I am in the process of setting up the heads on my first BBC and I am wondering if I should go with a 2.25 intake valve over 2.19s. Here is what I plan to do to the heads: 781 heads (bowls blended, short turn radius smoothed, guides smoothed, runners smoothed, port matched, exhaust fully ported and polished, valves slightly unshrouded, bronze valve guides, Manley Race-Flow valves, 3-angle valve job, milled to 113cc). I have heard mixed opinions on 2.25s. Some say you will pick up flow and performace with the 2.25s, while others say you will louse torgue and won't gain much flow because they will be shrouded more that the 2.19s. So BBC guys, what is your experience with 2.25s? I hope to hear from racer1320 and others on this one...

Here is what the specs on the rest of the motor will be:
-454 bored .060 over (polished lifter valley and oil passages)
-cast crank(turned .010 & .010, chamfered oil holes, micro polished)
-HD truck rods (polished beams, shot peened, resized, and ARP wave-lock bolts)
-TRW # L2465F60 forged pistons (.270 dome)
-10.4 compression
-balanced & blueprinted
-Isky cam (590/590 lift, 244/244 dur@.050, 292/292 adv dur, 108 lobe sep)
-Harland Sharp 1.7 Roller Rockers
-RPM air gap or vic Jr intake, havent decided (port matched)
-800 Holley DP (milled choke tower, milled throttle blades & screws, button head screws, now flows 900+ cfm)

Thanks,

------------------
Chris Hill
Old TC User Name Was "355 Monza"

-79 Malibu (Soon to have a fog fed 454 Big Block)

-Alston Backhalfed 76 Monza
10.98@125 w/1.48 60 ft (Motor Only)
10.06@137 w/1.40 60 ft (with nitrous, turning it off 3/4 way down the track) Should have high 9s with full nitrous run!

[This message has been edited by Chris Hill (edited 01-14-2001).]

[This message has been edited by Chris Hill (edited 01-14-2001).]

Chris,
For your particular motor, I would stick with the 2.19 x 1.88 valves.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100

Chris, go with the 2.25 intakes. With my closed chamber heads the larger valve increase flow by about 5%. More importantly this increased flow happens at every point through peak lift. My simualtion program said that if I increased flow by 5% I would see a 1.5 tenths reduction in ET. That's exactly what I got. Was this ET really from just the increased intake valve size? Maybe, maybe not. Afterall the heads now had a fresh valve job also. However the heads were still good having had only one season on them. Either way I didn't lose any torque/velocity.

My gains according to Engine Pro from Racing Systems Analysis were +28 HP at peak RPM which was up by 150RPM and +9 ft./lbs. of torque at peak RPM which too was up by 100 RPM.



[This message has been edited by racer1320 (edited 01-14-2001).]

Thanks for the fast replies Bill and racer!

I just ran my motor through my Motion Shoftware Simulation package (destop dyno, drag 2000, Camdisk 2). Here is what desktop dyno says with 2.19 and 2.25...

2.19 valves: 568hp@6000, 538tq@5000

2.25 valves: 576hp@6000, 543tq@5000

Hp and torque was as good or better through the entire rpm range with the 2.25s.

Thanks,

------------------
Chris Hill
Old TC User Name Was "355 Monza"

-79 Malibu (Soon to have a fog fed 454 Big Block)

-Alston Backhalfed 76 Monza
10.98@125 w/1.48 60 ft (Motor Only)
10.06@137 w/1.40 60 ft (with nitrous, turning it off 3/4 way down the track) Should have high 9s with full nitrous run!

[This message has been edited by Chris Hill (edited 01-14-2001).]

ATT. CHRIS, your soft ware sounds to cool, if you get a chance could you run my motor through it and tell me what i have,
509 ci. 10.4 to 1
dart pro 1 rec ports
595 615 238 246 @ .50 roller
corvett 6 pack
2 or 2 1/8 headers If you get a chance thanks, e mail me at www.jack5100@aol.com (http://www.jack5100@aol.com)
thanks Chris

Chris that has a 112 center line http://www.chevelles.com/forum/smile.gif

I can run your motor but I need more information. What kind of intake do you have? What is the adv. dur on the cam and is solid or hyd roller? What cfm carb(s)? Are your heads the 310, 325, or 345 versions? What size valves?

------------------
Chris Hill
Old TC User Name Was "355 Monza"

-79 Malibu (Soon to have a fog fed 454 Big Block)

-Alston Backhalfed 76 Monza
10.98@125 w/1.48 60 ft (Motor Only)
10.06@137 w/1.40 60 ft (with nitrous, turning it off 3/4 way down the track) Should have high 9s with full nitrous run!

I don't buy it for one minute.

The only way to prove there is a 5% increase in flow is to take the heads to the flow bench with the 2.19 valves, flow them, then put the 2.25 valves in a re-flow the heads. Then I will believe the numbers.

What we have here is vapor ware yelling you there will be an increase.

racer1320

Your decrease in et could be a crisp valve job. I have seen racers do this at NHRA events. You can also pick up a tenth by honing the cylinder walls and putting the same rings back in.

When it gets real serious, drain all but three quarts of oil out of the engine, that is good for a couple of hundredths.

