Engine build possibilities

I have been following the "can an engineer build a motor" thread with interest to find out the typical directions taken on the LT1 motors.

Interesting to see the way the build is going, as I am also an engineer (mechanical, retired) and totally understand the thought processes . In the engineering world, attention to obscure details often determines if and how well things work out, or not.

I have not dug into any of the the engine builds on the forum, just this one for the most part, so limited exposure to the different styles of builds. My high performance engine building was for decades focused on twin turbo Mopar small block V8s, and IMO there is a lot of similarities in builds for them if you want the best in street manners and in moderate output builds for heavy vehicles. Much of that similarity comes out as as a "less is more" in many cases. Also have done a few stocker kit rebuilds for people.

I do have a couple of questions that could save me a bunch of digging, I think. This is mainly about the stock iron heads, which is what I would be dealing with if and when I need to do a rebuild on my 96 RM that is currently at about 140K and still running well, but with a few oil leaks. If the trans or engine gets weak, I will pull and refresh/tweak both, I think.

Does anyone know off the top of their heads what the valve sizes, both stock and fittable are? Similarly the port volumes in stock forms and what they flow on the bench? Combustion chamber volume, head only, also, before being cut if possible, and max can be cut. Stock cam specs. The way the RM currently drives is quite impressive for a stock engine tuned to low end torque, so the basics are already there for what I would want to do with the engine. Not looking at a max hp high rpm and stall setup, just high efficiency and driveability with as much power as can be wrung out of it.

I have also seen the posts on detonation issues and how they are too be expected, which probably is correct as that is kind of what GM did back then. Run max advance and then back off when detonating. Everybody still does that, but do a better job of getting the base setup in place and matched to the gas so not as noticeable. Our 6.0 gasser in the Express 3500 (9600#) does it a very small amount that we don't hear, but can see it pulling out timing on knock retard (KR parameter) on the Scangauge. It is usually a quick 2-3 degrees. It is cool that I now have the spark map that read out of it with an HP Tuner. The RM build would also try to make the issue better on a RM freshening. Reducing detonation is the prime directive in turbo builds we messed with that a lot.

What I see in this build is nearly a stock rebuild with a bit of cam, added, maybe. Nothing wrong with that as it is affordable and relatively safe. I would intend to go some beyond that, mainly with induction/combustion stuff.

The most obvious thing I see that I think I would change would be the piston design, which like almost all stock stuff is double valve relief so not side specific. This can really mess up the combustion process, especially the quench effectiveness, in my experience. Good quench, that matches cylinder to cylinder, is one of the best way to reduce detonation and improve output and efficiency. Stock setups are normally fair to poor in this respect because of the valve reliefs, unequal quench pad depths if not closed chamber, varying combustion chamber volume, deck height and consistency, etc. All of these will affect the quench effectiveness and compression ratio, and thus flame speed, which will affect the detonation thresholds and cylinder balance. To me, the ideal setup would be if the setup could come out at the desired compression with flat top pistons with 2 valve reliefs only as deep as needed to the cam used. Set it up with a .040 compressed head gasket and you are good to go. It is unlikely that it would just happen to work out that well, so adjustments would probably have to be done in deck height, perhaps a slight pocket on the non quench side, etc.

I think matching the above setup with near stock port volumes on heads that are matched as needed and a bit of clearing out of restrictions would probably work out well. Port volume and cross section will be big in determining port velocity and cylinder filling, particularly at the lower rpms that this build will be, and it still should be quite reasonable to expect 1hp per CI without losing the bottom. I think stock compression is 10.5 which is pretty high for iron heads, but I think I would leave it there as long a the reverse flow cooling is in place.

Stock bottom end should be fine, but the rod pin to pin would need to be checked to keep a decent deck height balance. Rods moving to other cylinders can often be used to compensate tolerance build ups.

Has anyone done this kind of, admittedly engineer influenced, moderate bu

If I were you, I would not worry about a rebuild. Easily, your engine, that you have 140K miles on it, has another 100 to 150K trouble free miles left on it. There are a number of guys here who have gone over 300K. Other than 2 or 3 guys who have done a rebuild, you won't find any postings, as it just doesn't happen very often.

Unless you want to do a lot of work and spend a lot of money, just drive it. My first wagon that I bought in 1997 had 236K on it when I sold it. It ran as good the day I sold it, as the day I bought it with 49K.

My 2 cents

Tom

silverfox103 wrote:

If I were you, I would not worry about a rebuild.  Easily, your engine, that you have 140K miles on it, has another 100 to 150K trouble free miles left on it.  There are a number of guys here who have gone over 300K.  Other than 2 or 3 guys who have done a rebuild, you won't find any postings, as it just doesn't happen very often.

