OK before I start given out facts here in no-way am I and expert in any account. I’m a glorified parts changer at best who tries to do research and the more I learn the more I realize I don’t know. So I am prepared to be scrutinized on this. (But please feel free to input good info will help).
As some of you now I blew my head gasket so I took the time to put on a set of GT40 heads of a 97’explorer and I wanted to get compression up so my hard work goes to you. I found this web-site helps a lot but you must know all you measurements and be careful of your (.points.) and (-&+). http://www.csgnetwork.com/compcalc.html.
Now for the numbers. HO piston call for a -5.5 cc’s due to the eye brows and slight dish in them I don’t know much about SO flat pistons but I believe from listening to you guys there “0”. Now as for the -5.5 on the HO piston I got that # from a book so I don’t even now if that’s accurate enough but it seems close enough. The book also stated that the HO block calls for a .0135 positive piston crown to deck #. But I found that to be wrong in two ways 1 being my engine builder friend said there never out of the factory w/above deck pistons there always below deck and 2 mine was .007 above deck w/ he saw and said some one was ether in there before you or (decked the block) or you have a unique block from the factory. Any way it does prove one thing the book is a guide line and unless you measure your motor you will be wrong.
So the question I’m bringing up here is, is it worth changing the block when converting to HO well I say no if you keeping the stock cam like most of you say the stock HO cam will clear the pistons w/1.6 rockers and give you more then a half point of compression w/ is good for approx 15 more HP. But if you panning on putting in a aftermarket cam you need the eyebrow valve relief’s.
Now here’s a chart that shows you the difference between HO&SO pistons and by keeping the stock 64cc E7 head on either HO block or your SO block. Keep in mind I used the link above w/ “0” for piston to deck clearance and -5.5 for HO pistons and “0” for flattop pistons. These compression ratios are calculated w/a .041 compressed gasket. Keep in mind I used a .039 and gained a ½ cc.
Chamber CC’s/ HO pistons -5.5 cc/ Flattop pistons
64 cc/ 8.88 9.47
63 cc/ 8.98 9.59
62 cc/ 9.08 9.71
61 cc/ 9.19 9.84
60 cc/ 9.30 9.97
59 cc/ 9.41 10.10
58 cc/ 9.53 10.23
The pistons are out of the block on my '86 HO block assembly... It came out of a '86 LSC and was virgin. I never did measure them but from the feel, I'd guestimate the slugs are approx .005" out of the hole...
That is nice to know about the change in compression. That didn't even cross my mind. I'm still not sure if I want to find some E7's or GT40's and run a stock HO cam on my SO shortblock or if I want to just do the swap. I've been looking around for a Explorer engine for a while now and I think I found what I'm looking for. It's from a '97 Mountaineer with 83K for $450. I haven't called yet but I'm hoping it comes with the intake and injectors. Are those injetors compatible with our harnesses? And does anyone know if the Explorer 5.0's had forged pistons?
The injectors from the Explorer/Mountaineer will work,I'm using a set on my car right now.I don't think the pistons are forged,though.I may be wrong.
Well, that's good that the injectors will work and I hope the pistons are forged because I just talked to them today and I'm going to pick it up hopefully on Saturday. And right now I'm opening up another window to order exhaust and an E-303 cam. yeah for me!
Last year of forged pistons in a 5.0 was '92. All newer Ford 5.0's with factory installed pistons have hypereutectics.....
Oh well, I guess I will have to scratch the plans for a blower.
The 302 god says you are safe to boost 6psi on the hyper(insert rest of that word) pistons.
No I am not the 302 god.
:laughing:
eutectics.....
:grinno:
and yes you should be fine if you only run 6PSI..
Nick
The only thing ill say be careful about is the GT40 heads have a bigger intake valve so be careful. The E7 we know work from past write-ups and will minus the chamber size by 5.5cc. so I don’t have all the answers and now you’ll understand how I feel when I say the more I learn the more I can get myself in trouble and the more I learn the more I realize I don’t now.
Two words for flat tops.... TRICK FLOW!!!
I'm going to use the whole Exploder engine, not just the heads. That engine only has 5k more miles than mine. I ordered the E-303 cam, x-pipe, cat-back, 2400 stall, and I'm working on the headers on ebay. I still need to order the fuel pump, pres. reg, computer, and MAF sensor
Trick Flow heads work with flat tops?
Yup... Been running a set on a '86 GT short block for over seven years now...
And you have one up on the HO pistons your compression is up. If the chamber size is 64cc you will be approx 9.5.1 small chamber higher your compression and for every ½ point is an additional approx of 15hp.
Trick Flow heads are 61cc...
well if you look at the 1st post I give a chart at the end I made up I had it straight and in line but this forum lined it up wrong but w/61cc your compression is approx 9.84/1 that’s very close to 10/1 but probably betty due to the oxygenated fuels and its almost 30 more hp just in compression.
Just curious does anyone know what the piston to deck measurement is on an E6 motor.
Cause my compression #s on the first post is 0. Is that in the ballpark?
Dunno where you got your figures, but I'd bet they are a bit on the optimistic side... Maybe on a Free breathing, large cammed race engine compression is worth 30hp a point. But on a street engine with a moderate cam and full exhaust system, I'd guess maybe half that much...
At any rate the Trick Flow heads are a perfect match up for the flattops in a fairly hot street engine...
what camshaft are you running?
Stage1 Trick Flow... Great street cam, a little rumpy but not too much... With good heads, intake and exhaust system It needs a 3000 stall and 3.73 gears to make the car move on the bottom end...
Best in my full weight Bird is 13.11@105 on the motor and a 12.23@112 hitting it with a 80-90hp shot of juice... Would have easily gone 11s on the 150hp shot, but I didn't have tires to handle the hp...
I wonder if should have gotten a different stall with my e-303, it's a B&M 2400
I guess the TFS stage 1 have a higher rpm range than the e cam
A 2400 is good with the "E", the Trick Flow has a idle and bottom end similar to the "B", but pulls harder on the top end. In fact back in '99 just by listening to it, everyone thought I had a "B" in the motor. Few people had ever seen or heard the TF cam back when...
It might be on the optimistic side but most engine builders will tell you compression does=HP and to be exact I got my figures from this book page.208 http://www.bentleypublishers.com/gallery.htm?code=GFM5&galleryId=79 not saying its 100% correct because I caught some differences in the info from the book. The book states for every ½ point above 9:1 in an OE style 5.0 is approx 15hp