Flow bench, flow bench, flow bench! Real data rather than make believe data!




------------------
Wally
www.muncie4speed.com (http://www.muncie4speed.com)
Gold #67
2001 Chevy Silverado LT
67 Malibu "Small Block" second owner
90 SS454
71 Malibu "Small Block"

Chris, thank you for takeing the time for me, motor 509
dart pro 1 310cc
valves 225 188
cam solid intake 288 exhaust 296
corvett tri power 3 500cfms 1125cfm useable
manifold is a dual plane
thanks Chris ill watch this site

Chris, thank you for takeing the time for me, motor 509
dart pro 1 310cc
valves 225 188
cam solid intake 288 exhaust 296
corvett tri power 3 500cfms 1125cfm useable
manifold is a dual plane
thanks Chris ill watch this site
that has a roller from crane part #138511 grind # sr-238/350-2s-12 ig mech.

Wally, I said it could be the fresh valve job. But I also said the exsisting valve job was still good. Point here is that it didn't hurt my performance and infact I went quicker.

As I've said before for what we're doing I believe flow benches and dynos are a waste of money. Seen to many cars at the track with motors that were dyno'd and heads that were flowed to get that last cfm/HP that can't fall out of a tree.

I could spend a week flowing my heads and dynoing my motor but for what, maybe 5HP and a couple more cfm. Hardly worth it for a street/strip car and for the typical weekly bracket racer. Hell we've built a 305 stocker motor for I/SA that too has never been on the dyno. Out of the box it was .6 under.

Believe what you like but my motors have been built and changes made based on my findings using these programs. It's no accident that I'm posting the ET's that I do.

How many 2 ton cars do you know that are running in the 10's with a 454 on pump gas turning 6000 RPM?



The only way your going to get real data is on the track, NOT from a flow bench or dyno room.




[This message has been edited by racer1320 (edited 01-15-2001).]

My point, if there is a point to this, is that making claims based on the numbers spewing forth from a computer are suspect.

I don't think that flow bench time is all that expensive. I agree that Dyno time is for the most part a big waste for most people, it cost usually 500 or more and is out of reach for most.

I also agree that the race track is the real place to test but it always nice to know you made the right decision with your modifications, and the flow bench unlike a dyno does not lie.

As for your 4000 pound car that runs in the 10s with a big block, try 4700 and 9s with a Qjet and a 455 Pontiac, let me know when you are there and will have the "my crank is bigger than your crank" contest again.



------------------
Wally
www.muncie4speed.com (http://www.muncie4speed.com)
Gold #67
2001 Chevy Silverado LT
67 Malibu "Small Block" second owner
90 SS454
71 Malibu "Small Block"

509Camaro, I just ran your motor through desktop dyno. Here are the numbers...

Open Exhaust:
641hp@6000, 637tq@4500

If you had a single plane intake with a 1125cfm carb power would junp to: 680hp@6000, 656tq@5000

------------------
Chris Hill
Old TC User Name Was "355 Monza"

-79 Malibu (Soon to have a fog fed 454 Big Block)

-Alston Backhalfed 76 Monza
10.98@125 w/1.48 60 ft (Motor Only)
10.06@137 w/1.40 60 ft (with nitrous, turning it off 3/4 way down the track) Should have high 9s with full nitrous run!

Wally, I would agree that garbage in is garbage out. But if accurate data is entered and the results are interpreted properly the better programs have a very high percentage of accuracy.

The problem with flow benches is not the instrument but the user. Going after peak flow with disregard for an efficient port/velocity is the quickest way to poor performance.

BTW, that big old indian sure sounds like a NHRA Super Stocker to me. Not even close to comparing apples and apples.



[This message has been edited by racer1320 (edited 01-15-2001).]

What do the simulators say about 2.30's on the intakes?

hey chris i have 1 important fact for you on your combo. those trw 2465 pistons have a shallow valve relief. i tried to use them with my combo ,049 heads 2.19 1.88 valves and a comp 294S cam had almost no piston to valve clearance. had the pistons notched about .060 to .070. and it was still tight. ended up running a comp 282s cam. had 100 thous. a good minimum clearance on the intake and exhaust valves. with a perf. rpm 288 st10 4 speed and 410 gears, it goes 11.90's at 114 on the third pass before clutch split on 4th run. i recomend getting better pistons like SRP or the real deal JE's spend a little more now and less headaches later. you better also be real care too if you use 2465 and milling heads will bring the valve closer to piston. oh by the way i use exxon 93 and have no problems even when racing this combo good luck bro, let me know how it works out. chris 70 GMuscle

I was just wondering, with all this discussion on oversized valves,I did'nt hear anyone mention installing hardened valve seats. Would'nt the longevity of the head be affected running pump gas?

Paul, I've been running the same heads since the early 80's without hardened seats. Put countles miles and 1/4 mile passes on them running pump gas and have never had a problem.

Thanks Racer , Just got my heads back from the shop and thought I might have made a big no-no by not having them installed

Guys,I don't think you'll ever have a problem since the early valve seats are fine with stainless steel valves. I've never seen a problem with that pairing with unleaded gas. All car heads manufactured after 1971 were made with hardened valve seats so don't worry. just spend the money to get good valves, I prefer manley. Good luck.