Inliners International Forums General Discussion Engines Deciding what to do to my 250

New here, ill give ya guys the run down....69 nova stock. So we got a no p/s no a/c base model. the 250, power glide, and 2.73's. Not new to going fast, i mess with volvos mainly, ive got a stroked tweaked megasquirted turbo'd volvo....anywho

Plans for the nova? Wanna keep the outside stock looking, cause the car is unbutchered and complete. Motor has 193,000 on the clock, and could be freshened up. Sat for 25 years due to a blown head gasket, a quick resurface and a valve lapping it was purring again. Valve train is a little noisy, buts then again, its all original, head still needs guides and seats. So ill have to go through the motor at some point.

I dont need the fastest 6 on the block, and i dont need to rev the nuts off of it. I want a streetable, reliable, quick car. Quick doesnt need to be fast. Hard to grasp for some i know. Some of my questions are along the lines of how many carbs. I love the look of dual even triple carbs. If i went triple it would be progressive, and i know head work would have to be done. Porting? bigger valves? Ive read good things bout using a holly 390cfm, but ive never been a fan of holly for a daily driver, call me crazy! But ive taken more of them off and replaced them with AFB's on small blocks, topic for another time. But i love multiple carbs, and if i can get what i want that way, then ill do it that way, lol. So advantages, disadvanteges of the choices? Header or cast manifold recommendations?

Cam recommendations? Keepin it carb'd, no turbos, lol

And the motor, pistons and rods and the such. I dont know how the 69 was set up in terms of CR and if changing it will really be necessary. Strength of the rods, etc etc.

Sorry for the long post, just tryin to get some ideas of where i may want to go with it. I know about going with a TH350 or even a 200r4, changing the rear gears, but the motor is where my question is for now. Bottom line is id like a 300hp daily driver, or close to it. My volvo is just about there, and ive got 2 more cylinders and 100 inches with the 250, heh. Thanks for the help in advance!!

Mark

300 hp + PG + 2.73?
The amount of cam you'd need means a high-stall converter, which means it will slip at 60 with 2.73 gears.
The L6 needs more speed equipment than an SBC for the same HP per inch. 300 from 250 takes more parts than 420 from a 350.
A compromise: you could get a lot of the effect from doing an excellent job on the head, manifold, carbs, exhaust, ignition, but leave the cam alone until you re-do the block and sort out the chassis to keep the moderate RPM range and low-speed torque.

Get rid of the PG, 200R4 bolts in ,no driveshaft replacement/mod needed.
Relocate trans crossmember. Need to hook up trans TV cable correctly for trans to live & shift correctly.


200R4 will work better than a TH 350 ,lower 1st gear.
2.73''s,,,hmmmmm,,not good,,, unless you want to put in a SBC 400.
2.73's w/a 250 6 will not be quick N/A (normally aspirated)
Gear change will be a must. 3.42-3.73 & a 200R4 trans

300 HP,easy w/a turbo,not easy N/A worn out engine.
You will need to rev it to make 300 HP,not going to make 300 HP @ 4500 RPM.

I do not like Hollys either.
Edelbrock AFB or AVS good choice.

Run a small chamber 194 cyl head to bump up compression 1 point or use your stock 250 head (stock compression 8.5:1) & these pistons TRW L 2289 .030 over forged pistons for chevy 250.No chamfer
https://www.inliners.org/ubbthreads/ubbthreads.php?ubb=showflat&Number=61714#Post61714
Try & find SBC 307 cast pistons,4 valve reliefs w.no chamfer on top sides.
Stock rods, side grinded/polished & shot peened w/ ARP rod bolts.
Cast iron manifolds :
http://stoveboltengineco.com/index.php/c...product=1395980
Cyl head work will cost the most ,lump ports,larger valves etc.
use http://www.sissellautomotive.com/
or Larry AKA Twisted6: http://www.t6racing.org/

Run a stock style 8" HP SBC damper & have a machine shop machine the "V" groove/s in the damper to drive the accessory/s
Example: http://cgi.ebay.com/ebaymotors/SBC-Chevy...sQ5fAccessories
Or one of there 6.3/4" to keep the drive ratio close to stock.

