Im going to have the 200R4 rebuilt shortly,,,when talking to the builder,,he mentioned that the governor in my trans (out of a late monte SS) is supposed to shift at around 5500 at WOT,,,which is as far as I know,,,a waste to ring one of these nails up to!!! He said he could get it down to 4500 with a different governor!! Is there any reason to keep it shifting at the higher rpm?? I didn;t have the TV set properly,,,and never rung the engine up that high!!! Im thinking the 4500 shifts would do a better job at keeping the nail in the power band and torque range it was designed for!!! What would generally be the best shift point for a nail!!! So far my combo is a pretty much stock rebuild with a cam that Carmen Faso advised,,,200R4 (obviously),,,3.55 posi on 27" tall tires!!! Any idea (s) if im going in the right direction!!! Car is a cruiser,,,but like to get on it from time to time and possibly go to the track once or twice a year for giggles!!!
at 4500 rpm is to low. you need to shift at about 5000 rpms if you have a bigger cam and carb, no more than 5300 rpms. what size cam and carb do you have.
Can't remember what the cam specs are,,,have to dig out the folder with all that info,,,I remember tell Faso that i just wanted something a touch hotter than stock,,, Im running a FAST EZ_EFI set up,,,theyre something around 900 cfm if I remember correctly!!!! So the max for a nail is 5300,,,do they just fall on their nose after that with a mild rebuild?? Plan for the future is to do a few mods,,,docs mod,,maybe some light head porting and clean the stock manifolds up some,,,would like to get a set of Toms rockers one day and give them a whirl too!!!!
The throttle body for the efi is rated at 1000 cfm!! The cam specs off "the cam dr's analisys",,,(who ever the dr is I have no idea!!!) Intake & Exhaust Lobe center sep 114.1 cam degree lobe center -9.9 crank degree Intake valve opening -5 BTDC lobe center 114.7 ATDC valve closure 43.5 ABDC Duration 218.5 crank deg max cam lift .28579 net valve lift .45726 lobe "area" 22.8 EXHAUST valve opening 43.4 BBDC lobe center 113.5 btdc valve closure -5 atdc duration 218.5 crank degrees max cam lift .28535 max valve lift .45656 lobe "area" 22.72 Not sure if all that information was needed for cam specs,,,at least its here in case i ever misplace my copy!!! Is this a "decent enough" cam,,,like I mentioned earlier,,,its mostly a cruiser,,,street car,,,and may end up at a track once in a while just for laughs!!! I pulled the engine and transmission out on sunday,,,had to pull both,,,with the adapter in,,,there was no room left to pull the transmission back enough to get it off the dowl pins,,,with out the possibility of wrecking something!!! While im waiting for the transmission,,,I plan on doing the doc mod,,,do some port matching,,,and "possibly" even do a very light clean up of the heads!!! Would some clean up work,,,with this cam,,,and hopefully someday a set of Toms rockers move the power around at all,,,or enough to leave the trans shifting @ 5500,,,or would you guys still recommend pullling shifts down to the 5000 to 5300 range!!! Any idea what kind of hp/torque this engine "should" be putting out with cleaned up ports and this cam?? Thanks for any imput!!!!
What adapterkit did you use? I know what you mean about not being able to pull the tranny. My 2004r shifts at 5000 rpm under wfo. I might change that to 5300 someday. 4500 is to low for a hotter cam and 1000cfm efi and few other mods. If you are talking hp at the crank my guess would be about 330. tq about 450. Thats my guess others might chime in.Peak hp might be 4700. clean up on the heads will help with any cam. the rockers are a nice improvment on these nailheads. I wa just starting to get used to my 2004r and winter hit,cant wait for spring.
My "kit" if ya want to call it that,,,came from that guy in Oregon,,,it was far from a "kit",,,no dowl pins on the adapter plate,,,hub was machined too short,,,nothing was right about it,,,I should've sent it back,,but when I got it,,I just put it on the shelf and didn;t use it for 2 years,,,so I sucked it up and took it to a machine shop that a friend owns and we built it properly!!! From some of the previous advise on my post,,,and reading other posts,,,think I'll get the trans guy to pull the shifts down to 5000,,,thatll be plenty for what Im doing with it,,,and considered a safe limit!!!! What code is your 200R4,,,wondering what valve body is in it that it shifts at 5000???
My '' kit'' was also from the same guy. Needed a lot of work but seems to be doing good now. My 2004r is fom extreme automatics and Ithink they make a lot of there parts. After talking to a few builders and reaserch on turbo buick I went with Lonnie Diers. We thought 5000 was a good shift point. He told me I could put it in 1st and wind it till the rods came out of the nailhead and it wont hurt his tranny. I dont think I will try that but I did like the confidence in his work. I plan on playing around with the engine this spring and find out what the best shift point is. Anyone else have any thoughts ?
