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1968 327, 250hp

9K views 20 replies 10 participants last post by  WhitePerformance.com 
#1 ·
There are a few post requesting help with 327 builds. I think I listed a couple of them in the "Trackback" tab correctly (I think that is what that is used for).
I have a '68 327 that I believe is the 250hp (L73). I am looking to do a little revival of this motor and hoping to get a street-able combo where I can be a kid and spin tires if I want to, but realistically get from stop light to stop light and intersection to intersection as quick as possible. A guy I spoke with at a performance shop suggested the following combo:

-Promaxx 185cc Heads 64cc Combustion Chamber Flat Tappet Setup 272----859.00

-JB-817 Lifters---46.50
-TEK-1003-1205- ARP-3601-----167.50

-SCP1000 Scorpion Rocker Arms 1.5 Ratio---259.50

-110051-10 Howards Flat Tappet Camshaft----110.00

Can anyone provide a second opinion to help out. Currently paired to a 2spd PG, but will be mounted to a 4 spd when done and I think I am going to go with a 3.73 rear.

I listed the prices because this is about the total I am looking to speed when done (just under $1500)

Any help is appreciated.
 
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#2 ·
I don't race, so the babble below only has potential relevancy for a street car.

If the 250HP 327 was a high compression engine, maybe think about 72cc combustion chambers in case the pump fuel continues to get worse. I'm pretty sure the combustion chambers on a 327 were larger than 64cc. It'll run cooler and should not ping with the bigger chambers even with an aggressive timing curve, which can be fun between stop lights. Ask the builder what he thinks, unless you're the builder, then ask the performance shop guy.

I did a 350 build with 72cc ProMaxx heads I originally bought for a 11:1 60 over motor. Broke that motor a couple of times, gave it away, and wound up putting the ProMaxx heads on a low compression crate engine, and they work well with regular pump gas. Better with more octane of course, but still plenty of scoot for the street on regular.

I could not get small round tube thin flange headers to seal on those heads. Had to go with larger rectangular shaped tubes at the flange and a 3/8th flat flange and Remflex gaskets to get a seal. Stock iron exhaust manifolds might work, but never tried them. Intake ports are a little high as well. I had to use a Fel-Pro 1244 intake gasket on aftermarket intake manifolds. The machine work may have changed since I bought them 4 years ago, but those are the issues I ran into with ProMaxx heads.

With all that said, if the iron heads on the 327 are salvageable, you might want to just rebuild them and do some port work. Not sure if you would still be under budget doing that though.

Parts list looks good. I don't know about the cam, but spec wise it should do what you want to do between the lights with the 3.73 rear end.
 
#3 ·
The original 250hp 327 had 10.25:1 compression, flat top pistons with four valve reliefs. I would try to locate a good set of double hump heads, get a good valve job by reputable shop. Hydraulic FT cam and lifters, stamped steel rockers with long slots and performance pivots, Edelbrock manifold, small Holley carb, rebuilt HEI distributor with adjustable vacuum advance, headers with small diameter (1 1/2" or 1 5/8" primary tubes) with Turbo mufflers and dual exhaust exiting behind rear wheels, or out to the bumper. This will make a nice performing, streetable engine. There is no need to put expensive aluminum heads on this type of application.
Save your money for the 454 or 496 that you will end up wanting to build for the car someday . . . . . . . .
 
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#4 ·
Thank you guys for the info. Both of you are saying that this is a High compression motor. All other research that I have done indicates that this motor is some where between 8.6 and 8.75:1 ratio. Do you guys have any further insight with regards to this?

My understanding is that it has "290" heads on it, around 69cc. So, wouldn't I want to reduce that size to increase my compression ratio? And please forgive me if I sound ignorant, I am. I have some basic understanding and skill, but, I am new to understand the principle and tech behind this stuff.

Additionally, what RPM range can I expect to safely spin this motor too?
 
#12 ·
If it had 69cc combustion chamber heads, and it's an 8.6 - 8.75:1 motor, sure go ahead and put the 64cc heads on it for more compression. I though it had larger combustion chambers, like 76cc, when I made the earlier statements. I was also guessing that the 250HP 327 motor had higher than 8.75:1 compression.

