69 427 rebuild

[Joe R.]

Re: 69 427 rebuild

Thank you all for you input and suggestions. Is there any work that can be done to the interior of the stock exhaust manifolds to improve exit flow and keep the stock and correct exhaust manifolds and exhaust system. Also, what's the best way to restore the exhaust manifolds? Is powdercoating in the correct color "over restored"? Don

Don,

I don't know of any good way to improve the flow of the exhaust manifolds. But there are ways to improve the looks. You will probably get many opinions on this. I sent mine off to Jerry MacNeish. His reskinning process involves putting a thin coat of aluminum over the top of them. Then you use the rattle can paint he supplies to finish the job. Rust free on the outside forever! Here's the link:

http://www.z28camaro.com/restosvcs.html#manifold

Joe

[Dennis S.]

Re: 69 427 rebuild

Thank you all for you input and suggestions. Is there any work that can be done to the interior of the stock exhaust manifolds to improve exit flow and keep the stock and correct exhaust manifolds and exhaust system. Also, what's the best way to restore the exhaust manifolds? Is powdercoating in the correct color "over restored"? Don

Open tuned headers will fix your exhaust flow. Never heard of anybody grinding away on otherwise correct (and valuable) cast iron manifolds. All the manifolds were on the engine when painted at Tonawanda. The intake was covered by a loose-fitting mask, the exhausts received orange paint in varying degrees...probably quite heavy on the outside, virtually nothing on the inside, along with poor coverage on that area of the block. The orange engine paint burns off over time and leaves a yellowish residue in some places. Doing anything else, especially powder-coating , would be over-restoring. I've seen photos of this "fire hose" operation and read where the engines were painted in less than a minute.

[Duke W.]

Re: 69 427 rebuild

Thank you all for you input and suggestions. Is there any work that can be done to the interior of the stock exhaust manifolds to improve exit flow and keep the stock and correct exhaust manifolds and exhaust system. Also, what's the best way to restore the exhaust manifolds? Is powdercoating in the correct color "over restored"? Don

The OE manifolds are very efficient, but make sure the manifold openings match the head port openings with no overhang on the downstream (manifold) side.

Also, be sure the head pipe fits snugly in the manifold outlet with no overhang.

If there is any significant casting flash in the manifold interior, try to grind it off, but the interior can be difficult to reach with a grinding tool.

Duke

[Don W.]

Re: 69 427 rebuild

OK NCRS Team,

It looks like I've got the recommendations for the cam, pistons, rods, some head work (port), and no exhaust manifold work other than a good fit. Any input on valves, valve springs, lifters, push rods or any other areas I should focus on?

Thanks,

Don

[Duke W.]

Re: 69 427 rebuild

Make sure you replace the valve springs with the second design BB valve spring, which was a dual spring with integral retainer and umbrella seal. Your '69 likely had these as OE. The only source I know of for these assemblies is GMPP.

Everything else should be "OE equivalent" and is available in Federal Mogul brands from NAPA. You do not need to "upgrade" the valves.

Check Eagle, Scat, and Crower for replacement rods that have about the same mass and get a price for Magnaflux, resizing, and new bolts for your existing rods. lt's simple cost analysis - new vs. qualifying he existing rods.

Duke

[Joe R.]

Re: 69 427 rebuild

OK NCRS Team,

It looks like I've got the recommendations for the cam, pistons, rods, some head work (port), and no exhaust manifold work other than a good fit. Any input on valves, valve springs, lifters, push rods or any other areas I should focus on?

Thanks,

Don

Don,

This thread has some info on rocker arms and valve springs:

https://www.forums.ncrs.org/showthre...71061&uid=6326

See post #23 by Joe Lucia on the valve spring kit. Mark Nagy was looking for the kit a while back. I don't know if they are readily available or not. I bought mine from Weber Chevrolet. Mark was down to looking for the 3970627 valve springs separately from various sources to put together a set. Please let us know what the availability is, assuming that's the springs you go with.

On the push rods, has the block or heads been decked? If not you may be able to use standard length push rods. Or you may want to get a push rod length checker to make sure you get the geometry right.

Joe

[Joe R.]

Re: 69 427 rebuild

Make sure you replace the valve springs with the second design BB valve spring, which was a dual spring with integral retainer and umbrella seal. Your '69 likely had these as OE. The only source I know of for these assemblies is GMPP.

