madkaw

The one to the right

So it’s optimal at 9k - so that doesn’t mean you build an engine around them. I’m quite sure they are very efficient below that . What ID are they? Start shopping for a billet crank at 3500$ plus and then throw in another 10k on the engine build and you might get there

I’d bet that head has been cut , maybe not . Wouldn’t be very stellar CR - but maybe over 8:1

Do it . Hell - go to #3 . I suggested to my buddy to do his in his 78. It is tired motor too. He was surprised how much a difference it made . It should give you a bump in CR .

I have a knock sensor module installed , but have yet to use it . My max CR is 10.5:1 and we have 93 octane here . I have a N42 block so there is no knock sensor hole in the block , so I need to come up with an alternative . Currently running 35 timing , but have ran as much as 37 degrees .

3.90 gears and about 7200 rpm shifts . 8B4867CC-29D6-428F-A1D7-5F72482973E3.MP4

It’s hard to figure your goals . The L motor can handle about any rpm range . The torque allows for lugging along just fine and cruise at 3500 also . 3.90 is nice for getting up to speed quickly . These cars are 50 years old and keeping up with fast highway speed there is other considerations besides just rpms. Noise, stability , aerodynamics. The 71C would be worth the effort because it’s a better trans and rebuilt parts are more plentiful . It’s a stronger transmission period.

The automatics - some of them- had 3.54 gears and it was 3500rpm at 70. These engines like a cruise at 3k , it won’t hurt it . I have very close to your scenario with a 3.90 gears from a subbie. If you have a little higher rpm cam it would be nice . 3.70 is a nice compromise , but not the easiest gear set to find . There’s a drone zone for some Z’s I’m that 2500 rpm range

Running N42 intake ?

Not 100% that this was necessarily a fix , still tuning . When I searched on EFI support the recommendations had changed to 4ms for the D-585 coils. Someone actually got the GM dwell tables and copied them . Another guy came up with 3.7ms based on GM tables . Anyways MSextra recommends 4

So a cup that slipped over the output shaft ?

I tried that laser deal, but didn’t get the right laser and didn’t have a precise mounting jig for the trans . I think I trust my angle reader , but it doesn’t verify if the there’s a lateral issue .

So the trans is 2.9 up?

Well it’s harder to get an appointment with a dyno than my doctor . I’m booked out to November . Business is good enough that most shops don’t want to give up there dyno to walk ins , they have so much in house projects . It’s all corvettes and Mustangs , etc.. I did upgrade my injectors to 42 lbs and re-tuned with success. Did another 4.77 split , so happy . Might play with valve timing a little to get more top end, but I think I’m at the end with the N42 intake . My buddy is converting a diesel intake for me to run EFi . I’ll go from 31mm runners to 35mm and looonger runners . It will be interesting .

Well the new flywheel worked out well . I also bumped up my injector size to 42lb Bosch’s. Made the change in fuel requirement and it fired right up and idled well. Drove it around for about an hours and let Tuner Analyze do it’s thing . Most cells were a bit rich, but not off a bunch . Now I won’t have to worry about pushing my 26lb injectors to their limit . I even did a 0-60 time to verify tune and it was the same exact time down to the 100th second 4.77

I guess it also depends on what the builder decides is the safe minimum wall thickness too! Maybe Dave pushes the envelope or is basing it on his experience . I told him I would be pressurizing , but it would be lower psi , higher CR build if anything . Maybe I just got lucky

I am currently converting a diesel intake for my 3.2 . Be curious how it will run with those long runners . If anything , it will look beautiful on there - lol. It will be on the other end of the spectrum of my N42 intake

Rust that needs chipped away ? Are diesels more plentiful over there ? Very cool project

MN47(N47)?

Well- NA or turbo ? Keeping the dished pistons or going flat ?. Purpose of build , rebuild for stock EFi or modified ? Budget? Power goals ?

The junk yards have them , but you got to dig deep

I left the decision with Dave Rebello. I know he can offset bore to get the most out of the block. I also went with a N42 block after reading it had the highest nickel content and a better chance of being bored higher. Maybe because of the structure of the block . He must have felt pretty confident because I told him that there is a possibility of running as a turbo with a different head . I do not know what wall thickness I ended up with .

Believe me - I drool about it a lot . A better inductions system would still help in the meantime

Just thought I would start another thread . This was supposed to be a L28/54 MN47 , but it ended up with a Rebello prepared N42 /MN47. The N42 was sent to Rebello and he prepped it for JE 89mm pistons . LD crankshaft offset ground with Eagle rods to get me 3.2 The MN47 head was ported by me - no flow bench , just seat of the pants cutting. Ports were only opened up to 35mm . Manely 44/35 swirl valves with bronze guides . The head is at 39cc . The cam is a 535 lift Bonk cam . It’s advertise 535 , but I could only get that with 0 lash , so it’s more like 520 lift . Engine management is a Megasquirt 3X with 270cc 14mm injectors running on a stock N42 intake with a 240sx 65mm TB . Exhaust is a MSA 6-2 header with dual exhaust to the back . BHJ damper , Kameari oil pump and chain tensioner . GM alternator 90 amps D-585 ignition coils with MSD wires . 4 row radiator with single electric fan cam sensor from 4.0 Jeep modified by me . flywheel 12lb steel that doubles for my CAS . Currently rev limiter is set at 7500 . Power drops off before then with current cam and induction .His build wouldn’t have happened except for the knowledge base on this site . Thanks for all that contributed their knowledge . Dyno session is schedule a month out . Currently using butt dyno and GPS speedo to do 0-60 times . It will also do quarter mile . Best time is 4.77 to 60 with some tire spin . Timing is 37 degrees max with a 13.0 set for WOT AFR. 7DE94C66-077D-4635-A801-2A09769EC638.MOV 8B4867CC-29D6-428F-A1D7-5F72482973E3.MP4

I love my 3.9 . I also like cruising at 3k because it’s where things really smooth out and I think the motor is really comfortable and no drone at 3k . Also puts me right close to power band . 0-60 times getting close to 4.5 seconds . I don’t care much about “top speed” . I am eye balling the CD to replace my G-force T-5 someday , but tired of working on the car -lol. I don’t mind altering my tunnel, my car is already altered . It would cheaper for me to get the CD vs replacing the T-5 if it crapped out. The love hate about the G-force is the straight cut gears . Love the gear noise sometimes and then sometimes I want more refinement .