63 SHP

[jim cear]

Just drove my buddies 67 327/350, it winds right up to 5800 rpm. My 63 with an 097 cam, lash set at .10/.16, initial timing set at 10 btdc, ignition map was set by Dave Fielder and checked by me, just goes flat above 3500, I can hear the secondaries opening. The rate of rpm increase just slows way down. Should this motor wind up as fast as a 350hp? Thanks

[Mike M.]

Re: 63 SHP

it should wind nearly identically to the 350hp. somethings wrong with the old girl. mike

[Duke W.]

Re: 63 SHP

My OE 327/340 pulled strongly to 6500, but many considered it was stronger than most. The final configuration before I rebuilt it was OE, but the ignition map was '64-'65 SHP/FI spec with 14-16 degrees initial, which really improved the low end torque (especially considering I am pulling a 3.08 axle through a CR trans) and the 8" VAC improved idle quality and stability, which was pretty much non-existant with the OE 15" VAC.

Even though I have stated that the Duntov cam is not very well matched to a 327 with big port heads, it seemed to work better in actual fact than Engine Analyzer predicts compared to the other SHP cams.

I recall running a '64 FI from highway speed to about 130 (loooooooooooong time ago and the statute of limitations has lapsed )and it was a dead heat, but I downshifted to second and he probably went to third assuming he had a 3.70 or 4.11 axle.

I also had a buddy way back when with a '70 L-46 CR/3.70 and we faced off several times from highway speed - also essentially a dead heat.

If your engine "goes flat" at 3500 there is some issue. The 3500-4000 range is where mine would get a torque surge (that "coming on the cam" feeling) and really begin to pull strong.

Use a popsicle stick to push open the secondary air valve and it should open smoothly with little force. Then have a helper in the cockpit push the throttle pedal wide open and verify that both secondary and primary throttle valves are full open. If not adjust the carb linkage and/or throttle linkage as required to achieve full open on bothe th primary and secondary throttle valves.

Once the carb and throttle linkages are adjusted properly to open both throttle valves, you should see the secondary air valve flop open briefly when you blip the throttle full open from from idle.

The other mistake guys make rebuilding these engine is to use "low compression pistons" which yield probably no more than 9:1 regardless of what the piston manufacturers says. The combination of low compression and high overlap is a recipe for a dog!

Duke

[John D.]

Re: 63 SHP

Jim, Your problem reminds me of one I have heard quite often by car owners runing inferior points. They seem to be OK for a short period of time and then around 3500 they absolutely die. Sold all my NOS points at the flea and actually felt quilty doing so except one FI guy bought them all. That helped ease the guilt. Also those old NOS condensers are getting to be bad news for sure. We recently tested 35 NOS ones and only 14 were any good.
I used to shift my 65 agt 7000 RPM using a litle piece of rubber behind the points.Clem takes credit for this trick but I think I showed it to him. John

[Allan J. Wicklund]

Re: 63 SHP

Today I had the opportunity to drive Jim's 63, 327/340HP.. This engine is fresh and was built to original configuration other than 10-1 Comp.. The ignition is Petronix.(The symptoms we ar talking about were present with different Ignitions.). We tested the acceleration using 1st Gear only. The engine never Stumbled or made an unfriendly sound, such as Valve Float, Cough, or made you feel it was Starving for Fuel. Even the Exhaust report was clean cut. She winds up fine till the 3500-4000 range but then just starts loosing steam. Makes you feel that to go above 5000 is just asking too much of her. After the test driving the Carb. started to overload and drip out of the Jets with the motor off.

I've been around SB Chevies a lot of years and this one isn't offering up any clues as of yet.(Therefore I'm Clueless). The Carb. is getting rebuilt and checked for settings this week. Jim is running Hi-Test.

My 67 is also a fresh motored car. I have a 327/350HP. and built the engine with 9.5-1 Comp.. I run the older style Petronix and use Regular grade fuel. My Timing is to factory Specs. It Cranks fine for a Small Block. I shift up at 5800 and she still would go higher.

I'm thinking Jim's problem is the Carburetor. I just can't figure why!
Al W.

[Kent K.]

Re: 63 SHP

I'm probably pokin my nose where it dosn't belong. But it sounds to me as though the distributor weights are incorrect to permit sufficient advance with the RPMs. Just my &0.02 worth from reading all Duke's posts.
Regards, Kent Keech

[Duke W.]

Re: 63 SHP

If it gets to 3500 normally, the spark advance map is probably reasonably okay, but it should be checked.

If an engine gets to the mid range okay and then lays down without misbehaving (like backfiring) then the most likely cause is a flow restriction.

The other thing that comes to mind is the old practical joke of shoving a potato up the tailpipe, so checking for some kind of exhaust restriction should also be done beginning with the heat riser valve.

Duke

[Allan J. Wicklund]

Re: 63 SHP

Morning Fellas, I spoke with Jim this morning and the topic of the Heat Riser causing a restriction comes to mind. I think we will Gut the Riser and see what happens. We will report sometime next week. Al W.

[Duke W.]

Re: 63 SHP

At least make sure it is free and maybe wire it open.

Duke

[Jim Cear]

Re: 63 SHP

Heat riser is free, virtually new, but I've learned the hard way that does not mean it's operating correctly! easy to check this weekend.

[Clem Z.]

make sure it is not upside down

i found this same problem because the heat riser was installed up side down. i would also try a inline fuel pressure gauge and see what is happing to the fuel pressure at the time of the problem

[Jim Cear]

Re: make sure it is not upside down

Clem, its installed such that I am able , with a long screwdriver,to push down on the counterweight from above and open the valve. Is that the correct orientation ?

[Clem Z.]

Re: make sure it is not upside down

correct,the counterweight points down when open

[Jim L.]

Re: 63 SHP

Jim
For what it's worth, week valve springs will give you this same problem.
Did ALL the valve springs get replaced with the overhaul???
FWIW--Jim

[Philip C.]

cam going flat *NM*