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Old 09-19-2008, 08:48 PM
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350 power estiment???

Hello everyone, I was just wondering if you guys could help me estimate the hp and torque of our 350 chevy engine and a few smaller things I could do for extra power. Iím just trying to get a rough idea, because Iím always having people ask me about my project and of course one of the questions is how much HP will I have????

First of all I have a stock fresh remanufactured 350 out of a 1977 chevy c-20 camper special. Everything is stock on the engine except the carb, itís a quadrajet off of a 68 pontiac and itís a 800cfm carb, it replaced the original chevy carb. I donít know if that will make any difference or not???

Since the GVW of the truck was 8200lbs it has no SMOG crap on it. No cat., no smog pump, no EGR, etc, also there is no air conditioning. I know on chuckschevytruckpages they list the 350 for these regular trucks at for 175hp and 275 ft-lbs. Since I donít have any of the smog stuff I should be getting more than that correct???? But how much more???

Also what would your guyís estimate for power on my stock engine with a set of headers and a good exhaust be??? Right now Iím not sure if Iíll be going with shorty headers or full lengthÖ. Weíll have to see what will fit on our beetle on an S-10 or blazer chassis.

Iím not wanting to put heads or a cam in this engine, Iíll keep it mostly stock, this is just going to be a toy and I donít need huge amounts of powerÖ. Iíd rather put the money in the rest of the project.

Would it do any good to put an Edelbrock performer intake manifold on this engine what kind of performance improvements would I see with my setup, if any. If itís not going to do much for me Iíll just pull the stock intake off and take it to work and glass bead it and paint it, while I have it off is there anything I could do to improve the stock manifold???

Just one last thing and then I promise Iím done asking questions for now
The fuel pump is the one from before the engine was rebuilt and at least 10 years old. I figured I might as well spend the $21 for a new fuel pump while I'm at it. Would it do me any good to replace the mechanical fuel pump with a high performance fuel pump??? Or will it do me basically no good with a pretty much stock engine???


Thanks for all your help, I really appreciate it!


Talk to you all laterÖ

bye

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Old 09-19-2008, 09:30 PM
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Quote:
Originally Posted by zbhover
First of all I have a stock fresh remanufactured 350 out of a 1977 chevy c-20 camper special. Everything is stock on the engine except the carb, itís a quadrajet off of a 68 pontiac and itís a 800cfm carb, it replaced the original chevy carb. I donít know if that will make any difference or not???
Probably not. The engine only sucks in what it needs, and that engine probably only uses about 450 cfms of the available flow. You might actually pick up torque and not lose any HP by going with a 2bbl.

Quote:
Since the GVW of the truck was 8200lbs it has no SMOG crap on it. No cat., no smog pump, no EGR, etc, also there is no air conditioning. I know on chuckschevytruckpages they list the 350 for these regular trucks at for 175hp and 275 ft-lbs. Since I donít have any of the smog stuff I should be getting more than that correct???? But how much more???
Ditching the cat probably gives you a couple hp, but at the 175-hp level its not much of a restriction. Ditching the air pump probably gives you .00426 hp. The EGR costs no HP and in fact is a real helper on the MPG battle. You might consider adding it back on if its there. Emissions equipment was incorrectly blamed for all the low HP in the 70s and 80s, but in fact it was the low compression, small cams, and the fact that in 1971 they started rating HP a different way. The same 300 hp muscle car engine in 1970 might have been offered again in 1971, but it was now advertised at 230 hp with the new rating method.

Quote:
Also what would your guyís estimate for power on my stock engine with a set of headers and a good exhaust be??? Right now Iím not sure if Iíll be going with shorty headers or full lengthÖ. Weíll have to see what will fit on our beetle on an S-10 or blazer chassis.
Again, at the 175 hp level, it doesn't take much exhaust to be adequate. Headers that are full-length and small tube will always be a benefit. Keep the exhaust small-ish; no more than 2" duals or a 2.5" single should suffice. Headers and 2" duals should be good for an honest 5 hp/10 tq. I'm assuming this is going in a custom application from your description? If so, the chances of finding headers that will fit are very slim. Try to resist getting "shortie" headers just because they fit. Its true they can be better than manifolds in some situations, but for any HP they add they'll take away torque.

