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Old 09-07-2004, 10:32 PM
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351C build ?'s and input

I rebuilt my 69 351C about 3000 miles ago and kind of expected more out of it. was wandering if any experts could give me any input as to what I might have mismatched as far as parts or decisions on the build that might have made it better. take it easy on me it was my first build other than stock and cam specs baffle me.

69 351C bored .030
10:1 flat top pistons
1969 2v heads rebuilt stock 78cc approx.
Crane cam sheet says (intake@cam 2800@valve 484 / exhaust @cam 2947@valve 510 advertised duration IN 262 / EX 272) its basiclly an rv cam according to summit I think.
Crane roller rockers (pedestal type not the full roller system)
edelbrock rpm manifold dual plane
edelbrock 650 mech secondaries
Hedmann headers with flowmasters dual full exhaust with crossover
C4 tranny with b&m shift kit street/strip version
stock converter
8" rear with 3.00 gears and no posi

all this is in a 70 montego that weighs 3620 with me and a full tank and 275/50/15's on the ground. best run was 15 flat. on the dyno it rated at 260 best HP / 330 best TQ at the wheels. do these numbers seem right for what I have or have I made a miscalculation on something? thanks for the input

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Old 09-08-2004, 12:20 AM
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Questions?

I dont know if you will even bother reading this since its coming from a "kid"......but.....to my knowledge.......there were and are no 69 351C blocks.......the 351C was introduced in 1970 where as all 351's before that were 351W...or windsor.....as for the intake manifold your running......i have the edelbrock catalog in front of me as i type and there is no Performer RPM manifold available for the 351C.....perhaps you are running a windsor and not aware????........if you need any help identifying or comparing a 351C to a 351W just ask me.......I have a 1973 Mustang Mach 1 with a 351C so needless to say that i did all the research i could on that engine and i know it very thoroughly....like i said if you need any help.....just ask
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Old 09-08-2004, 01:12 AM
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I'm absolutely positive its a cleveland. it also has a mallory unilite distributor in it. the intake is a performer model no. 2750 for the cleveland 2v heads to allow for a 4v carb. the only reason I say it is a 69 is because of the time stamps on the casts. they are dated in october of 69 if I remember correctly. they did however come out of a 70 Cyclone. so as far as the dates you may be correct. but it is defintely a cleveland no doubt. Thanks for the reply heres a pic
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Old 09-08-2004, 01:49 AM
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Arrow

I think you need a lower rear gear and more camshaft. Of course with the cam comes a new torque convertor and so on. How fast did you want it to go?
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Old 09-08-2004, 05:20 AM
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Do you know your true static compression ratio? With those heads it's likely low . Even if you were at "0" deck clearance, the 78cc heads would give less than 9.0:1 cr.

What's the part # of the pistons?

Did you do any tuning while on the dyno?

Last edited by mstngjoe; 09-08-2004 at 05:47 AM.
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Old 09-08-2004, 06:34 AM
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You might be able to pick up some good Cleveland info here.
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Old 09-08-2004, 06:59 AM
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No, I didnt get to do any tuning while on the dyno. it was pretty much a free rush sort of thing. as far as the pistons they were the ones advertised in the summit rebuild kit as 10:1 the cheapest kit. I didnt want higher because of gas or lower because of performance. I believe they are stock replicas but stock was listed as 9:5 according to old brochures. I do know they were completely flat no dish or dome, just indents for the valves to clear. do you do a dry or wet compression check to find out? and as far as what I whant to do is to be able to break 100 in the 1/4. at maybe a 13.5 would make me happy. I was hoping that maybe a posi 3.73 or 3.80 ratio would get me there without tearing into the engine. my best run a stated was a 15 flat @ 93mph. but does my setup seem to match I dont have any conflicting parts? like carb or cam or something. does my performance numbers seem to go well with that build.
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Old 09-08-2004, 07:21 AM
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You can't accurately determine static compression based on cranking pressure.

You've got to have some basic specs: piston compression height,
deck clearnace, compressed thickness of the head gasket.....

Most 351C from the factory had the piston down the bore. So as I said, even if you had a "0" deck clearance and a .042 gasket, the 78cc heads give you approx 8.8:1 static compression at best.

This link has a very basic static compression ratio calculator:

http://www.fordmuscle.com/calculators/compression.shtml

But, you need to know some basic specs.
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Old 09-08-2004, 08:01 AM
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aaahhhh, I gotcha. ya so its probably 8.8, as far as all the specs of gaskets and deck heighth. to be exact. I dont know. its all stock with a plain jane gasket set. stock deck heighth, stock crank, stock everything except the cam, rockers, dist, intake and carb. sorry about that.
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Old 09-08-2004, 08:40 AM
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With that horsepower and 3.00 gears your lucky to be running 15's. I would try something in the 3.50 - 3.70 range.
Also those motors have ports big enough to drop golf balls through them, I would go with a bigger cam and put those large ports to some use.

Ben
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Old 09-08-2004, 08:47 AM
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Quote:
Originally posted by brainsboy
........I would go with a bigger cam and put those large ports to some use.
He needs more compression before he thinks about more cam.

My guess is that the piston is in fact down the bore some so the 8.8:1 is generous.
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Old 09-08-2004, 08:53 AM
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If you want to boost compression on your engine and not use the monster port 4v heads, look for some closed chamber 302 Australian Cleveland heads. They have the small combustion chambers and the 2v ports. I have seen them on Ebay go for as little as $50 a pair.
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Old 09-08-2004, 09:17 AM
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Quote:
Originally posted by onebadmerc
If you want to boost compression on your engine and not use the monster port 4v heads, look for some closed chamber 302 Australian Cleveland heads. They have the small combustion chambers and the 2v ports. I have seen them on Ebay go for as little as $50 a pair.
This is probably what I'd do first........but $50 is a bit much to hope for these days.

Here are a couple of examples:

http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW

These heads would of course need to have some money put in them. Add that to the core cost and you're talking some $$$.

Also:

http://www.powerheads.com/351c.html

These might be overkill, but if you look at what has gone into them and the flow numbers they advertise, it's a serious alternative.

There are also some aftermarket aluminum 351C available now. But they are very high dollar.

As the saying goes.....Performance costs money. How fast do you want to go?
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Old 09-08-2004, 10:57 AM
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I would work with what you have. If your just looking for a little more power then your not going to need to change your compression ratio. Im not sure where joe got under 9:1 but your compression is probably going to be pretty close to 9.1:1 to 9.5:1. This already takes in account for a LOW deck height, larger 4.1" dia head gaskets and valve reliefs. With 9:1 you may not have the camshaft selection you would with 10:1 but there are still lots of cams that will suit your needs for what you have.

Where the obvious and quick answer for everyone to say is more compression, you still have a great motor to work with only 3000 miles on it. You have many other options to get you closer to where you want, that dont need you to dig into the heart of the motor. Unless your looking for 10's 11's 12's in the quarter you can work with what you have.

Ben

Last edited by brainsboy; 09-08-2004 at 11:03 AM.
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Old 09-08-2004, 11:11 AM
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Thanks, Im not looking for a 10-12 second car. this was my first car from 17 years ago and I have already rebuilt it and built the engine. just wanted to know if my setup seemed good as far as cam and such. also wanted to know if possibly a different rear would make that much difference to get me to possibly a 13.5. it is also something I take on small state trips so I built it for driving more than racing. I appreciate all the input. I figure when my sone becomes 16 then we will redo it for the track.
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