428 fe help

I was at a jvc vendor meeting and met nick bruno he thought I would get some good insight if I posted my question here. I need some help on a 1968 mustang fastback w/428. From the research I have done I am pretty sure I need to change the cam. Your forum comes very highly recommended and from visiting your web site it seems like you know your BBF better than anyone. My local machine shop has some pretty sharp guys , however, they are not experts on FE motors.

I purchased the car from a broker out of Arizona who received the car from a bank auction. Here is what we know

1968 428 block
TRW L2245 .030 FORGED PISTONS
6.5QT COBRA OIL PAN
MELING OIL PUMP
EAGLE RODS
SOLID FLAT TAPPET LIFTERS
UNKNOWN CAM ( SEEMS TO BE VERY BIG)
EDELBROCK 6008 HEADS (76CC)
HARLAND SHARP ROLLOR ROCKERS
UNMARKED ALUMINUM INTAKE LOOKS SIMILAR TO STOCK
STREET DEMON 850 CARB
MSD BILLIT DISTRIBUTOR
MSD AL6A BOX W/6000 OVER REV CHIP
HOOKER HEADERS
2.5" STRAIGHT BACK EXHAUST 1PR MUFFLERS
C6 AUTO
2800 ATI STALL
3.25 REAR
F70/14 TIRES


WHEN CAR CAME TO ME IT HAD A 4500 STALL 6mpg AND A VERY STRONG ODER OF GAS. OIL PRESSURE WAS LOW.CHANGED OIL TO 20W 50 AND PRESSURE IS GREAT.
I TOOK CAR TO LOCAL SPEED SHOP FOR A DYNO TUNE AND TO ASSES THE OVERALL CONDITION. THE RESULTS WERE.

FAILED LEAKDOWN TEST CYLENDER PRESSURE 70-90LBS
Stall had so much slippage not sure if it ever locked up could not detect any shifts with transmission
TIMING VERY ADVANCED
WAY TOO MUCH FUEL / RICH
)

CHANGES WE MADE AT THAT TIME
Some valves had 0 lash / re-adjusted lash 125lbs cylinder pressure leak down passed
DROPPED TO 2800 STALL FOR MORE STREET DRIVABILITY
(transmission very tight on shifts)
Re -jetted carb down about 8 sizes runs clean tan plugs 13-14 air fuel #
12 MILES PER GALLON
277 REAR WHEEL HP @4000-6000RPM ( ALL THE POWER AT TOP)
( a peak at the cylinder walls displayed visible honing marks, the build seems recent)

Car is very drivable However, according to edelbrock the combination should be 9.5-1. the tech at the machine shop feels the hp #'s are a little disappointing and that changing the cam to too a "smaller profile" will increase cylinder pressure and I should see a large power increase especially from 1500-5800 rpm . perhaps consider milling the heads to bring the compression up just a tad . I can't help but wonder did the original builders just throw the biggest parts they could find? Did they intend to run boost? Why run such a big cam and high stall? Why 6008 heads and not 6007 series.

I would appreciate any advise and I. If I do change the cam /lifters spring ect. Would you recommend a specific type. Can I use my existing rockers/pushrods? if I stay with a soilid cam or should I consider a roller setup or just go to an original flat tappet hydraulic setup. I dont mind adjusting the rockers once a year. I kind of like the sound of the set up. This is for once a week driving to shows with a occasional ¼ mile blast. I don't want to be embarrassed by a new challenger or some import. What kind of hp should I expect with the right cam setup. Any other recommendations or questions please contact me below.

Thanks

Dave

I would put on a performer rpm inake first and fofmost. I have seen may fe intakes make or break the combo. Those heads are capable of making good power but are not very empressive out of the box. It is also hard to say a cam swap is in order with out knowing more about it. But without a question in my mind it would have a rpm intake. They have been known to be worth up to 60 hp over some of the other aluminum intake . My car was running 6.30s @110 mph with a 428

I would figure out the cam specs you have. It is not that hard with the cam in the motor with a cam degree set. Like what was said before, RPM intake. And if it is just a good strong driver, I would step down on the carb. Since you are not spinning it that hard you really don't need an 850.

welcome to the site Dave and it was a pleasure meeting you last night. There are plenty of guys on this site that will be willing to help you out

later nick

Agreed on the need for a good dual plane intake. That 2.5" exhaust isn't helping matters either. That is more of a mild small block sized exhaust. I'd step that up to a 3" dual setup with some form of straight thru mufflers. Rear gearing is weak for utilizing what you have also. You could step that up to a 3.73 and still have plenty of drivability for street/highway with the C6. Figuring out cam spec's with a degree set is spot on. JMO.

