Cam Specs for 69 & 70

[Pamela H.]

Re: Cam Specs for 69 & 70

Don't know how badly the crank is scored yet..it may have failed sooner there's more to the story...

Drove from Ohio , lost power in PA going up a mountain, and it was towed to a shop that found it was low on oil ... then drove it to VA when it lost power again and shut down... towed to the shop where it is currently being worked on...
We won't buy a crank if we don't need it... We are assuming the worst possible scenerio...
if we fried two rods, which was the original diagnosis, they need to be redone...$100.00 a pop to redo two, do we spend $150 on two or $300 on 8 rods? 8 rods of superior quality for a little more money...
Want 100 more hp ...just because...
Tryng to find a cam that won't make it seem like I'm driving a luxury sedan.

Pistons we've picked out will definitely increase CR (speedpro cast alloy .100 dome;
Car maybe doesn't need pistons but, definitely needs rings... has 90,000+ miles, its gonna get rings regardless, might as well get good rings...total seal rings..
trying to get close to an LS6 (trying to build the motor that the factory would have built if it weren't for the EPA regulations...trying to compensate for the butchered hp.

[Pamela H.]

Re: Cam Specs for 69 & 70

Had just had the Oil pan and pump replaced in Ohio, right before I left...it was not smoking, leaking oil and no oil on the underside...

[William C.]

Re: Cam Specs for 69 & 70

"Won't work" is very subjective depending on what you are trying to achieve. If this is a restoration, then it is way overdone and generally a waste of $$ unless you don't have a usable factory crank and set of rods. Lunatti grinds many camshafts, which one and what are you trying to accomplish? starting with 2 bolt or 4 bolt block and accompanying heads?

[Pamela H.]

Re: Cam Specs for 69 & 70

Yes, the car is relatively unmolested and in pretty bad shape. It has been sitting pretty much unused for multiple years in someone's garage. Needs lots of body work, complete paint job, new convertible top, more interior work and still have tons that needs to be done in the engine bay. I have spent the last year ironing out multiple issues to get it safe to drive in the inteim while trying to restore it, not trying to hot rod. Want to keep it as original as humanly possible but as long as the engine has to be rebuilt we want to tweek it for max performance.

Pistons we've picked out will definitely increase CR (speedpro cast alloy .100 dome;
Car maybe doesn't need pistons but, definitely needs rings... has 90,000+ miles, its gonna get rings regardless, might as well get good rings...total seal rings..
trying to get close to an LS6 (trying to build the motor that the factory would have built if it weren't for the EPA regulations...trying to compensate for the butchered hp.

Several alternate suggestions have been made and are truly appreciated...trying to get feedback on our ideas so we have the educated reasoning....

I appreciate the advice about the block... We are just having an estimate done at this point to see how bad things are and what they recommend. Still don't know if the crank is re-usable or not... Like I said, trying to plan for the worst case scenerio, then we can make decisions based on what's toasted and what's still salvagable. More questions coming..please stay tuned and SERIOUSLY, THANK YOU FOR ALL YOUR INPUT!!! 4 Bolt Block

[Duke W.]

Re: Cam Specs for 69 & 70

Is your car a 1969 L36 (427/390HP)? You've asked questions about mulitiple years, so it's not clear.

Also, which transmission does it have and what is the axle ratio?

Duke

[Pamela H.]

Re: Cam Specs for 69 & 70

'74/454 3.08:1, Turbo 400 A/C, PS,PB, PW, Tilt/Tele,
(every time I try to post a picture the site freezes and I loose what I've been writing!)
There is something I think may have been missed by some that have been participating in this discussion.

I am a contract traveler. I travel all over the country working as an Occupational Therapist. I am currenty working in Virginia for a LIMITED engagement (4 weeks maybe more/maybe less) Home is Ohio
When the car broke down it was towed to a Corvette shop. That shop is 4 hours away from where I am currently working. I don't have the luxury of being able to take my time on this. Yes there is an element of "rush" about this rebuild simply because I don't want to leave the car in VA if I'm on my way to Fla or Texas or where ever, and I'm sure the guys working on it don't want it just sitting around either.

Now, on to the next point...My brother's expertise or lack there of of restoration. As I said before, he is VERY knowlegeable about Corvettes and We are trying desperately to restore the car to original factory new condition or as close as possible with american made, "correct" parts, finishes etc. In trying to get answers to multiple questions If I/We/He steps on his foot once in a while, please try to remember that no, we are not experts, YOU are the experts and that is why I joined NCRS and why we are having this conversation. If we knew everything there was to know about restoration, we wouldn't need to be asking the questions...but please,don't act like we/he just fell off the boat. (well, maybe I did)
The ? about the 390 cam was in response to someone on the forum's recommendation when we asked about increasing hp.
We know that 2 bearings are spun,
We know that 2 rods are fried,
More than likely the cylinders are scored

[Pamela H.]

Re: Cam Specs for 69 & 70

Previously when we asked about the possible the number of big block convertibles that might have been built in '74, some member of the forum responded to the effect that our quest to discover more about the production numbers on our car was basically irrelevant....
What is correct? I have agonized about the correct color for the convertible top, and weather or not I could or should put a luggage rack on the car, The motor is in a hundred pieces on the shop floor, If I can gain 100hp and still have a Corvette that is 100% cosmetically correct, / I'm striving to achieve the hp #'s that the car could have had, should have had, would have had but for the EPA. Am I missing something? END OF MY RANT!

What is the correct finish on the transmission pan on a 400 Turbo?

[Pamela H.]

Re: Cam Specs for 69 & 70

[QUOTE=

With the little I know about your car and this engine project one piece of advice I can give you is to not remove any metal from the block or heads unless absolutely necessary, but few "engine builders" take the time to make the necessary measurements to determine what really needs to be machined to correct real problems. They just start cutting metal.

