327/275 build advice

gmc · Feb 2, 2010

After a lot of research (I can't believe the wealth of knowledge on this site) I am getting ready to dive into the drivetrain in my 69. Car currently has a basically stock 68 327/275. I will also be installing a 12 bolt w/3.42 and a TKO-600.
The engine is fairly fresh so I am only looking to build the top end. I'm hoping for @375 hp and 390 lb/ft. Car is mostly street driven and sees quite a bit of stop and go (may see occasional track use), so I'm looking for good low end power and a decent idle.
My plan:
RHS pro action cast iron heads 180 cc int and 64 cc cc.
Lunati voodoo 60103
1.5 rr
MSD pro billet HEI (already on car)
Edelbrock performer rpm air gap
Hedman elite full length w/1 5/8 pri
Magnaflow exhaust with x pipe

Carb??? can someone recommend a good carb for this setup?

Is this a good combination for what I'm trying to do? Any estimates on power?
Thanks.

68basecoupe · Feb 2, 2010

I believe Chevy High Performance did an article where they built a 327 with an edelbrock top end kit(roller cam I think) and got around 400 hp.You could probably do search on their website and find it.

TJS69 · Feb 2, 2010

Those are great heads and you will eclipse your power guesstimate. I would recommend a Holley 650 or a Quadrajet. I would think real hard about the Quadrajet, but some people have to have a Holley.

Eleanor's Nemesis · Feb 2, 2010

IMO you will be pretty close to your power goal....as much as I like Holley carbs you might find better success-especially if you drive it onthe street a lot-with a quadrajet. Most of the Q-jets found on chevy engines were of the 750 CFM variety. The small primaries will probably give you better fuel economy, maybe better throttle response too.

TJS69 · Feb 2, 2010

A Desk Top Dyno "Guess" is 376 HP and 398 ft/lbs. tq. Let's hope the bottom end will survive. Those heads should up the compression to about 9.7:1.

gmc · Feb 2, 2010

Eleanor's Nemesis said:
IMO you will be pretty close to your power goal....as much as I like Holley carbs you might find better success-especially if you drive it onthe street a lot-with a quadrajet. Most of the Q-jets found on chevy engines were of the 750 CFM variety. The small primaries will probably give you better fuel economy, maybe better throttle response too.

TJS69 said:
Those are great heads and you will eclipse your power guesstimate. I would recommend a Holley 650 or a Quadrajet. I would think real hard about the Quadrajet, but some people have to have a Holley.

It currently has a Holley 750 dp w/mech secondaries. The carb is way to big for the current config, it doesn't have a choke and is showing some wear. The concern I have with a Q-jet is my intake choice; I don't believe I can get the rpm air-gap in a spread bore. With the 650, would vacuum or mechanical secondaries be my best bet? Any thoughts on the 650 Speed Demon? Thanks again.

Eleanor's Nemesis · Feb 2, 2010

I've never used a Demon, had 2 friends that ordered 2 demons together and both had issues on visual inspection and got sent back. I know a lot of people are running Demons, maybe they are good stuff, but I have heard enough to stay away.
You can get a plenum adapter for the quadrajet, they are probably 25 bucks or so. If you decide to stay with a square bore carb I would go with a 650 vacuum secondary holley.

gmc · Feb 2, 2010

TJS69 said:
A Desk Top Dyno "Guess" is 376 HP and 398 ft/lbs. tq. Let's hope the bottom end will survive. Those heads should up the compression to about 9.7:1.

Tom,
Do you know what the weak link in the bottom end would be? I know some of the old 327s were rated close to 400 hp from the factory. Did they use different rotating assemblies or blocks?

Camaros-n-Chevelles · Feb 2, 2010

The 327 Large Journal Motors in 1968 and 1969 came with Cast Iron Crankshafts, except for the L79 which came with a Forged Crankshaft.
From 1962-1967, all of the Small Journal 327s came with Forged Steel Crankshafts.

The weak link will be the Cast Iron Crankshaft and Cast Pistons. I replaced mine with an Eagle 4340 Forged Crankshaft and made my 327 into a 383. The Block will need to be clearanced and you will need a new set of Eagle H or I beam Rods. Forged Pistons are a must. The result is well worth the effort.

gmc · Feb 2, 2010

Michael,
I just noticed you're in Wilmington; I'm in Jacksonville.

I never really thought about the Q-jet until it was mentioned here. After some research I think this is the route I'll be going. I can get a reman 750 for under $300 and I can run the standard performer rpm (spreadbore) intake which is quite a bit cheaper than the air-gap. Now I just have to find the fittings and fuel line to hook it up. Thanks for everyones help.

TJS69 · Feb 2, 2010

You can get a spread bore RPM performer #7104. Just not the air gap. This intake can be converted to a square bore, just by repositioning the studs. A holley 750 cfm would be too big for stock heads. With the RHS heads, it could be used at the track. The problem is the primaries are so big, it is hard to get it tuned for the street. I think the weak link in the bottom end would be the cast pistons. Stock cast cranks are wound up to 7000 RPM's all the time. As suggested, at a later date you can turn it into a 383 with no trouble and those heads will still work.