I don't know what the max safe RPM is for that motor.

Use the Air Gap intake you have laying around. They work well.
 
#7 ·
Thank you for confirming the ratio GLHS60.

Steve,

the TEK 1003-1205 is the parts number for a SBC top end rebuild gasket and bolt kit. Copy and paste it into google or any other search engine and it will list its contents.


The budget is for the motor build only, I have two Holley aluminum intakes in the garage, a single plane and an air gap that I plan on experimenting with. I also have a few QJ and Holley carbs (650 and 750) that I plan on inner changing with the intakes to finalize the results. Timing Chain and push-rods are not accounted for yet. I have a few different options in the garage for valve covers that will match up with those heads.

Thank you
 
#8 ·
SixEight,

Single plane intake manifold is not the correct choice for your application. Use dual plane intake and 650 Holley for best results,
 
#9 ·
Engine Guy, you are saying thisbeca use of the RPM range? if for some other reason, please learn me something. Also, what do you think about the new trick flow double humps that are supposed to be coming out.

additionally, in your experience (or anyone else) should I consider one of those Edelbrock easy street or victor complete top end kits?

Thank you
 
#10 ·
I have built a few cheap 327" engines that will really impress especially if you can hook them to the pavement.

If you are building it yourself and are handy with the tune...as you seem to possibly be since you have multiple carbs and are willing to try different ones in the build.

I hate to assume But I assume you can tune a carb for max benefit.

64 cc chambers and flat tops are easily used today with 91 octane. I would not go larger chamber.
Remove all sharp edges in the combustion area including valve reliefs.
I do this for any compression engine.

I ran 461 and 492 heads in the 327" builds .. I ported them, smallish cams like the XE268H and an old crower #207 grind which was about the same but .510" lift on a 108LSA.

dual plane intake used was the Performer RPM 1 5/8" headers 2.5" exhaust. minimal bends good flowing 3" mufflers.
There you have a 13 second ride with 4 speed with 3.08 or 3.36 gear.

I like the 3500lb clutch and pressure plate from a 1 ton truck.. of course that was the way I thought years ago.

There may be better clutches today.
But dumped the clutch at 4500 rpm in a 68 camaro with .308 gear and sticky 12.5" wide tires and it would pull a nice wheelie.

That one was 461 heads.
It does not take much to make a fun runner. I used the stock bolts and stock pushrods in them.1.5 Roller rockers were used.

Buddy had the 327" I built with his 492 heads and XE268H cam.
His rebuild consisted of AFR eliminator 180cc heads and Extreme roller hydraulic cam the 270 it really did not feel much faster than the one I built for him.

If I was to build a 327 fo myself I would use some ported 601 casting heads... leave the 1.84-1.50 valves.. chambers should end up around 58cc with unshrouding..I would use a 280H comp magnum flat tappet ground on a 106LSA if I really wanted it to scoot.. If i cared about MPG I would go 110 LSA or a smaller cam.
Screw in studs 110 seat pressure on springs.

Of course flat tops with piston to head around .040"
If you are bucks up I suppose aftermarket heads will work.
Especially if you do not get into porting your own heads.

I have used the 1.74-1.50 305 2 barrel heads on a 350" in a 3000 lb nova with the 280H and it went 12.51 ET with TH350 2200 stall 456 gears.

Ported heads of course.. more gear than you want.. but the 373 gear would not be far behind especially with a better head on a 327.

You need to know how to tune it.

Without that ability you need to over build as you can be leaving a bunch of HP on the table really easy.
 
#11 ·
Single plane manifold is designed for higher RPM torque than the dual plane. For an application such as yours, dual plane and small carburetor is best choice for driveability and low-end torque. I don't have any information on new TrickFlow double hump heads, sorry. Complete top end kits are somewhat expensive.
 
#13 ·
I would approach the problem differently. If the 327 is running fine, I would make the drive train changes first. A 4 speed and 3.73 rear will make a big difference in the cars performance (from the power glide); especially if you have dual exhaust (isn't your setup single exhaust?). From there, I would reassess how much 'more' (if any) I wanted. The difference may surprise you.

