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Discussion Starter · #1 ·
It's a vortec head 355 rull roller engine, 9.8 -1 comp. The previous owner built it to a magazine article in Hot Rod call "Agent 87". It should be 390hp at the crank. Peak HP should be at around 5600.

I took it to the track and it started to stutter after 5200 RPM like a rev limiter so I short shifted. Do HEI's have built in Rev limiters? Is this a fuel or timing issue? Help.
 

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Hard to say without knowing the cam and lifter type.
My 355 with solid flat tappet cam and stock Vortec heads (spring upgrade) frequesntly saw 6,200 and accidentally 6,500 a few times.

A freind with a stock ZZ4 (factory roller cam) says his runs out of gas at 5,400.
 

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Yep, my ZZ4 is pretty much all in by 5500, but will spin to about 5800.

Lots of questions, which manifold, springs, push rods and other parts of the valve train?
 

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Discussion Starter · #6 ·
Ok, heres all the info I have on the engine.

355 w/ TRW 9.8 to 1 pistions, Crane 272 cam, Crane 1.5 Gold roller rockers, HEI distributor, Road Demon 625 cfm carb, Performer RPM intake, Vortec heads, headman headers & 2 1/2" 50 series Flows.

TH350 with shift kit, B&M 2000 stall, 3.08 non posi, 225x60x14 street tires.

Best 13.6 @102, shifting @ around 4800 rpm.
 

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Sounds like valve float.

Usually when someone copies a magazine article engine, we often hear:
"I built my engine exactly like <insert article engine name> except <insert changes> and now it doesn't perform like it should. What's wrong?"
 

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That's the same cam I have in the junk 350; with the springs it had it would fall on it's face at a little over 5000. With some new springs it went 6500+
 

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That's the same cam I have in the junk 350; with the springs it had it would fall on it's face at a little over 5000. With some new springs it went 6500+

how much of the 5000-6500 was actually useful?
 

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how much of the 5000-6500 was actually useful?
Hard to say--with the 200 shot it pulled like crazy until I shifted!
It went 7.60 without the bottle which isn't bad for a 350 with a tiny hyd. cam and a dual plane/vac. sec. 750 combo.
 

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If those are stock unmodified Vortec heads you are possibly hitting the valve seals with the bottom of the retainers with that cam.
 

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Discussion Starter · #13 ·
I read that Crane Cams sells a kit 10309-1 spring & retainers that increase the valve pressure to help float & don't require machining. Anyone use these?
 

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Lets get back to reality ! the cam is done at close to 5000rpm ! pretty sure it has 216 @.050 duration . Oh and it more than likely is pushing 325hp .

install another cam with more lobe ,and springs to match ! then increase your rpm .
 

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If those are stock unmodified Vortec heads you are possibly hitting the valve seals with the bottom of the retainers with that cam.
YES. I was just about to ask if the heads were modified for a higher lift cam.

Edit: Here's a snippet from Chevy High Performance

CHP said:
This leads us to valvesprings, which require the most attention in a performance application. Since this is an OEM iron head, GM designed the valve guide to also serve as the inside diameter (id) locating device for the valvesprings. The guide’s large diameter acts like a sleeve that keeps the single-wire valvespring located >> properly. The guide is also machined at the top to mount a positive-style, 0.560-inch-diameter valve-guide seal. All of this conspires to limit total valve lift to a safe figure between 0.420 and 0.430 inch. The limitation is the clearance between the bottom of the retainer and the top of the valve-guide seal.

Accommodating more valve lift requires modifications to the valvespring seat and valve-guide areas of the head. The best route is to increase the spring-seat diameter from the standard 1.25 inches to 1.440 inches. Both Comp and Crane offer tools that use a valve-guide arbor to position the cutter. The Comp Cams cutter increases the spring-seat diameter while simultaneously reducing the outside diameter (od) of the guide boss. The Crane tool also cuts the valve-guide-seal diameter at the same time. Comp sells a separate tool that cuts a new guide seal and reduces the guide height to create additional retainer-to-seal clearance. Both cutters machine the top of the guide down to a 0.530-inch diameter, which is the standard size for positive-type aftermarket seals. This requires purchasing new valve-guide seals, since the factory uses a 0.560-inch guide to locate the seals. Another way to go is to have a machine shop cut the guide boss diameter to around 0.760 inch and reduce the seal height and use either the Crane H-11 tool steel spring (PN 99846) or the Comp spring (PN 981).