I took my car out for a big cruise a few weekends ago,,,car has a 401,,,200R4,,3.55"s and a 27.1 tire height!! Averaged a hair over 18 mpg for the trip,,all highway!!! My initial goal was for 20 mpg,,so im a bit short on that,,which isnt a big deal really,,,but has me wondering!!! At 70 mph (which i ran for most of the trip except for a 20 mile stretch at well over that speed) my car turns 2064 rpm!!! Even though its a nail with a fair bit of torque,,,Im wondering if I went to a 4.11 which would bump my RPM up to 2390 rpm if it would help the nail breath a bit better and possibly help fuel mileage since it would put the engine more into the meat of the torque curve!!?? I know slowing down would also help fuel mileage,,,but 70 seems about as low as I can run without having to listen to exhaust drone!!! So the higher gears would help get the engine out of the area where the exhaust has the drone!!! Any ideas/guidance/experience from the nailhead guru's is appreciated!!! Chris
Thats nice if you already have the OD trans, but heres food for thought. A ST 400 VP w/ a converter from a 300 ( higher stall) 3.23 posi gears good for highway cruise and off the get go with a switch pitch toggle or timer box, 28'' tires and a big q-jet. Heres my take on a smart mans OD. the math goes like this 65 mph x gear ratio x 336 divided by tire dia. = 2546 RPMs this basically what the OD trans is going to get but with no lugging. Plus added a trans go premium shift kit. with the q-jet running on primaries but has the option to step on it and open up coupled with the switch pitch keeping it within the sweet spot driving no need for a OD trans, has the option to race if need be or economy for the long trips, hopefully looking at 20 mpg with this stock set up. 425 nailhead and ST400 VP was the best set up buick came up with, in my opinion way ahead of there times. [h=1]The Hot Rod Homepage[/h]Keepin it Hot Rod [HR][/HR] [h=2]The Switch Pitch TH-400[/h]Share Summary: The reasoning behind installing an overdrive transmission is running a low rear gearing to get off the line, but still retain manageable RPMs at freeway cruising speeds. This seems like the best of both worlds, but this article will examine some reasons why an overdrive transmission is not always be the best solution. Traditionally GM overdrive transmissions such as the 700-r4 and the 200-4r were viewed as anemic pieces for gas sipping transportation appliances. The last several years have revealed that these transmissions can be modified to handle significantly more power then in base configurations. A well-built and properly adjusted overdrive transmission should be able to handle around 450 ft/lbs of torque. Is that enough for the engine combinations that people run in their hot rods? In many cases the answer is no and I for one, have been through enough “built” 700-r4s for a lifetime. So what then is the solution? The solution is the tried and true TH-400, more specifically the variable-pitch version of the TH-400. The variable-pitch, or switch-pitch TH-400 is nothing new as it has been around since 1965. Originally found in Buick, Olds, and Cadillac the switch-pitch offers two stall speeds, a low stall and a high stall. Applying a positive 12-volt signal to the appropriate terminal on the transmission case makes the selection of low or high stall. The high stall gives you the advantages of torque multiplication to get off the line with a taller rearend gear and the low stall decreases slippage for cruising or on the big end of the track. The variable-pitch stator is not the only advantage that the TH-400 holds over its more modern overdrive counterparts. A TH-400 will generally cost less then an overdrive and it can be built to handle some serious horsepower numbers. The TH-700 and TH-200 also require a T.V. cable to be installed and adjusted correctly or serious damage and shifting problems will result, and getting it correct is often harder then it seems at first glance. Another advantage of the TH-400 is a small spread between gears. First lets put some gearing numbers out there for reference: Gear Ratio Comparisons: [TABLE] <TBODY>[TR] [TD][/TD] [TD]1st[/TD] [TD]2nd[/TD] [TD]3rd[/TD] [TD]4th[/TD] [/TR] [TR] [TD]TH 400[/TD] [TD]2.48 [/TD] [TD]1.48[/TD] [TD]1.00[/TD] [TD][/TD] [/TR] [TR] [TD]TH 700[/TD] [TD]3.06[/TD] [TD]1.63[/TD] [TD]1.00[/TD] [TD]0.70[/TD] [/TR] [TR] [TD]TH 200[/TD] [TD]2.74[/TD] [TD]1.57[/TD] [TD]1.0[/TD] [TD]0.67[/TD] [/TR] </TBODY>[/TABLE] It is clear that the two overdrive transmissions in the comparison chart have lower first gear ratios as well as have the advantage of overdrive, but let us look at the numbers that are hidden between these ratios. Between Gear Gap Comparisons: [TABLE] <TBODY>[TR] [TD][/TD] [TD]1st-2nd[/TD] [TD]2nd-3rd[/TD] [TD]3rd-4th[/TD] [/TR] [TR] [TD]TH 400[/TD] [TD]1.00[/TD] [TD]0.48[/TD] [TD][/TD] [/TR] [TR] [TD]TH 700[/TD] [TD]1.43[/TD] [TD]0.63[/TD] [TD]0.30[/TD] [/TR] [TR] [TD]TH 200[/TD] [TD]1.17[/TD] [TD]0.57[/TD] [TD]0.33[/TD] [/TR] </TBODY>[/TABLE] Notice the large gaps between gear ratios. The TH-700 has a particularly nasty gap between 1st and 2nd. In fact if you combine the 1st-2nd and 2nd-3rd gaps on the TH-400 you get roughly the same gap as the 1st-2nd on the 700-r4. The result of this is that your first gear in the TH-700 may launch