67 Plum · Feb 2, 2010

TJS69 said:
I think the weak link in the bottom end would be the cast pistons. Stock cast cranks are wound up to 7000 RPM's all the time.

X2

The Performer RPM spreadbore intake with a qjet is a good choice.You can also get a Holley 6210 650 cfm spreadbore double pumper.I run one and really like it.

67 Plum · Feb 2, 2010

gmc said:
Car is mostly street driven and sees quite a bit of stop and go (may see occasional track use), so I'm looking for good low end power and a decent idle.

That is a big cam for a mostly street driven 327.

On a side note look at the missprint in the Jegs description for the cam.

(The most awesome ''268'' cam ever produced! Out-powers all others! This high performance street cam likes 2400 RPM stall, 700 cfm carb, dual plane intake and headers. Makes un-equaled power to 62200 RPM with proper valve springs.)

62,200 rpms WOW!

ace's68 · Feb 2, 2010

Your not going to have problems just because of a cast crank, I don't know where that is coming from.
Cast pistons, high compression, lean tune, and high rpm's YES.
A forged crank on a weekend warrior turning close to 7k with 400-450hp won't do anything to the crank, period.
Fwiw, my large journal cast crank 327 is 10.8:1 and turns close to 7k every time I go for a drive. Studded main caps.

rumrumm · Feb 2, 2010

You mention low end power and decent idle. You won't get either with that cam choice, but since you have a manual transmission rather than an automatic, you can get away with that cam since you can better control rpm. Your idle will be rough, but sound great, but know that your power band will not come in as soon as a smaller cam, hence less low end power. It amounts to a trade off. If you want 375+ hp out of a 327, you have to give up something to get it. Personally, I would go for it. Sounds like fun!!

ace's68 · Feb 2, 2010

I didn't look up the cam til now, but I have a similar cam @.050" its the comp 286H-10 magnum 238 @.050" .490/.490 on a 110lsa, with 10.8:1, 190cc aluminum heads I feel it makes at least 380hp at the crank, and a WOT pull from 2,500-6,400 comes in a snap.
Your not going to have problems making 375, probably closer to 400. I wouldn't be surprised if I put my engine on a dyno and it came out to 420, it pulls hard.
With 3.08's it's not the best cam for gearing, and a dog down low, but cruising and about 2,500rpm on it's a good choice, idle is choppy but not too radical.
I'd suggest running a little more rear gear, and get a good clutch, I wouldn't be surprised if mine begins to slip under WOT, it seems to spool up unusually fast.

gmc · Feb 3, 2010

ace's68 said:
I didn't look up the cam til now, but I have a similar cam @.050" its the comp 286H-10 magnum 238 @.050" .490/.490 on a 110lsa, with 10.8:1, 190cc aluminum heads I feel it makes at least 380hp at the crank, and a WOT pull from 2,500-6,400 comes in a snap.
Your not going to have problems making 375, probably closer to 400. I wouldn't be surprised if I put my engine on a dyno and it came out to 420, it pulls hard.
With 3.08's it's not the best cam for gearing, and a dog down low, but cruising and about 2,500rpm on it's a good choice, idle is choppy but not too radical.
I'd suggest running a little more rear gear, and get a good clutch, I wouldn't be surprised if mine begins to slip under WOT, it seems to spool up unusually fast.

Do you think the 262 would be a better cam choice? I imagine I'd pick up a little more tq, but loose some hp.?? It's not a daily driver, but I do like to drive it quite a bit when the weather is nice and traffic has gotten bad around here. I guess what I should have said was I am looking for a combo that should sniff the 12s if I get the urge to take it to the track and will sit in stop and go with the a/c on. I just don't want to be wishing for more after a few weeks. Then again I guess we never will have enough power.

Hope this makes sense.

I may go with 3.55 instead of 3.42. I thought about 3.73, but I think 1st with that gear would be a little too short.

TJS69 · Feb 3, 2010

The 268 should be fine for you. Again, if you had stock heads it might be a different story. Most people want to put too much cam with stock heads ! You are just the opposite. The Voodoo 268 is a good choice for your heads. Many people use the Comp. Cams XE-268 in their 327's and love it. The same cam designer, Harold Brookshire, designed both cams. Just go for it. You won't be sorry. If you are going to change gears, go with the 3.73's. They will get annoying on the highway, but remember 327's like to rev. When money allows, get an overdrive. You wouldn't notice much difference between 3.42's and 3.55's.

67 Plum · Feb 3, 2010

If you want a street strip car that runs 12s idles good with A/C on and isn't turning 3K at 60 MPH you better build a 383 not a 327.

ace's68 · Feb 3, 2010

I really don't think the 262 or 268 cams will support a car that does 12's.
If the advertised duration is like 212 or 215 @.050" that isn't enough cam, especially if the lift is in the mid .4"'s

327/275 build advice

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