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All this work and can't even spin the tires???

13K views 73 replies 25 participants last post by  dry 
#1 · (Edited)
Long time Lurker and now need your expertise!!

Ok here is the deal, My Corvette is a 74 L82 4 Speed car 73k original miles with the 3:72 rear end I have not been happy with the performance of the L82's Bottom End Torque so some changes were made.

Block was line bored .30 over and decked. the rotating assembly was balanced, forged flat tops, Crane Fire Ball II 290H Cam (1800-5200 rpm)-224/224 duration, 107 lobe centers,454/454 lift, Performer aluminum intake, Holley 4160-600 cfm single line, 882 stock heads professionally massaged and rebuilt with bronge guides etc, stock rockers, crane matched springs,Mallory unilite mechanical advance electronic ignition factory 20 degree mechanical advance "No Curve" timing is set at 18 btdc idling at 800 rpm, nice even compression across all cylinders, runnning 92 octane.......

Here lies the problem the car starts right up no timing drag hot or cold and runs great,no pinging, no stumbles or hesitations, temp stays about 190 drives great on the road 3500 rpm at 70 mph and runs well stop light to stop light when just driving it normal.........PROBLEM is when you try to stand on it from a stop light it doesn't have enough torque to even break the tires loose....this rebuild has about 5,000 miles on it so its broke in well and i am ready to find the right tune the car sounds awesome at idle but the torque performance didn't seem to change from what it was before the rebuild!!!

What am i missing here i just can't seem to figure it out, why have i not realized a torque increase etc...

All opinions and suggestion welcome!!
 
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#27 ·
op's original post
Block was line bored .30 over and decked. the rotating assembly was balanced, forged flat tops,
I agree with what everyone's saying here about the crap heads, dog of a cam etc etc but did the machine shop really use re builder pistons with reduced height? op says forged so I doubt it but stanger things have happened. And when they decked the block surely they must have had a clue as to were the piston was going to end up in the hole, hopefully 0 to 0.015 give or take. So with any luck he can swap the cam, heads and intake as mentioned and get his power back.
 
#29 ·
oldbogie said:
My SCR calculator (static compression ratio) gives you 8.6 to 1 with flat tops and these heads with a zero decked block and .019 gasket. My conversion to DCR dynamic compression ratio gives you a useful ratio based on intake closing point and what that does to mixture density is 6.4 to 1 which is way low, the DCR needs to be around 8 to 8.5 to one. The Fireball 290 is an old design cam with too much overlap, a very late closing intake combined with relatively low lift. You really have to be careful of pistons as has been mentioned, there are short deck pistons designed to maintain stock compression with decked blocks, if you have a set of these the static compression is in the sevens or less.

A quick and dirty improvement could be to advance the cam you have from 4 to 8 degrees. You need to check for cam to valve interference before firing the engine but with the low lift that's probably not going to be an issue. This cam has a nasty sounding street idle but in the big picture is no great shakes as a performance item, it has all the bad features (rough idle, weak torque curve) and few of the good ones (top end power output). Actually you intake and carb selection are pretty good considering this bump stick.

The carb's small for this combo and the Performer leaves a lot of power on the table, the Performer RPM is a much better unit. The carb and intake you have really aren't a problem till you wind this up and this doesn't sound like it was built to wind high so changing them right now is a moot point. If you change any of this start with the intake not the carb.

I don't understand what you're saying about the ignition timing, my first impression is that's it's well F'ed Up, but that comes from my intreperation of your description. Some questions to help me;

What is the static setting in degrees?

Does it have a vacuum advance? If so how much advance for how much vacuum?

Sounds like it has a centrifugal advance, that brings the question as to how much? When does it start in RPMs? What is the rate of increase in degrees per 1000 RPM?

Do you know how much total advance there is when it's all in, that is measured degrees against RPM not guesses and not some brochure data, but real measures.


Recommendations:

I'd start with advancing the cam from 4 to 8 degrees. This results in ending the intake cycle sooner against crank degrees which will help the bottom end but hurt the top. Then! Them heads gotta go, you spent a lot of money on those things making a silk purse out of a sows ear. They're now just a shiny expensive sow's ear that's as useless as before. And give me some real ignition timing data. This cam makes for a weak cylinder charge on the bottom end it takes a lot of compression and ignition lead to overcome at least some of that. Cut back on the octane to see if you can get this thing to ping, the fact it doesn't isn't telling me what I want to know. Don't worry for a street engine it takes a lot of pinging to do any harm.

