300 rebuild project

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pmuller9
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Re: 300 rebuild project

Post #51 by pmuller9 » Thu Nov 30, 2017 1:58 pm

Good News!
Bolt down roller rockers are now available.
https://www.summitracing.com/parts/scc- ... /overview/

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Re: 300 rebuild project

Post #52 by brandoncw » Thu Nov 30, 2017 7:18 pm

pmuller9 wrote:After you get the head apart, would you mind taking some measurements.

Install an intake valve in the head with only the spring retainer and keepers.
With the retainer pulled up tight, measure the distance between the underside of the retainer and the spring seat in the head.

I'm looking for the installed height of the valve spring.
The EFI valves are 4.75" in length while the 300 carb head valves are 4.81"
Just need to know if the installed spring height is also different.

Measure how much intake valve lift it takes to have the top of the valve head even with the surface of the head.
Thanks

Ok no problem. I have it apart already so ill take the measurements tomorrow.

A couple questions. Do you want the seal included in the measurement? And when you say "valve head even with the sureface of the head" do you mean hoe much left it takes to hit the bottom of the retainer or till the tip of the stem is flush to the head?

Here are a few pics i got of my head and my over due for a replacement camshaft

Im also working on a four wheeler for a guy. Only lead i had was sometimes it would start sometimes it wont. Can you guess whats wrong? Hint: timing
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Re: 300 rebuild project

Post #53 by brandoncw » Thu Nov 30, 2017 7:26 pm

pmuller9 wrote:Good News!
Bolt down roller rockers are now available.
https://www.summitracing.com/parts/scc- ... /overview/

Sweet. They arent very bad on price compared to roller sets ive seen before. Very possible i might get them for the heck of it. What is the stock lift ratio. Those say lift ratio of 1.73

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THE FRENCHTOWN FLYER
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Re: 300 rebuild project

Post #54 by THE FRENCHTOWN FLYER » Thu Nov 30, 2017 8:55 pm

brandoncw wrote: What is the stock lift ratio. Those say lift ratio of 1.73

Purportedly, 1.61:1, but it is likely less than that actual. That is theoretical, instantaneous.
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Re: 300 rebuild project

Post #55 by brandoncw » Thu Nov 30, 2017 9:16 pm

THE FRENCHTOWN FLYER wrote:
brandoncw wrote: What is the stock lift ratio. Those say lift ratio of 1.73

Purportedly, 1.61:1, but it is likely less than that actual. That is theoretical, instantaneous.

Theoretical? Why cant they have just measured the lift on one side of the pivot and then the lift at the other end, put it in a fraction and reduce to x/1?

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Re: 300 rebuild project

Post #56 by pmuller9 » Thu Nov 30, 2017 11:06 pm

Thanks for reminding me that I need 3 measurements.

The distance from the underside of the intake retainer to the spring pocket on the head. (Installed spring height)

Distance the intake valve moves till the retainer hits the valve stem seal.

With the head lying flat on the bench, combustion chamber side down, how far does the intake valve move till it hits the bench surface.

Thanks again

Great pictures. You have your work cut out for you.
May I suggest that before you invest a lot of time in the head, clean it up and have it magnafluxed for cracks.

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Re: 300 rebuild project

Post #57 by brandoncw » Fri Dec 01, 2017 7:58 am

pmuller9 wrote:Thanks for reminding me that I need 3 measurements.

The distance from the underside of the intake retainer to the spring pocket on the head. (Installed spring height)

Distance the intake valve moves till the retainer hits the valve stem seal.

With the head lying flat on the bench, combustion chamber side down, how far does the intake valve move till it hits the bench surface.

Thanks again

Great pictures. You have your work cut out for you.
May I suggest that before you invest a lot of time in the head, clean it up and have it magnafluxed for cracks.


Ok ill get those for you. And the first thing i was gonna do was wire brush the chambers and ports just to get them clean. The intakes are pretty nasty. But there isnt very much carbon build up on the exhaust or in the combustion chambers unlike my old 351w that had so much carbon that cylinder 1 exhaust valve no longer fully sealed. I got a quote on boring and hot tanking my block at $120 And ill have to double check but i think he was talking about cutting my valve seats and hot tanking the head for $100. Those prices dont seem to out of line. And he is reputable, most of the shops in my area pointed me to that guy.

