A GM3800 Series I LN3 rebuild

[Guest crazytrain2]

Found this on the web, thought I would share

http://www.a-body.net/forums/showthread.php?2944-Series-I-3800-LN3-performance-build

[Guest RaverReatta]

(Queue heavenly music) Hallelujah! Thanks for posting this.

[2seater]

Interesting write-up and it sounds very similar to what I did about 12 years ago. No doubt he went to a lot of work but I couldn't get the photos to open up for the oil feed mod done at the mains? Not sure what he means about dual feed unless he drilled into another oil gallery? The pistons used are from an L27 engine, '93-95 I believe, but, aftermarket pistons are de-stroked assuming decking of the block. I used the same compression height pistons, 1.443", except Silvolite brand, #1744h, which are actually +.047" or .003"-.005" proud to the deck. I learned later that the approx. .055" piston to head distance is actually in a sort of danger zone if boosted. N/A it works just fine, but another .020" off the block would be better. I think the stated compression ratio is overly optimistic. It will be closer to 9:1 or slightly under, with a 38cc combustion chamber and about 36cc in the piston cup, +a .060" head gasket. I may have missed it but the head gaskets should be the stock GM or Victor Reinz which are identical. Do not use Fel-Pro headgaskets or you will lose compression ratio. The other thing I may have missed is reversing the pistons (point the notch to the rear) which decreases the rod angle slightly. The piston pin is offset from the centerline approx. .025" so the total change is .050" when reversed. They are offset to reduce the possibility of piston slap when they reverse direction but if a hypereutectic piston is used, the tight piston to bore would make this a non-issue, plus the rods are approx. 6.5", over a 1.9:1 rod ratio. Opening up the oil suction feed holes and chamfering sharp corners is a good idea. One other area that can benefit from some work is the passages in the oil filter adapter, which loop around inside. Easy to do on the bench. The engine appearance looks to be an '88 so the symmetrical lobes on the regrind make sense. The '90 cam uses two different lobes which are smaller so a regrind will likely be different. I have mentioned this before but will do so again. Make sure the new timing chain has all of the links at the same level where it rides on the tensioner. Stock is a Morse brand chain. I used a Cloyes brand chain and the new style tensioner which is a bad combination IMHO. The tensioner wore through in only 38k miles, twisted the chain and destroyed the front cam bearing. Again, this is only my experience in one engine, but I will be installing the original style tensioner, which can be hard to find. Lastly, this is what I found on my flowbench regarding head flow and is an excerpt from a letter I wrote regarding a possible new cam:

" These are the average flow rates from the stock heads, although they were massaged a little 38k miles ago and untouched or cleaned up since. They were not ported or flow benched at that time. My bench was recently reconfigured from pitot to orifice style and I do not have an appropriate orifice for the initial very low flows. The inlet port had a 1/4" radius bellmouth and the exhaust was flowed a bit differently. The actual exhaust manifold stub was used to connect to the bench under vacuum with a 6" long open cylinder adapter bolted to the head on the chamber side. This is what I obtained:

.150"- I=72cfm. E=71

.200"- 104 95

.250"- 124 111

.300"- 153 120

.350"- 171 129

.400"- 186 135

.450"- 192 141

.500"- 196 145

[Guest Greg Ross]

Hal,

If you refresh that "A - Body" thread you'll get to view a few more images, but give it time to generate. Betsy Blue still runs but I'm building something else "entirely different"

Regards,

Greg

[jbeary]

I know that a 3800 with a supercharger isn't exactly plug and play for the Reatta. Considering the trouble it'd take to make modifications to the cradle and electronics, what engines (makes/models/years) make the best candidates for conversions?

[2seater]

Hal,

If you refresh that "A - Body" thread you'll get to view a few more images, but give it time to generate. Betsy Blue still runs but I'm building something else "entirely different"

Regards,

Greg

Thanks Greg. Any revealing what the new direction might be?

[2seater]

I know that a 3800 with a supercharger isn't exactly plug and play for the Reatta. Considering the trouble it'd take to make modifications to the cradle and electronics, what engines (makes/models/years) make the best candidates for conversions?

Not from direct experience, but from what I do know, the closest thing to plug and play is a S/C conversion. The transmission change is not strictly required.

[D-a-n-i-e-l]

I know that a 3800 with a supercharger isn't exactly plug and play for the Reatta. Considering the trouble it'd take to make modifications to the cradle and electronics, what engines (makes/models/years) make the best candidates for conversions?

a 91-95 supercharged complete engine is almost a bolt in. Just have to have the ecm reprogrammed. If you want to keep the original block you could rebuild a NA using the crank from the supercharged engine, but then you would have to track down all the brackets, accessories and a harmonic balancer.

[jbeary]

Thanks guys. There's a few seemingly complete supercharged 3800's at a local pull a part. They charge a base price no matter the engine type or size. None of these I saw still had a ICM and coil pack and while I know one was in a Rivera the other two were in Pontiac's. I know Daniel has done a lot great descriptive posts on this subject but without having to pour over these now can you all let me know if the best option for a swap would need to come from another Buick or could the ECM come from a Buick and the engine come from a Pontiac? Also, there's a base price for the engine including the transmission or just the engine itself and if bought separately these would cost more than if they were bought together. My preference would to buy both at the same time. Is this wise considering that the tranny bolts to the engine cradle? Seriously considering building one of these up but would need to know what to tell a machine shop or just go as stock as possible. Could never go as in depth as 2Seater has with his but would love more low end torque from my 89. The 91 I have seems almost perfect.

[D-a-n-i-e-l]

Thanks guys. There's a few seemingly complete supercharged 3800's at a local pull a part. They charge a base price no matter the engine type or size. None of these I saw still had a ICM and coil pack and while I know one was in a Rivera the other two were in Pontiac's. I know Daniel has done a lot great descriptive posts on this subject but without having to pour over these now can you all let me know if the best option for a swap would need to come from another Buick or could the ECM come from a Buick and the engine come from a Pontiac? Also, there's a base price for the engine including the transmission or just the engine itself and if bought separately these would cost more than if they were bought together. My preference would to buy both at the same time. Is this wise considering that the tranny bolts to the engine cradle? Seriously considering building one of these up but would need to know what to tell a machine shop or just go as stock as possible. Could never go as in depth as 2Seater has with his but would love more low end torque from my 89. The 91 I have seems almost perfect.

I still have a tuned chip for an 89. If you get an engine and install it I would give it up for little more than shipping. So all it would cost is around $45 for a adapter plus shipping. THERE IS NO NEED TO CHANGE ECM TO USE A SC ENGINE.

Sorry everyone seems to thing you have to change the ecm and it is getting annoying. It is only programming.

[jbeary]

That's good info Daniel. Thanks and will PM you about the chip. I should have posed the ECM question differently; will a Buick ECM work with a Pontiac engine? I know that many of these parts are interchangeable between makes and maybe that's the adapter you mention.