-aluminum heads can I bolt on (along with some other tweaks, of course) to take a bigger leap, to 500HP and 450 in torque? And not totally break the bank ... suggestions? Meanwhile, soul searching why, why, WHY do I bother ...
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