69 427 rebuild

[Dennis S.]

Re: 69 427 rebuild

Don
You are evidently not experienced in engine rebuilding and neither am I. Regardless of what recommendations you receive from people, either on this TDB or out on the street, you still need to find a rebuilder...either local to you (preferable) or somewhere far away (not so preferable) to actually do the work. If you cannot trust his advice on what to do, then how can you trust him to do the work that other people have told you needs to be done? There are way too many opinions floating around for you to decipher and make a decision.

I had my original '69 L36 rebuilt 2 years ago and am extremely pleased with the results. I knew a few things were wrong with my engine and sought the advice of two wise old souls who have spent the last 35-45 years making a living at actually doing this drill, not merely dabbling in it as a hobby. The rebuilder picked the engine up at my house, took it to his shop for teardown and gave both me and Dave Walters the entire rundown. Collectively we decided what to do...make just a little more power but try to keep it as close to stock as possible. The block needed to be bored .030 over and we went with Speed Pro L2300F forged pistons, even though they cost more...two lifters were stuck and the original cam was wiped so we decided to go with the Comp Cams 268H hydraulic flat tappet cam, lifters and springs kit...the block was not decked, the heads were milled and fitted with new stainless valves, thicker Fel Pro head gaskets used, rods were re-sized, crank was re-sized and polished, new bearings and bolts, new high volume oil pump, new double timing chain and gears, flywheel machined, engine and clutch balanced. At any rate, I met the rebuilder at the engine dyno and witnessed the break-in and three pulls...408hp at 5300...but 500 ft-lbs torque at 3125. That is something you can really feel in the seat of your pants. So far the engine has not puffed any smoke nor used any noticable amount of 20W50 oil. I love the slightly rough idle, which sounds great through my new Allen's 2-1/2" side exhaust, and can smoke my P235-60s without using the clutch. Life is good.

[James G.]

Re: 69 427 rebuild

Don
You are evidently not experienced in engine rebuilding and neither am I. Regardless of what recommendations you receive from people, either on this TDB or out on the street, you still need to find a rebuilder...either local to you (preferable) or somewhere far away (not so preferable) to actually do the work. If you cannot trust his advice on what to do, then how can you trust him to do the work that other people have told you needs to be done? There are way too many opinions floating around for you to decipher and make a decision.

I had my original '69 L36 rebuilt 2 years ago and am extremely pleased with the results. I knew a few things were wrong with my engine and sought the advice of two wise old souls who have spent the last 35-45 years making a living at actually doing this drill, not merely dabbling in it as a hobby. The rebuilder picked the engine up at my house, took it to his shop for teardown and gave both me and Dave Walters the entire rundown. Collectively we decided what to do...make just a little more power but try to keep it as close to stock as possible. The block needed to be bored .030 over and we went with Speed Pro L2300F forged pistons, even though they cost more...two lifters were stuck and the original cam was wiped so we decided to go with the Comp Cams 268H hydraulic flat tappet cam, lifters and springs kit...the block was not decked, the heads were milled and fitted with new stainless valves, thicker Fel Pro head gaskets used, rods were re-sized, crank was re-sized and polished, new bearings and bolts, new high volume oil pump, new double timing chain and gears, flywheel machined, engine and clutch balanced. At any rate, I met the rebuilder at the engine dyno and witnessed the break-in and three pulls...408hp at 5300...but 500 ft-lbs torque at 3125. That is something you can really feel in the seat of your pants. So far the engine has not puffed any smoke nor used any noticable amount of 20W50 oil. I love the slightly rough idle, which sounds great through my new Allen's 2-1/2" side exhaust, and can smoke my P235-60s without using the clutch. Life is good.

I see the name DAVE WALTERS. I assume it is the same Dave that worked with BILL MOCK......and CHIP MILLER on the BLOOMINGTON judging field......as well as many other Florida NCRS events of yester-year ?? You keep good company.

[Dennis S.]

