SBC timing issue

[Ericnova]

Downloadable and printable degree wheel link below.
Print it out, cut it out and glue it to anything round and stiff enough to put a crank bolt hoke through the middle and survive....plastic picnic plate, disposable pie tin, pizza pan, cookie sheet, cheap frisbee, a single 12" square vinyl floor tile, whatever you can figure out.

http://www.tavia.com/free_degree_wheel.html

Now all you need is the piston stop and the dial indicator and base.

[Baprace]

Hello all. I have a new 388 sbc scat 6" bottom end,DSS flat tops, Profiler 64/195's and a Howards 110981-08 HFT cam. I let the mach shop assemble
the shortblock. So I get it home and start to put it together and notice the cam is in straight up ( I asked for +4 ). OK I thought we'll see how it runs.
Get it in the truck drop the dizzy in at 6 before and it won't start and acts like it wants more timing. So we pull the dizzy and give it another notch
on the gear, motor then lights up and cam break in proceeds with no issues sounds good no heating ect. Shut down and inspect for leaks and
when we try to restart it kicks back and won't start, back off timing it fires up drive around block revs ok seems down on torque. Won't start the
next morning kicks back and blows the gear off the starter. Ok so I go to starter store and return with the mondo geardrive starter, this starts it.
By now I'm freaking out as we've timed a million sbc's with a vac gauge and never had a problem so I put my old timing light on it and it says
30 before! I go get my buddy with his good timing light and it reads the same. The camshaft has to be really off for this to happen,Right? What if they
installed the crankshaft gear @ 4+ and installed the chain & cam gear straight up could it cause this? I did not check the key index at the crank. I'll
be taking it back apart as soon as I can get some help or my sore back allows. Anyone have any ideas about or seen this before? Thanks in advance
for any replies.

I reread your first post, you could be onto something with using the correct dot on the crank gear, meaning if the engine is assembled using the +4* keyway slot on the crank gear, you must use the correct +4* dot on the crank gear to align with the cam gear dot, if the crank gear is using the +2* keyway slot then you must use the +2* dot on the crank gear to align with the cam gear dot. take your time with checking the cam timing , if you have any issues , stop and get back on this site and let the experts help you out, if you are not completly sure OR don't quite understand the language being used then ask again, better to lose a week of racing than wrecking a new race engine.

[F-BIRD'88]

With your love of BIG midrange torque and instant throttle response you went the wrong way on the new cam choice .
No amount of twisting around that bigger duration cam will change that .
You will be MUCH happier with a shorter duration cam
The Isky 274H Mega cam I pointed out will rock in that motor with the Weiand T Ram in that lil truck.
It will GLH. Ditch the cam u got.
#201274 Spend your money where it will do the most good.

[madmooney]

I got a couple of buds coming over to help me pull the pan and covers ect, but it will be next week. I hope we find something
staring us right in the face when we get it tore down.I think I need to give this cam a chance as the next smaller cam in this series
worked very well in the 360. Now have 28 ci more displacement I think it will handle 5* more duration, but Fbird you could be right
I know I have heard good things about the mega cam line.

[F-BIRD'88]

Not at idle it won't. and the more you advance that cam the nastier the curb idle and thus off idle throttle response.
It INCREASES the intake exposure to exhaust reversion at idle as the intake valve opens sooner by advancing it.

It will need locked out timing to get the base idle timing high enough at idle.
You may have a vacuum leak too.

[gmrocket]

Quick way to check the cam timing. Roll the engine to tdc on the overlap, measure the rocker arms,one exhaust is closing,intake is opening, if the cam is heads up, the rocker arms will be same height. If the cam is advanced the intake rocker will be open more than the exhaust. I would check your cranking compression just to see how much pressure you are trying to start. That may be the root of your problem.

..

[gmrocket]

Hello all and thanks for the replies. Jeff, I have 115 on the seat and 320 over the nose and the lifters do bleed off but it seems to
take several days for it to make noise at start up. I've seen the kill switch trick and it works pretty good. I have an old HyFire 6 that
will retard 0-10* below 500 rpm and it seems to have no effect. Maybe the starter is spinning it above 500 rpm? Camshaft was
chosen for max midrange torque and long service life on the street, it's designed for 1.6 rockers so .500 lift at valve.

Fbird you may be right about locking the dist but I would sure hate to and this cam is not really that big. The dist has 10* mech
advance all in @ 3500 to allow for cheap gas with the old shortblock. This is in a Chevy LUV so not a big truck like you guys are thinking,
just a street toy. Ran 11.90 with 360 and same cam only at 236 @ .050 dur on street tires.This new 388 is not that strong. I guess I need
to score a piston stop and a degree wheel. I do blame the tunnel ram on Fbird.

GMRocket the HyFire 6 and summit billet dist have been on the truck for years and have worked flawlessly,but anything is possible.
I have rerouted all the plug wires to avoid inductive crossfire although they have also worked for years with prior routing.
Rebelrouser, I had not thought of that,.I can probably hobble out there and get the plugs out and a valve cover off. Thanks all for
the ideas and advice.

You had the distributor out of the motor..it’s got nothing to do with how flawlessly it ran before.

[madmooney]

You all have given me much to consider, I think I'll go consider it while fishing tonight

[F-BIRD'88]

Get and install the end bracket brace on the starter motor.

[gmrocket]

You all have given me much to consider, I think I'll go consider it while fishing tonight

Have you at least done a cranking compression test? the way the cam is installed from your builder will actually give you less cranking psi and it should be easier on the starter...if he gave you your wanted 4+ that would give you more trouble cranking it over , not less.

Stan on here can give you a real good crank psi estimate and there are other online calculators. it saves you from tearing into it for no reasons.

if the cranking psi is what it works our to be, then its probably something else

[madmooney]

OK, managed to get a cranking compression test. Don't know starter rpm

#1 dry 180 psi 2 cc motor oil 185 psi

#2 190 195

#3 185 195

#4 175 180

#5 170 180

#6 185 190

#7 175 180

#8 185 195

I think ring gap is .017. Any thoughts on these numbers? Seem normal or not?

[bobmc]

I doubt that the cam is installed 8 deg advanced, the starter should have no trouble spinning the engine, set the initial timing about 20 deg and check the firing order one more time

[madmooney]

OK.

[MadBill]

If the cam is in 'straight up', and making several other S.W.A.G.s (240° @ 0.050" cam, 108° LSA, 10.0:1 CR, IVC = 48° ABDC, 29.20" "Hg. baro), the Wallace racing calculator, http://www.wallaceracing.com/calc-crank-press.php, comes up with a cranking pressure of 183.4 psi.

The lower pressure cylinders didn't come up much when wet, suggesting no ring seal issues but may will with a bit of running.

[madmooney]

Thanks Madbill, It only has a couple hours run time. Ericnova, I got the printable degree wheel, Pretty neat. Thanks.