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Topic Review (Newest First)
11-04-2012 12:24 AM
cobalt327
Quote:
Originally Posted by Clayton A View Post
Thanks guys, seems I have some work to do! It wouldn't be a project car if I didn't have things to tinker with right...
There's a chance that if the heads haven't given any indication of coil bind (broken springs, bent pushrods) or the valve stem seals being crushed out of existence by an insufficient valve spring installed height (like the engine smoking, especially at start-up), that the heads may have had the necessary mods already made to them to accommodate more lift than the stock heads will allow. I would expect the valves to have floated very easily if they were stock Vortec springs w/that cam, too- one more reason to suspect the heads might not be totally stock.

But if the seals look to have contacted the retainers or there are any other indications there's not enough clearance at max lift, there are several routes you can take to safely use more lift than the about 0.450" lift that the stock Vortec heads can handle in stock form. Read the info here for more. Another thread w/info on the Vortec head (thread has 59 pages!) is here.

But the bottom line is you may want to have the guide bosses turned down for aftermarket valve stem seals and shortened at the same time to let you use springs that will allow for more lift than the stock springs.

Be sure to check the clearances of the various points in the valve train when you mock up the assembly before final assembly. Better to find a problem before it causes damage!

Don't overlook using a tight quench distance to your advantage. A correct quench will help prevent detonation. This means you will want to measure how far down the cylinder the pistons are at TDC. This can vary due to how much the deck may have been milled as well as the compression height (CH) of the pistons. Some "rebuilder" pistons have a 1.54" CH instead of the factory 1.56" CH- this can cause the quench to be too wide unless corrected.

This barely scratches the surface but will give you a start.

Good luck.
11-03-2012 11:48 PM
cdminter59
SBC 350 Engine Advice needed

If you are worried about the bottom end being weak, check out this all forged steel rotating assembly. Forged 4340 steel crankshaft, Forged 4340 steel H Beam rods, and Forged aluminum dished pistons. Upgrade to ARP2000 rod bolts for up to 1100 hp. Eagle Competition Rotating Assemblies B12010030 - SummitRacing.com
11-02-2012 08:41 PM
BigEd36 I have to agree with Techinspector1, that is too much cam for your engine. I ran that cam in an oval track "claimer" 355 similar to your engine except it had no vortec heads. Low end power was nonexistent, it really came to life about 5500, not a hot setup in a cast crank, stock rod, cast piston engine that I didn't want to take much over about 6000 rpm so it could have a nice long life. That 355 is in the garage now, and before it goes back in a car that cam will be switched out for something with less duration.
11-01-2012 10:06 AM
oldbogie
Quote:
Originally Posted by 1Gary View Post
Bogie I get your point of a 383,but guys two yrs down the road get the etch and get bored with what they have and want more.They reach for the bottle for more and nitrous is hard on the bottom end.That's where I have a issue with building with a cast crank.It's about $300 bucks difference to get a very good forged stroker crank that will allow for the expansion of a build two yrs later.(Howards comes to mind)I suggest in builds like this a bottom end for all occasions.Yeah,upgrade rods two.Speed does cost,if the builder is coming up short on cash,he should wait and save more to get the good quality parts.After all,at the end of the day it is in his best interest.
I wouldn't disagree about the crank, but I'll say in restricted classes where a cast crank is mandtory, we've been getting excellent results with the 9000 lightweight SCAT casting against a manual gear box. These should ge further when teamed against an automatic as the shock loads are lower than what a clutch does to the shaft. But if you're going to feed it dentist juice then you're a lot better off with a forging.

Bogie
11-01-2012 08:36 AM
1Gary
Quote:
Originally Posted by oldbogie View Post
Read through all of this; for kid that didn't know what he was doing this is a damn great first effort. Now while you don't know the true compression, just that these flat top pistons rate 10:1, I'm assuming against a 64 cc chambered head, at this point the unknowns that could modify that up or down would be the head gasket thickness, deck clearance, effects of any head milling being different from the piston manufacturer's calculations. The Vortec heads would need modifications to the valve guides to accommodate this cam's lift even with a 1.5 rocker.