Unless you want to do a lot of work and spend a lot of money, just drive it.  My first wagon that I bought in 1997 had 236K on it when I sold it.  It ran as good the day I sold it, as the day I bought it with 49K.

My 2 cents

Tom

As I mentioned, that is the intent, but if it has to get work for oil pan gasket or such, I will just pull a rebuild it. I just like to have ducks in a row if I need to. It wouldn't be a high buck rebuild, at least compared to what I am used to with Mopar turbo engines, and the work isn't really a big deal for a rebuild like this. Biggest cost would likely be a set of pistons if I couldn't find off the shelf ones which is likely as most are two sided, I think. Hopefully, I won't have to worry about it and it will last as long as I do.

jasper.com

Rev Bob wrote:

jasper.com

Jasper does good work for a mass engine rebuilder, and backs them well, but no way they can do the details on all engines and afford it. The kind of details I am talking about will cost me next to nothing but some time so there really isn't any way to hire it done that is also affordable.

So, not for me, but as mentioned a lot that is the engineer thing.

I believe that engine will last as long as you without the rebuild. My Buick roadmaster had 322,500 miles on it when I sold to to one of my late son's friends about a month ago. If you wanted to freshen it up with some new gaskets to get rid of the oil leaks I would understand that for sure. Just my opinion but unless you plan on racing the thing save your cash and invest it into other things the car may "need". These are great engines (except for the opti spark and water pumps) and run strong for many years. I was the original owner on the one I just sold and can testify to that. I have another one here with only 112K on the clock and it runs like a brand new car still.

Just saw this thread after posting in lamune's thread. Yes, the manufacturing tolerances were pretty loose by current standards so there's lots of room for improvement if you're willing to measure everything.

There are lots and lots of postings from Camaro/Firebird and Corvette owners that have scienced all this out. Aluminum heads are the way to go. I have a heavily ported set here with 7/16 studs and rockers I'm about to sell if you're interested (PM me). New and custom cams are available as well from

[You must be registered and logged in to see this link.]

and

[You must be registered and logged in to see this link.]

sherlock9c1 wrote:

Just saw this thread after posting in lamune's thread. Yes, the manufacturing tolerances were pretty loose by current standards so there's lots of room for improvement if you're willing to measure everything.

There are lots and lots of postings from Camaro/Firebird and Corvette owners that have scienced all this out. Aluminum heads are the way to go. I have a heavily ported set here with 7/16 studs and rockers I'm about to sell if you're interested (PM me). New and custom cams are available as well from

[You must be registered and logged in to see this link.]

and

[You must be registered and logged in to see this link.]

I think you, and they, are correct if you are building a more all out, higher rpm, engine with higher stall and all the other things to go with it like needing bigger ports to get there. But, for an improved stock style engine for a daily and cruiser, I think the small port, small cam, stock stall, style of the stock engine will make for a more usable and pleasant drive. By all accounts, the iron heads appear the choice for that kind of setup as they are said to flow the best, but still have small ports. That is not to say the ports wouldn't benefit from being smiled on with some smoothing, unshrouding, and matching, just that keeping the volume low and velocity high. Do you happen to have the port volumes, crossections sizes, and flows for the iron heads in stock form?

The best place to do some improving on stock, beyond just improving tolerancing and fit, would probably be in getting to a more modern fast ramp cam. Near stock .050 durations but near .500 lift at the valve with 1.5 rockers. I probably would use the cast 4340 bathtub, roller tip versions as I have not been impressed with needle bearing units unless you go to the very high buck ones with full hardened inner and out races. Bath tubs work well as long as you heed the spring pressure ratings on them, I have found, and make sure you have full zinc package in your oil. Second place to get updated would be the quench to a much better .040 dimension, which requires all the parts be where the need to be dimensionally so don't grenade, but does yield some very real benefits like much improved detonation control, ability to run less timing at optimum so improved efficiency, cleaner chambers and pistons, etc. If you are going to get back to 10.5 compression from the less than that where the stock engines appear to be running detonation control gets more critical and you don't want to have to back off on base timing because of slow burn compared to what quench will give.

I have no idea if I will even need to do this engine, as the stock one is doing well, but I am a one of those that likes to have stuff ready to go if needed, and if I do it I want it to be right the first time (retired engineer so no surprise there). It also is very interesting to me to get all the ideas and opinions from those that are more involved in this stuff than I intend to be.

