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Hey All,

          I have a 302 Clevland from an XB we are wanting to do an upgrade to 351 for a XY GS build. Anybody out there recommend which way to go for a rotating assembly upgrade "parts and bits"?

Is it worth keeping the orginal heads for the build, I have read the 302 heads are good for a 351 convertion? 

Is there an engine builder in the Brisbane North area remomended to do this?

Thanks in advance.

 

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Crank and rods from a 351, and keep the closed chamber 302 heads.  

 

The combo suggested by ChestnutXE is good, but, not sure on the price of the pistons. Make sure you tell the parts shop you are using 302 rods, if you go that way. ACL used to make them, not sure who does now.... 

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Crank and rods from a 351, and keep the closed chamber 302 heads.  
 
The combo suggested by ChestnutXE is good, but, not sure on the price of the pistons. Make sure you tell the parts shop you are using 302 rods, if you go that way. ACL used to make them, not sure who does now.... 


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HI mate, I made a 351 with 302C heads, 4bbl intake and a Holley 600 I put a kit through. Went like bejesus, I used an Elgin E-907-P camshaft and it was lovely - good and torquey still down low with a nice rorty idle, then went pretty hard through the midrange when you put your foot down. Compression was about 10.7 to 1 but 95 octane was fine with total timing about 30 degrees and an idle timing of 15.

 

 

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Thanks Boingk, I dont know if these heads are close chambered or not how do I know what I am looking at? What lifters did you go with? Was averything else standard kit?

Thanks.

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Once you have the heads off, the OPEN chamber will be a full circle (looking at the 2 valves), the CLOSED chamber is sort of D shaped 

Most 302's had the closed chamber heads.  Lifters are the same, HT900 I think? Double row chain, water pump etc

 

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Thanks Boingk, I dont know if these heads are close chambered or not how do I know what I am looking at? What lifters did you go with? Was averything else standard kit?
Thanks.
If your 302 hasn't been messed with, the heads will be closed chamber. The only Clevos that were closed were early 4Vs and Aussie 302 2Vs (with smaller chambers again).

Closed chamber is a superior design for the way it promotes combustion. It creates turbulence just as the piston teaches TDC and promotes more complete combustion, it also keeps the burning mixture moving, to keep chamber temps more even and prevent hotspots (thus detonation).

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On 3/13/2020 at 9:27 AM, Gmskippy said:

Thanks Boingk, I dont know if these heads are close chambered or not how do I know what I am looking at? What lifters did you go with? Was averything else standard kit?

Thanks.

 

Yeah mate it was all pretty standard stuff. I didn't open the block up at all as it ran well and kept good oil pressure - I just replaced the camshaft, timing set, lifters and intake. Standard pushrods, new hydraulic HT900 lifters from Elgin.

 

I'd recommend new springs and retainers for your valves, but honestly mine was fine with the stock stuff. Mind you it wasn't being used hard, just the occasioanl hard run when getting onto the open road. It's still on the road, too, so can't have been too much trouble for the new owner.

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Keep it under 5 grand, it'll last for years.  At 6 grand the stock valves will pop there heads off and play with the pistons, and the 5/16" studs holding the rockers in will let go.

 

Each scenario makes a very distinctive noise, you'll know when it happens.  😆

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Hypertec make a dished (12cc?) piston to suit 351 crank & 351 rod with closed chamber heads($438.61), or can open up the chamber a bit with burr & use flat top piston,

https://www.precisionintl.com/StockSearch.aspx?Search=PFO351C81H

Hypertec also make shorter piston suit 351 crank & 302C rod, flat top $438.61

https://www.precisionintl.com/StockSearch.aspx?Search=PFO351C683H

 

zero decked 351 with flat top & closed chamber heads are easy 11.3:1 or standard deck around 10.3:1, zero deck 351 with dished 10.1:1

also known for the locks to pull through standard retainers over 5500, best to upgrade valve springs, retainers & locks, & is needed for larger then 0.500" lift cam

 

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Thanks guys for the help here a bit of googling coming up. I was looking all new gear in the heads all is OEM stock so don't trust it. Not sure of CAM shaft yet but we are wanting a cruiser with a bit of toe down low when we want some fun.

Is it worth port pollishing these heads??

I think I will check out  "Hypertec also make shorter piston suit 351 crank & 302C rod, flat top $438.61" 🤙

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16 minutes ago, Gmskippy said:

Not sure of CAM shaft yet but we are wanting a cruiser with a bit of toe down low when we want some fun.

Is it worth port pollishing these heads??

 

Here's my closed chamber 351C with the Elgin E-907-P:

 

 

The heads are definitely worth a quick go-over, even just to take of casting flash and smooth harsh transitions. This will give a nice bump throughout the range. For the cost of a $30 carbide bit from the local hardware store and a bit of elbow grease its well worth it. I wouldn't pay someone to do it as you're better off putting money towards aftermarket heads IMO.

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Can anyone tell me if these are close chamber heads?

Also I can not see any markings on any pistons apart from a O and a 5 or a 6.

Does this mean it is a virgin bore closed chamber head 302 Cleveland?heads.thumb.jpg.733b30f9a99a3ee37b2091c692004cb9.jpg

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Yes, closed chamber. Open would be a complete circle. Closed has those "ledges" which create a very small gap between them and the top of the piston. As the piston comes up, it squeezes the mixture out of these spaces and into the cavity to be burnt more completely.

The terms "swirl" and "quench" are used to describe what this effect does in comparison to what happens with a simple open chamber. Swirl promotes more complete combustion. Quench is the effect of the moving gases equalising chamber temps and eliminating hot spots.

Those numbers on the pistons don't really say much. Only way to tell is to measure the pistons or the bore.

A stock piston will be bang on 4.000", whereas the accepted limit on a clevo will be 4.030". Some have gone 40 over but that would be on an exceptional block. Most are too thin.

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Thanks gerg a great piece of info there I do appreciate the replies from everyone .  I'll check the bore dimention as described.👍

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