'87 HO-GT40P Engine Build Question

R

RXTbone

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Mar 30, 2005

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Jun 26, 2006

#1

• Jun 26, 2006

• #1

I've been researching this on the web, but haven't found any real answers. I'm working to build an engine on a budget - here's what I have.

'87 5.0 HO (EFI Removed)
stock cam
Weiand Stealth Intake
1.7 Rockers

I have a pair of GT40P heads that I want to use. I plan on adding a 600-650 Demon carb. My questions are as follows:

Should I use the 1.7's on the P heads? If I do, should I replace the stock P valve springs? If I want to bump up to an E cam, what will I have to change out from what I already have (springs included)?

I'm looking for right at 300HP, will this combo get me there?

Any help would be appreciated!

 

R

RXTbone

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Jun 27, 2006

#2

• Jun 27, 2006

• #2

*bump*

 

pistonhead351

flim hunter

May 1, 2005

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Jun 27, 2006

#3

• Jun 27, 2006

• #3

it will take a lot of porting and a better cam to get you to 300hp at the rw.

 

RaceDvr50

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Jul 26, 2005

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Jun 27, 2006

#4

• Jun 27, 2006

• #4

I am curious why you went away from the EFI set-up. The GT40P heads are about the best flowing thing that the factory put on an engine so they make a good start. Do you mean 300 RWHP or 300 at the crank? This set-up should easily put you over 300 at the crank. I believe the 1.7's should work with the GT40P's, I'm about to find out for sure myself. They used them as factory on the Cobra's with GT40's but if you want to test them out just install them and hand crank the engine over and make sure that your valve springs aren't fully collapsed when the valve is at it's highest lift. Check both intake and exhaust.

 

R

RXTbone

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Jun 27, 2006

#5

• Jun 27, 2006

• #5

This engine is going into a '66 Fastback - I didn't want to mess with installing an EFI setup, wiring, etc. I just happened to run into an HO with an intake setup and decided it would be an inexpensive install (as oppossed to rebuilding something). I already have the GT40P heads. I figured I could use those, with headers, and the little HO would be pretty stout. Actually, I finally found info on the valve springs. From what I understand, the HO would have the P's springs about maxed out - if I went to an E cam (or equivalent, suggestions welcomed), then I would need to upgrade them. I'm bolting this all up to a 4sp Toploader with traction lock rear end.

I figure all told - I'm looking at very close to 300 HP and that's about all I'm looking for...

 

R

RXTbone

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Jun 27, 2006

#6

• Jun 27, 2006

• #6

And thanks for the help, BTW!

 

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

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Jun 27, 2006

#7

• Jun 27, 2006

• #7

If you have the cash, here's what you do. Get the heads milled down so you increase compression. Stick with 1.6 roller rockers, and then get that E cam. You should be square with PTV clearance but of course always check it. Depending on how much milling is done on the heads, you should step up to the 9:1 range or so, and that'll help power a lot. The Stealth is an excellent intake, so you're good there too. I've seen this combo go mid 12s on a gutted car and high 12s on your typical Fox with slicks.

 

RaceDvr50

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Jul 26, 2005

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Jun 28, 2006

#8

• Jun 28, 2006

• #8

Um...... The HO runs 9:1 compression from the factory doesn't it?? With the GT40P heads the combustion chamber is reduced to 58CC's if I remember right so this would bump you about half a point from stock anyway 9.5:1

 

DMAN302

My mom says thanks for the pearl necklace.

Nov 8, 2003

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Jun 28, 2006

#9

• Jun 28, 2006

• #9

300 fly wheel yes...250-260 wheel power...a decent and common combo round here. the issue with the 1.7's is more piston type that head/spring issue as the E with those RR's is safely under .500 lift...though I would NOT HESITATE ONE SECOND TO CLAY THE HEADS to check PVC.

 

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

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#10

• Jun 28, 2006

• #10

RaceDvr50 said:

Um...... The HO runs 9:1 compression from the factory doesn't it?? With the GT40P heads the combustion chamber is reduced to 58CC's if I remember right so this would bump you about half a point from stock anyway 9.5:1

Click to expand...

I thought it was around 8-8.5:1? I know they're real boost friendly.

 

RaceDvr50

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Jun 28, 2006

#11

• Jun 28, 2006

• #11

Check this link

http://home.pon.net/hunnicutt/history_79_93.htm

87-? 5.0's were 9:1 from the factory

 

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

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Jun 28, 2006

#12

• Jun 28, 2006

• #12

RaceDvr50 said:

Check this link

http://home.pon.net/hunnicutt/history_79_93.htm

87-? 5.0's were 9:1 from the factory

Click to expand...

Cool, i stand corrected. I've never taken heads to get milled myself, the last set i had that were milled i bought that way.

 

RaceDvr50

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Jun 28, 2006

#13

• Jun 28, 2006

• #13

I actually just picked up my GT40P heads from the shop, had them tanked, valve job and milled a little. Haven't computed the compression bump yet since I have the factory heads on there right now.

 

R

RXTbone

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Jun 28, 2006

#14

• Jun 28, 2006

• #14

Thanks for the info - does anyone have experience with a particular spring set for the GT40P's, E cam and 1.7 rockers?