1966 427 425HP Valve Clearances

[Jack C.]

Re: 1966 427 425HP Valve Clearances

Joe - I am aware of a 396 locally (actually in a 67 Chevelle but same cam and lifters) and the owner located and purchased a NOS cam and NOS lifters. There is some of this still around. Would you have the GM part number for the original lifters?

[Joe L.]

Re: 1966 427 425HP Valve Clearances

Joe - I am aware of a 396 locally (actually in a 67 Chevelle but same cam and lifters) and the owner located and purchased a NOS cam and NOS lifters. There is some of this still around. Would you have the GM part number for the original lifters?

Jack-------

GM #5232439 discontinued April, 1967 and replaced by GM #5232550. The latter was discontinued in November, 1969 and replaced by GM #5232695 which was discontinued without supersession in July, 1999.

[Jack C.]

Re: 1966 427 425HP Valve Clearances

Jack-------

GM #5232439 discontinued April, 1967 and replaced by GM #5232550. The latter was discontinued in November, 1969 and replaced by GM #5232695 which was discontinued without supersession in July, 1999.

Joe - Thanks for the quick reply. I'll be doing a bit more homework before this engine goes back together.

[Jack C.]

Re: 1966 427 425HP Valve Clearances

Jack-------

GM #5232439 discontinued April, 1967 and replaced by GM #5232550. The latter was discontinued in November, 1969 and replaced by GM #5232695 which was discontinued without supersession in July, 1999.

Joe- A search for GM #5232439 returns a number of #5231585 GM lifters. Would these be a later number from another supplier? Thanks.

[Joe L.]

Re: 1966 427 425HP Valve Clearances

Joe- A search for GM #5232439 returns a number of #5231585 GM lifters. Would these be a later number from another supplier? Thanks.

Jack-------


GM #5231585 were edge orifice mechanical lifters. They were used for all small block with mechanical lifters but never for a Mark IV big block.

The lifter part numbers I previously mentioned were piddle valve lifters. This is the type used for all Mark IV big blocks.

[Jack C.]

Re: 1966 427 425HP Valve Clearances

Jack-------


GM #5231585 were edge orifice mechanical lifters. They were used for all small block with mechanical lifters but never for a Mark IV big block.

The lifter part numbers I previously mentioned were piddle valve lifters. This is the type used for all Mark IV big blocks.

Joe - Appreciate the education very much. Of course the sellers claim they fit everything.

[Joe L.]

Re: 1966 427 425HP Valve Clearances

Joe - Appreciate the education very much. Of course the sellers claim they fit everything.

Jack-------


The 5231585 will fit big blocks but they are not functionally correct for big blocks.

Curiously, the 5231585 were discontinued before the 5232695 and are usually much harder to find and more expensive than the 5232695.

[Jack C.]

Re: 1966 427 425HP Valve Clearances

Sorry to here of your situation, Jack. I've been advising AGAINST buying anything from Comp Cams for years because there are just too many reports of early failures of their products. My first choice for camshafts is Federal Mogul, but it appears that many vintage parts are being discontinued from F-M. Crane is my second choice. Both F-M and Crane cams are Parkerized as were OE cams, and this process aids break-in and long life.

Duke

Duke - Just got word from Summit that the CS165R has been discontinued by the manufacturer. On your second choice, Crane Cams, they are not listing a solid flat tappet cam. While researching springs and lifters I learned that Isky supplies USA made lifters from Topline Automotive out of Muskegon, MI. I may have them custom grind a cam to these specs for me and they can take care of the oiling groove as well eliminating the need to have that done later. Always appreciate your input.

Jack

[Chris H.]

Re: 1966 427 425HP Valve Clearances

Jack, just curious...why did you decide to stick with a flat tappet cam?

[Jim D.]

Re: 1966 427 425HP Valve Clearances

Jack, Do a search for Speed Pro KC165R. That's for the cam and lifter set. Jeg's and Napa Online show they are available. If so, they must be old stock.

[Jack C.]

Re: 1966 427 425HP Valve Clearances

Jack, just curious...why did you decide to stick with a flat tappet cam?