If you wanted 'more', enjoy the manual while you save up some money and build/buy a 383 sbc. Or, if you wanted 'MORE', you are likely in BBC territory. I say this because 'displacement' is a more street friendly improvement over 'rpms'.

Just a little nostalgia. In 1968 I had a 63 Impala with a 283 two barrel with a 3 speed manual and 3.36 rear. I used to go looking for cars like yours to dust off at stop lights. :thumbsup:
 
#14 ·
Everyone thank you, really. I think I am going to go with the parts I have plus the ones from the list the guys over at White Performance suggested. I am going to try that air gap out and if it doesn't pull right, I will try a true dual plane. Unless I get a big "NO" from some one after this post saying that I am going to ruin the motor. But, if I read all y'alls info correctly after comparing as may specs as I can for all of your suggestions, what I originally posted should give me a good run for a while. And, Japete, I have to pull the head due to a failing gasket, so I am gonna go with it.

Thank you all very much... I will update with results in a few weeks when it is done
 
#16 · (Edited)
the formula folks forget that GM used to make their Super Sport cars "memorable"
very simple
did not use 2.73 or 3.08 gears, went 3.31-3.55 or even 3.73 gears! Far more important to have good gearing in a SBC car compared to a BBC car

Powerglide + any street gear = boredom

Let us presume that you have the typical flattop piston with 4 "eyebrow" valve notches. With the big chamber heads as found in 307s, 2-bbl cars, etc.....around 9:1cr. Since you have "290" heads, guess what? (edit for correctness #291 heads) Winner, Winner, Chicken Dinner! These are 4 bbl heads, camel hump, 64cc chambers. They are like the earlier camel hump heads, just have the pad and threads for in-head water temp sender, late 1967 --1968 engines. Same cam, just the 290 heads gives you a 275 horse 327.

Do NOT go big chamber. Factory 327s have compression trouble, the pistons are generally down in the hole more than your other Chevy Engines. "10.25:1" advertised is a big stretch. 10:1 on a good day, probably less if you calculate.

That cam, who picked THAT?
https://www.summitracing.com/parts/HRS-110051-10/
235/243 .488/.507 110 LSA

pretty serious for someone in a street car. lots of duration @ .050 for higher-up power
you might want to talk to a cam guru, CAM KING here or Chris Straub
I had a hyd roller reground for my street 327 68 Camaro ragtop 222*/.510/114 LSA
I learned more later, would have a different spec cam... anyway, compare this to the classic 327/350 horse HFT cam 221*/.447/114 LSA
 
#17 ·
pulled the covers, 3927185. my ignorance on reading something else originally made me believe they were 290's. I apologize for putting this uncorroborated info out there. from what I have read on a few other sites these appear to have 70cc chamber, 1.72 intake, and 1.5 exhaust.
 
#18 ·
White Performance = Skip White, he who has sold thousands of fake HEIs to unsuspecting customers. In general, he sells the cheapest china junk money can buy. If I were you I wouldn't buy anything from him unless it comes in a sealed box from Sealed Power or whoever the manufacturer is. Even then, keep in mind that it's easy to print boxes.

Many have learned the hard way on his stuff.
 
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#19 ·
#185 heads, 2-bbl fodder, small valves, big chamber, around 9:1 CR.
my bad earlier, not "290" which is a BBC head, stuff that I usually play with, but correct # is 291

Should I presume a 68 Car? What exactly is this going into/currently residing in?
What part of the country are you in?

If you want something period-looking, get 291 camel hump heads (if 68)
if looks are somewhat less important, 461 or 462 heads, no temp sender on the head (if 68 or earlier)
if later car, you want the passenger side alternator, long water pump, heads with bolt holes in the front the 69-70 head #186 or 041 head is the hot ticket.

Cheap option are some 305 HO heads, great compression gain, passes for later heads due to the bolt holes

another option, if correct-looking is not important, step up to VORTEC heads. These will require an intake manifold, valve covers, etc as they are different that older style SBCs. Small chamber, better/modern port designs, good power exceeding the others, again, it will not quite look period-correct
 
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