Quote:
Would it do any good to put an Edelbrock performer intake manifold on this engine what kind of performance improvements would I see with my setup, if any. If itís not going to do much for me Iíll just pull the stock intake off and take it to work and glass bead it and paint it, while I have it off is there anything I could do to improve the stock manifold???
The performer might help a wee bit, but don't expect wonders. The stock intake isn't that restrictive. Maybe 5 hp? I would just stick with stock since you already have it. An aftermarket intake in your case wouldn't add enough to be worth the $150. Very poor HP to $$ ratio.

Quote:
Would it do me any good to replace the mechanical fuel pump with a high performance fuel pump??? Or will it do me basically no good with a pretty much stock engine???
Nah... as you know the carb has bowls that get filled as needed. The pump itself doesn't add any performance, it just fills the bowls. So, as long as it can fill the bowls faster than the engine sucks them dry, a stock pump is plenty good at keeping up with your demands. Going bigger will only lighten your wallet.

If you went with a Performer intake (5 hp), headers and exhaust (5 hp), illegally ditch the cat, (3 hp), and
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Old 09-20-2008, 11:40 AM
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Her is some more info I got, that a few other people said might help out with figuring out what I can get out of my engine and what I might want to do with it. Its looking like I might have to start looking into swapping out the cam


I pulled the drivers side valve cover off and the casting # on the head was 333882, so it looks like I have those better 882 heads. On a side note everything looked VERY clean under the valve covers, although it should with only 5000-6000 miles on everything....

I also checked the compression on all 8 cyls because a couple people said that you might be able to estimate the compression ration of the engine with that info???????? Anyways compression varied between 118 PSI and 120 PSI on all 8 cyls.




Thanks again for the ideas and help.....


bye
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Old 09-20-2008, 12:34 PM
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That's good that your compression is very even. Some new engines aren't that equal. Estimating compression ratio from cylinder pressure is very difficult, but you can ballpark it if you know the cam specs.

Before you go swapping cams, check your pistons. Chances are they are dished and you have about 7.8:1 compression if its a stock rebuild. Cams have to be matched to the compression or you'll be very unhappy with the performance. Low compression means small cam. Keep it under 200 degrees of duration @ .050" and you'll be OK. Any more and you'll be very disappointed with the performance. Chances are you have a 191/194 cam in there now if its factory replacement, which is well matched to the low compression.

Last edited by curtis73; 09-20-2008 at 12:59 PM.
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Old 09-20-2008, 03:15 PM
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Quote:
Originally Posted by zbhover
Hello everyone, I was just wondering if you guys could help me estimate the hp and torque of our 350 chevy engine and a few smaller things I could do for extra power. I?m just trying to get a rough idea, because I?m always having people ask me about my project and of course one of the questions is how much HP will I have????

First of all I have a stock fresh remanufactured 350 out of a 1977 chevy c-20 camper special. Everything is stock on the engine except the carb, it?s a quadrajet off of a 68 pontiac and it?s a 800cfm carb, it replaced the original chevy carb. I don?t know if that will make any difference or not???

Since the GVW of the truck was 8200lbs it has no SMOG crap on it. No cat., no smog pump, no EGR, etc, also there is no air conditioning. I know on chuckschevytruckpages they list the 350 for these regular trucks at for 175hp and 275 ft-lbs. Since I don?t have any of the smog stuff I should be getting more than that correct???? But how much more???

Also what would your guy?s estimate for power on my stock engine with a set of headers and a good exhaust be??? Right now I?m not sure if I?ll be going with shorty headers or full length?. We?ll have to see what will fit on our beetle on an S-10 or blazer chassis.

I?m not wanting to put heads or a cam in this engine, I?ll keep it mostly stock, this is just going to be a toy and I don?t need huge amounts of power?. I?d rather put the money in the rest of the project.

