I'm not a mechanic, I'm building a 38 Chev,have it running,but it's not running as strong as I hoped.I have a 350 trany (I like them),a 2:73 10 bolt posi,finding an axle in the right width took some time,never found anything else.I know some of you told me this is tall ,but final drive is less than a 700r with 3;73 or 3;42.From my driveway it's at least 10 miles to any stop sign.This car will mostly be highway driven, maybe pass.Someday I'd like to put in a 383sbc.
I have a good 76 4bolt sbc, I know it's low compression year.I used a RV cam 204/214 ,same as Performer stat, Performer intake and carb, shortie headers.I haven't recurved the distributor yet.
If I keep my heads, is there a better cam choice?
If I change to 64cc heads,choices SR torquer $800, S&D has vortec kits with intake for $1000, but I'm thinking if I have to spend this much ,I should look at aluminum heads.Whats good? I've asked about Patriot or Pro comp and been told they'r junk,but why? Are Edelbrock Etec heads a good choice?I'm leaning more to the vortex style as I'm reading they should help mileage.
Cisco
true the final drive in high gear is close but the over drives have the advantage of deep gears off the line. I beleive you can get what you are looking for with a gear change. I would go to a 3.42 or 3.73. an example would be if your engine makes 200 ft.lbs of touque the 2.73 gears would multiply this into 546 ft.lbs of tourque. a 3.73 at the same speed would be 746 ft.lbs at the rear wheels.Now this is just an example using a easy number to work with but you see the point. No head change by itself will give you anywhere near an extra 200 ftlbs at the rear wheels at the same speed.
In order to get a head that will perform significantly better than the vortecs in your application, you will probably be spending ~$1500-$2000. Even then, you will probably only be looking at a ~30 hp difference assuming you will have a somewhat low lift cam. `
I had a vortec headed 355 (listed below) that ran awsome once I threw some gear at it. I originally had a 700R4 with a 2:73 rear gear. I switched to a 3.90 and noticed more of a performance difference than I did when I switched from a 30 year old stock 307 to the new 355. If you are going to keep your gear, I would recommend a 2200 stall at least. I had a 1900 at it was not enough with the 2:73 gears. With the 3.90's it was about perfect though.
Sorry ,I took awhile to borrow a compression tester.I just took readings, and put the car back together,what a pain getting plugs back in.It's fricking freezing in the garage too, -30 outside.Now I re-read the instructions posted here on how to do it.Sorry,I did not warm up the car, been sitting for months, didn't open the trottle.The compresion was 80 -85 on 6 cylinders, maybe 65 lbs on 2.
My cam is a Summit 1102, same as performer.I don't have an adjustable timing chain.I've been looking a heads and mine are 487, large chamber but should be a good head. Cisco
I was impressed with GM fastburn heads there not that expensive either maybe even ported L98 heads they can be had real cheep, but it has 58 cc chambers. With it being a truck motor lots of torque would be good.
You HAVE to do your CR test over. Bring it up to operating temp. then pull all the plugs and block the throttle OPEN... Get someone to turn the engine over with the key and you hold the CR guage. Count 5 - 6 hits on the guage until the CR does not go up any more. Record your numbers on each cylinder and get back here with your results.. If you have a vaccum guage do that test also and record the number and if the needle is jumping arround on the guage and between what numbers is it moving arround..
Don't put ANY bux on the engine until you test the engine as much as you possibly can!!!! Very IMP... Where is Picton??? Get back with the numbers B 4 U do anything else...
warmed up the motor, starts well, runs smooth.Did compression test.Wired trottle open , 6 cylinders were 95-100lbs, one was 85, one was 75lbs.The gauge is Snapon so it's prob OK.Someone else did the tappet adjustments, if the lifters weren't pumped up and the tappets adjusted could the lifters now be taking the valve off the seats or are the heads toast/Or is my cam blowing it all out? thanks guys, Cisco
Crap, just got it together before winter.I'll do a leak down test, I think it's probably valves as motor doesn't smoke.Motor had 70,000 on it.
BTW ....Picton is in Ontario,Canada.I work in the town Avril Lavinge comes from.If it gets much warmer my 30 x 40 igloo garage will melt soon. P
Cisco
sounds like the cam is installed wrong. retarded cam timing will cause very low pressures like that.
As for heads......I would use a set of edelbrock heads, 64cc chambers, 170cc intake ports. I would also use the regular performer heads with the exhaust crossover (not the rpm heads). This will come in handy when it is cold outside and -30 is pretty cold.
vortec heads are nice and would match your cam very well. be they need special rocker arms, valve covers, and intake manifold and machine work to run a cam with more than 0.450" lift so it ends up costing the same or more. And they flow terrible on the exhaust side.
you should get fairly good performance even with a 2.73 gear if you can make some more cylinder pressure.
