Can we talk about 350 ci power

[cooters]

im not going to get into a long drawn battle but here it is. V advance comes in where mechanical advance doesnt have enough prm to push the weights out. Here is the test, do a timing test on your truck or car at 3000rpm then disconnect the v advance and tell me if the number is the same. If your car will even run at 50 degrees nevermind while pinging like crazy, consider it a bonus. Just try it. Maximum advance is max advance, the rotor can only advance as much as mechanicaly alowed due to design. take the cap off and turn the rotor, thats max advance.

[cooters]

without getting into a major discusion on timing, a motor will not run at 50 degrees advance, keep in mind 50 degrees of crank rotation means on a 350 spark would happen when the piston is .966 inches from the top of the cylinder. 34 total degrees timing is with mech and v advance

[Billla]

Originally Posted by cooters

without getting into a major discusion on timing, a motor will not run at 50 degrees advance, keep in mind 50 degrees of crank rotation means on a 350 spark would happen when the piston is .966 inches from the top of the cylinder. 34 total degrees timing is with mech and v advance

We'll have to agree to disagree. If an engine is > 3000 RPM steady-state with full mechanical advance in for a total of 36 degrees, is there manifold vacuum? If so, what is the vacuum advance doing at that point?

In any case, this is all well-documented in the notes I attached.

[stsalvage]

HELLO ALL i WAS READING ALL OF YOUR POST AND i THINK A FEW OF YOU HAVE CHIMED IN AND HELPED ME SO I'M TRYING NOT TO HAVE ANY ONE THROW A BRICK AT ME BUT I HAVE A 1965 3/4 TON LONG BED AND I'VE USED THIS TRUCK FOR THE BETTER PART OF 17 YEARS HAD 2 ENGS IN THIS BABY THE ONE I STARTED WITH WAS A WORE OUT 327 7 YEARS AGO I GOT A REBUILT FROM A ENG SHOP 350 2OO HP MABEY 220 I RAN A 4V COVETT RODCHESTOR CARB IT DID FINE WHEN I CHANED ENGS I UPDATED TO HEI BIGG DIFFRENCE MADE THE TRUCK PULL HARDER AND JUST MADE LIFE EASYER ON ME I WENT TO A 600 ELDALBROCK CARB AND INTAKE MAN IT COOL THE TRUCK DOWN 5-10 DEGREES AT 110 DEGREES DAYS HERE IN CALIF OUT HERE IN THE DESORT HEAT IS A ROBBER OF HORSE POWER


NOW I GOT A 1971 3/4 TON THAT A FRIEND OF MINE HAS AND HE WAS HAVING THE SAME PROBLEM AS YOU WHEN HE GOR HIS NEW ENGINE IT HAD NO BALLS SO HIS FATHER HAD A 1986 CAMARO 305 ENG THAT WASTED THE CRANK BUT THE HEADS WHERE NEW SO HE THOUGHT THE TRUCK HEADS WHERE JUST NOT UP TO PARE SO HE DROPED THE 305 HEADS ON THE 350 IT HAD A VERY MILD RVCAM IN IT AND MAN LETS PUT IT THIS WAY HE RUNS THAT 87 OCTANG IT PINGS AT 89 IT DOSE BETTER 91 GRATE SO THE CHEEP WAY MIGHT BE THE 305 HEADS THERE GOT A BIGGER CC CHAMBER LIKE 194 I THINK BUT HIS TRUCK PULLS LOADS AND RUNS FINE IT RUNS A LITTLE HOTTER BUT NEVER BLOWN A HEAD GASKET AND YES GET THE POINTS OUT OF THERE ONCE YOU GO TO HEI YOU WILL NEVER GO BACK

[WorkinLonghorn]

Thanks STSalvage. I've been sitting on the fence for a year now about whether to get an HEI,and now I think I will,only from a junk yard I think.Hopefully find one with good bushings etc.
I may look at re-jetting and other performance optiond for the Q-jet when it comes time to pull that trailer.
As to distributor timing advance,I believe the centrifical advance advances the actual lobes,whereas the vac advance pulls the plate with the points around,so you actually do get centrifical plus vacuum advance simultaneously at certain RPMs and part throttle.-cougar

[cooters]

305 heads do not have 194 valves, they have 184 or smaller valves. as for chamber a 601 head is a small chamber while a 416 head has a large chamber i agree that v advance can add to mech advance if you have a diaphragm with low vacuum operation. when total timing is set, you need the v advance connected.