This advice applies particulary to the block deck. If the block is original "matching numbers", machining the deck will be wipe out this data, and

My sense is that you are moving too fast with too little knowledge, and you may ultimately regret the outcome.

Duke[/QUOTE]

Couldn a compent machinist set the stops on the mill before he reached the VIN voss, and still be able to true up the block? What do you suggest?

[Duke W.]

Re: Cam Specs for 69 & 70

An OE block does not require "trueing" unless the deck is not parallel to the crankshaft or it is warped, which is RARELY the case. How do you know? Measure it, which takes about 30 seconds a side with a machinist's bar and a .0015" feeler gage... same with the head surface. Forget about finding a "competent" machinist. Their definition is different than yours and certainly mine. They will do your engine just as they have done every other engine for the last 20-40 years, and they neither understand nor care about Corvette restoration.

Your engine has an advertised CR of 8.5:1, and is probably closer to 8:1. It was designed to operate on 91 RON fuel, which has the same detonation resistance as today's 87 PON. Raising the CR and use of premium fuel has significant positive impact on torque and power ACROSS the rev range, while improving economy. Go to the "sticky" section and download my San Diego presentation to get a more thorough understanding of this issue.

My recommended "not to exceed" value for your engine is 10:1 for current premium fuel, and this must be carefully managed. If you contact me by email I will send you an article I co-authored for The Corvette Restorer on this issue. The first step is to measure deck clearance before disassembly. I'm sure this was not done, but it is not too late to recover.

Google Keith Black Pistons and see what's available, but, remember, the CR they claim is based on a specific deck clearance, head gasket thickness, and cylinder head combustion chamber volume, so you have to use the specifics for YOUR ENGINE.

The big block Corvette hydraulic lifter camshaft changed after 1972, but I've never gotten a handle on the differences, which are slight. You can either use this OE camshaft or the earlier 3904359 or 3883986 camshaft, and for "more power" install it four degrees retarded.

Get familiar with the napaonline.com catalog and cross reference to find the correct Federal Mogul OE replacement parts.

BY FAR THE MOST EFFECTIVE WAY TO GET MORE POWER is to massage the heads. This is discussed in a Corvette Restorer Article that I can send you in pdf, and the same basics apply to big blocks.

Use OE replacement valves if replacement is necessary and DO NOT install hardened valve seats. Save and reuse your original second design dual valve springs, unless someone has found and exact duplicate. To my knowledge an exact duplicate is not available. You will have to find out what valve guide rebuild technologies are available and decide which one to use. Some valve guide materials require specific stem plating and seal technologies. This can be a slippery slope.

The above assumes you are going to rebuild the heads, but if you just want to get the engine back together you can probably bolt them back on as-is, and worry about that some other time since they are likely not damaged.

I can't tell you a source for a replacement crank, if it's necessary. Hopefully the damage can be repaired by machining the crank journals to the next undersize.

For small blocks I recommend the Eagle SIR 5700 rod, which is very durable and inexpensive. Their catalog is online for your convenience, and I expect they have something suitable for big blocks.

Due to changes in the crank, rods, and pistons, the cranktrain will require precesion balancing.

With a TH400 and 3.08 axle you will much more appreciate the high low end torque of you engine than the top end power of a '71 Corvette low compression LS6, but with the above changes you can have LS6 top end and more low end torque than LS6 or your current OE configuration, and quite frankly you would very likely find a LS6 with your current drivetrain a poorer driving experince than the OE configuation.

Duke

[Pamela H.]

Re: Cam Specs for 69 & 70

Not sure where to find the "STICKY" section...

Will email...
Pam

[Alan S.]

Re: Cam Specs for 69 & 70

Hello Pamela,
About the luggage rack.... the rack was a popular dealer installed item. I put one on my 71 in 71. I only used it once because with anything on it the rear visibility was nil; especially since there was no right side rear view mirror.
The "minor deduction" for the rack is for the holes that are drilled in the rear deck to mount the rack...missing fiberglass.
I would say stay away from adding the rack... filling the holes if you change your mind is not an easy process to do successfully.
Good Luck with your engine!
Regards,
Alan

[Pamela H.]

Re: Cam Specs for 69 & 70

, rear visibility was nil; especially since there was no right side rear view mirror.

Thanks!!

What about the right hand mirror...Is it correct?, was it factory, was it a dealer option, (I do not have one, and as I am driving it frequently, I sure wish I did. That's one option I'd like to change ) what's the scoop?

[Terry M.]

Re: Cam Specs for 69 & 70

Thanks!!

What about the right hand mirror...Is it correct?, was it factory, was it a dealer option, (I do not have one, and as I am driving it frequently, I sure wish I did. That's one option I'd like to change ) what's the scoop?

The right hand rear view mirror for 1968-1972 Corvettes became available over the counter some time in 1973. It was never a factory option and never a dealer installed piece until after that date.

Judging deductions are just like the luggage rack. There is a deduction for the missing fiberglass because of the holes drilled in the door. Usually one or two points.

[Joe R.]

Re: Cam Specs for 69 & 70

Pam,

The sticky section is up at the top of this board.

Joe

[Joe R.]

Re: Cam Specs for 69 & 70

BY FAR THE MOST EFFECTIVE WAY TO GET MORE POWER is to massage the heads. This is discussed in a Corvette Restorer Article that I can send you in pdf, and the same basics apply to big blocks.

Hey Duke,

Don't forget that the fine Compression Ratio article is available online here:

http://stlouisncrs.org/news_files/St_LouisNCRS_ChapterNewsletterSummer2012.pdf

Scroll down to page 5.

Joe