The parts used in this build would produce an engine that runs between 380 and 400 horses on a crankshaft dyno. I guess the real question is what do you want power wise and how do you really plan to use it. From where this is at getting more power as a 350 will take better heads and camshaft to support running the engine up over 6000 RPM, this might also need some bottom end improvements. I'd really start at the oil pan as well; this engine is standing on the edge of what is safe and reasonable with a stock pan. If it isn't done already, the bottom end needs a trap door 7-8 quart pan, a crank scraper, and a good windage tray because when the revs start seeing 6000 plus getting oil off the crank and back into the pan starts to be an edgy problem with the OEM set up to where if one thing goes slightly wrong and you own a pile of junk in less than a New York minute.

The other way to go is bigger by putting in a 383 kit. This really fattens the torque and horsepower curves without having to resort to all sorts of exotica that is necessary to get a smaller engine to this kind of power as the smaller engine must be spun faster to get the power. Spinning faster requires living with power that is weaker in the lower RPM range which drives you to lower gearing to get the revs up to where the power is. Internal to the engine it pushes into much better quality parts and balancing as the forces go up to the square of the RPMs so that which is tolerable at 5800 revs is not at 7000. The old adage that “speed costs money, how fast can you afford to go?” is more attached to making an exotic engine build power than it is to making a larger engine, which is why Detroit tended to reach for the boring bar rather than multiple Webbers and solid roller cams back in the muscle car days. In this case a 383 at 5800 RPM will be happy with a good quality cast crank for example maybe even GM powder metal rods with parts balanced to a gram or 2, a 350 turning 7000 for the same power is going to be looking at a 4340 forging for the crank and rods with the balancing done at .1 gram or better. It’s this level of better that gets expensive very fast.

Bogie
Bogie I get your point of a 383,but guys two yrs down the road get the etch and get bored with what they have and want more.They reach for the bottle for more and nitrous is hard on the bottom end.That's where I have a issue with building with a cast crank.It's about $300 bucks difference to get a very good forged stroker crank that will allow for the expansion of a build two yrs later.(Howards comes to mind)I suggest in builds like this a bottom end for all occasions.Yeah,upgrade rods two.Speed does cost,if the builder is coming up short on cash,he should wait and save more to get the good quality parts.After all,at the end of the day it is in his best interest.
11-01-2012 05:49 AM
Clayton A Thanks guys, seems I have some work to do! It wouldn't be a project car if I didn't have things to tinker with right...
11-01-2012 05:35 AM
E.Furgal
Quote:
Originally Posted by ap72 View Post
depending on the duration the cam may or may not be a good match for your heads, the lift isn't hurting anything at all.