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Re: 300 rebuild project

Post #58 by THE FRENCHTOWN FLYER » Fri Dec 01, 2017 9:30 am

brandoncw wrote:
THE FRENCHTOWN FLYER wrote:
brandoncw wrote: What is the stock lift ratio. Those say lift ratio of 1.73

Purportedly, 1.61:1, but it is likely less than that actual. That is theoretical, instantaneous.

Theoretical? Why cant they have just measured the lift on one side of the pivot and then the lift at the other end, put it in a fraction and reduce to x/1?

A rocker arm used on two different lobes will have two different ratios. The published ratio is the instantaneous ratio measured at the midpoint of the lobe lift on the cam that was originally intended to be used on that engine.

I have done dyno testing on various brands of rockers, including OEM Ford and plotted lift curves and there is a wide variation in theoretical-vs-measured ratios.
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Re: 300 rebuild project

Post #59 by arse_sidewards » Fri Dec 01, 2017 11:59 am

THE FRENCHTOWN FLYER wrote:
brandoncw wrote:
THE FRENCHTOWN FLYER wrote:I have done dyno testing on various brands of rockers, including OEM Ford and plotted lift curves and there is a wide variation in theoretical-vs-measured ratios.


Care to share a few data points?
1994 F150 4x4 8ft EEC-IV
-460 rocker arm Guinea Pig: 3rd world quality "file to fit" machining

-exhaust leak that sounds like a bucket of playing cards being fed into the radiator fan
-66" leafs ('11 Superduty), extended radius arms.

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Re: 300 rebuild project

Post #60 by brandoncw » Fri Dec 01, 2017 1:20 pm

pmuller9 wrote:
The distance from the underside of the intake retainer to the spring pocket on the head. (Installed spring height)

Distance the intake valve moves till the retainer hits the valve stem seal.

With the head lying flat on the bench, combustion chamber side down, how far does the intake valve move till it hits the bench surface.

The measurements are in the order of the questions asked.

Intalled spring height: i got 1.620" may not be exactly accurate but ought to be very close

Spring retainer to stem seal: 0.510"

Valve to table: 0.340"

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Re: 300 rebuild project

Post #61 by brandoncw » Fri Dec 01, 2017 1:36 pm

THE FRENCHTOWN FLYER wrote:A rocker arm used on two different lobes will have two different ratios. The published ratio is the instantaneous ratio measured at the midpoint of the lobe lift on the cam that was originally intended to be used on that engine.


Sorry i still dont quite understand :?
Mathematically it doesnt matter how much you change one side in a ratio it will always reduce to the same numbers. To make things simple lets use a ratio of 2:1. If we double the lift (change 1 to 2) the ratio changes to 4:2 which will reduce back to 2:1. I understand that the cam lobes may have different lift heights but it shouldnt change the ratio of that rocker, just the amount of lift.

<edit> i think i figured it out. Since the rocker pivots and technically moves in a circular motion, and the valve moves in linear motion some of the lift is lost through te rocker sliding back and forth instead of all the lift moving with the valve
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Re: 300 rebuild project

Post #62 by pmuller9 » Fri Dec 01, 2017 1:52 pm

Thanks for the measurements.

The installed spring height on a carb 300 head is closer to 1.7 which makes sense since the valve is .060" longer, 4.810" versus 4.750"

Same with the distance to the valve stem seal.
If a person throws in a cam with over .500" lift with stock EFI valves they will have a problem.

I like to use 4.910" SBC valves which gives plenty of margin on both counts.

The valve to table top explains why there is almost never a need to have valve pockets in the piston.
It also a dimension you may need for combustion chamber modification. Will explain later.

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Re: 300 rebuild project

Post #63 by pmuller9 » Fri Dec 01, 2017 1:57 pm

brandoncw wrote:
THE FRENCHTOWN FLYER wrote:A rocker arm used on two different lobes will have two different ratios. The published ratio is the instantaneous ratio measured at the midpoint of the lobe lift on the cam that was originally intended to be used on that engine.