Would it do any good to put an Edelbrock performer intake manifold on this engine what kind of performance improvements would I see with my setup, if any. If it?s not going to do much for me I?ll just pull the stock intake off and take it to work and glass bead it and paint it, while I have it off is there anything I could do to improve the stock manifold???

Just one last thing and then I promise I?m done asking questions for now
The fuel pump is the one from before the engine was rebuilt and at least 10 years old. I figured I might as well spend the $21 for a new fuel pump while I'm at it. Would it do me any good to replace the mechanical fuel pump with a high performance fuel pump??? Or will it do me basically no good with a pretty much stock engine???


Thanks for all your help, I really appreciate it!


Talk to you all later?

bye
SMOG equipment by itself doesn't reduce power by measurable amounts. There or not won't move the power output by more than a 3 or 4 in any direction.

The problem to getting more power is found in the cam and compression. The addition of the bigger carb will not realize its potential till changing the cam and increasing the compression happens. The engines from the first generation of the SMOG era suffer greatly from the factory's choices in cams, compression, and to the extent that piston crown design featuring round reliefs created cheap to make but highly inefficient combustion chambers that were given to easy detonation. It's rather like Detroit's engineers were at a loss for design solutions when lead was removed from fuels as they had for a generation depended upon lead in fuel to make up for their lack of sophistication in combustion chamber design.

So you really can't get much out of that engine without going into it. The 882 head doesn't offer much potential but you can cover its weaknesses with more compression and certainly more cam. It really doesn't take much to get 300 horses out of the 350, getting the compression up around 9 to 1 and adding a cam with only 200 degrees of duration measured at .050 inch lift is all it takes. But you should also need to improve squish/quench which are vital to getting power and attaining detonation resistance. This is rather hard to do with open chamber heads and dish pistons. In an ideal world the heads to go for would be Vortec/Fastburn style heads and the pistons would be flat-tops or D dished. The gap between the head's and piston's squish/quench surfaces would get to about .050 inch inclusive of the crown to deck clearance and head gasket thickness. These changes will add an easy 40 to 60 hp over what ever you do with the 882s and the rest of the engine. The improves heads could let you run it on regular at least midgrade with nearly 400hp if you include the changes to the Comp cam and pistons in the next couple paragraphs.

But first, by milling the 882 head .030 and using the thinnest shim style head gasket, putting in a cam like the Comp XE268H, with your big Q jet and a set of headers this will easily produce about 330 hp at an easy 5000 rpm. Not the most efficient solution but certainly effective. A set of 1.6 roller lifters will easily lift the power to 340. Beyond that you need to get serious about different heads and pistons which will let you tease 400 and on.

But there isn't much you can do with the stock cam and compression to get more power by adding bolt on stuff nor removing smog equipment (if there was any) as this isn't where the problems are with getting power out of this motor.

Bogie
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Old 09-21-2008, 02:04 PM
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Well I did a compression test again on the engine...........

Not enough sleep yeasterday I guess for some reason I checked it cold and didn't open the throttle............ I knew better

oh well..... I'll blame it on my wife, I was trying to get it done before she got home because I had to do some work on her car.....

Anyways with the engine hot and throttle open the readings ranged from 147 psi - 150psi.

After I was done checking the compression I took it for one last test drive, and its running great, even with the HEAVY truck it gets up and goes pretty good, and you can really feel it when the secondary barrels open up on the quadrajet.

I think it will be more than enough power for our 69 convertible beetle project even if we do keep it stock..... Although more power is always better right

If we come up with a little extra money sometime during the project, I'll probably get a different cam for the engine, and maybe if I get brave I'll pull off the heads and take them to work and throw them on one of our bridgeports and mill of .030" like oldbogie said. We'll see what happens along the way.

Hopefully next weekend I'll have time to pull the engine then I'll part out this truck to put towards buying a blazer for the chassis or see if a junk yard won't trade me for a blazer.........


Thanks again for all the ideas and help.


Talk to you all later...

bye

Last edited by zbhover; 09-21-2008 at 02:19 PM.
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