Make one change at a time and test, don't rip it apart and do a bunch of stuff then hope it all works, then you never know what did and didn't work for it.

Bogie
Ok, Thanks everyone for the input and opinions let me start by trying to answer some of the response questions.

(1) Yes it is a close ratio 4 speed winds out in 1st gear about 55 mph with a 3:72 posi.

(2) It is a Zero decked blocked but is not using short decked pistons it is using the actual factory .60 over forged replacement pistons.

(3) The 290H Cam was picked due to its nasty sounding old school street profile along with the fact Cranes profile and tech's assured me i could get some low end grunt with it.

(4) The car pulls real strong from 3k rpm on to about 5500.

(5) the intake is the performer rpm sorry i left that part out.

(6) Timing static is 18 degree BTDC +4 cam advance and the mechanical advance is factory +20.

(7) Advance is active at 850 rpm from off idle ,All in at 3200 rpm for a total of 42 degrees BTDC.

(8) There are no headers just factory logs into a 2.25" magnaflow system true dual from logs out.

(9) This a Non A/C Car so no accessories other than water pump and alternator.

****Anytime you turn the car off you smell gas--NO LEAKS or DRIPS--And you always have to depress gas pedal one time prior to starting cold or hot***

PS---Anybody has a good set of small block heads etc that WILL help my cause i have a bunch of Mk IV BBC I MIGHT be interested in trading some of it--stuff like Ross forged 51cc .60 over Pistons, Trw hyperkin .60 over, Edelbrock 7075 polished with bird catcher top, BBC Dimple rods,1971 factory replacement rectangular port heads bare castings plus manley ss valves and crower springs-plus other stuff was going to build for this car BUT think going to stay SBC....
 
#30 ·
Custom10 said:
op's original post


I agree with what everyone's saying here about the crap heads, dog of a cam etc etc but did the machine shop really use re builder pistons with reduced height? op says forged so I doubt it but stanger things have happened. And when they decked the block surely they must have had a clue as to were the piston was going to end up in the hole, hopefully 0 to 0.015 give or take. So with any luck he can swap the cam, heads and intake as mentioned and get his power back.
After sifting through all the information on this thread I'd have to agree with you Custom10 . Cam , heads , and intake will probably get him where he needs to be without starting from square one . And also the least time consuming and most economical and won't have to pull the engine back out . :)
 
#31 ·
dry said:
Ok, Thanks everyone for the input and opinions let me start by trying to answer some of the response questions.

(1) Yes it is a close ratio 4 speed winds out in 1st gear about 55 mph with a 3:72 posi.

(2) It is a Zero decked blocked but is not using short decked pistons it is using the actual factory .60 over forged replacement pistons.

(3) The 290H Cam was picked due to its nasty sounding old school street profile along with the fact Cranes profile and tech's assured me i could get some low end grunt with it.

(4) The car pulls real strong from 3k rpm on to about 5500.

(5) the intake is the performer rpm sorry i left that part out.

(6) Timing static is 18 degree BTDC +4 cam advance and the mechanical advance is factory +20.

(7) Advance is active at 850 rpm from off idle ,All in at 3200 rpm for a total of 42 degrees BTDC.

(8) There are no headers just factory logs into a 2.25" magnaflow system true dual from logs out.

(9) This a Non A/C Car so no accessories other than water pump and alternator.

****Anytime you turn the car off you smell gas--NO LEAKS or DRIPS--And you always have to depress gas pedal one time prior to starting cold or hot***

PS---Anybody has a good set of small block heads etc that WILL help my cause i have a bunch of Mk IV BBC I MIGHT be interested in trading some of it--stuff like Ross forged 51cc .60 over Pistons, Trw hyperkin .60 over, Edelbrock 7075 polished with bird catcher top, BBC Dimple rods,1971 factory replacement rectangular port heads bare castings plus manley ss valves and crower springs-plus other stuff was going to build for this car BUT think going to stay SBC....
As cobalt327 predicted that close ratio 4 speed is why it is hard to break traction .
 
#32 ·
I repeat my initial thought: Borrow a good double pumper and put it on for a test drive. I have spent hours tuning on a carb with only small improvements only to end up trying a different carb and get a huge improvement with no additional tuning. I keep a couple old non-HP racing 750 carbs around for just this purpose.
 
#33 ·
adantessr said:
After sifting through all the information on this thread I'd have to agree with you Custom10 . Cam , heads , and intake will probably get him where he needs to be without starting from square one . And also the least time consuming and most economical and won't have to pull the engine back out . :)
you're talking about at least a grand there... To save what? An unknown short block that is probably in as bad of shape as the top end.
 
