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Topic Review (Newest First)
08-13-2010 11:04 AM
dry There has been alot of good information passed along here and my question in the beginning was why did i not gain enough torque to break the tires loose and appreciate all of the responses.

I believe that has been answered and the answer is because of my cam choice,comp ratio, and choosing to keep stock heads along with the close ratio 4 speed. The car sounds old school good and runs extremely well from 3k up which is a good thing that the original L82 didnot do well before.

I appreciate everyones input and suggestions and think i may just rebuild the 71 rectangular port big block 454 i have in the corner over the winter to L88 standards or better (with input from the folks here) and eventually swap engines.

So for the time being it is what it is and i will just try to fine tune what i have in order to get it running as crisp as possible for what it is. I am sure it can be cleaned up a little more by way of carb tuning, initial and advance timing along with headers and exhaust.
08-13-2010 08:35 AM
topwrench OK I didnt read every comment but here is my 2 cents worth,and if someone else said this then by accident Ill repeat it.
First thing I would do is to snatch intake dizzy and heads, bring pistons(every one of them) to TDC and measure deck height, this will tell u if the eng has to pulled or not,ok so lets say you find 0 deck and a reasonable c.r. piston.
Now youll know weather problem is in top end or not.
If deck is at or close to 0 and you have flat tops,then get rid of that cam,n choose another when u put cam in,time cam "straight up",this is not just aligning timing marks and if u dont no ,ask.
2nd thing I would do after cam ,is, get rid of heads n use somethig close to mid 60s c.c.
I think the carb is no problem for now,you may want to change this to a larger carb later,650 or so,although 50 c.f.m. are really not gonna make a lot of difference.
Your timing sounds right, I take it total (mech+ initial)is about 38 or so,of course check pointer when u time cam.
With 0 deck,flat tops,good cam ,ign initiated properly,and correct intake,this engine should make that vette go pretty good,headers would definetly be a big + too.
accolades to bogie,very,very knowlegable eng builder.
Hope this helps.
08-13-2010 06:46 AM
spikebot 81
Quote:
Originally Posted by dry
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!!
After looking at all 5 pages there is a lot of good info and yes the 882 smoggers are the worst. You can build a engine that will roast the tires at will but keep in mind these older vettes where made to hook up. With the independent rear suspension and a weight ratio of 48% front and 52% rear its tough to spin em from a dead stop. My 81 has 882 smoggers on a rebuilt engine from the previous owner. With the auto trans I can get the rears to burn but it takes some doing. Hooken up with street tires is a good thing
08-12-2010 03:09 PM
dry
Quote:
Originally Posted by cobalt327
Yes, you can. 3.73 rear gears (what the OP has) is the highest you'd want to use, but to get a 9:1 first gear (considered about the highest you'd want for a good launch) will require 4.11:1 rear gears. To get a 10:1 first gear, would take 4.56's. But either of those gears will adversely affect the cruise capabilities, though- he's still saddled w/a 1:1 4th. gear, as in no OD.

But I like the way you think!
I am already at about 3500rpm at 70 mph, i really don't want it any tighter on the highway, good thought though.
08-12-2010 01:53 PM
cobalt327
Quote:
Originally Posted by bigdog7373
Just a thought: could you offset the close ratio transmission with different rear gears maybe?
Yes, you can. 3.73 rear gears (what the OP has) is the highest you'd want to use, but to get a 9:1 first gear (considered about the highest you'd want for a good launch) will require 4.11:1 rear gears. To get a 10:1 first gear, would take 4.56's. But either of those gears will adversely affect the cruise capabilities, though- he's still saddled w/a 1:1 4th. gear, as in no OD.

But I like the way you think!
08-12-2010 12:52 PM
bigdog7373 Just a thought: could you offset the close ratio transmission with different rear gears maybe?
08-12-2010 12:10 PM
turbolover Get a new cam. Don't waste your time trying to fix what you have when it needs to be changed. For 100 bucks plus a few gaskets you can fix a lot of your problems. Then tune it. Then headers when you can and tune it again.
08-12-2010 11:33 AM
ericnova72 I myself don't think the vacuum is going to get a whole lot better with the cam having 300 seat-to-seat duration. Headers would help a great deal, and so would advancing the cam 4-6 if you aren't going to change it.
08-12-2010 11:26 AM
cobalt327 Now, you do as you see fit- but there's no reason that you can't use both mechanical and vacuum advance w/that cam. Just so you know there are other options to a locked timing.

If you have a 218 degree @ 0.050" cam w/0.450" lift, it should be doing better than what you're seeing for vacuum. If you DO lock it at 36-38 or whatever (what heads do you have, anyway? lol), unless something else is wrong, the vacuum should pick up. If not, you aren't done yet!
08-12-2010 11:17 AM
dry
Quote:
Originally Posted by cobalt327
That matches up w/the following specs on a Cam Dynamics (same as Crane) cam, except for the lift:

SBC Hyd. Rough idle, 283-400CI, good mid-range torque, OK for Auto w/street perf. conv. in 327-up CI, Power brakes req. 99590-1 Vac. res. system, aftermarket carb, int, & exh. advised.
Basic RPM 2200-5200
Cam use oval/drag Series grind # 3/4 Race 300-06 H
Dur. @ .050 218* 218*
adv. Dur 300* 300*
Lobe separation 106*
running clearance hot .000 .000
Gross valve lift .450 .450


I would at least check the lift to see what you really have, as long as you are sure who's cam it is in the first place. A lift of 0.450" will be 0.480 w/1.6 rockers. Possible that's what's going on here?
You are correct the cam is 450/450 i didn't realize i hit the wrong keys I was getting flustered yesterday. I RECHECKED some numbers last night and quit going from my memory crap-------Ok the vacuum is around 7.5" and bouncing at a 750 rpm idle if you raise the idle to 1000 rpm it almost quits bouncing and holds at 10". Ok the piston numbers someone had asked for i found on a receipt from GM DIRECT and the # is 1464695-GM. I also rechecked the cold cranking pressures all plugs out and carb closed 163-165 across the board. Also i noticed my fuel pressure gauge is bouncing from 3-7lbs (i am guessing it has gone bad, its not oil filled, i plan on replacing it today for verification)This is all recent data without trying to rely on my memory as of last night.