Camshaft, .480-.500 lift 220 degrees duration @ .050 in. & ex. lobe center of 114.
Stall on converter 2200-2600 with Lock-up depending on cam & compression you end up with. you get

Realy quick & dirty run down off the top of my head.


MBHD

Mark,

Welcome...

As an alternative to trying to get 300HP from the 250... consider installing a GM late model inline 6 from a trail blazer. They are either 275 or 290 HP stock. For a stock engine run the GM PCM. Easiest method is to buy a rolled/crunched envoy/trailblazer. These engines are known here are the 4200. GM knows them as the LL8.

If you get lucky a complete wreck might be had for about $1500-2000.

There will be some fabrication to get it installed. Mainly engine mounts. An aftermarket rear sump oil pan is available.

If you have done a MS conversion then wiring to do the conversion most likely is doable.

x2 ,a better choice !

MBHD

I'm using a 250 in my Nova wagon and using an Offenhauser manifold with a 500 cfm Edelbrock carb, a Comp Cams 268H Magnum cam and kit along with Langdons cst headers. I'm not sure of the HP but compared to the stock engine it's pretty perky, but it's not a canyon carver. I'm usiing a Saginaw 4 spd. so can't comment on the auto trans,but

Wow, people that know what they are doing, nice! Heh 300 may be more work then I wanna do lol. I figured its gonna take much more to get what I want (300) as opposed to what I would like (actual drivability) outa the 6, but what I will be happy with is prolly not even close to 300. 300 may not have been a number I should have thrown out there, but i got some good info. Not gonna boost this motor, gonna keep it N/A. I guess I really just wanna wake it up, get it to kick.

I know im gonna have to eventually change out the PG and 2.73, also gonna have to install power brakes, and rid the car of the front drums heh. Lots on the table. But i always cruise local classifides and junk yards, so gears and a trans wont be an issue when Im ready. Lemme see if i can fine tune some q's

Carbs, realistically everything tuned properly, is there a benifit to going with 1 4bbl, vs. 2 simultaneous 1bbl vs. 3 progressive 1bbl. I under stand the atomization issues with one carb in the middle of the long motor. But in the long run, with my but dyno as the deciding factor, is there really an advantage or disadvantage to any of the choices?

Stock head limitations? Is porting worth the time and effort with stock valves? If I reuse the head it will need seats anyway, as it doesnt have hardened seats. But like with my volvo head, porting gives you little without bigger valves, as proved on a flow bench. SO whats the best bang for the buck with the head. Read a little about lump ports, but is it really advantageous to go that far without the bigger valves? Would the time and $$ be better spent with a decent port job?

If I use the cast headers from stovebolt, do I use a water block for heating the intake manifold?

Lastly the bottom end. 8.5 is so perfect for boost! But not gonna do that here, lol. SO stock CR is 8.5. Stock pistons, a 194 head will bump that to 9.5? Now if i use the 250 head and the TRW pistons mentioned will that also bump the compression?
The cam that MBHD mentioned, custom grind? Something I can buy that close off the shelf?

Ignition system i can figure out. Will prolly start with a nice HEI setup, points gotta go!

I know there are a ton of ways to go here, just keep in mind im not building a race car. A compression bump, nice cam and some head work, carbs and exhaust will prolly put me where i want to be. Best headwork for the buck, what cam with out loosing all my vacuum and what pistons to bump the CR

Mark

I'll let others speak to the multi-carb route.
Yes to heating the intake.
Yes to HEI.
Other cams to look at - Schnieder Cams in CA.
Stock head limitations? You hit it on the head (pun intended)
Lumps in the intakes, larger valves, with mild blending is the simple and cost effective answer. Lots of info and several vendors of lumps on this board.

Ditto on the HEI, the jury is out on the 194 head, TLowe ran some dyno tests this year that show that's more of an urban myth as far as making more power, the port lumps will help build power and if you get the manifolod from Langdons you can order it with the water plate and the casting bungs are welded in and won't leak. With the cast headers the exhaust rap will make you sound faster and sound a lot kooler than a bent 8.

So lumps are prolly in order, they dont look too hard to install, watched a video on youtube. Cams ill do some more research.

So then compression ratio is still up in the air and the multi carbs.

Great info so far!

