Re: Bowtie Block Question
I have a line on a used Bowtie Block. I dont have the part number the guy said he got it off a busch car race team and it is an older block but he had some machine work done to it which is what I am not to sure of without seeing the block I just wanted to know if anyone may know what he is talking about. This is what he told me
It is .050 over with sleeves that are not in the water jackets(I am sure the bowtie block have enough matrial to do this) it need to go .060 to clean up where the engine dropped a valve. He "thinks" the cam has been machined for roller cam bearings. and he says the lifters have been moved and are bigger diamiter he thinks .925(he said a ford diameter?) It has billet caps all the way back.
He is my question has anyone had lifters moved to help line up with head/rocker arms and if so what heads were used???
Roller cam bearing would they be a normal size for our cam of odd ball.
My worries are I am going to get this block and I wont be able to find any supporting parts to assemble it heads, cam, intake, lifters....
He wants around 2200 plus some shipping I think that is a little high for a used block but maybe not.
Any help would be appriciated.thanks
Run from this block…
1.) You do not want a block that has been set up for roller cam bearings. We do not have even fire cams that fit these setups. Actually LSM Cams can make a C&C’ed one for about $900. Roller bearing cam setups were for high rpm circle track motors that used odd fire cranks. You can’t use them for long term street miles.
2.) .05 over what? The bowties came in either 4.00 or 4.125 bores. .050 over on a 4.00 block would be 4.050. .050 over a 4.125 would be a 4.175. Either way you are probably getting thin somewhere. Not all sides of a cylinder have the same wall thickness unless the cores were perfectly aligned during casting. I have not seen too many that were.
Also, according to the owners statement this may be a sleeved motor. What he means is that when the sleeves were installed they didn't have to cut the bores so thin that they cut through the cylinder walls prior to pressing in the sleeves. That’s all good, but most sleeved motors can't go .050 - .060 over as then the sleeves get thin. Darton sells sleeves for Bowtie blocks and the sleeve wall thickness is .076. So at .050 and needing .060 to clean it up you are about through the sleeve. Sleeves sometime are a good thing and some high hp turbo guys will prefer sleeves as they get a better cylinder wall material (iron ductile) which is a harder surface and stronger than the cast iron block cylinder walls. In your case this block probably has a very old style sleeve with older type of metal alloys than today’s sleeves. It will cost you $600 to $800 to properly resleeve the block.
3.) The larger dia lifters bores are fine but not needed and will not be of any benefit for our lower rpm motors and lighter spring pressures. If you were running a solid roller cam doing 7,500 -8,000 rpm with 650# and up spring pressures then the bigger rollers can help take the pressure.
If the bores have been moved it was for the big 18* bowtie heads. It is probably a very old block setup as most race teams started using the tall Isky offset lifters to overcome the push rod flex vs moving the lifter bores. The Isky offset lifters were widely use by the mid to late 80's. If you run the 18* bowtie heads be prepared to spend the money for big valves, lifters, and shaft rockers. You will also need a custom set of pistons (vs shelf pistons) as the chamber cc of the 18* heads will be in the 55 cc range and you will need to lower the compression ratio through a bigger dish in the custom piston.
4.) Is this a dry sump motor? If so then you will have to change the rear cap. A billet rear cap for a wet sump motor is $400 and then you have to have the motor line bored again.
5.) Is it a one or two piece rear seal block? Some blocks can go either one or two piece with the proper adapter. Some of the older blocks are only two piece seal setups and you will need a two piece crank.
Here is a message I recently sent to another board member regarding core shift and suggesting to only purchase blocks that are sonic checked for wall thickness.
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There were many different casts of bowtie blocks made over the years and many improvements from the early 80s blocks to the later late 90s - 02) blocks. The last blocks were cleaned, bored and final cut on C&C equipment. They were probably the best blocks. As with any cast type blocks, some castings had "core shift". This is where during the casting processing the forms shifted slightly. When the bores where cut in the centers the walls of the cylinders may not have ended up equal on all sides. This determined how much bore a block could have could have before one side or other would get two thin.
GM sold new blocks with a sonic test card which showed the tested cylinder wall thickness. What happened is the race teams that bought blocks over the years always picked the best blocks and the less desirable blocks set on the shelf. Today if one would find a new block (some are around) it probably has some thin wall area in some of the cylinders limiting its bore size or not allowing the motor to be rebored if a cylinder got scratched. A near perfect block with the cores about as perfect as possible would allow for a block to go to 4.180 and still have .180 -.200 wall thickness left (which is about the thinnest we want to go with an 800 1,000 hp turbo motor). A NA motor at 500 hp could take a near perfect casting to a 4.200 bore because they could use a thinner wall thickness..
I recently got a brand new in-the-crate block for someone that that was satisfied to only do a 4.00 bore as the block could only go to 4.20 bore before one bank of bore had the outside walls getting below .180 thicknesses. The other sides of those cylinders were like .400 thick walls. That’s from core shift at the time of casting. The block looked perfect on the outside (only a sonic check will tell the truth).
I never buy a bowtie block unless it is sonic checked (unless I get one so cheap that I can junk it if needed). Some ppl think these blocks are some kind of jewelry and fight over getting one of these blocks not knowing if it will work or not. These blocks are much stronger than a stock block by far, but not all of them may be a good one on the inside. Also the circle track guys modified the decks, oiling systems, lifters bores, cam bores and timing chain bosses on many of the blocks. Some of these mods can be worked around (costly) and some we can not live with for our applications.
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Most bowtie blocks sell for $1,500 to $3,000 depending on the block condition and timing of the sale (sometimes there are several ppl needing one. Other times no one is looking spend the $$ on one).
Having said all this, the roller bearing cam setup is a no – no for us. Other than that you could resleeve and convert the block to a wet sump for a grand or so. If there were no other problems you would have a decent block if you only had to pay about $600 - $800 for it, providing you wanted to deal still with the offset lifter bores.
Hope this is helpful,
John