I appreciate everyones opinions and help----as someone insinuated in an earlier post i have posted erroneous info and wasted you guys time that may be but it was not on purpose and i appologize for that!

All the most recent factual data is posted here now and it really looks like it doesn't change anything. I guess from all your opinions i will lock the timing down at 36 degrees, get a set of long tube headers and go to 2.50" exhaust pipes and deal with it. I am starting to think that with muncie 4 speed close ratio transmission and the above changes is probably going to be the best i can get with out pulling the engine down again and if i do that i might as well build a 383 which is not going to happen in the near future.

There has been a ton of $$$'s in this frame off rebuild all went well except trying to de-smog a 250 hp L82 and bump it to 375-400hp L82

Any other input will be appreciated and if not it is what is for the time being.
08-12-2010 09:49 AM
cobalt327
Quote:
Originally Posted by dry
Sorry I pulled the wrong cam # info to begin with don't know why i even had that cam # so here is the real deal...

Ok let the flaming begin F-BIRD is CORRECT! I dug thru all my paper work and found the actual Crane Cam Specs and Here they are "So does this change anything"

Series grind # 3/4 Race 300-06 H (Cam use oval/drag)
SBC Hyd. Rough idle, 283-400CI, good mid-range torque, OK for Auto w/street perf. conv. in 327-up CI, Power brakes req. 99590-1 Vac. res. system, aftermarket carb, int, & exh. advised, compression ratio 9:50 to 10:50 highly advised.
Basic RPM 2200-5200
Dur. @ .050 218* 218*
adv. Dur 300* 300*
Lobe seperation 106*
running clearance hot .000 .000
Gross valve lift .480 .480

My final build sheet reflects a compression ratio of 9.57:1

I am also going to recheck my vacuum and cranking pressures.........
That matches up w/the following specs on a Cam Dynamics (same as Crane) cam, except for the lift:

SBC Hyd. Rough idle, 283-400CI, good mid-range torque, OK for Auto w/street perf. conv. in 327-up CI, Power brakes req. 99590-1 Vac. res. system, aftermarket carb, int, & exh. advised.
Basic RPM 2200-5200
Cam use oval/drag Series grind # 3/4 Race 300-06 H
Dur. @ .050 218* 218*
adv. Dur 300* 300*
Lobe separation 106*
running clearance hot .000 .000
Gross valve lift .450 .450

Wouldn't be the first time the wrong cam was boxed and sold, because this cam would have much better vacuum than you're seeing- unless you have other problems.

I would at least check the lift to see what you really have, as long as you are sure who's cam it is in the first place. A lift of 0.450" will be 0.480 w/1.6 rockers. Possible that's what's going on here?
08-12-2010 09:15 AM
Toofun Racing
No burner vette street machine

Try this: Have the fly wheel refaced, then
Install new clutch and pressure plate and throwout bearing.
Have someone who knows what they are doing set the timing.
Do a compression check, and start thinking about worn cam lobes.
08-11-2010 11:03 PM
F-BIRD'88 if the cam in your motor is the Crane 300-06H with .480" lift
it should be this lobe
If so it does not work with low cr, bad heads or restrictive manifolds
It does not get busy till 3000+rpm
bad choice for this motor

The car stinks of gas when you shut it off cause you have disabled the OEM charcoal canister fuel evap system. The aftermarket holley 600 carb does not have provisions for this fuel vapour evap emissions device. Should have kept the origional L-82 Q JET and used it on the Qjet/spreadbore flanged version of the Performer RPM intake manifold. The old 4MV style Qjets flowed 750cfm. You took a step back using a 600cfm carb on this motor.
08-11-2010 10:24 PM
F-BIRD'88 Ya it changes things.

I am very familar with all the Crane cams past and present.
There is a inconsistancy in your specs.
That is an old "energizer" 3/4 race grind.
The .480" spec does not jib with 218@.050"

Crane has .480" hyd lobes with either 228 or 238 deg @.050"

Either of which won't have a lot of grunt below 3000rpm.
If low rpm grunt is a thing you wanted, you have the wrong cam in the car-
and the heads are killing it and the low cr is killing it.
Corvettes do not use a "log manifold" They use a ram horn style center exit
manifold on the corvette. The good (corvette) ones that make power have 2.5" exits not 2.25".

What is the actual crane part number of the cam in your motor?
Are you looking at the original Crane cam card or something written down?

The build sheet cr spec and the actual engines real compression ratio
very likely are two different things. The low cranking compression
is a good indicator of that.
From you idle vacuum it looks like you have the 238deg cam and a mechanical cr of 8.5:1 not more than 9.1:1.

you can fix this car but you first have to determine what you actually got for a motor and be willing to make some changes.
What you got so far, is not going to do what you want it to do.
08-11-2010 08:16 PM
crussell85 5 pages of posting and now the information changes. Maybe you should start over with telling everyone what your setup is all the way down to what size of tire and what fuel you run, I think it will be helpful to the people that have been trying to help you and hopefully still will.
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