Break in oil will be dumped after the cam break in. Dyno runs will be on Brad Penn 10W-40 racing oil. I think we have to empty the oil before shipping to Italy. It is a shame. Aldo and I discussed oil. It is hard to get racing oil there. Aldo planned on GM EOS and regular oil at least for the first 1000 miles. Then Amsoil AMO 10W-40. 1378 PPM Zink. My machine shop guy recommended Lubriplate 15W-40 to me today as it is available there and has good zink levels. Rated SJ SL. I don't know anything else about it.

 

i talk with Kevin-63mako and he is concerned about the power numbers that the engine will show...he is right but it's my fault, not his.
63mako says that such an engine would require a 900-950cfm carb to get full potential , possibly 640hp with an open plenum intake, big carb , full timing, hi oct gas...

but I have to live with this engine...so I decided for semi open plenum intake, 800cfm DP , 98 RON gas , suitable timing, street not strip or track jetting...
this was my target.
so I expect no more than 570hp @6500rpm , full power at 6000-6200rpm, then start to drop...
It would have been great to have handy a 950cfm carb and make a power run with the motor in the FULL power mode, then switch to my STREET mode...but these jobs and parts don't come for cheap and I have to give up.

63mako probably will be not very happy...I am ...because my target to have a more streetable, hi rpm reliable, L88 updated motor is done

thoughts welcome

p.s. the original 69 L88-ZL1 was 570hp@6500 rpm with 12:1 CR , 103 oct gas and open plenum. If I'm able to get those 570hp with less street troubles, I'm happy and it's a great build

 

Hi

Well spoken. Stay realistic . No need to know the max possible if you can't use it anyway.

570 is enough. I have much less with the original L71 setup, but still too much to fully use it on the street. A 800 CFM DP will be difficult enough to tune for low RPM.
I tryed a 850 Holley DP for 1 summer and couldn't find enough benefit versus the extra fuel burn to keep it. I drove the L71 for years with a Camaro 375 HP high rise rectangular intake and 650 Holley DP and was happy with the fuel burn and power. Similar low end power range as the tri-power I use now . Only at high power ( 4000 RPM upwards ), the tri_power kicks harder.

Great thread to read, thanks for posting it.

Rgds. Günther

 

I understand. There are a lot of ways to build a motor. You can go aftermarket block. Stroker crank. AFR heads. Roller cam.

This is a nostalgic old school type build. I have seen dyno results from 524 HP to 600 for L88, ZL1 type builds. This has a little better heads than original, A little better cam, a little smaller carb and compression dropped to 11 to 1. It will sound like the original and power should be over 525 and under 600. It probably won't pull to 7000 with this carb but it will probably be a little better driver. I stopped by the shop today at lunch. It was almost ready for cam break in. I couldn't stay as I had to work but everything was on the motor and dyno hookup was done except for the exhaust temp sensors, prime and distributor hooked up. It should be broke in now. I am not working tomorrow so I will be there for the tuning and power runs.

 

BEAUTIFUL . (I know , it's my motor. in Italy we say : every child , even if ugly, is beautiful at his mother's eyes...)

 

(Quote) The spring pressures were uniform. 120 on the seat 350 open @ .600. This is between the two recommended springs from comp but don't match the pressure listed by GM for these heads but should be perfect for this application. (End quote)

Reading through this entire post quickly the above section caught my eye.

This is my own opinion here only and based on some experience I've had with some of the "F.A.S.T." class racers running stock, solid-lifter platform, LS-6's.

The spring pressure you are going to come to find is not "stiff" enough to get safely to 6500 RPM, let alone 7000??

We initially tested with the same pressures as your's and found the units would not get up to the 6500 area. When we upped the numbers to 140+ on the seat the problem went away!

You won't have enough seat pressure to keep the valve train stable, keeping the valves on the seats through the cycle, at the higher RPM band!

Those heads have the .343" stems, which helps some, but regardless of the stem size, the seat pressure should be at 140# minimum!!

This spring-pressure area can still be addressed without too much hassle, with the outers only installed. May require a different number, but a simple fix now!

Thanks, Gary in N.Y.

P.S. One other item, I didn't see your exhaust system components listed, but "on the dyno" I would recommend using the headers OR manifolds that are going to used in the vehicle? I say this because there could be as much as a 40 HP difference from the "wrong" header choices. Those dyno headers seem large, but hard to tell from photos! We recently tested cast iron manifolds against headers and found much more torque with the "factory iron" over the headers and only a "few" HP less!!

 

interesting...
on my previous L88 engine on my 69 I had hooker big undercar headers 2225, 1 1/8 prim.
now going for smaller shorter hedmans with 2" prim but shorter because of ground clearance that has become a bigger issue than max power

about spring pressure,thanks for the advise, but I leave the decisions about to 63mako and the engine builder.I think too late now for further adjustments ...anyway my engine will see seldom 6500rpm and a lower spring pressure would probably save my cam lobes...

let's say that considering my driving habits, I'm more focused on a good throttle response between 3000 and 6000 rpm.when i have fun with the car , I do a type of road racing with speeds ranging between 50 and 100mph

 

The engine is ready for final tuning and dyno. The drain under the dyno is clogged so plumber is called. Today or Monday. The springs comp recommends for this cam are 924 or 930. The springs supplied with the heads fall in between these two choices in seat pressure and open pressure.
The comp 924 spring has #112 seat pressure and #320 open pressure @ .600 lift

The other spring 930 has #153 seat pressure and #365 open pressure @ .600 lift

Your GMPP springs have #120 seat pressure and #350 open pressure @ .600 lift

The 930 spring would probably be a better choice for max rpm use but the life expectancy of the cam and valvetrain could be reduced. The supplied springs on the head are stronger than the factory L88 springs so I think they are a good compromise. I did do my reaserch on this. This said we will keep an eye on the upper RPM numbers on the power runs and see if this is an issue.
As Aldo says he does not plan on using this motor as a race engine. If he limits his RPM as he says the springs should meet his needs as they are in the range recommended by the cam manufacturer.
There are a lot of different ways to build an engine and you can always make more power. He wants the sound and manners of the L88 with good upper RPM power but is not drag racing and is also looking to have a streetable, dependable build so the 2" headers and 800 carb. Tough to have both but doing the best we can to accomplish the goals he has set.

