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 |  brake issue -- 67stang, 03/08/2004
67 mustang GTA 390 auto trans
mild cam
before rebuilding motor, brakes would stop once then would be hard, by the way power brakes,
after build, mild comp cam, still the same and pulling about 10 lbs vacuum, put on vacuum resevior, still the same,
when i pulled hose from booster, some vacuum released so holding some vacuum
if car idles for any amount of time hard brakes, driving down highway i get one pump of pedal then it goes hard, and hard to stop car...
is my vacuum resevoir bad,
what are the thought on this...
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|  | RE: brake issue -- giacamo, 03/08/2004
do you have disk,s or drums. |
| |  | RE: Doesn't matter whether disc or drum. -- Gerry Proctor, 03/09/2004
While 10 in/hg is hard to manage with a vacuum boost, it's not impossible.
Your system should be able to hold enough reserve vacuum to give you two or three power-assisted applications.
I suspect that you have a bad check valve but you should investigate the whole vacuum system.
If you have one of those vacuum pump diagnostic gauges (like a Mytivac), hood it up to the booster and pump it down. It should hold vacuum indefinetly. If it leaks down, you have a leak in the diaphram or the booster seals.
If the booster checks out, replace the check valve on the booster. You should also install a check valve from the manifold vacuum hose to the reserve cannister.
Your brakes are still going to suck if you don't have at least 14" hg in the reserve but as long as you can get to that much vacuum and have it hold, your brakes should work the way you want them to. |
|  | RE: One other thing... -- Gerry Proctor, 03/09/2004
If you want a kick-ass brake boost than doesn't care how little vacuum your engine generates, check this out for your car: http://www.hydroboost.com/products/Mustang_Cougar/index.html
It plumbs inline with the power steering pressure side. Yes, your car has to at least have a ps pump (whether you have it drive a ps ram or not). I run Hydroboost on my Corvette. Gives you brakes like you wouldn't believe.
And if your booster checks out fine but your engine just doesn't generate enough vacuum to make the brakes safe, you can also go with an electric vacuum pump that takes the engine out of the equation: http://www.stainlesssteelbrakes.com/products/Accessories/
Neither one of these is cheap but sometimes you do whatever it takes to make the outcome right. |
| | | RE: One other thing... -- 67stang, 03/10/2004
thanks for replies, it is a disk brake front, the vacuum resevoir has check valve, i already replace check valve on booster, gauge on the resevoir shows about 15-16 when i rev it up, or under normal driving conditions, but just get one pump especially if cruising and try to stop, will check booster as you stated,
thanks
glenn z |
| Edelbrock RPM cam & rhoads lifters -- AK, 03/08/2004
I have 428 Fe in street use, which includes Edelbrock heads, RPM intake and RPM cam. (HEY, don't blame me, i didn't chose the cam!).
I don't wan't to change cam, has someone tried Rhoads lifters and/or retarding cam advance to help poor idle and low-range torque? |
|  | RE: Edelbrock RPM cam & rhoads lifters -- Gerry Proctor, 03/08/2004
Rhodes will help by reducing the running duration but the real problem with the RPM cam is the tight LSA at 108 degrees.
And you'd advance the cam, not retard it, to improve the low rpm torque.
A far better solution is to get a cam that more appropriately matches your driving style.
I passed on the RPM cam over one that has very wide LSA (112 degrees) that better favors the airflow capacity of the RPM heads. |
| | RE: Edelbrock RPM cam & rhoads lifters -- bprewit, 03/08/2004
I found a few tricks to getting better idle quality and actually a bit more low end torque/throttle response by tuning the carb a bit. I have a holley 750 vaccum secondary and found that to keep the slightly higher idle I needed to adjust the secondary butterfly idle screw a bit. It is a tiny flathead screw on the secondary side right by the butterfly shaft where the vaccum diaphram linkage connects. That allowed me to close the primary side butterflies a bit more and not expose as much of the transition circut which helped acceleration off idle. Also for the idle I needed to drill 1/8" holes- one in each of the primary butterflies opposite the side of the idle/transition circuts. That helped to lean out the mixture at idle and I could fine tune the idle mixture screws better giving me a much more stable idle. Hell I even went a step further and added a primary metering block to the secondary side, completed the idle mixture circuts by drilling the main carb body and throttle plate, blocked the primary/secondary connecting circut, and now have 4 corner idle adjustment and excellent idle quality. Another thing that made a big difference was adding a 4 hole carb spacer. I have tried no spacer, 1/2" and 1" open spacers, 1/2" and 1" 4 hole spacers and found good and bad things about each one. The open spacers especially the 1" gave me hard pulling top end, no spacer gave me explosive midrange, and a 1/2" 4 hole spacer gave me better low end throttle response and torque. Try different spacers of different heights to see what your particular engine combo likes for your style of driving. |
| | You will get tired of Rhoads lifters quickly. -- Royce P, 03/08/2004
They make the most godawful clattering noise.
