69 427 (maybe) with possible valve spring issues

[Robert O.]

[Russ S.]

Re: 69 427 (maybe) with possible valve spring issues

Did you check your float level?

[Duke W.]

Re: 69 427 (maybe) with possible valve spring issues

Assuming the heads are '69 vintage, they should use traditional gasketed plugs. The best to use today for normal road driving is AC R45XLS or equivalent in another brand, preferably non-resistor type. The OE heat range 3 is way too cold for normal road operation. I think taper seats were first used in '71.

Since your engine may have been assembled from a parts bin, carefully check the head seats to see if they are taper type or conventional gasketed type. There's no way manifold vacuum should fluctuate between 10 and 19" at idle. At what idle speed did you measure and how much does it fluctuate. You need to enure that you tee the vacuum gage into a full time manifold vacuum source. The VAC signal line may be ported. If the carb has an external choke vacuum break, teeing into that should work. You should also give us more details about the Holley carb. Is it an OE type or aftermarket? List number? Does it have a provision for ported or full time vacuum advance or both. OE '69 427/390s have Q-jets on an oval port aluminum manifold that mates to oval port heads.

It would probably be best to pull the valve covers, ID the head and check the valve springs. Are they the early single spring/damper type or that later dual type? You should also try to ID the cam - at least lifter type. Vacuum at whatever idle speed you use can also give a hint.

It appears you should also monitor oil consumption and determine the rate.

Duke

[Robert O.]

Re: 69 427 (maybe) with possible valve spring issues

Duke, thanks so much. i am going to copy and print your input and get busy checking each item on your list. i will see how many of your questions i can answer tonite or tomorrow. I am going to pull the valve covers momentarily to get the head castings. the block is a 3963512. the 2-plane intake is rectangular port (edelbrock C 427). As far as the vacuuym gage set up, i first "T"d it into the vacuum post on the manifold; i then hooked directly into the same vacuum post. result was identical. tested from 750 to 1000 to 1500 to 2000. only difference in the rapid needle oscillations was a slightly wider range. thanks so much. will reply after doing some more testing.

[Robert O.]

Re: 69 427 (maybe) with possible valve spring issues

no, Russ. i missed that, but will do that ck after getting the plugs and valve covers back on it. thanks

[Robert O.]

Re: 69 427 (maybe) with possible valve spring issues

Assuming the heads are '69 vintage, they should use traditional gasketed plugs. The best to use today for normal road driving is AC R45XLS or equivalent in another brand, preferably non-resistor type. The OE heat range 3 is way too cold for normal road operation. I think taper seats were first used in '71.

Since your engine may have been assembled from a parts bin, carefully check the head seats to see if they are taper type or conventional gasketed type. There's no way manifold vacuum should fluctuate between 10 and 19" at idle. At what idle speed did you measure and how much does it fluctuate. You need to enure that you tee the vacuum gage into a full time manifold vacuum source. The VAC signal line may be ported. If the carb has an external choke vacuum break, teeing into that should work. You should also give us more details about the Holley carb. Is it an OE type or aftermarket? List number? Does it have a provision for ported or full time vacuum advance or both. OE '69 427/390s have Q-jets on an oval port aluminum manifold that mates to oval port heads.

It would probably be best to pull the valve covers, ID the head and check the valve springs. Are they the early single spring/damper type or that later dual type? You should also try to ID the cam - at least lifter type. Vacuum at whatever idle speed you use can also give a hint.

It appears you should also monitor oil consumption and determine the rate.

Duke

Today, May 2, 2016, I learned:

Heads are: 6272990 / Hi-PERF / C 15 77 / GM 1 T (2 4 6 8) & GM 2 T (1 3 5 7)
They appear to be rectangular port.

Gold-colored huge rocker-arms stamped Crane 13-170 / with square box -11.

Springs are “dual” and really beefy.

Holley 3310-4 / 0178 or 017B 6R 6931

[Joe L.]

Re: 69 427 (maybe) with possible valve spring issues

Today, May 2, 2016, I learned:

Heads are: 6272990 / Hi-PERF / C 15 77 / GM 1 T (2 4 6 8) & GM 2 T (1 3 5 7)
They appear to be rectangular port.

Gold-colored huge rocker-arms stamped Crane 13-170 / with square box -11.

Springs are “dual” and really beefy.

Holley 3310-4 / 0178 or 017B 6R 6931

Robert-------


Your heads are SERVICE-only cast iron cylinder heads for SHP applications once available from GM under GM PART#6260482. They were never originally used on any PRODUCTION engine. However, they are very similar to those used on 1970 Chevelle LS-6 and, except for material, very similar to 1969 L-88/ZL-1 and 1971 LS-6. They are open chamber, 118cc combustion chambers. Unlike the 1970 LS-6 cylinder head, the 6260482 had induction hardened exhaust valve seats.

I'd need to have more information and/or photos on the valve springs to tell you anything about them. They could be the 1970-72 GM springs or, more likely, some aftermarket springs.

The Holley 3310 is a very common, primarily aftermarket Holley carburetor although it was used for 1965 Chevelle Z-16. I think they might still be available from Holley.