Re: 69 427 rebuild

I see the name DAVE WALTERS. I assume it is the same Dave that worked with BILL MOCK......and CHIP MILLER on the BLOOMINGTON judging field......as well as many other Florida NCRS events of yester-year ?? You keep good company.

Dave's still kickin' and recently received a special 30 year award recognizing his judging efforts at Bloomington. I would have never bought this car if his shop was not less than a mile from my house. His knowledge, guidance, patience, warehouse full of parts and fasteners, as well as use of special tools has been invaluable to me. Besides, he is a really great person just to get to know...and actually younger than me. He brought both of his L88s to the local corvette club's annual show 2 months ago. Dave is a real car guy...after spending 12 years restoring his white '67 coupe, he actually DROVE THE CAR all the way from Miami to Bloomington for one of the L88 reunions. Can you believe that? Of course, he was followed by a truck carrying 55 gallon drums of race fuel. The '68 convertible is original paint and drivetrain, unrestored with only 3700 miles. Absolutely stunning period-correct cars that were only drag raced. Here are a couple of pics. Not every day that you see a pair like this at your local Chevy dealer. Needless to say, they sounded real nasty pulling out of the parking lot.

I really did not mean to hijack Don's thread on rebuilding his 427...but I have seen other long-time posters here take the liberty of going off on their own tangents and figured...what the heck.

[David B.]

Re: 69 427 rebuild

"Any suggestions on the type of head work I should have?"


Don,
I didn't mean to imply that you should have any head work done, other than the typical valve, guides, seals, as may be needed. I meant that you won't be able to forecast an accurate compression ratio in advance unless you know that the combustion chambers have not been modified in the past by measuring the volume. Personally, I wouldn't get any head work done other than what is needed.
Dave

[Mike R.]

Re: 69 427 rebuild

I have to disagree with some of the others here I have been down this route 20yrs ago with a 69.

A properly chosen roller will make dramatically more power at both the high and low end than a flat tappet or hydralic cam since the profile can be more aggressive. I liked the 288R cam from Comp Cams. That you don't have to worry about how much zinc is in your oil is another plus. You don't need to remove the intake manifold heat shield unless he is possibly talking about hydraulic rollers.

A 454 will make a little more power but you will need a new balancer and flewplate in addition to the crank, probably not worth it.

Compare the price of new rods against reconditioning the old ones with new bolts.

Head bolts don't wear out....

Running the stock compression ratio should be no problem even if you are at sea level.

I align honed my L84 block and but it in a CNC. It turned out that the decks (which were original) were different heights, tilted and sloped back to front. Fortunately the low spot was the stamp pad and the block trued up without touching the stamp pad. Cast iron was not as consistant 40 yrs ago as it is today and blocks stress relieved with use and clearances changed.

BUT...The One Thing I would think about is having One entity do the overhaul AND installation AND have them break in the engine (if flat tappet cam). Then there won't be any finger pointing if there is a problem.

I have a 69 427/390HP with auto and 3.08 rear end. I considering a rebuild and these are the suggestions I have from a local build. I have an estimated 8:1 current compression from a mechanic in AZ based on his dyno tune activities a how far he could retard the timing. Major points are:
Consider a roller cam which requires removal of the intake manifold heat shield and adds $800
Max 10:1 compression; maybe ~ 9.8:1
Add different oil system to the valve train
Heads: 3-cut valve job + venturi cut on exhaust
New pistons, rod bolts and head bolts
Keep rods; x-ray and balance full set up
Line bore and deck block except for pad
Since I have a late Nov build with 454 heads; consider a 454 crank
Have the auto trans checked and re-sealed while the engine is out

[Michael H.]

Re: 69 427 rebuild

I have to disagree with some of the others here I have been down this route 20yrs ago with a 69.

A properly chosen roller will make dramatically more power at both the high and low end than a flat tappet or hydralic cam since the profile can be more aggressive. I liked the 288R cam from Comp Cams. That you don't have to worry about how much zinc is in your oil is another plus. You don't need to remove the intake manifold heat shield unless he is possibly talking about hydraulic rollers.