Chris - Several reasons, and the result of analysis practically leading to paralysis, to quote the saying. Where to start . . . This is a one owner survivor car (obviously the engine did not survive sitting since 1981, and as they say, they get parked for a reason). Nonetheless, I really did want to rebuild it back factory correct in spite of the known spring issues and availability of today's parts. I am going to drive the car, but obviously not as a daily driver. Although as Duke points out he is not a fan of Comp Cams, and a number of others relayed similar contentions during my follow up research, I don't want to be quick to blame Comp. The BB spring issue that has been discussed at length with varying suggestions and beliefs on which is the right way to go is where I believe the main issue was. This is the one area I apparently should have done some additional homework beforehand but I went with a local head machinist and engine builder recommendation. One contributing factor to the failure was that although Comp Cams tech line blessed the chosen spring with their cam and lifters, it was a bee hive style spring with no inner spring to remove for break in, and I did not use a different lighter set for break in that is recommended by numerous experienced others. Some speculated that my chosen spring would have been fine if I had used a lighter set for break in. Everyone has a theory but I am not reusing these springs and I will be doing careful measurements myself this time around. I since have also been contacted by fellow member Mark Nagy who also owns a 66 425 HP car and he has been exceptionally helpful describing his successful engine rebuild back to original flat tappet, and apparently has a friend who also has a 66 425 HP car with similar success. Although he used a Lunati cam and lifters (I did not want to go with Lunati because it is slightly higher total lift and I trust Sealed Power as I have them in two other cars, both small blocks, but one is a solid lifter LT-1), he swore by the Isky 8005A springs when properly set at a 111 - 112 pound seat pressure. Also, on his engine they were able to remove the center spring for break in. According to him, once broke in and full springs installed, they dyno-tested his engine (much to his chagrin at the time) to 6,800 RPM without failure. His friend apparently drives his every weekend. As I mentioned, I trusted the head machinist through an engine builder friend to get the heads / springs right. I ordered a spring tester to do this myself so I can see where the current springs actually measure and to check the seat pressure on the Isky springs I have chosen to use. Isky sells a +.060 Retainer to get the seat pressure to the 111 - 112 pound range so the cam will live (again, I will be carefully measuring this). According to Isky, the compression rate per inch is sufficient to prevent valve float on higher RPMs while setting the seat pressure where the cam and lifters don't eat themselves up (see dyno test with these springs above). This is the current plan with actual cam now in research again. I'll report back with actual findings once I have the numbers of the current spring seat pressures used during failure and the specific setup of the Isky replacement springs.

[Jack C.]

Re: 1966 427 425HP Valve Clearances

Jack, Do a search for Speed Pro KC165R. That's for the cam and lifter set. Jeg's and Napa Online show they are available. If so, they must be old stock.

Appreciate the suggestion but no. Jegs shows ships from supplier with an estimated date of Nov 6 (same as Summit until they got word it would not be coming). I called my local NAPA and none in stores, they would likewise order from "supplier" and receive the same reply.

[Chris H.]

Re: 1966 427 425HP Valve Clearances

Jack, understood. Main reason I decided to go roller is the ZDDP issue and secondly more power under the curve with a modern grind. The cheapest way to go for sure is flat tappet, and you get vintage idle lope and valve clatter, which I will miss. To me though, well worth the sacrifice.

[Jim D.]

Re: 1966 427 425HP Valve Clearances

Appreciate the suggestion but no. Jegs shows ships from supplier with an estimated date of Nov 6 (same as Summit until they got word it would not be coming). I called my local NAPA and none in stores, they would likewise order from "supplier" and receive the same reply.

It was worth a shot. I must have got one of the last ones when I built mine. Mine came from Rock Auto but I see they're not even listing it anymore. It sure has a nice idle with those lifters clacking away. Good luck.

[Jack C.]

Re: 1966 427 425HP Valve Clearances

It was worth a shot. I must have got one of the last ones when I built mine. Mine came from Rock Auto but I see they're not even listing it anymore. It sure has a nice idle with those lifters clacking away. Good luck.

Jim - What did you choose for springs and lifters? Thanks in advance.