[Robert O.]

Re: 69 427 (maybe) with possible valve spring issues

Robert-------


Your heads are SERVICE-only cast iron cylinder heads for SHP applications once available from GM under GM PART#6260482. They were never originally used on any PRODUCTION engine. However, they are very similar to those used on 1970 Chevelle LS-6 and, except for material, very similar to 1969 L-88/ZL-1 and 1971 LS-6. They are open chamber, 118cc combustion chambers. Unlike the 1970 LS-6 cylinder head, the 6260482 had induction hardened exhaust valve seats.

I'd need to have more information and/or photos on the valve springs to tell you anything about them. They could be the 1970-72 GM springs or, more likely, some aftermarket springs.

The Holley 3310 is a very common, primarily aftermarket Holley carburetor although it was used for 1965 Chevelle Z-16. I think they might still be available from Holley.

Joe, I am going to post a couple pics of the rocker arms on my facebook page: bobbydean. thanks so much for the very useful info you have just provided.

As of 9:33pm, these pics are on my facebook (bobbydean) and are "public" so anyone can see them


bob owens

[Leif A.]

Re: 69 427 (maybe) with possible valve spring issues

Bob,
I would be willing to bet that most here do not have a Facebook account. Try posting your pics directly to this thread...it's quite easy.

[Robert O.]

Re: 69 427 (maybe) with possible valve spring issues

Leif,

here is the photo of heads you requested

Crane Rocker Arms.jpg

[Joe L.]

Re: 69 427 (maybe) with possible valve spring issues

Leif,

here is the photo of heads you requested

[ATTACH=CONFIG]70227[/ATTACH]

robert------


From what I can see of the springs and valve spring caps, they could be GM pieces. I can't say, for sure, though without seeing one of the springs and retainers off the cylinder head.

[Robert O.]

Re: 69 427 (maybe) with possible valve spring issues

Thanks Dave. I have just been in the garage this morning doing some"clean-up" before re-installing the valve covers and new AC R44XL plugs. As i mentioned in one update, when i pulled the valve covers, i found Gold Crane Cam Rockers sitting on top of what appears to be some really beefy push rods. The springs are also really beefy and have a second inner set as well. The heads are 6272990 454 heads, rectangular port, large valves, hardened exhaust valve seats, and 325cc runners. The intake is a rec-port edelbrock 2-plane sitting under a Holley 750 4160. I completed a compression test with all cylinders reading (and holding) 170-180psi. I will carefully look once again at all the valve springs before i button it back up. NOTE: the only reason i suspected a valve spring was due to the vacuum gage reading. I have not noticed any power loss, faltering, or misfire. I checked the vacuum because i wanted to see if i could find a source of the fuel consumption. I am headed back to the garage now to do a re-check of the springs so if you reply, it may be a while before i get back on line.

[Joe L.]

Re: 69 427 (maybe) with possible valve spring issues

Thanks Dave. I have just been in the garage this morning doing some"clean-up" before re-installing the valve covers and new AC R44XL plugs. As i mentioned in one update, when i pulled the valve covers, i found Gold Crane Cam Rockers sitting on top of what appears to be some really beefy push rods. The springs are also really beefy and have a second inner set as well. The heads are 6272990 454 heads, rectangular port, large valves, hardened exhaust valve seats, and 325cc runners. The intake is a rec-port edelbrock 2-plane sitting under a Holley 750 4160. I completed a compression test with all cylinders reading (and holding) 170-180psi. I will carefully look once again at all the valve springs before i button it back up. NOTE: the only reason i suspected a valve spring was due to the vacuum gage reading. I have not noticed any power loss, faltering, or misfire. I checked the vacuum because i wanted to see if i could find a source of the fuel consumption. I am headed back to the garage now to do a re-check of the springs so if you reply, it may be a while before i get back on line.

Robert------

GM had problems with the big block valve springs used for most 1965-69 applications. These were a single spring with a damper. However, I don't see how you could have these springs since they were long-discontinued and replaced by the time the heads you have even became available. They were replaced with a dual valve spring without damper. These were probably the best valve springs ever released for a street big block. You may or may not have them on this engine.

Usually, you can tell if you have a broken valve spring by trying to rotate the valve springs. Any broken valve spring will usually rotate comparatively easily.

[Robert O.]

Re: 69 427 (maybe) with possible valve spring issues

The springs on my engine are dual springs, very beefy. i think they are after-market since the rockers are Crane gold. The push rods appear to be heavier than stock as well. I think the previous owner had the Crane cam and valve train installed as a package.

[Joe L.]

Re: 69 427 (maybe) with possible valve spring issues

The springs on my engine are dual springs, very beefy. i think they are after-market since the rockers are Crane gold. The push rods appear to be heavier than stock as well. I think the previous owner had the Crane cam and valve train installed as a package.

robert------


From what I could see in your photo the springs look like they fit into stock-size valve spring pockets. Many aftermarket springs are larger and require valve spring pocket enlargement.

Big block pushrods generally come in 3 OD sizes---5/16", 3/8", and 7/16". The vast majority are 5/16" and 3/8". L-88/ZL-1 used 7/16".