Mark

Ok, so heres another direction. Blow through turbo on a stock head and cam, or a head with some work. Cam change? What are the thoughts for that, and keeping the PG and 2.73? I guess im not really sure which way I wanna go, more info i have and experiences from people the better i can make a decision, lol

Mark

No real reason to keep the glide. Kick it to the curb.

Sure, blow through carb, worked over head,don't really need lump ports when forcing air/fuel throught the intake port(not as critical),but it does not hurt either to do a lump port..
Larger intake valves 1.85" in 1.60" exhaust,hardened shallow exhaust seats.,mild porting bowls, sort turn radius's

Cam change ,yes,nothing radical & run a wide lobe center of 115 or more.Most likely custom grind, I like Comp Cams & they will grind what ever specs you want basically..

If you want a cam grind listing,just ask. Most off the shelf grinds I would not run.
I can look if I remember to ,,,LOL.


MBHD

So the turbo idea is in teh back of my head, prolly wont be done, but here is what im thinkin, it will be one of two choices, and i need to know some cam specs for each choice, as i dont know what to look for when i request a custon grind.

Blow through turbo, prolly low boost 5-8psi, lump ports, valve size to be determined.

3 1bbl's progressive, lump ports, bigger valves, etc.

SO what cam would i be looking at getting made for each application? Obviously when the rebuild is done different pistons would be fitted for a turbo setup.

Mark

You can use the same cam for all your carb set-ups.

Personnally, I would stick to just one carb, less plumbing,less chances of leaks,way easyier to work on.

MBHD

Ok, cool. SO then the cam you recommended towards the top of this thread the one i should go with? Ive messed with more than a handful of multi carb setups, and while it may take a little more maintenance, I love the cool factor, lol! Plumbing isnt an issue for me, and leaks I dont see being a problem. So ya, one more q. The HEI dizzy, can I pull that from a truck with a 292? I see many more of those than 250's in the bone yards. I know to get a rebuilt one is cheep enough, but you cant beat half price day at the pick n pulls.

Mark

autocomman,

could you tell me what your goals are? Basic, set-up of your carb/s,turbo,no turbo,etc.
Thanks
You can run multi carbs if you like,been there done that,now I like to keep it simple,but that's me.

292 HEI are the same & will work on a 250,,corect guys???

MBHD

Goals.....lemme see how I can put this. Basicallt the car is 100% original. While thats neat, and most of the car will stay stock looking, the motor is tired. I cant give you a number, ive found that a HP number can be meaningless sometimes, except for bragging rights. At least in a daily driver. My old 3,300lb volvo was 165hp and 220 ftlbs torque at the wheels. This was fine for a daily, it did what i wanted and surprised most people. but i wanted it faster...

For the nova, its not bad with the 155 is came with, but it does leave some to be desired. Im sure with the torque of the 6 ill be happy where ever that lands, 200hp would prolly be a nice round number easily obtainable. And while a blow through turbo would be simple enough, and definatly be different, I dont see that for this car. A multi carb setup is what im going for. The glide will be in there at least for now. If the car is kept over the next few years it will prolly come out for the 200r. But I still wanna do up the 6. So, goals.....im guess is 200-250hp would sit nicely in the car. Multi carb setup, prolly 3 singles on a progressive linkage with the HEI. Id like the car to idle decently. It idles like glass now, even with the 193,000 on it though i know the idle may suffer from a cam. It will tend to be driven normally, unless im drivin it, lol. But even this it must retain a DD type setup. Reliable, and easy to drive. But when i put my foot in it i wanna have the confidence i can pass someone without out second guessing it. I wont be revving the nuts off the motor, no reason to.

And I know the glide is holding it back, and so much more can be had tossing it to the curb, and same with the rear gears. But the motor is my concern here. I want it to put you in the seat a little, so people go WTF? its a 6? Hope that clears things up, if i need to be more specific i can try. And id like to retain some vacuum for a brake booster

Mark

I think the 2.73 makes it tough.... thats a talll first gear with a glide, you'd do the car a favor getting gears closer to 3.73.

autocomman,
in reality, with out changing the trans & rear gears,it will just be a dog normally aspirated,,your only hope to pull that bad of gearing would be to install a 292 even then, I think you will not be happy with the end result.