Good morning!!! Ask arround to find a trusty engine/machine shop in your area.. Yah gotta be near the Ottawa Valley or close thereabouts... Did you put oil into the cylinders after you had the low readings??? Try and get a spoonful into each spark plug hole and see if your readings go up or if they stay the same... Staying the same means valves and going up readings means rings... Either you do a leakdown test or get the above trusty shop to do it... Make your decision after that as to exactly how much you would spend, what exactLY you want the engine to accomplish... Sit down with the engine shop person of your choice and discuss exactly exactly what you want and how much you want to spend... Keep it all under one roof ... so to speak as if you go to 4 different spots, if something goes astray (wrong) they will have built in excuses as to "well we did not tell you to do that or buy that or go that way". Do it right the first time and yah won't have to go back and do it over... Maybe the shop will have a great deal for you sitting on the shop floor for a great price with a guarantee / warranty???
Lotsa people will give their own ideas and some are great, but yah gotta start with a good base or all the heads / cams / intakes / carbs ain't a gonna do you right if you start off with a "wheezer"
Don't spend a dime until you do the above, for your own sake!!!
"if" the rotating assembly is sealing decent and all is ok, your vac guage will tell you....a rv cam motor should read 25Hg+ when decelerating back to idle from about 3k...read this link for diagnosing a motor with a vac guage (kinda cool, the guages are "animated")
to get a even more accurate reading, rig your vac guage so you can read it while driving (windshield wiper hose and a T in the manifold vacuum advance line and duct tape it to the windshield?)
"if" the rotating assembly is sealing as it should it will read 25Hg+ (28Hg=really good) and steady(!) when down shifted 3rd to second at 3k rpms "with a load on the motor" (which is really what you want to know, how well is it sealing while actually driving)
"ballpark" with a rv cam your comp test readings should be atleast:
8/1+CR=140-150psi
9/1+CR=140-170psi
10/1CR=180+
the specific cam and how it's installed and at what "altitude" are you doing the test does impact the results you see "some" (ex: a motor that tested 180 at sea level will test around 160 at 5,000 ft)
ps: that link points out just some of the reasons you DO want to have a vac guage "in" your car...to see a new problem immediately
OOPS, never done a CR before. I was using a hose with CR tester that had a short male connector at spark plug hole like the sprk plugs, looked at the long connector hose today and tried it.Compression was way up,instead of 95lb was 150-160, but 2 cylinders were still down at 130-135Lb.Oil brought them up to 145lbs.Don't know why 2 cylinders won't be down like that.Guess motor is screwed.
I have a friend that deals and plays with cars.He has a SBC that he had custom built ,took motor out when he sold car and it's been sitting.I know he never drove the car much.He offered the motor to me. It has a good crank and rods,10:1 forged flat top pistons, 461 heads,290*/500" cam.The down side for me is maybe the compression, but for sure the cam.He ran a 3500 stall convertor and I don't want to.
I have a TH350, 2:73 10 bolt, performer intake and carb, shorty headers with 2'' exhaust.I live in the country, no stop and go traffic, so all I want is to cruise in this car. I've spun enough rubber on 2 or 4 wheels in my day.
I have a Summit 1102 cam,(204,214@ 420,442),will this cam work well for me with that compression? Should the valve springs in the new motor be OK with the 1102 cam.Think I can run 87 octane?
Cisco
Crap, just got it together before winter.I'll do a leak down test, I think it's probably valves as motor doesn't smoke.Motor had 70,000 on it.
BTW ....Picton is in Ontario,Canada.I work in the town Avril Lavinge comes from.If it gets much warmer my 30 x 40 igloo garage will melt soon. P
Cisco
I can't get the car out because there's 2 feet of solid ice in front of the garage.What happened to global warming? I've had stuff growing this time most years. Cisco
Are your Aunt and Uncle related to Avril? LOL The fish moved to deeper water after the Zebra mussels cleaned the water, not as much ice fishing now.Used to be lots on the ice in front of the house, haven't seen anyone in years now.Besides who likes frozen fish?I don't even feed my cats fish and I have 13 ,oops 16 of them.have to include the German breeding stock
too. Cisco
Cisco,
those numbers are fine and the good news is you very likely can burn "elcheapo" brand 87octane with maxed timing...
nah, leave it together..... rule of thumb is if all cylinders do test within 10%....keep on driving....135 X 1.10% =148= close enough
when you "can" test drive and downshift with the vac guage...the vac guage is likely to read 24Hg+ and steady...when it does read <23Hg after alot more miles tear it down (and likely you will be adding a qt of oil every 1,000 miles at that point)
on any motor "some" cylinders live a much harder life (do more work with a less than best A/F mix) so the do wear faster
if this is a fresh build.....ignore the comp test results and vac readings till you get 500+ road miles on the motor (and re-torque and re-tune the whole motor)
Cisco,
the "catch 22" of building a street (low) rpms performance motor is that there is not a hell of alot of power (TQ) there to begin with to add onto....
