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I am rebulding a 351 clevo with a few small mods:
stock intake manifold opened out to flow like a performer,
600 holley squarebore with vac, sec
power boss cam, specs: at .050 Inlet 214 deg, 505", exh 224 deg, 535". 112 lobe centers.
tri y pacemaker extractors thru 2 1/2 in system.

could someone please tell me what kind of power this package can make?
i am stepping up from a shized 302.
 

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Resident Budget Racer
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I have an XD Van, running a 351+.060 same cam as you, Ported 302 heads,Edelbrock performer,600 Vac Holley,C4+2100 Stall,3.23Diff,Tri-Y pacemakers and single21/2inch.
It has run [email protected] over the quarter with the muffler off,and will hopefully see high 13's with a 750 Vac and a bit of sorting.

I am making about 300fwhp, I'm guessing you would make near that.

Have you thought about rebuilding and running your 302 heads?
 

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socially irresponsible
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so many people are obsessed with 4v valves. not too many street cars i know spend 90% of their life doing 6000+ rpm. anyway, i read somewhere that you only need longer duration on exhaust when using 4v heads due to the poor scavenging of the exhaust port. when using 2v opens the same duration cam will do. the cam i chose is 219dur @50 and .505 lift, the low lift enables use of single springs. very noticable idle. nice middle of the road cam.
 

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youre right on Nak,too many people screw 2vheads up by putting 4v valves into them.they don't need them.same with the 302 heads.stick with your open chambers and have them ported by someone who knows clevo heads.
 

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I was talking to George Haddad few years ago about the same thing and those were his words...he said that without the 4V valves the clevo heads will not flow more then 300bhp...so who am I to argue with someone that build performance motors as a job
 

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I8AHSV said:
I was talking to George Haddad few years ago about the same thing and those were his words...he said that without the 4V valves the clevo heads will not flow more then 300bhp...so who am I to argue with someone that build performance motors as a job

fair enough, I8AHSV, but the cam specs the guy gave us didn't suggest anything that i thought would need the 4v valves. just a nice everyday 300-320hp engine without the bad low end characteristics typical of early gt's etc.
 

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Slurry Boostin
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with the specs you've given and considering all other things in the equation, I'd expect around 270-290hp at the flywheel.
 

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I8AHSV said:
I was talking to George Haddad few years ago about the same thing and those were his words...he said that without the 4V valves the clevo heads will not flow more then 300bhp...so who am I to argue with someone that build performance motors as a job
Even amongst engine builders the opinion is divided, but I8AHSV new things have been learnt in the last few years.

This is my summary based on the current common opinions from engine builders and enthusiasts that have atleast tried out all the options:

. with 2V heads stay away from 4V inlet valves, harms performance rather than helps it, even if the outright flow figures show otherwise. 4V exhaust valves are another story...

. 4V heads are not the b all and end all. Bigger outright flow numbers and HP potential compared to 2V's sure, but their low rpm performance is abysmal. If you have a real high revver with gearing to suit ie a purpose built drag car aiming for quarter miles in the 8-10's you might need them. The rest of us with street driven cars are better off with 2V's. There are guys now doing 'smart' flow work on the 2V heads and get them working much better than was being done a few years ago. There's alot more to good heads than outright flow potential.
 

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I8AHSV said:
I was talking to George Haddad few years ago about the same thing and those were his words...he said that without the 4V valves the clevo heads will not flow more then 300bhp...so who am I to argue with someone that build performance motors as a job[/QUOTefwiw a standard head can pass about 200cfm @28,enough to support 300bhp.I have been developing a set of open chamber 2vs and am currently at 230 cfm at 28 with standard valves,enough for 470 odd hp and with ongoing development with another member of this forum hope to see around 240-250cfm, without resorting to 4v valve sizes
 

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Performance Ford Magazine - Volume 3 Edition 4

Airflow Dynamic 2V 351 Cleveland Alloy Heads

$2,700.00 for a bare set, 100% pure alloy 356 heat treated (to T6 specs), 202-cfm exhaust ports, relocated spark plug holes, 60cc chambers, hardend valve seat inserts, bronze valve guides. Intake ports can be easily ported to 330cfm to flow 680 horsepower (They flow 620hp @ 202cfm).

Contact:- Competition Engines (03) 9548 5116

There's a set of 2V heads that flow well over 300hp. Who the hell is George Haddad?
 

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George Haddad is a very reputable GM engine builder... Chevs and Holden V8s are his thing as is setting up drag cars.
I would rarely if ever disagree with someone with someone of George's credentials .. but in this case he is wrong. In the early 90s there was a lot of work going on with standard sized valves in 2v heads getting way more than 300Hp ( Bob Kotmel was writing the articles based on what was going on in the Muffler Shop in Mackay ( from memory ..been a long time ) Steve Gay spent a lot of time working on making them flow without resorting to massive porting and 4V valve sizes.
 

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Catching Bugs
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Most 2 v heads that have been worked u will find that the 4v inlet has been ground down to a size inbetween a 4v valve and a 2v valve.

to keep the airspeed.
 

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Anyone remember an article in Street Machine "Fast Asleep". It was a 10 sec XE with 2v intake and 4v exhaust valves. It said there is virtually no porting on the intake side, only around the seats. The intake flow was 520hp at 500 thou ( yeah I've got it in front of me lol ). The high airspeed with the smaller runner and valve was the key. The exhausts are a different story with more work on the runners and 4v ( 1.75 in ) valve. Btw Steve Gay did the heads.
 

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Is that a white s-pak from queensland?

About 3 years ago or so?

Impressive and fairly informative article.
 

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xacoupe said:
George Haddad is a very reputable GM engine builder... Chevs and Holden V8s are his thing as is setting up drag cars.
I would rarely if ever disagree with someone with someone of George's credentials .. but in this case he is wrong. In the early 90s there was a lot of work going on with standard sized valves in 2v heads getting way more than 300Hp ( Bob Kotmel was writing the articles based on what was going on in the Muffler Shop in Mackay ( from memory ..been a long time ) Steve Gay spent a lot of time working on making them flow without resorting to massive porting and 4V valve sizes.
With respect to whoever quoted George, i suspect he has been mis-quoted.

I know of George and his work first hand. He is one of the most highly regarded engine builders in the county, and has the records to prove it.
 

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Racer said:
With respect to whoever quoted George, i suspect he has been mis-quoted.

I know of George and his work first hand. He is one of the most highly regarded engine builders in the county, and has the records to prove it.
you may well be correct
 

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TTNOS8 said:
Is that a white s-pak from queensland?

About 3 years ago or so?

Impressive and fairly informative article.
Yeah thats the one, Sept 1997. There was a lot of letters written after the article ( mostly from disgruntled Holden fans ) accusing him of cheating, using hidden nitrous etc. He offered to pull his manifold for $100 to prove himself, but no-one stepped up to put their money where their mouth was.
 
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