Once these machining operations have been completed, you have the choice of several aftermarket valvesprings to match your cam profile. These machining operations will produce enough clearance to allow between 0.525- and 0.550-inch valve lift before running into valvespring coil-bind. Given a 1.440-inch valvespring seat diameter, Comp and Crane offer several single and dual springs that will work with the stock valves.
 

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I have seen a bad set of plug wires do this also a bad coil.
Also a bad centrifugal advance in dist.
I say this is a Ignition problem.

I do not believe it's a fuel problem at this point.
maybe a combination.

Seriously I do not see this is a valve spring problem.

You say the cam is a 272 crane?
Do you have more specs?
Already stated, (Valve spring retainer clearance) a high lift cam above .525 will cause a problem if guide in the head had not been cut down for clearance.

IMO!
Al
 

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Discussion Starter · #17 ·
I have seen a bad set of plug wires do this also a bad coil.
Also a bad centrifugal advance in dist.
I say this is a Ignition problem.

I do not believe it's a fuel problem at this point.
maybe a combination.

Seriously I do not see this is a valve spring problem.

You say the cam is a 272 crane?
Do you have more specs?
Already stated, (Valve spring retainer clearance) a high lift cam above .525 will cause a problem if guide in the head had not been cut down for clearance.

IMO!
Al
Unfortunately no. This is all the info I have unless I strip down the engine. Two owners before me said it was a Crane 272. Thats all I know.
 

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Unfortunately no. This is all the info I have unless I strip down the engine. Two owners before me said it was a Crane 272. Thats all I know.
There is no 272 Roller listed.
There is this flat tappet hydraulic cam, a 272 cam, Grind Number: H-272-2 (REPLACES HMV-272-2)

It's a marine cam.:eek:

http://cranecams.com/?show=browsePa...-400 C.I.&partNumber=113941&partType=camshaft

This could be your problem!
marine cams are for mid range torque and 5000 rpm is about max!
 

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This one I have isn't a marine cam Al, it's this one--And with the valvesprings it came with it was done at 5400 rpm:
Part Number: 100052 Grind Number: 272 H10
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1957 1987 CHEVROLET 8 GOOD IDLE, DAILY USAGE, OFF ROAD, HIGHWAY TOWING, FUEL EFFICIENCY PLUS PERFORMANCE, 2600-3000 CRUISE RPM, 8.75 TO 10.0 COMPRESSION RATIO ADVISED. (50 STATE LEGAL, PRE-COMPUTER, C.A.R.B. E.O. D-225-21) BASIC RPM 2000-5000
Engine Size Configuration
262-400 C.I. V

Valve Setting: Intake .000 Exhaust .000 HOT

Lift: Intake @Cam 3027 @Valve 454 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 3027 @Valve 454
Rocker Arm Ratio 1.5

Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 27 BTDC 65 ABDC 272 °
Exhaust 67 BBDC 25 ATDC 272 °

Spring Requirements: Triple Dual Outer Inner
Part Number 99848
Loads Closed 114 LBS @ 1.700 or 1 45/64
Open 303 LBS @ 1.270
Recommended RPM range with matching components
Minimum RPM 1600
Maximum RPM 5400
Valve Float 5600

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 3 BTDC 33 ABDC 105 216 °
Exhaust 43 BBDC (7) BTDC 115 216 °
 

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Discussion Starter · #20 · (Edited)
OK...

How should I fix this? I need to rev higher than 5000 right? Not going to get much speed with 27" tires & 4.56 gear floating at 5000! Who knows what cam I really have... I didn't build it so who knows. Maybe I should pull the chain and check? I just bought a 8.5 rear end with 4.88's, got home, checked the number and found out they are 4.56s!!!

So... should I re-cam & spring? Or just re-spring? I don't have the dough to buy new heads and intake so what are some options/suggestions with my current shortblock & heads? 90% strip & 10% street. Thanks guys, I know I have been asking alot of questions on alot of different topics, but I went racing ONCE and I'm hooked! HELP!
 
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