the rv 204/214 cam will make almost as much TQ at 2k as the stock 190/202(?) cam for good normal acceleration....and a bit quicker "wind up" for passing a truck (with your relatively tall 2.73 gears good for mpg)
any cam much bigger kills that 2k street rpms number.... DD example from another thread on a 8.5CR motor:
222/222 vette cam=72ft/lbs @1k, 243ft/lbs@2k
same motor with a oem 190/209= 160ft/lbs @ 1k, 309ft/lbs @ 2k
243ft/lbs vette cam x2.73 gears=663ft/lbs at the tires
309ft/lbs stock cam x 2.73= 843 ft/lbs at the tires= roughly 30% more actual force twisting the hides at 2k rpms
bottem line is the "stock" motor build (250hp?) is the most and soonest maxTQ possible in the street rpms range...stock small 2V, stock intake, stock cam, etc....takes alot of careful planning and tweeking to actually get more TQ at street rpms than a plain vanilla 8.5CR 87octane 350
a year of planning and 2 years worth of tweeking my 208/214 cam 302 motor and I do know it would perform better driving normal with a stock 289 cam...but I don't want to give up 0-60mph in just a tad over 5 seconds with 3.55 gears and chirping the tires on the 1-2 shift with a automatic
The engine that is in my car is 70,000 mile 1976 4 bolt sbc out of a truck,487 heads.I put a new RV cam, oil pump,stock timing set,Edelbrock manifold & carb.It is the one with 2 cylinders down.My 74 Vet had 3:08 and it was way quicker and had nothing done to it.3:08 vs 2:73 aren't that far apart are they?I just don't think this motor has the balls it should.
My friends motor that I'm thinking of using is the 10:1 sbc with the big cam.I'm wondering weither to use my RV cam or something else in it.I want mpg not tire burning torque.
I guess what I have to decide now is if to change the motor or not.I'm keeping my th350. How much of a lower gear can I use without hurting mpg?Using a axle calculator ,car doing 2000rpm ,car is 60 mph.
Cisco.
re-curve the dist will help it grow some gonads...
sorry my post wasn't clear...for a really responsive motor on the street you do want to have way more than the minumum needed TQ available...so that just a little pedal the rpms jump very quickly when accelerating normal (hard for me to keep my car steady at 2k=40mph=320ft/lbs x 3.55 gears=1136ft/lbs in a 3400lb car=1ft/lb per 3lbs of car weight)...touch the gas and it jumps to 60mph!
(and when the grand kids are in the car you can light'em up)
each additional full compression point added only adds "up to" 4% to the power...your at roughly 9/1 and say 260hp....put a rv cam in a 10/1 motor would be only 10hp more "possible" AND require 92-94 octane likely
I am chuckling because you started out asking for a 90% hwy cruiser "only" and 87 octane and mpg (=9/1CR 87 octane rv cam) ....now yer askin' fer "vette' performance (and 87 octane and mpg!).... that's a oxymoron... or.... go buy a $71,000 ZO6...505hp and 25(?)mpg hwy on 94 octane
ya gotta choose your priorities...or get out your wallet and buy a OD tranny and much lower gears....or just stick a simple NOS kit on it.... (and have 87octane and mpg and "vette" performance)
Cisco,
apology!
I was chuckling because you "clearly" stated your "priorities" in your post #15...
and repeatedly asked for "best mpg possible"...
then you compared the performance of this "truck motor" designed for low end TQ to a "vette" motor designed for high rpms performance (apples to oranges)
a car only uses around 40-60hp to maintain hwy speed depending on the car wt...so motor rpms @ hwy speed does pretty much determine mpg....go any deeper than about 3.08 gears and mpg will be less and that's not nearly enough to to give it some balls
best solution for best performance and best mpg on the "truck" motor is a OD tranny to keep it at 2k=60mph with much deeper gears to give it some gonads when it downshifts WOT
Thanks, Red.
74 Vette L48 ,2 bolt,piece of crap low CR, but burned out, chirps when shifts, doesn't glue you to the seat when accelerating,gets 25mpg.I drove it until everything went,then I sold it for almost what I paid new.
76 4 bolt truck motor ,487 heads, low CR,with my cam ,intake,headers,I'm saying it should run stronger,A 3:08 isn't that much dif than a 2:73 is it?
The truck motor doesn't pull, doubt it will burn and gets 15mpg and it should be the better motor.
The way it is here,I can't find a SBC in a wrecker.I found a camaros LS motor and trany for $6500 at a wrecker last week.If my motors dying ,it's gotta go.My cheapest opition is my friends motor,but with 10:1, I don't think I want it.A fresh build will be $5000 for a sbc.I'd like a cheaper solution.(dreamer)
My car sat at a hot rod shop for 2 1/2 years.I dragged it home,stripped it back to frame,re-did almost all the shops work in 4 months.I have some body issues and glass to replace,then I'll paint it myself.Once that's done I will not want to take it apart.The other issue is what do I paint on it.I raise pedigree cats(truth,see below).Do you think I'd get thumbs up for flaming cats on the fenders? LOL
Cisco
Kerakterkatz ( character cats )
Maine **** cats with character http://kerakterkatz.tubazaar.com
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