#35 ·
adantessr said:
It doesn't look like an unknown shortblock to me it you look at the original post :Block was line bored .30 over and decked. the rotating assembly was balanced, forged flat tops,
Good call, I forgot that part when I read the rest. I assume the short block will match the top end, but its not always the case...
 
#37 ·
dry said:
PS---Anybody has a good set of small block heads etc that WILL help my cause i have a bunch of Mk IV BBC I MIGHT be interested in trading some of it...
You need to post this in the classified section of the Forum. At the top of the page you will see "Classifieds". Click on that to get started- the open forum is not for dealing parts.
 
#38 ·
turbolover said:
Sounds like you pissed a lot of money away on crap. Which is why it is important to be an educated consumer (I hope other can read this example and take it as a lesson learned).

As already stated, your pistons are most likely in the hole .040" or more, you're probably running a .045" gasket, you have some of the worst heads ever produced by chevy, and one of the laziest cams still sold (with WAY too much seat duration). If you tried to sell that engine you could probably only get about $250 for it as there is literally nothing of value in it.
QUOTE]

I am asking for opinions on helpful suggestions, but i think you missed something somewhere !! My short block is fresh from the machine shop and was a sub 60k mile engine when taken apart. I can't imagine a factory GM L82 4 bolt main long block with gm steel crank, pink rods, forged pistons etc would bring $250.00 bucks......Jeezzz

So flame on still needing pump gas street tune knowledge
 
#39 ·
adantessr said:
I agree . I think it will all work out for him . It sounds like he's got a good foundation to build on . Better $1000 than $3000
With what he has I would swap the cam and heads, as everyone has already stated. I can't believe any decent machinist wouldn't have said something when he was putting all that money into 882 scrap iron. And he probably paid a pretty penny for that cam when he could have gotten a much better one from Elgin, Erson, or Summit for less than $100 for the kit.
 
#40 ·
turbolover said:
I can't believe any decent machinist wouldn't have said something when he was putting all that money into 882 scrap iron.
It is NOT the job of a machinist to tell a customer any such thing. For all the machinist knows, the engine is going back into a #'s matching 'Vette. His "job" is to give the customer what he came there for- and if that's a rebuilt set of 883's- then so be it!

It is the job of the engine's owner to have done his homework BEFORE investing his cash into a less-than-stellar set of heads, IMO.
 
#41 ·
turbolover said:
With what he has I would swap the cam and heads, as everyone has already stated. I can't believe any decent machinist wouldn't have said something when he was putting all that money into 882 scrap iron. And he probably paid a pretty penny for that cam when he could have gotten a much better one from Elgin, Erson, or Summit for less than $100 for the kit.

When I knew nothing about engines and went for a rebuild, the machinist "upgraded" me to 882 heads. What a joke.
I know now to do my homework before getting things done.
No more stock heads for me.
 
#42 ·
cobalt327 said:
BS. It is NOT the job of a machinist to tell a customer any such thing. For all the machinist knows, the engine is going back into a #'s matching 'Vette. His "job" is to give the customer what he came there for- and if that's a rebuilt set of 883's- then so be it!

It is the job of the engine's owner to have done his homework BEFORE investing his cash into a less-than-stellar set of heads, IMO.
Where I come from selling something that you know is a bad deal or someone doesn't need is a violation of professional integrity. We lose a LOT of money buy not trying to sell our customers things they don't need, and in return we get a lot more customers coming to us because we run an honest business.

No one is required to have professional integrity, I've come to expect it because it is expected of me, but as Cobalt pointed out no one is required to do more than asked.

BTW "Cobalt327," is that a reference to the color, the mineral, or the car?
 
#44 ·
turbolover said:
Where I come from selling something that you know is a bad deal or someone doesn't need is a violation of professional integrity. We lose a LOT of money buy not trying to sell our customers things they don't need, and in return we get a lot more customers coming to us because we run an honest business.

No one is required to have professional integrity, I've come to expect it because it is expected of me, but as Cobalt pointed out no one is required to do more than asked.

BTW "Cobalt327," is that a reference to the color, the mineral, or the car?
So, by your criteria, it's the job of a machinist to not rebuild any heads below- what? "standard"? Or to only rebuild engines that are deemed "worthy"? Your basis of "Integrity" is flawed to the extreme- there are guys who LIKE the 883 heads- look at any bomber class/ hobby stock dirt track race and you'll see DOZENS of sets of 883's being run.
 
