68 L89 Rebuild

[Noel O.]

I made a couple of posts a few years back but his time I have the cash and I am serious. I plan to do a partial restoration on my 68 L89 Coupe. This will include a an engine and transmission rebuild. I need some help with this. The car is Feb 68 build with correct 321 block and two plug 842 heads, but I feel the motor has a psiton set and possibily a cam that are not stock. I say this because the car runs "OK" on 93 pump, but just does not sound and feel like other big blocks I have had experieice with in the past. Needless to say I want to get this right he first time. What are the things I really must do and what are the thinkgs I need to avoid. I want get as much out of the motor as possible but at the same time keeping it streetable. This does not have to be a stock rebuild. There seems to be so much about compression ratio and cam it seems difficult to know what to do. I have read about BB rebuilds using hypereutectic pistons with 12/13 :1 and computer ground cams/roller valvetrains is this practical on a budget? will it really work ont he street? is there a sginificant amoutn of additonal head work required?

Also, does anyone know of a good resoration shop in the Putnam/Westchester NY area. Nj, PA and New Englans are OK too. I just want to find someone who is good with access to a good engine builder and a fair labor rate.

Many, many thansk in advance....I really need the help

[Duke W.]

Re: 68 L89 Rebuild

Your best bet is to do a "stock blueprint" rebuild. This would include all OE or OE equivalent parts including the cam and pistons.

The best way to get more top end power out of any production Chevrolet engine is to competently pocket port/port match the heads and perform a multiangle valve job IAW widely published recommendations. With aluminum heads that have valve guide inserts and seat inserts you want to be sure that the head rebuild is done competently by a shop that understands aluminum heads. They are common, and in particular, specialize in European and Japanese engines that have aluminum heads., but they may need some help with parts selection since aluminum BB heads are rare, but the basic overhaul procedures are the same as any other aluminum head.

You've got a rare and valuable car. Don't screw it up with a bunch of aftermarket parts that might not work well or turn it into and amateur R&D project. The OE configuration is very well engineered, and with the exception of some hand work on the heads to improve top end power, if that's what you want, keep it original.

There are no "magic cams" or "magic pistons" or magic anything else out there that will make the engine run better and maintain its original character.

Details are in your COM and there are various "how to" books out there (check HP Books) that get into the details of big block engine overhaul and blueprinting.

Develop a WRITTEN plan for all inspections, machine operations, and replacement parts BEFORE you start the job, and find a machine shop that will do it YOUR WAY!

You probably have a lot of studying/homework to do before you start spinning wrenches.

Duke

[Joe L.]

Re: 68 L89 Rebuild

Noel-----

A few days ago I believe that I received an e-mail from you on this subject. I prepared a quite lengthy response in reply. However, when I sent the reply, the message was almost immediately returned as undeliverable. I sent it as a reply, so there is no chance that I got the e-mail address incorrect; it went to the address you sent it from. From time-to-time this happens when I respond to e-mails and I strongly suspect it's because of some "e-mail preferences" or "spam filtering" that the original sender uses. I find it EXTREMELY frustrating when this happens. Since I do not routinely save copies of outgoing e-mail responses, all of my effort is lost. I have a personal policy that I WILL NOT recompose a response in these cases.

In any event, I tend to agree with Duke and that is the general gist of what I said in the forever-lost response I prepared. There are a few caveats that I will mention, though. First, if you are sure that the engine has the original compression ratio (11:1, nominal) and it runs ok on pump premium, then you can maintain that ratio with the rebuilt engine. I would check this out carefully, first though. If the compression has been previously lowered, then I would not recommend going above 10:1 in the rebuilt engine. This will not change the sound of the engine in any discernable way. To go above 10:1, unless you KNOW the engine will tolerate that, is, in my opinion, unwise. If it doesn't, then you're going to be stuck with pre-ignition or another major engine tear-down to change the pistons.

Personally, regardless of compression ratio, I would use hypereutectic cast pistons. These are more than strong enough for any street application and will provide improved durability and oil control.

I feel that a properly selected hydraulic roller camshaft would be a better choice for most street engines. However, for an L-89, it's probably best to go with an original camshaft. It's GM-discontinued but available in reproduction.

[Noel O.]

Re: 68 L89 Rebuild

Duke/Joe,

Many thanks for your responses. This is really helpful. Joe, appologies for problems you may have had sending an email to me. I have not seen anything and I am afraid I do not have an explanation for this. I appologize for the wasted effort. Regarding the pistons, I am not sure of what pistons are in the car, but fealt that they were not 11:1 because the car seemed to run OK on 93 pump gas.

Guys thanks again and if yo have any other thoughts please let me know.

[Mark #28455]

Re: 68 L89 Rebuild

I also tried to contact you by e-mail and was met with the same message. I also have an L89 (1969) and recently rebuilt the engine. With the 842 heads, I would limit myself to 10:1 compression. As for how the cars run, we all seem to remember them as much faster than they really were! A new Corvette runs 12's in the 1/4 mile but the L89's were running 14's! (tire spin, etc).

Keep it as stock as possible. The main change I would consider is buying a 4 1/4" stroker crank - internally balanced from Eagle for about $650. Run it with the flat top Keith Black pistons and a stock cam and you will be SHOCKED at the low RPM grunt your engine will have (and run great on pump gas).

Whenever you start messing with "high perf" aftermarket racing stuff, you shift the powerband higher in the RPM range (which doesn't run well on the street with stock exhausts). If anything, you are looking for a shorter duration cam to boost the lower RPM operation (ie: Joe Lucia's recommendation about the hyd. roller cam). I am currently assembling a 532 stroker motor for another car and it will run a little over 10:1 with a hyd. roller cam with 235 duration and only .530 lift with late model vortec heads. (I had the heads flow bench tested and found no significant benefit over .500 lift). It will run great in the STREET RPM range - 1500 to 5000.

Good luck,
Mark

[Noel O.]

Re: 68 L89 Rebuild

Thanks mark....sorry to those who tried to email me....I will get that straihtened out ASAP...what are your thoughts. What are your thoughts on the head work suggested by Duke?

[Noel O.]

Re: 68 L89 Rebuild

the eail I have in their now should work...thanks