Oil return hole size in Dart IE Sportsman 9.5 Ford block

[BirdMan]

A mexican 302 block that I have has .375 front dia. and .475 rear dia. oil return holes and never an oil return problem and have had rpm to 8600. My Dart block has .375 front and rear and am concerned about potential oil return problems, as is and with Edelbrock Victor heads, as is.

I have a Bullet SR cam, Crane lifters, Crane shaft rockers, Victor 7721 heads w/lefthand oil return hole .375 and righthand is .500 and matches head gasket dia. of .500.

Question 1 - On the heads can I enlarge the .375 lefthand hole to .500 and have enough casting wall thickness to support it?

Question 2 - On the Dart block can I drill the block to .500 and have enough casting wall thickness to support it?

I don't want to have an oil flooding problem in heads after assembly so if the above modifications are not feasible then the only thing I can do is drill and tap heads for external oil return hoses to oil pan?

[Racerrick]

When I build 351w for wet sump racing I drill a 1" hole into back of the block at the bottom of the valley and another just above the pan rail then I solder up a 1" copper pipe with 2 elbows to fit the holes and JB weld it in. That will end all drain back problems on a 351w blocks.

[Mpcoluv]

The old Boss 302 Engine Modification book shows external drain lines plumbed from the valve covers to the oil pan.

[Racerrick]

The old Boss 302 Engine Modification book shows external drain lines plumbed from the valve covers to the oil pan.

Yea I do that too but only for the oval motors on the right head. If you oval race a 351w and don't do what I telling you, she might last 50 laps on a 1/2mile before the mains spin and then its boom.

[Mpcoluv]

When I build 351w for wet sump racing I drill a 1" hole into back of the block at the bottom of the valley and another just above the pan rail then I solder up a 1" copper pipe with 2 elbows to fit the holes and JB weld it in. That will end all drain back problems on a 351w blocks.

Do you have any photos of that?
I can't visualize how that would route. Is the copper pipe bent or straight?

[BirdMan]

I forgot to insert some needed items in my first post.
Oil pan is Canton 15-680S (7 or 7 1/2 quart cap.)
Oil pump is Melling 10833 cleaned up (going to make test stand to test)
Lifters are Crane Pro 44544
Ring combo is top - .031 dykes
2nd - .170 wall 1/16" napier
3rd - 3mm Lt tension

This is a bracket engine with max rpm no more than 8,000. Probably for normal bracket racing 7,000 max. We do plan to run in NHRA S/St on a 10.90 index with throttle stop, probably.

[Racerrick]

When I build 351w for wet sump racing I drill a 1" hole into back of the block at the bottom of the valley and another just above the pan rail then I solder up a 1" copper pipe with 2 elbows to fit the holes and JB weld it in. That will end all drain back problems on a 351w blocks.

Do you have any photos of that?
I can't visualize how that would route. Is the copper pipe bent or straight?

I might be able take a picture as I have block in the shop but I can't remember if it been modify yet, cause it the last thing I do before I assemble them. You need a real clean surface, free of oil for the JB weld to stick.
Its 3 pieces of straight copper with 2 elbows, they are solder together in the shape of a U. Insert the legs of the solder U piece into the holes and jb weld them. I done it this way for years and never have any trouble, The races are 250 laps.
Other drill holes and seal off the whole back of the block with the block saver plate. Way too messy in my book.

[gasman5.0]

Scribe.

[BirdMan]

I am more concerned with any excess oil in valvecover causing oil intake problem. I'm asking if 3/8" oil return holes from heads will keep the oil level in valvecovers to an acceptable level.

[AA Performance]

I am more concerned with any excess oil in valvecover causing oil intake problem. I'm asking if 3/8" oil return holes from heads will keep the oil level in valvecovers to an acceptable level.

What do you mean by an acceptable level? There is no acceptable level as you need to drain all the oil back to the pan as fast as you can .Weather a 3/8 hole is large enough depends on how much oil your getting up top in the first place. If your not sure then drill or modify the system so you are.

[BirdMan]

Okay the real question is, has anyone drilled the oil return holes in a Dart IE Sportsman Block to 7/16" or 1/2" and any problems doing so? Can it be done?

[gasman5.0]

When I build 351w for wet sump racing I drill a 1" hole into back of the block at the bottom of the valley and another just above the pan rail then I solder up a 1" copper pipe with 2 elbows to fit the holes and JB weld it in. That will end all drain back problems on a 351w blocks.

Do you have any photos of that?
I can't visualize how that would route. Is the copper pipe bent or straight?

I might be able take a picture as I have block in the shop but I can't remember if it been modify yet, cause it the last thing I do before I assemble them. You need a real clean surface, free of oil for the JB weld to stick.
Its 3 pieces of straight copper with 2 elbows, they are solder together in the shape of a U. Insert the legs of the solder U piece into the holes and jb weld them. I done it this way for years and never have any trouble, The races are 250 laps.
Other drill holes and seal off the whole back of the block with the block saver plate. Way too messy in my book.

If you wouldn't mind sharing a photo or two I sure would like to see how you have it draining back. I can't visualize whats going on with the U shaped tubing.

Thanks Darrin

[mbrooks]

i have an aluminum sbf dart block with afr205 heads, no modifications to oil return except extra holes in valley, with no oil restrictors to top end, and the dry sump tank does not fluctuate at any rpm.

[Caprimaniac]

Following PDQ’s tradition and bringing up old threads...

Same question as above, but a World Products alu block.

Deck surface oil return hole in front is much smaller than the reat one (makes sense). Will enlarging front holes be a safe procedure?

In dragracing I do not see a big + doing this, but in roadracing alot of har braking and oil going to the front. And should have good drainback there.

[n2omike]

Following PDQ’s tradition and bringing up old threads...

Same question as above, but a World Products alu block.

Deck surface oil return hole in front is much smaller than the reat one (makes sense). Will enlarging front holes be a safe procedure?

In dragracing I do not see a big + doing this, but in roadracing alot of har braking and oil going to the front. And should have good drainback there.

Even with stock blocks, the rear oil return holes in the block/head usually line up, and the front ones are offset to the point they are up to 50% blocked. If you want it perfect, you need to grind the block to match. Either that, or grind the head, but then you can't swap the heads from side to side.