[Green Machine]

Billa is right about mechanical and vacumn advance. You could weld the mechanical advance weight and the vacumn advance will still work. Yes mechnical advance moves the rotor and the pole piece clockwise causing advance. The vacumn advance moves the pickup coil counterclockwise causing advance. One is not tied into the other, but related of course.

[cooters]

if you weld the mech advance you will have no advance at wide open throttle so this only works in circle track racing. Every setup is based on a specific application but the main principles apply

[WorkinLonghorn]

OK,thanks for the replies. I may need a new damper because all the timing marks are WAY off.This is the way it came back from the shop.
Also that original 4MV Q-jet seems to rum real lean because when i start off under partial throttle it kinda sea-saws between power and lower power until I'm well under way.It's very pronounced. I checked and double checked float level and put in a kit but it still happens so I'm thinking it needs re-calibrating.
I just went out to get a casting # but it is blank.And I notice the pad is the short style from later engines.Probably not even a 4-bolt.
>>To give you some idea of how professional this guy was he just cut my AC lines to facilitate engine removal.
I am now drooling over the idea of getting some new Vortec heads with the settlement money. Would add some good HP right?

[Blue85]

sorry to hijack, but how is total timing determined? I have never used a timing light on a vehicle, always powertimed, don't most timing tabs only go to like 6 or 8 degrees. Can't believe i'm asking this question lol.

[Billla]

I would double, double check the damper before assuming the marks are way off. I wouldn't say it can't happen - it does - but I see other issues way more commonly when these don't line up.

I would definitely sort out the timing before getting into the carburation - this is a broad generalization but the timing is way easier to get baselined and by doing this first it ensures you're not chasing timing demons by adjusting the carb.

A blank casting number?

Vortec heads are great heads for the money and flow as well as some of the aftermarket iron heads. I wouldn't expect a significant HP gain without a cam in the .450+ range; stock Vortecs are lift-limited to .475 but there are a couple of ways around that.

[Billla]

Originally Posted by Blue85

sorry to hijack, but how is total timing determined? I have never used a timing light on a vehicle, always powertimed, don't most timing tabs only go to like 6 or 8 degrees. Can't believe i'm asking this question lol.

I posted a thread on this with attachments; worth a search.

To set total timing, you need either an advance timing light or a degreed balancer - along with accurate TDC indexing.

http://store.summitracing.com/egnsea...115+4294853094

http://store.summitracing.com/egnsea...115+4294840140

[WorkinLonghorn]

Vortec heads are great heads for the money and flow as well as some of the aftermarket iron heads. I wouldn't expect a significant HP gain without a cam in the .450+ range; stock Vortecs are lift-limited to .475 but there are a couple of ways around that.

Thanks Billa. I called the local Chevy Dealer and the guy in parts says the vortec is ONLY for f.i. engines so forget it.(!) So I called a "performance" GMC place and they said $650 a pair assembled or $1250 for aluminum but those have an even smaller comb. chamber.
>>Let's say I'm 8.0-1 now with 76 cc heads,the vortec cast iron heads are 64cc so I will be going up,which is good.
The cam i'm looking at is Comp Cams High energy 260H that has 4.40"lift.

[Billla]

Originally Posted by cougar

Thanks Billa. I called the local Chevy Dealer and the guy in parts says the vortec is ONLY for f.i. engines so forget it.(!) So I called a "performance" GMC place and they said $650 a pair assembled or $1250 for aluminum but those have an even smaller comb. chamber.
>>Let's say I'm 8.0-1 now with 76 cc heads,the vortec cast iron heads are 64cc so I will be going up,which is good.
The cam i'm looking at is Comp Cams High energy 260H that has 4.40"lift.

Sometimes you don't get the best answers from non-GMPP Chevy dealers. Summit and SDPC sell these for ~$580/pair/assembled. I have to assume the aluminum heads he's talking about are the "fast burn" heads w/62cc chambers - I haven't used those heads but in that price range I would start looking hard at other aftermarket heads. Opinions vary, but I frankly don't see a lot of sense in aluminum heads in a truck unless you're into flow numbers that can only be accommodated w/high-end heads...which are usually aluminum. In my opinion, the adages that aluminum heads allow higher CR and allow the engine to run cooler have been completely debunked in the last year or so with some good magazine tests.

Changing the chamber cc from 76->64 nets about a .9 increase.

Good pick on the cam - you *might* want to consider the 12-231-2 or 12-235-2 4x4 cams unless you're going to be revving into the 5's on a regular basis.