The Performer RPM FE cam is a loser too. It is too mild for drag racing and no good for street performance. Best to just change it.
Royce |
| | | RE: You will get tired of Rhoads lifters quickly. -- bprewit, 03/09/2004
The performer rpm cam is in no way trash nor is it no good for street performance. It takes some tuning to get the right combo with your engine but why the hell swap the cam when easier to make minor mods to carb and intake setup? |
| | RE: Edelbrock RPM cam & rhoads lifters -- giacamo, 03/08/2004
roads lifters in my opinion ar trash thay make your engin sound like sh,,,t not worth the money. |
| | | RE: Edelbrock RPM cam & rhoads lifters -- ak, 03/09/2004
Thank you for your opinions, guys!
I must consider to change that cam to a better one. Maybe hydraulic CompCams camshaft? |
| | | | That is probably your best bet. -- Royce P, 03/09/2004
Comp makes a 270H or a 275 DEH for example that are ground on a 110 degree LSA. This will give great mid range power and restore the vacuum signal for good street manners. I have the 270H in one of my 427's and like it a lot. It works with the stock torque converter. The car (1968 Cougar GTE) is more of a restoration / show vehicle to be but power is quite impressive. So much so that I have destroyed the rear end and transmission (in seperate incidents) while fooling around with different distributor curves and carburetors.
Edelbrock really ought to quit selling that Performer RPM FE cam. No one ever likes it.
Royce |
| Vapor Lock -- Greg, 03/07/2004
I am new to this forum and any help will be greatly appreciated. I have recently purchaced a 68 Mustang 'Resto-Mod' and have been having a problem that's getting progressively worse as the weather gets warmer. When the water temp gets to around 180 the car starts to run very rough and eventually will die. The car will run fine after it cools off until the next episode. I have a Mallory 110 electric fuel pump and filter installed at the fuel tank and the normal pressure at the carb pressure gage is 7psi. The last time the car quit I left the key on to keep the pump running and opened the hood to check the fuel pressure. The gage was reading 6psi but was fluctuating quite a bit. I watched in amazement as the pressure slowly dropped from 6 down to 0psi and the water temp was still only 190. I let the car cool for about 20 minutes and turned the pump back on and the pressure was a steady 7psi again. Is this how vapor lock indicates on a pressure gage or do I have a fuel pump that is failing? I have been told that with an electric fuel pump you should not have any vapor lock problems. To date I have replaced the fuel filter, replaced the fuel line with steel braided and a pressure gage, installed a phenolic carb spacer and replaced the coil thinking it could be an electrical problem. Any ideas? Thanks in advance for any suggestions or coments.
Greg |
| | RE: Vapor Lock -- giacamo, 03/10/2004
try anuther pump ? |
| What is the correct intake for a 67 390 GT? -- Trevor, 03/07/2004
What is the correct intake for a 67 390 GT? Should it be a C6AE-A, or is a C7AE-E correct. I think the C7AE-E is from a 428 - Someone told me that they were the same as the 390 GT takes, but then someone else told me they weren't. Does anyone know for sure? Trevor |
| | RE: What is the correct intake for a 67 390 GT? -- Royce P, 03/07/2004
It should have a large "S" cast into the runner in front. The date code should be within a week or two of the block casting date.
Royce |
| | | RE: What is the correct intake for a 67 390 GT? -- Trevor, 03/07/2004
The C7AE-E (which is a 428 intake, I think) does have a large "S" on it, which is why the one guy told me it can be used on the 390 GT. Were the C7AE-E's also original equipment on the 390 GT? |
| | | | RE: What is the correct intake for a 67 390 GT? -- russ, 03/08/2004
the intake i took off my 66 says c6ae9425g and has a S on it |
| | | | Depends on the date cast into the intake -- Royce P, 03/08/2004
Earlier 390GT's had the C6, later ones the C7. Both intakes look about identical. There is no difference I can see except the C7 used the large thermostat housing.
