350 Chevy intake manifold

[ethyl]

My '67 Classic 18 has a rebuilt 350 Chevy with high lift cam, 10:1 pistons, roller rockers, Edelbrock Torker manifold and 650 vacuum secondary Holley carb. I'm wondering if performance could be improved using a different manifold( like a Performer )and also if this is too much or too little carb. for the engine( it will turn up close to 5000 rpm with a 23 inch Ballistic prop. Close to 70 mph ) and at idle does not smell too rich. Thanks in advance for any input.

[MOP]

IMO the Performer is a decent choice as it works well in the RPM range we run, it also improves mid range torque. Several like the Air Gap but from doing my homework it likes the higher RPM ranges, also warm up time to smooth running take a bit longer. The 650 is plenty of carb a 750 on our app is to much, I have a 750 on my 383 and would like to down size to a 650. Several of the guys have said -0- improvement going to a 750 over a 650.

Phil

[BigGrizzly]

I guess I will chime in. My choice for that motor would be the performer or performer RPM they have better economy at cruise and netter bottom and mid range power and will not show any noticeable top end performance below 5500 Rpms. as for the carb yours is fine I personally like the 600 cfm, but 650 is good too. Alot will jump in and say a 750 is what they run, but our experience is that that is just not so on that motor on a dyno or application. II eill defy anyone who says that they put a new 750 and a 600 correctly set up on that engine and says the 750 is faster and better. Remember that 5,000 RPMs is the same speed regardless of what carb is on it.

[mrfixxall]

yes! YES! But! Im currently running a 750cfm which means the carb will flo up to that number but doesent mean it exceeds it bg carbs rate their carbs at 650 cfm but in realty the carb will flo up to 830 cfm if the engine need it....me personally prefer that carb with modifications being dont to the engine. yes to what mop said it does take a bit longer to warm up with a airgap manifold but the benefits with haveing the space that air flows through keeps the fuel charge cooler from the oil not splashing on the bottom of the intake is worth the xtra 5 min of warm up time..your running a 650 with vacume secondarys, i prefer mechanical secondarys i like the punch when you wack it to full throttle..

EDIT!! one mor thing about vacume secondarys.I like the mechanical secondarys for another reason,ive had in the past a vacune secondary carb stick wot on me once(spring broke in the vacume diaphram) and the linkage rod fell off,i guess thats what i get for having a friend help me:)

[BigGrizzly]

Actually I am partially with Mr Fix, one boat has vacuum secondaries, with ajustments in springs to tune for opening. The other had MECH but is a blower motor so vacuum won't work. As for the size big isn't always better. I am also sure that Mr Fix has a tad more hp and more RPMs too. My little 351 Ford Cleveland with 350+ ponies does very well with the 600 CFM carb. My opinion on your boat is despite the manifold I would leave it and drive it, If it works leave it alone. If it were me and I had the intake I would do a performer RPM. Remember a raw water cooled engine runs a lot cooler then a car engine does. and you really don't need the air .

[ethyl]

Thanks for the information.What do you guys think about Rochester Quadrajets? Also, when my boat gets over 63 or 64 mph it tends to porpois no matter how I trim it out. I don't see any obvious irregularity to the bottom but have not held a straight edge to it. Is this a common problem? Thanks

[MOP]

I love Qjets! Great economy and excellent punch when you need it!

[BigGrizzly]

The problem with Q jets is the tuning. as for the :dolphin: two things are trim and props. Now with props there are more opinions then in an election.

[joseph m. hahnl]

Thanks for the information.What do you guys think about Rochester Quadrajets? Also, when my boat gets over 63 or 64 mph it tends to porpoise no matter how I trim it out.

I like Webber AKA <Edlebrock> simplistic in design easy to maintain very few parts to rebuild. a Piece of cake to clean

"Oh" Isn't a Quadrajet a spread bore?