[mnunn454]

Originally Posted by cougar

Yeah,there's something fishy here because with original motor I ran it at TDC as specified.Now it's so far advanced it's off the scale.I'd need timing tape just to see where it is,It's about on the top of the damper at idle.I can't remember if I had that damper re-worked,I think they just put a sleeve on it or something.(for the oil-seal surface)....-cougar

You may be onto something here. If the damper's timing mark is now in the wrong place you could be running very retarded timing w/o knowing it.

Suggest pulling #1 plug and insert a plastic straw. With a buddy bumping the starter with the key until the straw is extended fully and before it starts retreating. Is the TDC mark on the balancer lining up with (somewhere close to) TDC on the timing tab? If not, you've found the source.

No problem though. Rather than changing balancers or timing tabs (you can if you want) I'd just advance the timing by 2 degrees at a time until I noticed it pinging a tad only when romping on it under load. Then I'd stop there and make a note of what the marks say for future reference.

Regarding compression ratio, 8.0 sucks for any engine (It's about right for a supercharger though ). After checking out your current head casting numbers to get a handle on chamber size, then you'll know if you need pistons or heads to get the C/R back into the 9.5 to 10.0 range. If you end up having to go that deep, have the cam checked to ensure it's appropriate for your application.

Good luck.

(PS: Sure you won't consider a Blown 454?)

[67chevemall]

My guess is with the RV cam you traded a little horsepower for more torque.
As long as it isn't broken I would just drive it and put your cash into a go fast machine like a CR 500.
$0.02

[WorkinLonghorn]

OK,thanks for all the info.I may spend this w/e sorting out the timing,and yes I may just let 'er ride. Since it's not due to retire from work duties for a few more years,I may just be dreaming about major improvements.
Here is a picture of the blank block # pad. Now why would these shysters have to eliminate that number? It was sold as a "4-bolt",so maybe it isn't?

[bobthecop]

Sounds to me like you both lost your a$$ in this deal. lol

[WorkinLonghorn]

Sounds to me like you both lost your a$$ in this deal. lol

LOL,right.But trust me,I got the better bite.

[boraxman]

Who sold you this motor, I want to make sure I never go there

[WorkinLonghorn]

Actually I don't have a beef with them anymore,and they are run by a sort of mafia,so let's just say that if you are considering any engine work in Glendale Calif. or at a shop that gets it's engines from Glendale,drop me a PM.

[skchevota]

I would say that if you have 150psi on a compresion test then you are good there. I would definatly go with an HEI, if you get one from the wrecking yard, check the bushings and the mechanical advance, also deffinatly change the modual. They just tend to quit at the most inconveniant times. As for timeing, all 350s very depending on year mainlt due to cam profial differances. If it was a cheap rebuild, they probebly put in a regrind which is mor than likely your probluems. also I would wonder if they timed the cam properly..... BTW RV cam means nothing, they generaly use a smaller cam for more botum end torque, however this comprimises HP. Also check your carb, If it was rebuilt it could be a culprit as well. I have had more bad Q jet rebuilds in my day than I can remember. IMHO Q jets suck! I had one on a BB and it had no power and ran like crap. I put on a holly 600 and it ran great, I just think that to many people put new gaskets and a float in them and call them rebuilt, but there is useualy hadr parts that are worn after 30+ years as well. Good luck

[cooters]

q jets can be a pain but once you figure them out they work well. To go back on the great timing debate, when you set your timing at around 8 degrees base timing, then put the vacuum advance back on to achieve about 16 degrees of timing, the vacuum advance is already advanced right at idle so once you reach rpm the advance weights come out and advance the timing to a desired 34 degrees or so. The vacuum advance no longer has enough vacuum above this range. Because the vacuum advance is already advanced before the mech adv comes in, it cannot add any more advance to the timing. Just thought i would clear this up. Before changing balancers, just set the timing ahead and see how the truck responds and starts

[bigjimzlll]

Most likely the numbers are gone from the pad because when you "deck" the block(good thing) they disappear.

I personally don't like using vacuum advance. It was invented to help burn exhaust gases at just off throttle(emissions) There is no performance to be gained.

If you do use the vacuum advance, I like to limit it to 10-12 degrees advance(instead of the 20+) In a performance engine I like to limit the mechanical advance also. This allows you to run more initial advance(helps with a bigger cam)

[cooters]

im with you big jim, there is no reason to run vac adv. Got any pics of your 1/4 mile machine?