Royce |
| | | | | RE: Depends on the date cast into the intake -- giacamo, 03/08/2004
if your a purest use the c7 it,s a 67 it will, mach your 67 or use the c6 it,s a 66 intake wich thay used on 67,s to |
| | | | | | RE: Depends on the date cast into the intake -- Trevor, 03/08/2004
I'm still not clear whether it should be a C7AE-A, a C7AE-G or a C7AE-E - or could it be any one of these as long as it has a big "S"? Trevor |
| | | | | | | RE: Depends on the date cast into the intake -- giacamo, 03/08/2004
you can use any one of them .the a e g are production coads that don,t really matter i,d use the best looking one...... |
| | | | | | | Look at the date cast into the intake! -- Royce P, 03/09/2004
Both C7 and C6 were used during the year. I don't know when the change occured to the smaller thermostat but the date cast into the intake should be about two - six weeks before your car was built.
Otherwise the intakes are identical. If you don't care about originality use either one.
Royce |
| is it my carb?? -- matt, 03/06/2004
ok, i have a 390 with a dual feed holley 650. the carb gaskets have all been changed, i replaced the power valve twice and installed a power valve saver to insure i wouldnt need to change it again. when i start the car it revs up to about 2200rpm occasionally it will cycle on its own but usually it will just slowly rev down and then sputter out. i have checked the fuel adjustments, timing, firing order, changed the plugs and wires, which produces no change. im coming to an end with ideas. i love my car and want to drive it again. can anyone help me? |
| | RE: is it my carb?? -- bprewit, 03/07/2004
OEM type holley or aftermarket? Vacuum secondary or double pumper? Also does it have a metering block for secondaries or is it a metering plate? |
| | | RE: is it my carb?? -- matt, 03/07/2004
aftermarket holley. vaccuum secondarys. duel feed not double pumper. and i think its a metering plate for the secondarys because there is no fuel to air mixture control pins for the secondarys. |
| | | | RE: is it my carb?? -- Tim P., 03/07/2004
sound like the air bleeds might be blocked or the gasket on the metering block might be swelled and causing it to stall at idle they make a plate to prevent this. |
| | | | | RE: is it my carb?? -- Travis Miller, 03/07/2004
Borrow another carb from a friend and bolt it on your engine. You will know real quick if your carb is bad or not. |
| | | | | | RE: is it my carb?? -- giacamo, 03/08/2004
you may have the wroung carb gaskets. |
| | | | | | | RE: is it my carb?? -- matt, 03/09/2004
i got the correct gaskets for the carb by matching them with the list number on the horn |
| Why fool with this 427, is image everything? -- marcus68, 03/06/2004
Need some serious reinforcement from you FE guys. Just got back from running my 392 stroker on the dyno. Relatively mild build with 650 street avenger carb made 436HP@5400, 498 ft lb torque @3400. Cost is almost exactly $10.00 per HP. Now I'm working on replacing this motor with a low-riser 427, basically stock except for Comp 282S cam and 2x4 intake. Figure it'll be lucky to equal the 392 ratings and is going to end up costing twice as much by the time I get it installed. This is supposed to be a daily driver. Now I want a 427 that it takes all day to change the plugs on, am I crazy or is it worth it? |
| | If Image didn't matter, -- Lou, 03/07/2004
you would drive a ricemobile. |
| Exhaust system -- Nick, 03/06/2004
I have a 68 galaxie 390 fe, What size exhaust tubing should I go with is 3" too much? |
| | How and where do you plan to drive this car? -- Lou, 03/06/2004
n/m
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| | RE: Exhaust system -- john, 03/06/2004
Will 3" fit? If so I dont believe it is too much. I run 3.5", magna flow dumps in front of rear tires. Loud as all get out, but does not really kill torque If that is what you are worried about. 410, Erson tq50 street dominator, 1 3/4 inch headers. |
| Single plane intake modification? -- bprewit, 03/06/2004
There is a trade off between a single plane and dual plane intake....dual plane excellent throttle response and good bottom end though starts to lose on top end. Single plane makes for bad low end and slower throttle response but makes good horsepower in higher rpm's. Ok this is what I was told and taught so if im wrong somebody correct me. Anyways I was wondering if a single plane intake could be made to use a divider plate. A divider could be made to different lengths to tune a engine differently I am guessing by reducing or enlarging the plenum size. Anyone tried this before? I know its not going to be the best of both worlds but maybe could make slightly better low end without sacrificing much top end? Just an idea and curious if anyone has tried it before?