Everything else should be "OE equivalent" and is available in Federal Mogul brands from NAPA. You do not need to "upgrade" the valves.

Check Eagle, Scat, and Crower for replacement rods that have about the same mass and get a price for Magnaflux, resizing, and new bolts for your existing rods. lt's simple cost analysis - new vs. qualifying he existing rods.

Duke

Duke,

How much horsepower and torque can the OE rods and rod bolts withstand? Same question on the aftermarket brands you mentioned.

Joe

[Ronald L.]

Re: 69 427 rebuild

Joe - Don,
Mark and I were on the same page at the same time, springs were not readially available and I think he got one AM set, I went with Comp Cam springs for a 390HP cam. Just purrs now that its all back together now fi it would stop raining.

[Duke W.]

Re: 69 427 rebuild

Duke,

How much horsepower and torque can the OE rods and rod bolts withstand? Same question on the aftermarket brands you mentioned.

Joe

It's not really a matter of horsepower or torque assuming a mildly massaged engine. It's a matter of fatigue, which is RPM and time. The actual highest load condition on the rod is during the exhaust stroke when there is no cylinder pressure to offset the tension load on the rod from centrifugal force.

I think the OE BB rods are reasonably durable for a mildly massaged road engine, but they may be marginal for racing. The L-88s were known to break rods in racing, especially long distance races.

I don't have any specific data on the relative durability of OE vs. the modern replacements I mentioned, but most modern aftermarket replacement rods are probably at least as good if not better, and most replacement bolts are stronger.

That's why I say it's a matter of cost. If it costs nearly as much to qualify and rebuilt OE rods as the price of a new set, the new set is probably the better way to go, especially on the higher revving mechanical lifter engines.

Duke

[Joe R.]

Re: 69 427 rebuild

It's not really a matter of horsepower or torque assuming a mildly massaged engine. It's a matter of fatigue, which is RPM and time. The actual highest load condition on the rod is during the exhaust stroke when there is no cylinder pressure to offset the tension load on the rod from centrifugal force.

I think the OE BB rods are reasonably durable for a mildly massaged road engine, but they may be marginal for racing. The L-88s were known to break rods in racing, especially long distance races.

I don't have any specific data on the relative durability of OE vs. the modern replacements I mentioned, but most modern aftermarket replacement rods are probably at least as good if not better, and most replacement bolts are stronger.

That's why I say it's a matter of cost. If it costs nearly as much to qualify and rebuilt OE rods as the price of a new set, the new set is probably the better way to go, especially on the higher revving mechanical lifter engines.

Duke

Duke,

I hope I'm not belaboring the point too much, but what does "mildly massaged" mean? 50 HP? 100 HP?

Let me ask another question. I would assume that no BB with decent street manners would have as much power as the L88. So would the L88 rods be a good choice? What is the GM part number for the L88 rods? I'm assuming they're not the same as other BB rods.

Thanks,
Joe

[Duke W.]

Re: 69 427 rebuild

Again, it's not a matter of torque or power, unless the increase is substantial.

The key is RPM because rod stess increases with the square of revs, so a 10 percent increase in revs increases rod stress by 21 percent, which gets you closer to the fatigue limit.

The fatigue limit is the stress level where a cyclically loaded part will effectively last "forever", but typical manufacturing surface flaws can often lead to fatigue failures even if peak stress is below the fatigue limit. That's why rods and cranks should be Magnaflux inspected because a small crack that is not visually detectable can lead to a premature fatigue failure.

Mildly massaged, for example, means massaging the heads on a L-72 which will increase peak power 10-15 percent, but you keep the redline at 6500.

A serious 427 racing engine that turns 7500 is more than mildly massaged, and even flaw free OE rods will probably not last long because they are being stressed 33 percent more than the OE engine at 6500 and the racing engine is turning high revs all the time whereas the road engine may see peak revs only occasionally.

Substantial increases in torque or power from boost - say 40-50 percent or more with no increase in revs can be tough on rods, but in this situation a piston usually fails first.

Yes, the L-88 had upgraded rods relative to other BBs, but they still broke. Joe L. can probably give the complete history. I don't know if GM still offers L-88 type rods, and if the do, they are likely an old design that is not as good as aftermarket, which are also cheaper.