A 454 will make a little more power but you will need a new balancer and flewplate in addition to the crank, probably not worth it.

Compare the price of new rods against reconditioning the old ones with new bolts.

Head bolts don't wear out....

Running the stock compression ratio should be no problem even if you are at sea level.

I align honed my L84 block and but it in a CNC. It turned out that the decks (which were original) were different heights, tilted and sloped back to front. Fortunately the low spot was the stamp pad and the block trued up without touching the stamp pad. Cast iron was not as consistant 40 yrs ago as it is today and blocks stress relieved with use and clearances changed.

BUT...The One Thing I would think about is having One entity do the overhaul AND installation AND have them break in the engine (if flat tappet cam). Then there won't be any finger pointing if there is a problem.

[Mike R.]

Re: 69 427 rebuild

We are not talking about using the same profile but rather using a roller of the same duration. The roller will make more power because it will lift the valve higher, and keep it open longer for any given duration. The difference in duration gets larger as the lift goes up. So the "area under the curve" will be MUCH greater for a roller. If you look at typical lobe profiles of a 280 degree @.015 cam you get

Flat tappet
242deg @050
153deg @.200
Lift .580 (!.7 rocker)

Roller
242 @050
164 @200
Lift .646 (1.7)


The roller has 11 degrees more duration at .200 and the delta will get bigger at higher lifts. it also has 10% more lift.

If you swap a flat tappet for a roller of the same duration on a BB you will be amazed at the difference.

[Michael H.]

Re: 69 427 rebuild

We are not talking about using the same profile but rather using a roller of the same duration. The roller will make more power because it will lift the valve higher, and keep it open longer for any given duration. .

I see what you are saying. I think. You're talking about higher early velocity and acceleration at the valve.
That's not exactly how it works, though. Any flat tappet cam can be ground to have the same acceleration rates. (within reason) It's not unique to roller cams.
A flat tappet cam can be ground to have the exact same lift, duration, acceleration and velocity as a roller. (until you get to VERY high lift, duration and acceleration numbers, far higher than any reasonable street/strip cam)

[Mike R.]

Re: 69 427 rebuild

That is not what I said (or meant to say). If you compare two cams of equivalent duration at .015 or .050, the roller will have more duration at .200 because the flanks are steeper. There is a limit to how steep a slope a flat tappet will folllow and a roller lifter cam follow a steeper slope.

You can see this in the number I provided earier. The two cams will have the same idle quality because the duration @ .015 and .050 is the same. The roller has 11 deg more duration at .200 and probably over 20 deg more duration at .400 (I don't have actual figures for .400) as well as a much higher max lift.

That makes no sense, at all. If the flat tappet cam and roller cam are the same open duration at the valve, how can the roller hold the valve open longer without changing the duration??????

If you want the valve to lift higher, or be open longer, you can easily do that using a flat tappet cam by simply changing the profile of the lobe. You don't have to have a roller lifter to do that.

[Mike R.]

Re: 69 427 rebuild

Here is a graph of a flat tappet lobe and a roller tappet lobe with the same duration and same lift. You can see that the roller lobe has more duration at any given lift beyond .050 More area under the curve. In the real world the roller lobe would be designed with more lift too.

I see what you are saying. I think. You're talking about higher early velocity and acceleration at the valve.
That's not exactly how it works, though. Any flat tappet cam can be ground to have the same acceleration rates. (within reason) It's not unique to roller cams.
A flat tappet cam can be ground to have the exact same lift, duration, acceleration and velocity as a roller. (until you get to VERY high lift, duration and acceleration numbers, far higher than any reasonable street/strip cam)

[Michael H.]

Re: 69 427 rebuild

That is not what I said (or meant to say). If you compare two cams of equivalent duration at .015 or .050, the roller will have more duration at .200 because the flanks are steeper. There is a limit to how steep a slope a flat tappet will folllow and a roller lifter cam follow a steeper slope.