Your shop has a very good reputation in this market it appears, and gets mentioned a lot across a wide swath of places, and I have been on your site several times. Not surprising, I found your stock cams a bit hot for what I would want to do, but what I am looking to do is certainly and outlier in most circles. IIRC, you also do customs at a reasonable cost, so that certainly would be an option. I used custom grinds on the later Mopar turbo engines as decent on the shelf designs were not available. It would probably be something near stock duration at .050 with maybe a minus 10 degrees overlap at .050, but would have to look at how the centerlines work out for that. Definitely split duration to exhaust, maybe 10 degrees, and possibly higher exhaust lift compared to intake.

Interesting stuff, for sure, I hope your business is surviving well during all the turmoil and sickness go on now, tough times.

So just to clarify, I am not a shop owner and my name is not Lloyd Elliott. I just have done a ton of research and both of those shops make good products.  The heads I'm selling were ported by someone else.

I will say that Lloyd Elliott is very keen on street drivability if that's also of interest to you. If you get to the point where you're serious and have the rest of your motor spec'd out, call him and get you a cam.

Be aware that the stock iron heads can only handle about .550" of valve lift; anything more than that and they need work. The aluminum LT1 heads can be found very cheap; the last set I had took me five months to sell them for $125 for the pair.

Agree on the faster ramp lobes, within reason on valvespring life and max RPM. Also the Elgin stamped 1.6 rockers are a great buy if you stay below 6100rpm.

Regarding deck height, the last short block I had measured at a machine shop had 0.002 difference in piston height across the deck which is probably within GM manufacturing spec at the time. So with regard to head gaskets I'd plan for 0.003" off the deck just to true it.  Do you remember how out the mopar decks were when you were building them?

sherlock9c1 wrote:

So just to clarify, I am not a shop owner and my name is not Lloyd Elliott. I just have done a ton of research and both of those shops make good products.  The heads I'm selling were ported by someone else.

I will say that Lloyd Elliott is very keen on street drivability if that's also of interest to you. If you get to the point where you're serious and have the rest of your motor spec'd out, call him and get you a cam.

Be aware that the stock iron heads can only handle about .550" of valve lift; anything more than that and they need work.  The aluminum LT1 heads can be found very cheap; the last set I had took me five months to sell them for $125 for the pair.

Agree on the faster ramp lobes, within reason on valvespring life and max RPM. Also the Elgin stamped 1.6 rockers are a great buy if you stay below 6100rpm.

Regarding deck height, the last short block I had measured at a machine shop had 0.002 difference in piston height across the deck which is probably within GM manufacturing spec at the time. So with regard to head gaskets I'd plan for 0.003" off the deck just to true it.  Do you remember how out the mopar decks were when you were building them?

Sorry about the misunderstanding of who you are, my bad!

My plans, if needed, fall well within the limits you mention. Looking to stay under 500 lift on both sides with 1.5 rockers. This will be a 5000rpm engine in design and use. Current cam off the shelf would be Comp 07-500-8, 206/212, .48/.48 and Lunati 20080678, 206/215, .47/.49 if they fit the LT1 properly which I haven't been able to tell very well. They are both in the $300 range so may be able to get an Elliott for not a lot more if the pricing the forum lists are close. Custom would always be the first choice for me if reasonable. Since I would like roller tips, and I prefer the cast strength but bathtub design, the Comp or PRW in 1.5 look to be decent. Pistons almost certainly would be one of the Keith Black hypers as almost everything else has 4 reliefs or is forged.

The Mopar decks and rods were both not very good, as was most everything back then. .002 in any direction and random was the norm. The good of that is that you could mix and match rods into cylinders to get the pistons in the right place in relation to the deck. Back then nearly every set of rods you saw had the cylinder numbers changed on them, and sometimes the pistons, too. Trying to build turbo motors at home in those days was considered borderline impossible, so the attention to detail and caution had to be right at the top. First V8 version was rolled out in 1989 with a spread bore Holley double pumper mechanical secondaries with full metering on both ends. It was blow through so all the fuel increase had to come in the secondaries (double the delivery) so pretty interesting. It was at 14 psi intercooled. We always went to the CarCraft summer cruise in St Paul,Mn, and there would be typically us and maybe one or two other homebuilt carb turbos there. None, except us ever showed up more than one year as they couldn't get them driveable, or keep them in one piece. It ran 4 years on the carb and then switched to EFI for probably 10 more to 50K miles. I then put in the second engine that had the smaller heads, higher compression, etc which was still in the car when we sold it about 4 years ago. I tore the 50k mile engine down and measured everything and compared to the original measurements going together. It showed nearly no wear at all, still see the crosshatch on the thrust side even, so that engine would have probably gone well beyond 150K miles.