Sorry i still dont quite understand :?
Mathematically it doesnt matter how much you change one side in a ratio it will always reduce to the same numbers. To make things simple lets use a ratio of 2:1. If we double the lift (change 1 to 2) the ratio changes to 4:2 which will reduce back to 2:1. I understand that the cam lobes may have different lift heights but it shouldnt change the ratio of that rocker, just the amount of lift.


It has to do with the change in geometry.
As the pushrod increases the angle of the rocker it gets closer to the pivot point however the distance from the pivot point to the valve stem remains the same so there is a change in the ratio just from that perspective.

If you want to do the check, put a dial indicator on the lifter and one on the valve and chart both lifts at small increments of cam rotation.

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Re: 300 rebuild project

Post #64 by brandoncw » Fri Dec 01, 2017 2:01 pm

pmuller9 wrote:
brandoncw wrote:
THE FRENCHTOWN FLYER wrote:A rocker arm used on two different lobes will have two different ratios. The published ratio is the instantaneous ratio measured at the midpoint of the lobe lift on the cam that was originally intended to be used on that engine.


Sorry i still dont quite understand :?
Mathematically it doesnt matter how much you change one side in a ratio it will always reduce to the same numbers. To make things simple lets use a ratio of 2:1. If we double the lift (change 1 to 2) the ratio changes to 4:2 which will reduce back to 2:1. I understand that the cam lobes may have different lift heights but it shouldnt change the ratio of that rocker, just the amount of lift.


It has to do with the change in geometry.
As the pushrod increases the angle of the rocker it gets closer to the pivot point however the distance from the pivot point to the valve stem remains the same so there is a change in the ratio just from that perspective.

If you want to do the check, put a dial indicator on the lifter and one on the valve and chart both lifts at small increments.

Yep i just figured that out lol. I had to think about it.

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Re: 300 rebuild project

Post #65 by THE FRENCHTOWN FLYER » Fri Dec 01, 2017 7:26 pm

And don't forget the possibility of differtent cams having different base circle diameters, especially aftermarket high lift cams that need to reduce the base circle diameter in order to have enough lobe height.
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Re: 300 rebuild project

Post #66 by brandoncw » Sun Dec 03, 2017 6:15 pm

Hey guys I just got back from a weekend adventure thing. I was looking online earlier this week and forgot to ask if these would work. I found some cool looking 2 bbl carbs advertised for Volkswagen engines on feebay. I was thinking to modify my efi intake and use the CNC plasma table to cut me out mounting plates, thread in some studs, and put three of them on. Then ill probably play with jets and tune it till it runs right.

Here's the link: https://www.ebay.com/p/2x-Carb-Carburet ... serReviews

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Re: 300 rebuild project

Post #67 by THE FRENCHTOWN FLYER » Sun Dec 03, 2017 9:11 pm

Those look nice. At 1200 cc a VW engine is about a fourth as big as our 300 so three would be OK for a street engine. Many folks run 45s on hopped up 300s and racers use either 48s or the rare 58s. They are sure a lot less pricey than Webers.
Go for it.
Post pics and results.
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Re: 300 rebuild project

Post #68 by brandoncw » Mon Dec 04, 2017 2:06 pm

Ok, ill get to work on the manifold maybe next week while i wait on my block and head to clean up in a lye and water mixture. (yes i know this stuff can be pretty nasty if not handled correctly) then after the block an head have sat in the stuff for a week or so ill put them in an electrolysis tank to get rid of any rust, then it will get a little oil sprayed on to keep the rust away. Hopefully by the time all that is dont ill have enough money scratched together to get the machine work done. Should be about $220

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Re: 300 rebuild project

Post #69 by brandoncw » Thu Dec 07, 2017 8:24 pm

Well these intakes clean up really nice with a bit of elbow grease. Not even close to done yet though. I was wondering what the best method for cleaning the black crud out of the inside of these. My plan of attack is to get one of them cheap bottle brushes with the wire handle, stick it in a drill, fill the intake with oven cleaner and brush the heck out of it
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Re: 300 rebuild project

Post #70 by woodbutcher » Fri Dec 08, 2017 4:33 pm

:hmmm: Don`t even think about using oven cleaner on aluminum.You for sure won`t like the results.
Good luck.have fun.Be safe.
Leo
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Re: 300 rebuild project