An RPM intake will help some but don't expect a huge difference, especially at street RPM.
unless those vortec heads where machined.. that cam is stacking coils... and I'd fear bent pushrods..
10-31-2012 10:39 PM
wwilliams181 Vinnie is right .. those heads wont hold much lift.. or valve spring without some machine work the valve spring pocket and guide.. in reference to is the cam too much for the heads... i say no.. most would say the head is done at 6200.. we run a similar combo every sat. night on a dirt track.. turn the engine 7000-7200 with a 2 barrel. Some may say that that is way too high for the head and cam. We thow gear at the car until the engine runs out of breath.. that is usually around 7000 rpm. what are you really trying to do.. ? win an engine builder shoot out or have a good time with your car? I think you will be find.. make sure you dont have any clearance issues with the heads and run the thing.. If you want something better by a set of Elde Aluminum RPMS..
10-31-2012 02:38 PM
oldbogie
Quote:
Originally Posted by Clayton A View Post
I recently acquired a 1971 Chevelle from my dad!!!! The engine sounds real good but I think the combination of parts are hurting the engine more than they are helping. I built the engine when I was 18 (12 yrs ago) and didn't have the first clue as to what I was doing. Dad knew how to put an engine together so that is exactly what we did. Now at I look back at some parts I used and I think we made a few mistakes. The engine block is a 1980 - 1985 350sbc Casting number 14010207 bored .40 over. The heads are Vortec Heads (bought new from Summit) Casting number 12558062 (milled for a higher c/r) I am thinking about changing the valve springs and rockers....any suggestions?, The intake is a Edelbrock Performer 2116. The carb is a Edelbrock Performer 1406. The cam is a Crane Cam with a 516 lift (I think the lift is way to high for these heads, can't remember the duration). Stock 350 crank that I had checked by a machine shop. I don't remember the brand of pistons but I do remember they were flat top style and a compression ratio of like 10:1 (Not engine c/r but the pistons). Not sure what the actual C/R of the engine is. I plan to go back through this engine and try and get all the right parts that I need to produce the best HP.
Any suggestions on what to do to produce the best HP from this engine? I plan to re-use the heads and crank but would consider swapping out the rest. I believe my dad has a Performer RPM intake that I plan to use.
Read through all of this; for kid that didn't know what he was doing this is a damn great first effort. Now while you don't know the true compression, just that these flat top pistons rate 10:1, I'm assuming against a 64 cc chambered head, at this point the unknowns that could modify that up or down would be the head gasket thickness, deck clearance, effects of any head milling being different from the piston manufacturer's calculations. The Vortec heads would need modifications to the valve guides to accommodate this cam's lift even with a 1.5 rocker.

The parts used in this build would produce an engine that runs between 380 and 400 horses on a crankshaft dyno. I guess the real question is what do you want power wise and how do you really plan to use it. From where this is at getting more power as a 350 will take better heads and camshaft to support running the engine up over 6000 RPM, this might also need some bottom end improvements. I'd really start at the oil pan as well; this engine is standing on the edge of what is safe and reasonable with a stock pan. If it isn't done already, the bottom end needs a trap door 7-8 quart pan, a crank scraper, and a good windage tray because when the revs start seeing 6000 plus getting oil off the crank and back into the pan starts to be an edgy problem with the OEM set up to where if one thing goes slightly wrong and you own a pile of junk in less than a New York minute.

The other way to go is bigger by putting in a 383 kit. This really fattens the torque and horsepower curves without having to resort to all sorts of exotica that is necessary to get a smaller engine to this kind of power as the smaller engine must be spun faster to get the power. Spinning faster requires living with power that is weaker in the lower RPM range which drives you to lower gearing to get the revs up to where the power is. Internal to the engine it pushes into much better quality parts and balancing as the forces go up to the square of the RPMs so that which is tolerable at 5800 revs is not at 7000. The old adage that “speed costs money, how fast can you afford to go?” is more attached to making an exotic engine build power than it is to making a larger engine, which is why Detroit tended to reach for the boring bar rather than multiple Webbers and solid roller cams back in the muscle car days. In this case a 383 at 5800 RPM will be happy with a good quality cast crank for example maybe even GM powder metal rods with parts balanced to a gram or 2, a 350 turning 7000 for the same power is going to be looking at a 4340 forging for the crank and rods with the balancing done at .1 gram or better. It’s this level of better that gets expensive very fast.