you like a rocket, but the huge gap is going to lug your engine and drop RPMs, hurting performance. The TH-200 has a more favorable gear separation then the TH-700, but the TH-400 still has a slight edge. Now to address the flaw in my argument that I am sure many of you are thinking about. The TH-400 does not have an overdrive gear and if you don€™t run an overdrive then how can you possibly expect to have a respectable freeway cruising RPM? The solution to this is easy, run a taller rearend gear. I argue that the many hotrods rarely, if ever, see the drag strip and spend a lot more of their time on the road. So why then do we put in a low rearend gear that makes freeway driving unpleasant and limits out terminal velocity to 115 miles per hour. An overdrive transmission will make up for our low rear gearing, but this introduces several problems. Overdrive was never intended to be an acceleration gear, which it is being forced to become if you are running a deep rearend. High drive shaft speeds Running a 4.11 gear with a TH-700 sounds like a good idea until you consider that with a 275/40R17 tire at 100 mph your drive shaft is spinning at somewhere in the neighborhood of 5383 RPM for comparison a TH-400 with the same tire and a 3.08 rearend gearing will turn 4034 RPM. The same comparison at 150 mph yields 8075 for the overdrive versus 6051 for the TH-400. Spinning the drive shaft that fast takes horsepower and can have other problems like magnifying the effects of driveline alignment problems, drive shaft imbalance, and driveline component wear. With the right setup, a switch-pitch TH-400 provides a viable alternative to the modern overdrive. Controlling the converter: There is a multitude of possible methods for controlling when and how the converter changes from high to low stall. Use a delay box to have the converter go to low stall after you leave the starting line. An RPM switch could have the converter lock up once your car is into its power band. Wiring a relay to the brake switch would allow you to put the converter in high stall for stoplights in a car with a radical camshaft. A simple switch can be used to allow full driver control of the system. For most those who want to have the most control of their driving experience this probably the best option. [article on wiring a switch pitch transmission] Where do I get my hands on a switch pitch TH-400? I purchased the unit in my 1966 Malibu from PAE Enterprises in Texas. They offer both Chevy and BOP cases for a resonable price. PAE also sells conversion kits so those of you that already have a TH-400 are in luck. PAE’s contact information can be found in the sources section of this article. Sources: How to Work with and Modify the Turbo Hydra-Matic 400 Transmission by Ron Sessions ISBN: 0-87938-267-8 P.A.E Enterprises, Inc. 4401 Turf Rd. Bldg E El Paso, TX. 79938 915.855.6009 915.857.4727 -> Tech Line 8-10am and 4-5pm MST M-F www.paeenterprises.com Posted in Articles | ---------- Post added at 08:02 AM ---------- Previous post was at 07:17 AM ---------- Hell I might even think of getting that 72 Airstream I had my eye on and towing it with my 65 Rivi to car shows. God knows this rig has the power and trannty to do this.
Not saying your tranny guy doesn't know what he's talking about but I have never seen one of those Monte Carlo SS transmissions shift that high. I'd leave it alone until you find out where it's really going to shift, then fine tune it from there. It's cheap and easy, just takes some patience.
Guess I shouldve started a new post,,,what I meant to ask in my last post is,,, what RPM does a nailhead get most efficent?? I've read that for gearing purposes,,you should aim for 60 mph when the engine is running a bit below max torque,,
For what it is worth my Skylark is getting around 16mpg hand calculated driving normal. Just bought the car last fall and only driven it a few hundred miles and know little about the driveline. The previous owner told me it was a 1964 401ci with approx. 78k miles. He claim to have freshened the heads, he put a Mallory ignition system in it and a new 600cfm Edelbrock carb. He said it has a TH400 tranny but it may be the SP400, dont know enough to tell yet myself and the rear was out of a mid/late 60's Pontiac Temptest with what he though were 2.73 gears or somewhere in that range. I have not pulled the rear cover yet to verify the ratio. What rpm it runs at i do not know as the only tach that was in it was a huge aftermarket gaudy race tach that i told him he could keep. But the engine by ear seems to be running around 2200-2500rpm my guess. When cruising it has plenty of punch when nailing the gas and pulls strong up to 85-90mph which is the fastest i have had it so far. Personally my plan down the road is a shift kit, lower gears "probably 4.10's" and a gear vendors overdrive.
Woodchuck, It may be a ST300 check the tag or look for the kick down at the carb or two spade detent on the tranny, if its the 400 keep it and read the post I have.
65 MPH was the highway (freeway) speeds back in 1965 , these buicks and other cars were engineered to cruise at 65, 70 ish on that leaded ethyl. so Im guessing 2500 rpm would be a sweet spot for the 65 Riviera and still pleanty of punch down low + the kickdown passing gear that was on the switch pitch.