2800 stall is like a stock 428cj converter,little too small, need a tight 3000 to 3200ish, the intake is most likly a 428 pi or 427 one of the best for these engines. 428's really dont make a lot of power below 3000/3500. needs least 350 gear or 370, with either still very street drivable. try to fig out what you have for lift it might not be as big as you think, you wont be happy with a 325 and a 2500 stall. at the least change the gear so you can add TQ to the rear wheels. you could also go with a 428 scj super stock cam also,drivable ,and will also work with that intake.


and get the 2.5 ehx off there if your looking for real power,

I would also recommend that you talk to this guy.

http://www.survivalmotorsports.com/


If you buy his book, he might autograph it for you.

cletus66 wrote:I would also recommend that you talk to this guy.

http://www.survivalmotorsports.com/


If you buy his book, he might autograph it for you.

i emailed Barry this morning , but he might be at PRI

To be a solid contender vs. the newer pony cars and import boost buggys you'll have to honestly make about 150rwhp more and gear it properly. I think there is probably quite a bit more potential there to approach that without doing a complete overhaul but I'm no expert. I think the combo has to be a bit better matched. if the engine makes good oil pressure and your happy with the bottom end, leave it then. Working the rest of the car's combo should get you there.

Constructive comments purely intended:
Converter is a now little bit too tight for your power goals. It'll work ok, but just not optomized. Exhaust system is way too restrictive. Compression is perhaps a point to low. Gears definately need attention. Cam is a big fat ?. Intake may be a decent stocker, maybe not. An Edel 7105 or BT High Rise 428scj would work sweet if the one you have don't cut it. Carb is a little big but I believe it'll work.

Exhaust and gears I'd do right away. They are a given. You'll see an immediate sizable gain in seat-of-the-pants umph. Get the posi overhauled while you're in there.

If you spec out the cam and decide it must go, I'd do another solid flat tappet selected to maximize those rpm series heads with the automatic at a better compression ratio. Like an Isky 351360. Maybe you can slide in a thinner head gasket to bump the compression up some. Milling them 30 thou would get you there. Check your P/V clearance of course. I'd think those heads on a stock stroke 428 with the proper cam/intake & carb ought to be able twist out 500hp at the crank all day.


Also, what fuel pump & system? Is it feeding the carb enough volume through out the pull? Stock 3/8th fuel lines, possibly bent, and an inferior or clogged filter can kill it. What's the timing curve look like? What air cleaner? What kind of jetting did you end up at?

Don't replace that intake until you find out what it is for sure. It sounds like it could be a Blue Thunder intake. They have no markings other than the firing order. A Blue Thunder intake is definitely as good as an Edelbrock RPM.

paulie

thanks!!!

I mistyped on the exhaust . it is a 3" w/ straight through mufflers. The intake has absolutly no markings other than firing order.I looked at the blue thunder web site and I will try to determine which one it could be.My next two steps are to change to a 3.73 rear gear set and determine exactly what cam is in.if I remove the water pump will there be any markings to identify the cam?


Thanks
dave

Sometimes on the end of the camshaft the manufacturer scribes a grind number. You may get lucky. But to see it you'd have to remove the timing chain & cam gear so I'd have a degree set on hand since you're into it. Even if you figure it out from a grind number and decide its decent for what you're after you can be sure it's timed in there properly.

Glad you aready have a 3" exhaust. I figured that would bump your rwhp number up a bit. So that isn't contributing obviously. There has to be something going on there. 277rwhp, with roughly a 20% drive train loss spinning thru the converter & heavy ass C6 is 350hp at the crank.

thanks again for all the help . i think I will change gears in jan. and see where the cam is. I think the cam is too large and its bleeding off cylinder pressure. as far as the timing the mark and aftermarket balancer shows 58 deg total advance which cant be correct as far as i can see however we have played the timing up and down by ear then driving the car and it runs best at that setting. any less it hesitates any more will ping.

dave

It was good talking to you on the phone the other day. I thought I should at least post a little on the forum here to close the loop for guys reading along. The best guess is that this engine had bee pieced together by the prior builder with a variety of parts that were either poorly chosen or readily available from existing inventory or "deals". It ends up being a great example of how the combination can go wrong - a race style cam and converter, a street gear, rather low compression for pump gas and a large carb all working against one another.

Depending on the desired performance a couple changes in any direction will greatly improve the package. Adding some compression and rear gear would make it a viable street racy type of package, pulling back the cam would bring it into line for a more street oriented build. The cam is an unknown, but a piston stop, a magnetic dial indicator on #1 intake retainer, and a 7" degree wheel bolted to the damper can help identify what we're dealing with without tearing the whole thing down. The fact that it wants a ton of timing makes me wonder if the timing set is installed a tooth off - retarded.

Very well wrote Barry!

A question if I may? Check the stroke, in case the pistons are more than a .100" down in the cylinder @ TDC. This could be the answer for the extreme ignition timing along with the poor performance related to the parts included. IMO, I don't think the intake manifold and/or the cylinder heads are penalties unless they have been "mascaraed". Compression ratio, camshaft and carburetor may be suspect.

Just my $0.02!
Dave.