#45 ·
I am asking for opinions on helpful suggestions, but i think you missed something somewhere !! My short block is fresh from the machine shop and was a sub 60k mile engine when taken apart. I can't imagine a factory GM L82 4 bolt main long block with gm steel crank, pink rods, forged pistons etc would bring $250.00 bucks......Jeezzz
So flame on still needing pump gas street tune knowledge
Hang in there we do read what you are posting. Seems that you are on the right track with the swap/sell/trade idea. Unfortunate that you have to get back in there and tear down again. If you have flat tops at near zero deck you need to keep the SCR and DCR in check. You mentioned pump gas so this now becomes a balancing act between cam & heads. If you plan on an all out tire burner then you probubly won't be driving it everywhere so you can build on higher SCR/DCR, use premium and a big cam. If you plan on driving it around lots and using regular 87 gas then you have some tricky match making to do between heads/cam cause you have the flat top slugs already.
 
#46 ·
cool rockin daddy said:
Three things jump out at me. I would get rid of:

1. 882 heads

2. stock exhaust manifolds

3. 600 cfm carb

Gotta let your engine breathe if you want it to make power. Your choking that thing to death.
So even though the heads were ported and 3 angle valve job with the 2.02/1.60 valves they are still that restrictive? the block was zero decked to gain some more comp? What can be done if anything to improve my current set up for the immediate time being---Timing is 42 all in at 3200 to much? Fuel? Remember its a close ratio 4 speed.........Again i am open to all opinions and good or bad, just looking to maximize what i have right now....
 
#47 ·
dry said:
So even though the heads were ported and 3 angle valve job with the 2.02/1.60 valves they are still that restrictive? the block was zero decked to gain some more comp? What can be done if anything to improve my current set up for the immediate time being---Timing is 42 all in at 3200 to much? Fuel? Remember its a close ratio 4 speed.........Again i am open to all opinions and good or bad, just looking to maximize what i have right now....

42º is Too much, even for that engine, 38º is probably closer to what you need.

All the porting and valve jobs in the world can't make a prince out of that frog (882's). IMO a good machinist with professional integrity would have brought this up to you before you dropped all sorts of money into them. I would also change you cam. Competiton Products, Summit, and a few others sell cam kits for less than $100.
 
#48 ·
turbolover said:
42º is Too much, even for that engine, 38º is probably closer to what you need.

All the porting and valve jobs in the world can't make a prince out of that frog (882's). IMO a good machinist with professional integrity would have brought this up to you before you dropped all sorts of money into them. I would also change you cam. Competiton Products, Summit, and a few others sell cam kits for less than $100.
Thanks i will drop out some timing, I agree with you on the heads its just my "wad" has already been shot for the time being i am just trying to maximize right now. As far as the cam it is a retro old school sound and thats what i was looking for due to the # car shows and cruise nights the car sees....It pulls real hard once off the line and up through the gears. I am just trying to find some bottom end and maybe a head change is the only way i can get it. So whats your opinion on carb if the motor is being choked the death how is bigger carb going to help at all?
 
#49 ·
dry said:
So even though the heads were ported and 3 angle valve job with the 2.02/1.60 valves they are still that restrictive? the block was zero decked to gain some more comp? What can be done if anything to improve my current set up for the immediate time being---Timing is 42 all in at 3200 to much? Fuel? Remember its a close ratio 4 speed.........Again i am open to all opinions and good or bad, just looking to maximize what i have right now....
post #13 post # 13 post #13
 
#50 ·
Are you unwilling to put headers on it?? This would help a lot.

Current carb could be worked on to help, specifically the secondary spring and the accelerator pump shot.

You didn't need to buy an outdated poor cam design to get "that old school sound", a modern cam grind can give equal sound and significantly better performance.

While the 882's are not the best, with the work that has been done to them they are at least better than stock, you can work around them a little. A cam change and headers would result in a 50hp/75 ft.lbs gain.

If you have to stay with the exhaust manifolds, look at cams for manifold rules circle track racing, they can help.
 
#51 ·
(1) You stated that the compression readings where even across all the cylinders..................What was the pressure reading?

(2) What do the plugs look like? White, Black, Soot, oily, Powdery?


(3) Do you have a vacuum Gauge? If so, what is the idle reading? Does it bounce, or is it steady?

(4) Was the mark on the balancer checked to see if the "zero" was in fact at top dead center? 42* sounds high unless the outer ring has slipped.
 
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