You can see this in the number I provided earier. The two cams will have the same idle quality because the duration @ .015 and .050 is the same. The roller has 11 deg more duration at .200 and probably over 20 deg more duration at .400 (I don't have actual figures for .400) as well as a much higher max lift.

But the mechanical limit of a flat tappet cam is far higher than any street cam will be. The limit is the point where the lobe runs off the side of the lifter. The contact area. If the duration and ramp speed is extremely high, the point of contact between the lobe and lifter face is actually off the edge of the lifter. That's why many race engines use wide base, or mushroom lifters. The increased diameter allows a faster lift curve without running the contact point off the edghe of the lifter.
However, that point is WAY beyond what any street cam could ever be. Duration and acceleration numbers high enough to require that would definitely not be considered street cams.
You can grind any cam to have incredible acceleration and velocity numbers but this kind of stress requires a lot of valve spring. Those numbers don't change because it's a roller lifter.

[Michael H.]

Re: 69 427 rebuild

Here is a graph of a flat tappet lobe and a roller tappet lobe with the same duration and same lift. You can see that the roller lobe has more duration at any given lift beyond .050 More area under the curve. In the real world the roller lobe would be designed with more lift too.

A flat tappet lobe can be designed and made to have the EXACT same profile. The roller has nothing to do with it. If you want faster ramp speeds/higher acceleration and early velocity, you grind it into the cam.

[Joe R.]

https://www.forums.ncrs.org/showthre...=2667&uid=3933


I'm with you on replacing the head bolts. They do stretch by design, it's cheap insurance to replace them. I would replace the rods and rod bolts, too.


The best way to get more power while appearing stock is to get your heads ported. I hear Brezinski Racing is one of the best. You should gain 40 to 50 horsepower, plus a few hundred RPMs.


NAPA carries Federal-Mogul (same as Sealed Power). Here's the cam:


https://www.napaonline.com/Catalog/C...204438782&An=0


It is probably available as a cam plus lifters kit, but I don't know the part number for that.

Joe

[Duke W.]

Re: 69 427 rebuild

Mostly good advice here. The 427/390 is an excellent engine configuration that produces massive torque and good top end power. If you want more top end power, you get it by massaging the heads, not some "magic cam".

My advice is to rebuild the engine with OE equivalent replacement parts, which are readily available with a target CR not to exceed 10:1. You do this by managing your compression ratio, which starts with measuring deck clearance before the block is disassembled. (see the Summer 2009 Corvette Restorer for a detailed article on this issue.)

If the crank spins freely once the rods/pistons are removed align boring is not necessary. Once it's out, main bearing alignment can be checked with a machinists bar and .0015" feeler gage. Likewise for deck and head flatness.

Very few OE engines need any kind of align boring or block deck or head surfacing.!

Do not remove metal unless absolutely necessary!

The rods are okay, but should be Magnaflux inspected, which requires removal of the bolts, which requires resizing. Given the cost, a set of modern aftermarket rods may be a less expensive alternative.

Once deck clearance is known, you can do "what ifs" with compression ratio calculators to determine the optimum piston/head gasket combination to achieive the target compression ratio.

If you want "more power" retarding the OE cam 5 degrees in combination with massaged heads will give you a useable power bandwidth to the valve train limiting speed, which will be in the range of 6000-6500 without a significant loss of low end torque. Also be sure to use the second design OE valvsprings, which have been discussed here many times before.

The most important thing is for the owner to have a clear objective of what he wants the engine to be, and then manage the project. Vendors such as machine shops should only do what YOU direct them to do - no more, but most will want to do it "their way", which usually involves a lot of machining and aftermarket hot rod parts. Find a shop that will do things your way - a shop that will actually MEASURE before arbitrarly removing metal. You're paying them to provide a service and you are the boss. Remember that!

Most OE engines were very well engineered, even by today's standards, which is amazing given the crude analysis tools they had at the time. Some may have an Achilles heel - early SB rods and the first design big block valve springs, but later production production parts - big block valve springs - and aftermarket rods for small blocks solves both problems without being detectable.

Duke

[Don 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