Here is a photo of the inner springs being installed after break in.



Here it is reassembled with comp rockers reinstalled and valves set.

 

http://www.cranecams.com/?show=brows...tType=camshaft

I would send the springs back and get #953 but used a 1.925 to lower the seat slightly. Springs loose 10-15# within a year of use

 

Maybe a shim underneath would help????


JIM

 

#930 1.550 1.150 .795 Y 153 @ 1.900 383 @ 1.250

#953 1.535 1.135 .749 Y 148 @ 1.900 456 @ 1.250

With a 1.900 installed height you have 383 & 456 pounds @ a lift to 1.250 or a cam with .650 lift. the L-88 cam you chose is .564 minus the lash. So you might only have 320 & 390 pounds at max lift.

IMO - valve float is so destructive and the 390 pounds open is not much when you are talking BBC valve weight My small block has 580 pounds open as a comparison with a solid roller.

 

Not always a good plan if the springs max lift is close to the cam lift like these springs

 

not a "spring's " expert...but i argue that the measured pressure of my springs is lower than advertised...so it's not possible to rely on manufacturers' specs

the springs on my heads are those supplied with them by GMPP . here are the data I have from GMPP
140 lbs @1.94" 368 lbs per inch

63 mako. any new from Tim's shop about dyno pulls?

 

That is just simple math. 140 pounds at 1.94 installed height and a spring rate of 368 if compressed one inch. Lets say that you have .550 lift after lash. or 55% of one inch 368 X .55 = 202.4 plus 140 = 342.4 open pressure

So the Comp Cams 953 spring is 456 pounds per inch 456 X .55 = 250 plus a seat or closed pressure of 148 = 398 open

 

Aldo and I discussed this at length. This was his call. There are 2 springs recommended for this cam by comp. The springs supplied with Aldo's heads fall in between these two springs in seat pressure, open pressure and actually have a little stronger rate than the two recommended. They have only been run for about 500 miles and saved the price of buying new springs. If it was a roller cam you might want to go a little sronger but with the flat tappet design I feel comfortable with the using the spring that falls in between the spring pressures recommended by the flat tappet cam manufacturer for this cam. Just think if I made the call to go with a stronger spring and ended up with a wiped lobe on this new build. I did put a call in to Comp this morning. I talked to Red. I have dealt with him before and he is the guy that seems to be the one you can trust there. He gave me a thumbs up on these springs.
One more time through the spring pressures.
Comp 924 spring 112 closed, 320 open @.600, rate 347 advertised (recommended by comp)
Comp 930 spring 153 closed, 383 open @.600, rate 354 advertised (recommended by comp)
GMPP 970 spring 140 closed, 360 open @.600, rate 368 advertised (supplied with heads)
Actual mearurement on GMPP 12492970 spring 120 closed, 350 open @ .600

 

kevin-63mako, less than 500 miles on those springs...let's say 250 then i was forced to stop to make the new engine build. after all the troubles had , my first target is reliabilty.yes power , but first no problem with cam failure, valve lash that gets loose and so on. in terms of reliability and budget I'm fine with the GMPP springs ( they came assembled with heads at a nice price), i just aplologize that you will not see the dyno numbers that you wanted and that the engine is able to do.considering the amount of time and passion you put on it , it's not just my motor but your too. these words to thank kevin , now that we are almost at the end...

 

Just got back from the shop. Tuning. Engine runs well but have some issues. The carb is going lean. Need bigger jets on both primary and secondary. If you set the initial to idle total is too advanced. Have to reduce mechanical. This cam is really nasty. Don't even think we can run any vacuum advance on this. I don't think the original L88's ran vacuum advance and I am figuring out why now. The mechanical advance springs are too stiff. Still advancing @ 4000 rpm. Will post back when we get this sorted out. Running through a couple heat cycles and readjusting valve springs. Here are a couple teaser photos.

 

with my previous L88 engine i needed 18 deg initial timing to keep it running at 1000rpm. i measured 37deg at 3000rpm.never measured above. no pinging heard both when i had closed chambers and 11.4 CR 102oct and when i switched to open and 10:1 CR and lower oct gas

no vacuum advance

yes, i leaned the jetting a bit trying to get better MPG and to reduce the unburned gas smell at the exhausts.spark plugs looked fine, not lean, a bit rich

 

Need a B28 vacuum can. It is 5 to 6 days to get it. Not enough vacuum to run anything else. The LT1 can on the TI distributor starts at 10 and goes to 12. This thing won't pull a steady 10 pounds of vacuum at idle. Hope the headlights work. The B28 can will ship with the motor. We will get the initial and mechanical right with no vac advance and do the power runs. Bigger jets and different power valve in carb. Shop drain still clogged so didn't finish today but the roto rooter was supposed to be there today so hopefully tomorrow it will be done.

 

changing air bleeds is the best way to richen a low vacuum carb

You set the timing at 4000 and unless you alter the amount of mech advance initial falls where falls