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| | RE: Single plane intake modification? -- john, 03/06/2004
Low rise single planes work well. Torque can be increased by using a carb spacer |
| Carb jetting help! -- bprewit, 03/06/2004
I am having some problems getting my jetting correct on my engine. The engine is as follows:
390 .060 overbore
10:1 compression
236/236 .571/.571 cam
Single plane intake w/1" open spacer
Holley 750 vacuum secondary
3.70 gears C6 tranny 2500rpm stall
Ok I currently have a 10hg power valve in primary metering block and a 6.5hg power valve in the secondary metering block. #72 jets primary and #74 jets secondary. I stepped up from #70 primary and #72 secondary since the engine would surge at cruise speed. With the larger jets the surge is gone but it still seems to lean out over 5K rpm. I have changed the secondary springs going lighter until a bog was felt then back to previous stiffer spring and ended up with purple secondary spring. Finding jets in this small town is not possible so using a index chart I am drilling out my jets to the size needed so I dont want to go too big as there is no way to go back after drilling. The plugs are still very white in color so I know its lean and also notice a temp increase (10-20 degrees) with higher rpm's. Should I keep the primary size and only increase the secondary size? Or should i increase both primary and secondary one step larger? I pull about 12hg vacuum at cruise rpm so the primary power valve is right on the money but not sure about sizing the secondary power valve. Any help/ideas/suggestions is greatly appreciated. |
| | RE: Carb jetting help! -- bprewit, 03/06/2004
I posted this before some careful thinking about drilling the jets and came to the realization that probably not real intelligent as they list the same orfice size for serveral jets so im guessing that simply drilling the correct size hole dosent guarantee the correct jet. I think I will buy the jets to stay on the safe side! Still need help on which size to try though! |
| | | RE: Carb jetting help! -- greg, 03/06/2004
Modern gas tends not to color the plugs as much as it did way back when, unless your running really, really rich, try looking at the ground electrode, you should be able to see where it gets hot, will be a bluish color and then fade back to the color of the plug shell, usually little more than halfway away from the end seems to be about right, (from what I've read and used, it's the only way I was able to use to get my boat jetted correctly), what's your vaccum at idle? I know others wont agree but I usually remove those secondary power valves and block with a plug and up the secondary jets 6-8 sizes and go from there. |
| | | | Power valve -- Royce, 03/07/2004
Your power valves ought to be 6.5 with 12 " vacuum at cruise, maybe 5.5 to be safe. To run a 10 power valve you need at least 18" at cruise in my humble opinion.
Royce |
| | | | | RE: Power valve -- bprewit, 03/08/2004
Hey royce I actually tried different power valves even as low as 4.5 and found that one which would open at 2" vacuum lower than my cruise reading gave me the best mixture quality. It seems to be one of those things that is best to try just try different ones and find out which works best. I read too many different holley books and every one had a different opinion on how to size them so just played it by ear and ended up with a 10. |
| | | | | | Stock size is 6.5 -- Royce P, 03/08/2004
If a 10 is working for you something else is way off. Plugged passeges, wrong metering block, low fuel pressure, something is not right at all.
Royce |
| | | | | | | RE: Stock size is 6.5 -- bprewit, 03/09/2004
Actually 8.5 was stock in the 750 carb that I have. There are no plugged passages, or other problems. To keep from jetting the carb rich as hell for crusing the power valve should open 2hg less than manifold vaccum at cruise rpm. The only reason I state that this works is with single plane intake, decent sized cam, large valves, the 750 is actually a bit small for this engine which causes a pretty high vacuum reading at cruise rpm which would keep closed a low number power valve and cause a very lean mixture. |
| speed o motive -- david_r, 03/05/2004
Has anyone ever bought a kit from Speed O Motive? I'm talking about the all in one piston, rings, rods, bearings, and crankshaft kits? How did it work out in terms of delivery time and quality? Thanks for your input! |
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