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-   -   BBC push rod mystery (http://www.hotrodders.com/forum/bbc-push-rod-mystery-232460.html)

Bobbity 05-02-2013 02:32 PM

BBC push rod mystery
 
I have a 1976 GMC truck454. After a (long ago) disassembly of the valve train, I replaced the rockers, cam & lifters with Comp Cams stuff. I thought I had lost the push rods, but just found 'em. Here is the problem: I ordered new magnum rods, 3/8" O.D. as everywhere sez that's the size the 454 uses. But,when I went to install them, they're too big for the guides. But, Comp Cams sez the 5/16 rods are only used i small blocks. I did eventually look at the old rods, sure enough, they're 5/16 O.D. So, *** have I here? I sure don't want to install new guides, as I could booger a head gasket, or two. They (CC) said they wouldn't warranty any parts if I use my old rods. They're straight, etc., just old. Any suggestions not involving Tannerite or Thai hookers?

BOBCRMAN@aol.com 05-02-2013 04:23 PM

Whoever you talked to at Comp Cams should be fired..

Big blocks have used 5/16 pushrods since the early seventies. In base engines and truck engines. Most common pushrod you will find in a stock 454.

Buy some 3/8 guide plates and you will be running again..

Bobbity 05-11-2013 08:46 AM

Well, as much as I hate to do it, I bought some guide plates for the 3/8 rods I got. I hope I don't incur any head gasket problems as a result, but, I'll take a flying stab at it. I now have the Comp Cams Magnum 3/8" push rods, so I added their guide plates to the mix.

S10 Racer 05-11-2013 01:56 PM

The guide plates are installed with the rocker studs, not head bolts so you will not have a head gasket problem. Make sure the push rods are for use with guide plates, some are, some aren't.

496CHEVY3100 05-11-2013 02:27 PM

Since all big block chevys use guide plates pushrods from CC should be hardened ,,USE an adjustable pushrod length checker to make sure you have right length, I used Comp cam ,lifters push rods valve springs.,roller rockers,timing chain and gears,,the pushrods were to short I had to order 125 th longer on intake and 250 th longer on exaust ,the ones that came with cam kit would not work the rubbed my guide plates had tp grind small amount with die grinder then reinstall until I got the clearance I needed,;)

1971BB427 05-12-2013 09:34 AM

It's a pretty common mistake to end up with 3/8" pushrods on a BBC engine. When looking around at most hi performance suppliers like Jegs or Summit, they carry almost nothing in 5/16" diameter, and tons of 3/8"-7/16" offerings. I didn't even see any 5/16" pushrods offered by Comp, so I'm guessing someone there (unkonledgeable) just spec'd the smallest they carried.
I'm running 7/16" Crower pushrods on my 454. I like the larger diameter, and my Edelbrock heads are setup for the 7/16" already.

496CHEVY3100 05-12-2013 11:46 AM

Quote:

Originally Posted by 1971BB427 (Post 1675012)
It's a pretty common mistake to end up with 3/8" pushrods on a BBC engine. When looking around at most hi performance suppliers like Jegs or Summit, they carry almost nothing in 5/16" diameter, and tons of 3/8"-7/16" offerings. I didn't even see any 5/16" pushrods offered by Comp, so I'm guessing someone there (unkonledgeable) just spec'd the smallest they carried.
I'm running 7/16" Crower pushrods on my 454. I like the larger diameter, and my Edelbrock heads are setup for the 7/16" already.

I am running comp 3/8 but when I ordered longer pushrods I got the .130 not the standard.80 they are much stronger,because I am running a milder cam and springs than what you are probably running ,I only have 540 lift.

1971BB427 05-12-2013 03:02 PM

Quote:

Originally Posted by 496CHEVY3100 (Post 1675030)
I am running comp 3/8 but when I ordered longer pushrods I got the .130 not the standard.80 they are much stronger,because I am running a milder cam and springs than what you are probably running ,I only have 540 lift.

You're way more lift than my engine. I'm only .518 lift. My cam is designed for 2,000-5,900 rpms. More low end power and torque.

cobalt327 05-13-2013 02:31 PM

Be sure to use sealer on the studs that enter the ports.

496CHEVY3100 05-15-2013 06:08 PM

1 Attachment(s)
Quote:

Originally Posted by 1971BB427 (Post 1675075)
You're way more lift than my engine. I'm only .518 lift. My cam is designed for 2,000-5,900 rpms. More low end power and torque.

You got me to thinking about intended RPM range ,this is what I have Comp 270 Marine with correct rotation they offer both ,,told me it would run with a 2400 converter and should have 16-18 in vacumn ,I

1971BB427 05-15-2013 08:02 PM

Quote:

Originally Posted by 496CHEVY3100 (Post 1675913)
You got me to thinking about intended RPM range ,this is what I have Comp 270 Marine with correct rotation they offer both ,,told me it would run with a 2400 converter and should have 16-18 in vacumn ,I

Those look like great specs for a BBC cam! I've always liked short duration cams with lots of lift in a BBC to make power and torque. I had a Crane cam with 284/284 duration, .528" lift and 114 LSA in my 427, and it had a great powerband, with super lowend response.

1971BB427 05-15-2013 08:09 PM

Had a very disappointing setback today while assembling my 464 BBC. Was down to the last bolt, on the last head, and the final torque increase, when the ARP stud pulled out. The threads in the block stripped out, so had to pull the head to see what happened.
It's the hole that the alignment plug is in, so pulled that also. I can actually get to the backside of the hole and see the damge all the way through. I'll have to order a 7/16-14 helicoil kit to fix it.
Until I get the kit, my assembly is on hold. Tried to buy one locally, but the hardware store wanted $120, and Summit only wanted $22, so I'll wait for Summit.

496CHEVY3100 05-16-2013 09:25 AM

Sorry to hear bad luck, I have good luck with summit shipping,your falcon is looking good you are moving fast ,on the cam I ordered short duration for low end torque since I am running 496 cu in it takes lots of air 225-188 valves 113 cc heads I needed extra lift a 331 rear gear 29in tires .probably will never turn it over 6000 any way reve limiter set at 6 k, if I turn it to 6 it should drop to around 45 on shift that will keep it in power band ,I will run the clock once to get a et,then it will be street driven after that.:thumbup:

496CHEVY3100 05-16-2013 09:54 AM

Just a thought ,did you Mag around bolt hole to check for hairline cracks ,should be OK but it would be better to find it now.

1971BB427 05-16-2013 10:24 AM

Quote:

Originally Posted by 496CHEVY3100 (Post 1676094)
Just a thought ,did you Mag around bolt hole to check for hairline cracks ,should be OK but it would be better to find it now.

No, since it's a complete engine I didn't have it down to magnaflux. I don't think it's an issue, as it's been recently rebuilt, and I would hope they would have magged it then.
I'm going to get the helicoil kit from Summit Fri., so hopefully have it repaired then. Need to get some red loctite before then and loctite the insert in place.
I'll switch gears and do some interior work until then. I have a new headliner to put in, and curious what kind of mouse nests I'll find up there when I cut the old one out!

That 496 you've put together should be a killer combo! Lots of grunt, and very streetable setup. I'm running 30" tall cheater slicks, so went with 3.73 ratio rear. I also will run the Falcon mostly on the street, but probably run a couple nostalgia events each summer too.


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