In most cases, buying aftermarket rods is cheaper than qualifying/rebuilding OE rods. That wasn't the case 30 or 40 years ago, but it is today.

Duke

[Joe L.]

Re: 69 427 rebuild

Duke,

I hope I'm not belaboring the point too much, but what does "mildly massaged" mean? 50 HP? 100 HP?

Let me ask another question. I would assume that no BB with decent street manners would have as much power as the L88. So would the L88 rods be a good choice? What is the GM part number for the L88 rods? I'm assuming they're not the same as other BB rods.

Thanks,
Joe

Joe-----

The L-88 engine was available for 3 model years, 1967, 1968, and 1969. The connecting rods for the engine differed over the period.

1967-68 used rods GM #3909846. This rod used 3/8" rod bolts. It was discontinued without supercession in 1985..

The 1969 L-88/ZL-1 rod was GM #3969804. This rod used special boron steel, 7/16" rod bolts. This rod is the strongest PRODUCTION rod which GM ever offered for a big block. It was discontinued without supercession several years ago.

The best PRODUCTION-type rod still available for big blocks is the GM #10198922. This is the successor to LS-6 rod. It uses 7/16" rod bolts but not the special boron steel variety. The 10198922 also has a somewhat thinner cross-section than the 3969804 but it's close to being as strong and is lighter. It can be improved by the addition of ARP-2000 rod bolts.

[Don W.]

Re: 69 427 rebuild

Any thougts on why the below parts don't show up in GM parts direct when I put them into the part number search? I also assume these will work on a '69 427 even though the below referenced engines are 454's. Also, do the Keith Black Pistons #360 referened above have rod options with the pistons? Don

GM PART # 10198922
CATEGORY: Engine Connecting Rod
PACK QTY: 1
CORE CHARGE: $0.00
List Price:$123.75Price:$100.98You Save:$22.77 (18%)

DESCRIPTION: ROD ASMForged Connecting Rod This rugged LS-6/LS-7 connecting rod is forged from 4340 steel, Magnaflux inspected and shotpeened. It has heavy-duty 7/16" diameter rod bolts with knurled shanks (P/N 14096148). This rod is machined for pressed piston pins, and is color coded white. This is also the Gen. V 454 & 502 rod. (Order P/N 12496661 for engine kit of eight rods.) Technical Notes: All big-block Chevrolet connecting rods are 6.135" from center-to-center. Recommended bolt torque is 73 ft./lbs. Use production rod bearing P/N 12329715

[Joe L.]

Re: 69 427 rebuild

Any thougts on why the below parts don't show up in GM parts direct when I put them into the part number search? I also assume these will work on a '69 427 even though the below referenced engines are 454's. Also, do the Keith Black Pistons #360 referened above have rod options with the pistons? Don

GM PART # 10198922
CATEGORY: Engine Connecting Rod
PACK QTY: 1
CORE CHARGE: $0.00
List Price:$123.75Price:$100.98You Save:$22.77 (18%)

DESCRIPTION: ROD ASMForged Connecting Rod This rugged LS-6/LS-7 connecting rod is forged from 4340 steel, Magnaflux inspected and shotpeened. It has heavy-duty 7/16" diameter rod bolts with knurled shanks (P/N 14096148). This rod is machined for pressed piston pins, and is color coded white. This is also the Gen. V 454 & 502 rod. (Order P/N 12496661 for engine kit of eight rods.) Technical Notes: All big-block Chevrolet connecting rods are 6.135" from center-to-center. Recommended bolt torque is 73 ft./lbs. Use production rod bearing P/N 12329715

Don------


The rod kit, GM #12496661, is discontinued. So, you have to purchase the 10198922 rods individually. That's unfortunate because the kit of 8 rods was a great buy.

The GM #12329715 bearing is also discontinued. I do not know if a replacement is available but, certainly, aftermarket replacements from Federal-Mogul, Clevite, etc. are available.

The KB pistons are not supplied with connecting rods. You can use the stock GM connecting rods with the KB pistons. The KB pistons will work with either floating or pressed pin type rods.

[Don W.]

Re: 69 427 rebuild

For the KB 360 Pistons; this is the only web hit I can find. Is there another part number or description? Don

http://shop.enginekits.com/osb/itemdetails.cfm?ID=792