Bogie
10-31-2012 01:28 PM
Clayton A
Quote:
Originally Posted by techinspector1 View Post
What I recommend is that you figure out your static compression ratio and then call up your favorite cam grinder and ask for a recommendation.
Sounds good,
Thanks!
10-31-2012 01:16 PM
techinspector1 What I recommend is that you figure out your static compression ratio and then call up your favorite cam grinder and ask for a recommendation.
10-31-2012 01:05 PM
Clayton A
Quote:
Originally Posted by techinspector1 View Post
Here's your cam.....
Saturday Night Special, Part #110691, operating range 3,200 to 6,800 rpm's.
Flat tappet hydraulic, Performance usage, good mid and upper RPM torque
and HP, bracket racing; Street, Heavy, ProET, SuperET,
etc., autotrans w/3500+ converter, oval track; Street
Stock, Enduro, Hobby, etc., 1/4-3/8mile circle track, 10.5:1 to 12.0:1 static
compression ratio advised.
Advertised duration: 294/300
Duration @0.050" tappet lift 238/244
Lobe separation angle 106 degrees

Valve timing @0.050" tappet lift:
Intake opens 17 degrees BTDC
Intake closes 41 degrees ABDC
Exhaust opens 52 degrees BBDC
Exhaust closes 12 degrees ATDC

Intake valve lift with 1.5:1 ratio rocker arms, 0.480"
Exhaust valve lift with 1.5:1 ratio rocker arms, 0.495"

So, to answer your question, would this be too much cam for these heads? The answer is yes. The heads will stall and sign off way before the cam is done pulling. You fellows have to realize that the L31 heads were designed by GM to make the proper hp and torque to haul grandma and the kids to Disneyland, not to do things like bracket racing (description of the cam above). They're great street heads and will flow better than any other PRODUCTION Chevy cast iron head, but they are not miracle heads.
When I built this engine I didn't have a clue of what I was doing and was just throwing parts together. I still don't know what I am am doing but at least now I am smart enough to ask people that do! lol What type of cam do you recommend for the heads?
10-31-2012 12:50 PM
techinspector1 Here's your cam.....
Saturday Night Special, Part #110691, operating range 3,200 to 6,800 rpm's.
Flat tappet hydraulic, Performance usage, good mid and upper RPM torque
and HP, bracket racing; Street, Heavy, ProET, SuperET,
etc., autotrans w/3500+ converter, oval track; Street
Stock, Enduro, Hobby, etc., 1/4-3/8mile circle track, 10.5:1 to 12.0:1 static
compression ratio advised.
Advertised duration: 294/300
Duration @0.050" tappet lift 238/244
Lobe separation angle 106 degrees

Valve timing @0.050" tappet lift:
Intake opens 17 degrees BTDC
Intake closes 41 degrees ABDC
Exhaust opens 52 degrees BBDC
Exhaust closes 12 degrees ATDC

Intake valve lift with 1.5:1 ratio rocker arms, 0.480"
Exhaust valve lift with 1.5:1 ratio rocker arms, 0.495"

So, to answer your question, would this be too much cam for these heads? The answer is yes. The heads will stall and sign off way before the cam is done pulling. You fellows have to realize that the L31 heads were designed by GM to make the proper hp and torque to haul grandma and the kids to Disneyland, not to do things like bracket racing (description of the cam above). They're great street heads and will flow better than any other PRODUCTION Chevy cast iron head, but they are not miracle heads. Stock valve lift was less than 0.420" with these heads and I'm really surprised that some cam grinder hasn't stepped up with an off-the-shelf hydraulic roller that will work with the stock springs and rail rockers that come on these heads. Like, you could build the motor 9.5:1 SCR and use a cam that closes the intake valve at around 35 degrees ABDC with a very short lift, like around 0.400" and make excellent power on crap gasoline. All you guys seem to think that you need valve lift to the moon, but that's not true on a daily driver. Pull your head out of your kazoo and put down the hot rod magazines.
10-31-2012 11:44 AM
Clayton A
Quote:
Originally Posted by vinniekq2 View Post
a lot of vortecs need to be modified for lift over 450. vortecs also need exhaust port work
What type of modifications? What do I need to do? I don't know a whole a lot about this subject so could you give me the specifics?
10-31-2012 11:30 AM
vinniekq2 a lot of vortecs need to be modified for lift over 450. vortecs also need exhaust port work
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