Post #71 by brandoncw » Fri Dec 08, 2017 4:46 pm

woodbutcher wrote::hmmm: Don`t even think about using oven cleaner on aluminum.You for sure won`t like the results.
Good luck.have fun.Be safe.
Leo

I was told dont let tye oven cleaner set too long as it will eventually dissolve the aluminium. Just leave it on long enough to break up the crap then rinse it off.
Plan b might be just soak it in acetone to see if that will loosen it up

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Re: 300 rebuild project

Post #72 by wallen7 » Fri Dec 08, 2017 5:30 pm

Do you know any one with a media blast cabinet? That would be a quick easy way to clean without all the chemicals. I also know folks that have run a ball hone for medium-heavy truck wheel cylinders in side ports to clean them.

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Re: 300 rebuild project

Post #73 by brandoncw » Fri Dec 08, 2017 6:24 pm

wallen7 wrote:Do you know any one with a media blast cabinet? That would be a quick easy way to clean without all the chemicals. I also know folks that have run a ball hone for medium-heavy truck wheel cylinders in side ports to clean them.

The collision repair at my votech school has a sand blasting cabinet. I dont kbow anything about what grit of sand they use though. It might be too course. Id like to blast it with plastic beads. But of course id like to have a lot of things. The only place left to clean really is the insides of the ports, thats why i was just gonna use chemicals, get to the hard to reach spots and loosen the crap up in there. 375k of exhaust reidue builds up quite thick :lol:

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Re: 300 rebuild project

Post #74 by wallen7 » Fri Dec 08, 2017 8:56 pm

Sand will clean it, just go slow and easy, don' t stay in 1 spot too long. after you finish you can polish the runners a little with sanding rolls and a die grinder. the wash it good with solvent and blow it dry. I am assuming that you are going to fab a box plenum to mount carbs.

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Re: 300 rebuild project

Post #75 by brandoncw » Sat Dec 09, 2017 7:27 am

wallen7 wrote:Sand will clean it, just go slow and easy, don' t stay in 1 spot too long. after you finish you can polish the runners a little with sanding rolls and a die grinder. the wash it good with solvent and blow it dry. I am assuming that you are going to fab a box plenum to mount carbs.

Ok, ill see if the instructor will let me use it. I plan on fabbing a plenum yes. My idea for the paint sceme of the engine is either black or charcoal grey gloss, with chrome valve cover, pushrod cover, exhaust, and maybe oil pan

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Re: 300 rebuild project

Post #76 by brandoncw » Mon Dec 11, 2017 10:47 am

Ok i got permission to use the blast cabinet, ill get the intake all cleaned up and prepped for welding. I have a few questions regarding plenum design. For the three 2 bbls carbs i mentioned, how large should the plenum be? Should i divide the carbs to supply only 2 cylinders each? Or leave it all open so it can all mix together?

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Re: 300 rebuild project

Post #77 by THE FRENCHTOWN FLYER » Mon Dec 11, 2017 12:20 pm

I would NOT blast the manifold. You can't be sure every bit of grit is gone. I have seen a rash of engine failures related to this cause. Don't obsess over a squeaky clean runner. Wash / brush it out with solvent and go.

I would make the plenum half of the engine displacement, i.e. 150 cubic inches, or a little larger. Bigger than that gives more max HP; smaller than that gives better throttle response. I prefer to not divide it - others do.
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Re: 300 rebuild project

Post #78 by brandoncw » Mon Dec 11, 2017 2:08 pm

THE FRENCHTOWN FLYER wrote:I would NOT blast the manifold. You can't be sure every bit of grit is gone. I have seen a rash of engine failures related to this cause. Don't obsess over a squeaky clean runner. Wash / brush it out with solvent and go.

I would make the plenum half of the engine displacement, i.e. 150 cubic inches, or a little larger. Bigger than that gives more max HP; smaller than that gives better throttle response. I prefer to not divide it - others do.

very good point on the sand possibly finding its way into the engine. ill just use acetone and a bottle brush on a drill as planned before then. ill upload pics of my progress when i start getting the fab work done.

Also i don't see any harm in covering the holes and blasting just the outside to prep for painting, do you?

As for the dividing, In theory i should be able to narrow down which carb needs to be tuned a little bit easier than if the plenum was open. Just my thought on it, feel free to give me your take on it.

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