I understand about being on a budget,but your gear set-up needs to change.
Adding a turbo will work great with those gears because of all the added torque it will provide.
Also,w/a turbo & your gearing it will really put a load on the motor & you will be hard pressed not to go into boost w/just a bit of throttle.

I cannot think of a combo that you will be happy with that gearing for a DD on a normally aspirated 250 engine.
Maybe it's just me,but you might be OK with the very slow take-off & the 2nd gear shift @ 80+ MPH.

My moms 73 4 dr Nova had a PG & 3.08 gears & ran 20-22 sec in the 1/4,it was stock. 3000+ altitude track

If you had an early lightweight Nova, that would help,but a 69 Nova is no featherweight.This cam will work.

03242
262HDP
1800 – 4500
262 / 272
0.478 / 0.490
204 / 212
112 But would like a 114 lobe center





MBHD

Autocomman,
I've followed your thread as it is not unlike my own build (starting point is a 250-powerglide-3.08 Nova 63ss).
So I am starting with a tad more gear and almost 300 lb less weight, but otherwise similar.

I agree with all the suggestions so far (and the order), whether you do the trans and gear first or last is of course up to you, but I agree with these guys it is the best single mod you could make (the 200-4r trans). That said, I too am doing things in the reverse order (engine first, then trans/rear). I suppose what triggered my order was, my 292cid was sitting outside and got rained on once, so my goal was to get it back under the hood.

With that I will use my Gonkulator computer (take it with a grain of salt but it's easier than wrenching....) to show how your car might proceed so you can put some numbers to "ok" vs "quick" vs "fast".

Here is what the Gonkulator thinks you have now.
Stock 250/155
3.03 60ft
12.77 at 58.7mph 1/8 mile
19.57 at 71.0 1/4 mile

For comparison, Motor Trend tested a 69 Nova 250/155, th350 trans, 3.08 rear. With 2 people aboard they got
19.00 at 71.0 1/4 mile

Well, if you think that is "ok", have we got good news for you.

The single most effective mod you could make under the hood would be to swap the 250 for a stock 292:
2.88
12.06 at 61.0
18.63 at 73.8

However, more effective than that even is to leave your stock 250 there and swap in a 200-4r trans:
2.60
11.58 at 59.4
18.23 at 72.9
That is a 1.3 sec change in 1/4 mile from a single mod. Wow.
Add a 3.55 gear (give or take) for
2.48
11.31 at 59.7
17.98 at 73.0
This is still your bone stock 250 and dinky stock exhaust!

OK, what if you do the engine first?
I computed the engine described by Hank MBHD - and a selection of four intake systems:
Offy-4bbl and Carter/Edel AFB 500cfm on top
Clifford-4v and Carter/Edel AFB 500cfm on top
Offy-3*1bbl and 3 Roch BV carbs on top
Offy-2*1bbl and 2 truck 292 Roch B carbs on top

All four of these 254cid ~9.5 compression combos gave the same result within about a tenth and 1mph or so:
Torq 280 at 3500 give or take a few
Powr 240 at 5200 give or take a few
2.85
11.70 at 67-ish
17.40 at 85-ish

Now adding the 200-4r and 3.55 gears, again all the intakes did about the same within a tenth and a mph or so
2.35
9.90 at 72-ish
15.45 at 87-ish

As you can see, even moreso with the built engine, the 200-4r and gear added the most - nearly a 2 second improvement. They are a must-do - and you now have a car that is quicker than many factory 327 Novas and even a few factory GTO's.

So that is the story, many of us (me) kinda have to use 1/4 mile numbers to describe what "ok" vs "fast" vs "bow-wow" is. Hope this helps.

I completly understand im doing this backwards. Right now I think its mainly research. Ive done the trans swap, gear conbo stuff on cars before so I hear where you guys are coming from. What im looking at is a tired motor that if i keep the car im gonna have to go and rebuild. The PG and rear is still fine, so its not up there on the list. But the motor is at the top of the list cause if its condition. And if i gotta go through it, then i wanna do it once and do it the way i want, then add the other things later, such as the 200 and the rear gears. The cam, head and intake info is what i was looking for in the end, thanks for that MBHD! Now I know where I will want to go, of course pending some cash flow, lol!

Mark